Nukes Flashcards

Question

Tc WBC vs In WBC labeled

Answer 1

Just like MIBG can be labeled with either 1-123 or 1-131 | you can label WBCs with Tc or Indium.

Answer 2

Both will have hot spleens. Additionally, Tc is a higher count study and will typically look cleaner.

Answer 3

The trick here can be imaging at 4 hours vs imaging at 24 hours. At 4 hours you can see lung uptake. At 24 hours the lungs are clearing up, but you start to get some bowel uptake. Just like an In-WBC the spleen is still darker than the Liver.

Answer 4

no renal, no GI

Answer 5

You can do bone scans with several different tracers, the main two are 18F Sodium Fluoride and Tc-MDP. If you were trying to differentiate the two, the primary take home point is F-18 PET is way way way better than Tc-M DP. By “better” I mean that the image quality and sensitivity of F18 is multiple orders of magnitude better than Tc-MDP. It also has a shorter examination time. So, why do you never see l8F? Because it costs more, and insurances won’t pay etc... Politics and Finance are the reasons. Another potentially testable factoid would be which organ gets the highest dose? The organ receiving the highest dose is Bone with MDP, and Bladder with ,8F (overall l8F > Tc-MDP) — probably... honestly y o u ’ll read different things in different sources.

Answer 6

This is a common trick, popular in case books & case conferences - asking you to distinguish F-18 bone scan vs Tc-MDP bone scan vs PET-FDG with marrow stimulation. This is how you do it: * Tc-MDP will have bone and kidney uptake. It will be a blurry fuzzy piece of crap. * ,8F will be beautiful, super high resolution, and look like a MIP PET. * FDG -PET with bone stimulation - will look similar to the F-l 8, but will have brain uptake. Also, this can show increased uptake in the spleen.

Answer 7

methylene diphosphonate (MDP) tagged with Tc-99m. This is prepared from a kit which has MDP and stannous ion. You add free pertechnetate and the stannous ion reduces it so it will bind to the MDP. If you don’t have enough stannous ion (or you get air into the vial or syringe - that can cause oxidation) you might get free Tc (salivary gland, thyroid, stomach uptake). After you inject the tracer ( 15-25mCi) you wait 2-4 hours to let the tracer clear from the soft tissues (so you can see them bones).

Answer 8

Phosphonate binding to bone (ehemisorption). | Distribution is based on blood flow and osteoblastic activity.

Answer 9

MDP and HDP are both bone agents so don’t get confused if they say HDP to purposefully confuse you.

Answer 10

OsteoBLASTIC activity (why pure lytic lesions can be cold) Blood Flow

Answer 11

Bone (dull), but also the Epiphyses in kids Kidney (not seen *or very faint = Super Scan), Bladder Breasts (especially in young women) Soft tissues - low levels

Answer 12

Increased focal uptake is very nonspecific, and basically is just showing you bone turn over. So a metastatic deposit can do that (and this is the classic indication). But, you can also see it with arthritis (classically shoulder) and healing fractures (most commonly shown with segmental ribs).

Answer 13

It’s normal to see some persistent visualization of the skull sutures, BUT when this is marked you may be thinking about renal osteodystrophy.

Answer 14

Some mild diffuse breast uptake is normal (especially in | younger women), BUT focal uptake can be cancer.

Answer 15

You are supposed to have renal activity (not seeing kidneys can make you think super scan), BUT when the renal cortex is hotter than the adjacent lumber spine you should think about hemochromatosis.

Answer 16

This often occurs in the setting of chemotherapy (especially if the study is looking for bone mets). This also can be seen with urinary obstruction.

Answer 17

``` This can be several things, but the main ones to think about arc (1) Too Much Al+3 contamination in the Tc, (2) Cancereither primary hepatoma or mets, (3) Amyloidosis, (4) Liver Necrosis ```

Answer 18

This is a common trick to show an auto-infarcted spleen - common in sickle cell patients. These same patients are going to have scattered hot and cold areas from multiple bone infarcts.

Answer 19

In most cases this is some type of heterotopic calcification (dystrophic or mets). The classic MDP hot lung met would be an osteosarcoma. Ultimately, it’s not specific and can be seen in a ton of other random situations (fibrothorax, primarily tung tumors, radiation changes, sarcoid, berylliosis, alveolar microlithiasis, Wegener’s, etc...).

Answer 20

When you see a single hot lesion, the false positive rate for attributing the finding to a met is high. Only about 15% to 20% of patients with proven mets have a single lesion (most commonly in the spine). In other words, 80% of the time it’s benign. A classic exception is a single sternal lesion in a patient with breast cancer. This is due to breast CA 80% of the time.

Answer 21

This is a hot geographic area, confined to the sacrum, often with a characteristic butterfly or “H” shaped (Honda sign). Osteoporosis is the most common cause, but it can also occur in a patient who has had radiation.

Answer 22

This can be seen with | (1) free Tc, or (2) Bisphosphonate therapy.

Answer 23

In older populations, bone scans may be negative for several days. A bone scan obtained at 1 week will exclude a fracture.

Answer 24

A horizontal linear pattern of tracer uptake is the classic look for an osteoporotic fracture (especially if they are multiple and of varying intensity). If the tracer extends from the vertebral body into the posterior elements or just involves the pedicles then you should think cancer. Lastly, followup of the osteoporotic fracture should show tracer activity decreasing (cancer isn’t gonna do that).

Answer 25

MDP is for bones, but it will also localize to injured skeletal muscle. The classic way to show this is very hot quads, calfs, shoulders in a marathon runner (or military recruit) - as a way to show rhabdomyolysis.

Answer 26

sacral insufficiency fx

Answer 27

sacral insufficiency fx

Answer 28

This is a “Tramline” along the periosteum of long bones, which is associated with conditions o f chronic hypoxia (CF, Cyanotic Heart Disease, Mesothelioma, Pneumoconiosis). However, when you see this - you need to think lung cancer. Apparently it’s actually seen in 10% o f patients with lung cancer. Next Step? CXR, Chest CT e tc ...

Answer 29

the pattern is typically outside to in, with the eventual development o f mature cortical bone. In some cases this abnormal bone proliferation can reduce joint motility and cause pain. Therefore, in some cases surgical resection is performed to preserve the function o f the joint. Enter the MDP Bone Scan. The main reason you image this is to see if it’s “mature.” Serial exams are used to evaluate if the process is active or not (not = “mature”). If it’s still active it has a higher rate o f recurrence after it’s resected. The idea is you can follow it with imaging until it’s mature (cold), then you can hack it out (if someone bothers to do that).

Answer 30

Avascular Necrosis (AVN) as discussed in the MSK chapter, this can occur from a variety of causes (EtOH, Steroids, Trauma, Sickle Cell, Gauchers). The trick on bone scan is the timing. • Early and late AVN is cold. • Middle (repairing) will be hot.

Answer 31

Seen primarily in older patients (8% at 80), it’s classically shown five ways 1. Super Hot Enlarged Femur 2. Super Hot Enlarged Pelvis, 3. Super hot skull, 4. Expanded hot “entire” vertebral body 5. Metabolic Superscan - from widespread Pagets. Although, as a point of gamesmanship if they show you a metabolic superscan the answer is probably hyper PTH.

Answer 32

Classically involves BOTH the vertebral body and posterior elements.

Answer 33

Both Osteosarcoma and Ewings will be hot. Primary utility o f the bone scan is to see extent of disease. With regard to benign bone tumors the only ones worth knowing are the HOT ones and the COLD ones. Osteoid Osteoma is worth knowing a few extra things about (because they lend themselves easily to multiple choice questions).

Answer 34

The lesion will be focal and three phase hot. A central hot nidus is often seen (double density or hotter spot within hot area). A normal bone scan excludes this entity.

Answer 35

Be aware that in case books / case conference this is sometimes shown as a super hot mandible. Could also be shown as a leg that looks similar to Paget.

Answer 36

* Prostate Cancer Loves Bone Mets (85% of dying patients have it) * Prostate Cancer bone mets are uncommon with a PSA less than 10 mg/ml * Lung Cancer bone mets tend to be in the appendicular skeleton * Lung Cancer can have hypertrophic osteoarthropathy (10%) * Breast Cancer bone mets are most common to the spine, but the solitary sternal lesion is more specific * Neuroblastoma frequently mets to the bones (metaphysis of long bones) * 1-123 and 131 M1BG are superior for detection of neuroblastoma bone mets

Answer 37

MIBG, 1-131, or Octreotide is abnormal, & concerning for mets.

Answer 38

* Radiation Therapy (usually segmental) * Early Osteonecrosis * Infarction (very early or late) * Anaplastic Tumor (Renal, Thyroid, Neuroblastoma, Myeloma) * Artifact from prosthesis, pacemaker, spine stimulator, etc.... * Hemangioma ** this is variable * Bone Cyst (without fracture)

Answer 39

``` • Both are sclerotic on plain film / CT • The Prostate Met should be very HOT on Bone Scan • The Bone Island should be cold, or faintly warm • Osteopoikilosis should be cold ```

Answer 40

``` • Fibrous Dysplasia • Giant Cell Tumor • Osteoblastoma • Osteoid Osteoma • Aneurysmal Bone Cyst *donut sign (centrally cold) ```

Answer 41

* Bone Scan is way better (more sensitive) than skeletal survey for blastic mets * Skeletal Survey is superior (more sensitive) for lvtic mets * Skeletal survey is the preferred evaluation for osseous involvement in myeloma

Answer 42

If a bone scan “equivocal lesion” is found the next step is a plain film. If the plain film shows no corresponding lesion this is MORE suspicious for mets. Next step at that point would be a MRI.

Answer 43

This is a common trick, where the scan shows no abnormal focal uptake, but you can’t see the kidneys. The trick is that everything is hot.

Answer 44

diffuse mets | metabolic

Answer 45

Diffuse skeletal metastatic activity (breast and prostate are the common culprits).

Answer 46

``` From metabolic bone pathology; including hyperparathyroid, renal ® osteodystrophy, Pagets, or severe thyrotoxicosis. ```

Answer 47

- The Skull will be asymmetrically hot on the metabolic super scan.

Answer 48

A common sneaky move is to show you a bone scan, with no renals. But it’s because there is a horseshoe kidney in the pelvis. Could be phrased as a next step question, with the answer being look at prior CT to confirm normal anatomy.

Answer 49

This is a sneaky situation shown on bone scan, where a good response to therapy will mimic a bad response. What happens is you have increased radiotracer uptake (both in number and size of lesions) seen 2 weeks to 3 months after treatment.

Answer 50

* On plain film lesions should get more sclerotic | • After 3 months they should improve.

Answer 51

Bone scans can be done in a single delayed phase, or in 3 phases (flow, pool, and delayed). A lot o f things can be “3 phase hot”, including osteomyelitis, fracture, tumor, osteoid osteoma, charcot joint, and even reflex sympathetic dystrophy.

Answer 52

The benefit of using 3 phases is to distinguish between cellulitis (which will be hot on flow and pool, but not delays), and osteomyelitis (which is 3 phase hot). In children, a whole body bone scan is often performed to evaluate extent. Additionally, because o f subperiosteal pus/ edema you can actually have decreased vascularity to the infected area (cold on initial phases) but clearly hot on delayed phases. In the spine, gallium (combined with bone scan) or MRI are the preferred imaging modalities

Answer 53

You can also use a bone scan to evaluate response to treatment. Blood flow and blood pool tend to stay abnormal for about 2 months, with delayed activity persisting for up to 2 years. This is especially true when dealing with load bearing bones. Gallium67 and Indium111 WBC are superior for monitoring response to therapy.

Answer 54

Sometimes called “complex regional pain syndrome,” it can be seen after a stroke, trauma, or acute illness. The classic description is increased uptake on flow and blood pool, with periarticular uptake on delayed phase. The uptake often involves the entire extremity. About one third o f adult patients with documented RSD do not show increased perfusion and uptake (which probably means they are faking it, and need a rheumatology consult fo r fibromyalgia). In children, sometimes you actually see decreased uptake.

Answer 55

Tc can be tagged to sulfur colloid with the idea o f getting a normal localization to the bone marrow. You can actually perform Tc sulfur colloid studies to map the bone marrow in patients with sickle cell (with the idea to demonstrate marrow expansion and bone infarct). However, the major utility is to use it in combination with tagged WBC or Gallium. Both Tc Sulfur Colloid and WBCs will accumulate in normal bone marrow, in a spatially congruent way (they overlap). The principal is that infected bone marrow will become photopenic on Tc-Sulfur Colloid. Now, this takes about a week after the onset of infection, so you have to be careful in the acute setting. WBC, on the other hand, will obviously still accumulate in an area o f infection.

Answer 56

is activity on WBC image, without corresponding Tc S u lfu r Colloid activity on the bone marrow image

Answer 57

less uptake

Answer 58

more uptake

Answer 59

When imaging the spine, WBC frequently fails to migrate showing a photopenic area (WBC = False Negative in the Spinel. This is why gallium is preferred for osteomyelitis of the spine.

Answer 60

more uptake

Answer 61

false negative

Answer 62

Differentiating infection from aseptic loosening is challenging and the most common reason a nuclear medicine doctor would get involved in the situation. Bone scan findings o f periprosthetic activity is very nonspecific, because you can see increased tracer activity in a hip up to 1 year after placement (even longer in cementless arthroplasty). Typically, there would be diffusely increased activity on imaging with Tc-MDP in the case of infection (more focal along the stem and lesser trochanter with loosening) - but this isn’t specific either. Combined Tc-Sulfur Colloid and WBC imaging is needed to tell the difference.

Answer 63

A negative bone scan excludes loosening or infection

Answer 64

Most commonly seen in the tarsal and tarsal-metatarsal joints (60%), in diabetics. When the question is infection (which diabetics also get), it’s difficult to distinguish arthritis changes vs infection with Tc-MDP. Again, combined marrow + WBC study is the way to go.

Answer 65

the need for a fourth phase in diabetic feet. As these patient’s tend to have reduced peripheral blood flow, the addition of a 4th phase at 24 hours may help you distinguish between bone and delayed soft tissue clearance.

Answer 66

(1) Kids - Tc99 will have a lower absorbed dose & shorter imaging time (2) Small Parts - Tc99 does better in hands and feet

Answer 67

(1) It has a shorter half life -6 hrs- which limits delayed imaging, and (2) It has normal GI and gallbladder activity which obscures activity in those areas.

Answer 68

• The vast majority (like 90%) o f the labeled cells are Neutrophils. This allows you to “trace” anything that triggers neutrophil migration (inflammation / infection). • The radiation dose that the Indium deposits on the neutrophil doesn’t mess with its function (supposedly). Lymphocytes on the other hand, tend to be killed by the radiation (they don’t turn into cancer). • In the normal situation the critical organ is the spleen. • If the cells become fragmented - the Indium binds with transferrin and you see more uptake in the liver and bone marrow.

Answer 69

you’ll want to get the angiography room ready. In 2014, textbooks and papers still frequently lead with the following statement “Pulmonary’ angiography is the definitive diagnostic modality and reference standard in the diagnosis o f acute PE. " In reality, pulmonary angiography is almost never done, and CTPA is the new diagnostic test of choice. V/Q scan is usually only done if the patient is allergic to contrast or has a very low GFR. The primary reason V/Q isn’t done is that it’s often intennediate probability, and the running joke is that if you don’t know how to read one, just say it’s intermediate and you’ll probably be right. The idea behind the test is that you give two tracers: one for ventilation and one for perfusion. If you have areas of ventilated lung that are not being perfused, that may be due to PE. Normally Ventilation and Perfusion are matched, with a normal gradient (less perfusion to the apex - when standing).

Answer 70

For perfusion, Tc-99m macroaggregated albumin (Tc-99m MAA) is the most common tracer used. MAA is prepared by heat denaturation of human serum albumin, with the size of the particles commercially controlled. You give it IV and the tracer should stay in the pulmonary circulation (vein-> SVC-> right heart -> pulmonary artery -> lung *STOP). The tracer should light up the entire lung. A nonnal perfusion study excludes PE. Areas of perfusion abnormality can be from PE or other things (more on this later). The biologic half life is around 4 hours (they eventually fall apart, becoming small enough to enter the systemic circulation to eventually be eaten by the reticuloendothelial system).

Answer 71

There are two ways to do the ventilation; you can use a radioactive gas (Xenon-133) or a radioactive aerosol (Tc-99m DTPA).

Answer 72

The physical half-life is 5.3 days, the biologic half-life is 30 seconds (you breath it out). Because it has low energy (81 keV) it is essential to do this part of the test first (more on this in the physics chapter). Additionally, because the biologic half life is so short, you only can do one view (usually posterior) with a single detector (dual detector can do anterior and posterior). There are 3 phases to the study: (1) wash in (single max inspiration and breath hold), (2) equilibrium (breathing room air and xenon mix), and (3) wash out (breathing normal air).

Answer 73

This one requires patient cooperation because they have to breath through a mouth guard with a nose clamp for several minutes. It is also essential to do this part of the test first.

Answer 74

You can do quantitative studies typically to evaluate prior to lung resection, or prior to transplant. You want to make sure that one lung can hold its own if you are going to take the other one out.

Answer 75

Quantification is NOT possible if you use Tc-99 DTPA aerosol. You can do it with a combined Xe + Tc MAA because the Xe will not interfere with the Tc.

Answer 76

This is a classic way o f showing you a shunt (it got into the systemic circulation somehow, maybe an ASD, VSD, or Pulmonary AVM).

Answer 77

A capillary is about 10 micrometers. You need your particles to stay in the lung, so they can’t be smaller than that. You don’t want them to be so big they block arterioles (150 micrometers). So the answer is 10-100 micrometers.

Answer 78

few situations. You don’t want to block more than about 0.1% o f the capillaries, so anyone who has fewer capillaries (children, people with one lung). Also you don’t want to block capillaries in the brain, so anyone with a right to left shunt. Lastly anyone with pulmonary hypertension (or who is pregnant).

Answer 79

Nope. The normal dose of Tc can be added to fewer particles.

Answer 80

This is the classic way of showing “clumped MAA” , which happens if the tech draws blood into the syringe prior to injection.

Answer 81

This indicates Air Trapping (COPD)

Answer 82

This is fatty infiltration of the liver (xenon is fat soluble).

Answer 83

Quick Wash Out only one or two views Activity homogenous in the lungs

Answer 84

Slower Wash Out - multiple projections “Clumping” common in the mouth, central airways, and stomach (from swallowing).

Answer 85

You should think 2 things: (1) Free Tc, or (2) Right - to - Left Shunt

Answer 86

tracer in the brain

Answer 87

You reduce the number o f particles. If the normal amount o f particles is around 500K., you would reduce it to around 100K.

Answer 88

reduce the particles

Answer 89

Nope. You keep the dose the same - otherwise the study is non-diagnostic.

Answer 90

What about a neonate ? Do you do anything different? A: Yes - major particle reduction. Down to 10K- 50K particles (depending on who you ask). The reason is that kids have less capillaries than adults. An adult number of particles (500K) could functionally cause a PE - by blocking the majority of the capillaries.

Answer 91

Get a CT or MRI. DDx is gonna be a mass, fibrosing mediastinitis, or Central PE. O f those which is the MOST COMMON? A: Most sources will say “central obstructing mass” i.e. “bronchogenic carcinoma”

Answer 92

te hnically low probability

Answer 93

The body handles Ga+3 the same way it would Fe+3 - which as you may remember from step 1 gets bound (via lactoferrin) and concentrated in areas of inflammation, infection, and rapid cell division. Therefore it’s a very non-specific way to look for infection or tumor. Back in the stone ages this was the gold-standard for cancer staging (now we use FDG-PET). 1 should point out that Gallium can also bind to neutrophil membranes even after the cells are dead, which gives it some advantages over Indium WBC - especially in the setting o f chronic infection.

Answer 94

Gallium is produced in a cyclotron via the bombardment of Zn68, at which point it’s complexed with citric acid to make Gallium Citrate. The half life is around 3 days (78hours). It decays via electron capture, emitting gamma rays at 4 photopeaks

Answer 95

93 keV - 40% 184 k eV -2 0% 300 keV - 17% 393 keV - 5%

Answer 96

Images are not typically done sooner than 24 hours - because background is too high. The critical organ is the colon. Remember “critical organ” = the first organ to be subjected to radiation in excess o f the maximum allowable amount.

Answer 97

Liver (which is the highest uptake), bone marrow ( “Poor Mans s hone sca n”), spleen, salivary glands, lacrimal glands, breasts (especially if lactating, or pregnancy). Kidneys and bladder can be seen in the first 24 (faintly up to 72 hours). Faint uptake in the lungs can be seen in < 24 hours. After 24 hours you will see some bowel. In children the growth plates and thymus.

Answer 98

Uptake is in both cortex (like regular bone scan) and marrow. Degenerative change, fractures, growth plates, all are hot - just like bone scan.

Answer 99

infection, | but also CHF, atelectasis, and ARDS.

Answer 100

The utility o f Gallium in Sarcoidosis patients is to help look for active disease. Increased uptake in the lungs is 90% sensitive for active disease (scans are negative in inactive disease). Additionally, Gallium can be used to help guide biopsy and lavage - if looking to prove the diagnosis. The degree o f uptake is graded relative to surrounding tissue (greater than lung is positive, less than soft tissue is negative).

Answer 101

* Lambda Sign - The nuke equivalent to the “ 1 -2-3 Sign” on Chest x-ray. You have increased uptake in the bilateral hila, and right paratracheal lymph node. * Panda Sign - Prominent uptake in the nasopharyngeal region, parotid salivary gland, and lacrimal glands. This can also been seen in Sjogrens and Treated Lymphoma.

Answer 102

* Gallium can be used to show early drug reaction from chemotherapy (Bleomycin) or other drugs (Amiodarone). * Gallium is elevated in IPF (idiopathic pulmonary fibrosis) and can be used to monitor response to therapy.

Answer 103

Gallium Hot, Characteristic Gallium Pattern is Diffuse Bilateral Pulmonary Uptake

Answer 104

Gallium Negative, Thallium Positive

Answer 105

- Lung Uptake at 72 Hours

Answer 106

Intense lobar configuration without parotid or nodal uptake.

Answer 107

• Abdominal and Pelvic Infections - In-111 WBC is superior to Gallium (Gallium has some normal GI uptake). • Malignant Otitis Media - Will be both Gallium and Bone Scan (Temporal Bone) Hot. • Spinal Osteomyelitis - Gallium is superior to Indium WBC for spinal infections.

Answer 108

The thyroid likes to drink Iodine (it’s sort o f its job). Imaging takes advantage of this with Iodine analogs. The distinction between “trapping” and “organification” is a common question.

Answer 109

Analog is transported into gland. I23I, l3lI, and 99mTc all do this.

Answer 110

The major advantage here is that it’s cheap as dirt. The disadvantage is that it has a long half life (8 days), and that it’s a high energy (364 keV) beta emitter. The high energy makes a crappy image with a 'A inch crystal. It’s ideal for therapy, not for routine imaging. It’s contraindicated in kids and pregnant women.

Answer 111

Remember that this guy is trapped but not organified. Background levels are higher because only 1-5% o f the tracer is taken up by the thyroid gland. A common scenario to choose Tc over Iodine is when they’ve had a recent thyroid blocker on board (iodinated contrast is the sneaky one).

Answer 112

Thyroid formation takes place in fetus at 8-12 weeks

Answer 113

This guy has a shorter half life (13 hours) and ideal energy (159 keV). It decays via electron capture and all around makes a prettier image. The problem is that it costs more.

Answer 114

Analog is oxidized by thyroid peroxidase and bound to tyrosyl moiety. I23I and l3ll do this. 99mTc does NOT do this. Instead 99mTc slowly washes out o f the gland.

Answer 115

* Tc-99m: You can resume breast feeding in 12-24 hours * 1-123: You can resume breast feeding in 2-3 days * 1-131: You should not breast feed - pump and dump.

Answer 116

You give either 5 micro Ci o f 131 or 10-20 micro Ci o f 123. This is conventionally reported at 4-6 hours, and 24 hours. Normals are 5-15% (4-6 hours), and 10-35% at 24 hours. A correction for background is done on measurements prior to 24 hours (using the neck counts - thigh counts).

Answer 117

Renal Function (increases stable iodine pool, reduces numbers) Dietary Iodine - variable and controversial Medications - thyroid blockers, Nitrates, IV Contrast, Amiodarone

Answer 118

graves Early hashimoto Rebound after Abrupt withdrawal of antithyroid medication Dietary Iodine Deficiency

Answer 119

Primary or secondary causes of Hypothyroidism Renal failure Medications (thyroid blockers, Nitrates, IV Contrast, Amiodarone) Dietary iodine overload

Answer 120

About 75% of the time, if you have hyperthyroidism the cause is going to be graves. Graves is an autoimmune disease where an antibody to the thyrotropin receptor stimulates the thyroid to produce hormone. TSH will be very low, where T3 and T4 will be high. The classic clinical scenario is a middle aged women with a protracted course, pre-tibial edema, and exophthalmos. Scintigraphy is going to give you a homogeneously increased gland, with uptakes increased at both 4 hours and 24 hours. Sometimes the 24 hour uptake is lower than the 4 hours (or even at a normal range) - this is from rapid thyroid hormone production.

Answer 121

The pyramidal lobe is seen in about 10% o f normal thyroids. In patients with Graves disease it is seen as much as 45% of the time. Therefore, it’s suggestive when you see it.

Answer 122

Diffuse homogenous uptake

Answer 123

The classic scenario is an elderly women with weight loss, anxiety, insomnia, and tachycardia. The gland is typically heterogeneous, with uptake that is only moderately elevated. The nodules will be hot on the background o f a cold gland.

Answer 124

The toxic goiter will have hot nodules on a background o f cold thyroid. The Non-toxic one will have warm/hot nodules on a normal background of the thyroid.

Answer 125

Uptake High : 70s (typically > 50%) | homogenous

Answer 126

Uptake Medium High: 40s (typically <50%) | heterogenous

Answer 127

The most common cause of goitrous hypothyroidism (in the US). It is an autoimmune disease that causes hyper first then hypothyroidism second (as the gland bums out later). It’s usually hypo - when it’s seen. It has an increased risk of primary thyroid lymphoma. Step 1 trivia; associated with autoantibodies to thyroid peroxidase (TPO) and antithyroglobulin. The appearance o f the hypothyroid gland is typically an inhomogeneous gland with focal cold areas. The hyperthyroid (acute) gland looks very much like Graves with diffusely increased tracer.

Answer 128

If you have a viral prodrome followed by hyperthyroidism, and then thyroid uptake scan shows a DECREASED % RAIU you have de Quervains (Granulomatous thyroiditis). During this acute phase, the disease can mimic Graves with a low TSH, high T3 and high T4 The difference is the uptake scan. After the gland bums out, it may stay hypothyroid or recover. If they ask you about this, it’s most likely going to try and fool you into saying Graves based on the labs, but have a low % RAIU.

Answer 129

20-40% Cold Nodules = Cancer | < 1% Warm Nodules = Cancer

Answer 130

Most thyroid nodules are actually cold, and therefore most are benign (colloid, cysts, etc..). In fact, cold nodules in a multi-nodular goiter are even less likely to be cancer compared to a single cold nodule. Having said that, cold nodules are much more likely to be cancer when compared to a functional (warm) nodule.

Answer 131

This is a nodule that is HOT on Tc" but COLD on I123. Because some cancers can maintain their ability to trap, but lose the ability to organify a hot nodule on Tc, it shouldn’t be considered benign until you show that it’s also hot on I 123.

Answer 132

A classic move is to show you a thyroid that will take up Tc, but NOT Iodine on 24 hour imaging. This can be from a couple o f things: (1) congenital enzyme deficiency that inhibits organification, (2) a drug like propylthiouracil that blocks organification. Now if they just show you an Iodine Thyroid with low uptake on 24 hours, this is de Quervains, or a burned out Hashimotos.

Answer 133

both malignant and non-malignant thyroid disease.

Answer 134

Papillary is the most common subtype (papillary is popular), and it does well with surgery + 1-131. Medullary thyroid CA (the one the MENs get), does NOT drink the 1-131 and therefore doesn’t respond well to radiotherapy. Prior treatment can also make you more resistant to treatment, and re-treatment dosing is typically 50% more than the original dose.

Answer 135

* Medullary Subtype CA (will not drink the tracer) * History of prior 1-131 (“easy gland has been killed o ff ’) * History o f Methimazole treatment (even if years ago)

Answer 136

``` Neuroendocrine in origin, so can occasionally (around 10%) have uptake on MIBG or Octreotide. They will be cold on thyroid scan and don’t drink the treatment 1-131. If forced to pick - I’d go with Octreoscan for medullary CA. Associated with MEN 2a and 2b ```

Answer 137

So, normally the patient gets diagnosed and then they go for surgery. After surgery they will come to nuclear medicine. You expect that they will have some residual thyroid (it’s really hard to get it all out). Prior to actually treating them you will give them a tiny dose o f 1-131 to see how much thyroid they have left. If the uptake is less than 5% this is ideal. Uptake more than 5% will result in a painful ablation (may need steroids on top of the NSAIDs) and may need to go back to the OR. Next, you will treat them. You want their TSH really ramped up. The higher the TSH the thirstier the cancer /residual thyroid tissue. An ideal TSH is like 50 (30 would be a minimum).

Answer 138

o (1) is to stop the thyroid hormone (post op they are obviously hypothyroid), o (2) is to give recombinant TSH “Thyrogen.”

Answer 139

Dosing is dependent on the stage of the disease; 100 for thyroid only, 150 for thyroid + nodes, 200 for distal. They are told about the precautions etc... Then you give them the dose. Before you let them go home, you test them to see if they need to go to the hospital.

Answer 140

NRC limit is 7mR/h measured at 1 meter from the patient’s chest (some agreement states use 5 mR/h). The number to remember is 33 mCi of residual activity (or 30 mCi in some strict agreement states).

Answer 141

* Can cause pulmonary fibrosis if given to patient with lung mets. This is really only the case of macro-nodular disease (as opposed to micronodular disease). That isn’t necessarily a contraindication * Sjogrens have a greater risk of salivary gland damage * Salivary gland damage is dose related - so cancer treatment patients have a greater risk

Answer 142

Urine is the main way it is eliminated but sweat, tears, saliva, and breast milk are other routes.

Answer 143

``` There is a whole bunch of crap they are asked to do. Drink lots of water (increase renal excretion). Suck on hard candy (keep radiotracer from jacking your salivary glands). Patients are encouraged to stay away from people (distance principal). Sleep alone for 3 days (no sex, no kissing - keep that dirty dick in your pants!). Good bathroom hygiene (flush twice, and sit down if you are a guy). Use disposable utensils and plates. Clothes and linens should be washed separately. Most of these things are done for 3 days. ```

Answer 144

* No breast feeding. If you take I131 your breast feeding days are over (at least this time around) . * No getting pregnant for at least 6-12 months after therapy

Answer 145

* If you participated in the therapy, you need your thyroid checked 24 hours later. * If the patient got admitted to the hospital the RSO needs to inspect the room after discharge before the janitor can clean it or the next patient can move in. * Thyroglobulin is a lab test to monitor for recurrence. Anything over zero - after thyroidectomy, is technically abnormal, although the trend is more important (going up is bad) ' Severe uncontrolled thyrotoxicosis and pregnancy are absolute contraindications.

Answer 146

If you see an Iodine Scan, and you see uptake in the liver , this is ALWAYS a post treatment scan.

Answer 147

Give I131 immediately following dialysis to maximize the time the I131 is on board. Decrease dose as there is limited (essentially no) excretion until next dialysis. Dialysate can go down sewer. Dialysis tubing needs to stay in storage.

Answer 148

I131 can also be used to treat hyperthyroidism. Dosing depends on the etiology; 15 mCi for Graves (more vascular), 30 mCi for multi nodular (harder to treat the capsule). Again the TSH must be high for the therapy to be effective. By 3-4 months, there should be clinical evidence of resolution of signs and symptoms of hyperthyroidism, if 1-131 therapy was successful.

Answer 149

As an aside, there is no such thing as an “emergent hyperthyroid treatment.” You can always use meds to cool it down. The standard medication is Methimazole. However, if there is an allergy to Methimazole, the patient is having WBC issues (side effect is neutropenia) or the patient is pregnant -use propylthiouracil (PTU). PTU is recommended during pregnancy.

Answer 150

It’s controversial, but some people believe that thyroid eye disease will worsen after 1-131 treatment. If you are prompted, I would just have optho look at their eyes, bad outcome is likely severity related. *You might not want to treat a bug-eyed dude (depends on who you ask).

Answer 151

Since we are talking about hyperthyroid treatment, there is no better time than to discuss the W.C. effect. Essentially, this is a reduction in thyroid hormone levels caused by ingestion of a large amount of iodine. The Wolff-Chaikoff effect lasts several days (around 10 days), after which it is followed by an "escape phenomenon.” The W.C. effect can be used as a treatment principle against hyperthyroidism (especially thyroid storm) by infusion of a large amount of iodine to suppress the thyroid gland. The physiology of the W.C. effect also explains why hypothyroidism is sometimes produced in patients taking several iodine-containing drugs, including amiodarone.

Answer 152

* Most common cause is a hyperfunctional adenoma (85%). * Second most common cause is multiple gland hyperplasia (12%). * Third most common cause is cancer (3%).

Answer 153

dual phase and dual tracer

Answer 154

In dual phase technique, a single tracer (Tc"-Sestamibi) is administered, and both early (10 mins) and delayed (3 hours) imaging is performed. The idea is that sestamibi likes things with lots of blood flow, and lots of mitochondria. Parathyroid pathology tends to have both of these things, so the tracer will be more avid early, and stick around longer (after the tracer washes out of normal tissue). SPECT can give you more precise localization.

Answer 155

both thyroid and parathryroid

Answer 156

uptake remains in abnormal parathyroid (hyperplasia in this case)

Answer 157

Sestamibi parathyroid imaging depends on mitochondrial density and blood flow

Answer 158

Caused by things other than parathyroid pathology that like to drink Sestamibi. • Thyroid Nodules • Head and Neck Cancers • Lymphadenopathy

Answer 159

In dual tracer technique two different agents are used and then subtraction is done. The first agent is chosen because it goes to both thyroid and parathyroid (options are either Tc99- Sestamibi or 201- Thallium Chloride). The second agent is chosen because it only goes to the thyroid (options are either 1-123 or Pertechnetate). When subtraction is done, anything left hot could be a parathyroid adenoma.

Answer 160

* Mo Tracers, Mo Problems * Motion: subtraction imaging can’t tolerate much motion * Stuff Messing with the Thyroid Tracers: recent iodinated contrast, etc...

Answer 161

The parathyroid gland can be surgically implanted into the forearm - typically done with hyperplasia surgery where they carve out 3 1/2 glands.

Answer 162

Successful surgical treatment of hyperparathyroidism is often defined as intra-operative reduction of PTH by 50%.

Answer 163

Thyroid adenoma (most common), thyroid cancer, parathyroid cancer.

Answer 164

Small sized adenoma (most common), 4 gland hyperplasia. A negative study in the setting of abnormal / suspicious labs should raise concern for these things (multiple gland hyperplasia or a small adenoma).

Answer 165

On any study, parathyroid or a heart, if the tracer is MIBI than you should NOT see lymph nodes. If you see lymph nodes they are suspicious (maybe cancer). Next step would be ultrasound to further evaluate them. Oh, and don’t forget about focal breast uptake (also cancer), - Breast Specific Gamma Imaging (BSGI) uses MIBI for a reason.

Answer 166

brain death

Answer 167

lipophilic perfusion agents proportional to blood flow

Answer 168

lipophilic perfusion agents proportional to blood flow

Answer 169

metabolism

Answer 170

Can be used for Parenchymal Imaging) HMPAO ECD

Answer 171

(Not used for Parenchymal Imaging - i.e. no SPECT) | DTPA

Answer 172

Tc HMPAO (hexamethylpropyleneamine oxime) and Tc ECD (ethyl cysteinate dimer). HMPAO and ECD can be used in both dementia imaging and for seizure focus localization. These studies are typically performed with SPECT. The idea behind brain SPECT is that you can look at brain blood flow, which should mimic metabolism. These two agents are neutral and lipophilic, which lets them cross the blood brain barrier and accumulate in the brain. Where and how much they accumulate should follow flow (and metabolism).

Answer 173

Neutral and Lipophilic ``` Accumulate in the cortex proportional to blood flow (Gray Matter > White Matter) ``` washout is fast Uptake favors the frontal lobe, thalamus, and cerebellum

Answer 174

Neutral and Lipophilic ``` Accumulate in the cortex proportional to blood flow (Gray Matter > White Matter) ``` Washout is slow (more rapid clearance from blood p o o l) Uptake favors the parietal and occipital lobes * Makes comparison between HMPAO and ECD difficult

Answer 175

Both agents pass blood brain barrier and stick to gray matter proportional to CBF HMPAO washes out faster ECD washout is slower, has better background clearance, and does not demonstrate intracerebral redistribution.

Answer 176

Unlike HMPAO or ECD, this agent is lipoPHOBIC - and is best thought o f as an “angiographic tracer” because it stays in the blood (or CSF if you put it there).

Answer 177

DTPA does NOT cross the blood brain barrier and therefore cannot be used for brain parenchymal imaging. *You can NOT do SPECT Has the advantage over HMPAO and ECD in that it can be repeated without delay DTPAs main utility is for shunt studies. NPH, and Brain Death.

Answer 178

``` The idea is that a seizure focus will be hot (hypermetabolic and hyperperfusion) during the seizure “ictal.” Then cold between seizures “interictal.” You need to inject tracer (HMPAO or ECD) within 30 seconds o f the seizure to get a good study. PET can be used, but is less practical. ```

Answer 179

Thallium is produced in a cyclotron, decays via electron capture, and has a half life of around 3 days (73 hours). The major emissions are via the characteristic x-rays o f its daughter product Mercury 201 - at 69 keV and 81 keV. The tracer is normally given as a chloride and will therefore rapidly be removed from the blood

Answer 180

Thallium behaves like potassium, crossing the cell membrane by active transport (Na+/ K pump). Tumors and inflammatory conditions will increase the uptake o f this tracer. The higher the grade tumor, the more uptake you get. As Thallium requires active transport, it can be thought o f as a viability marker - you need a living cell to transport it.

Answer 181

Thyroid, salivary glands, lungs, heart, skeletal muscle, liver, spleen, bowel, kidneys, and bladder. Any muscle twitching will turn hot.

Answer 182

If you are going to use it with Gallium, you must use the Thallium first as the Gallium will scatter all over the Thallium peaks.

Answer 183

Toxoplasma Infection is Thallium Negative Lymphoma is Thallium Positive Kaposi Sarcoma is Thallium Positive (Gallium Negative) Tumor is Thallium Positive Necrosis is Thallium Negative

Answer 184

The tracers used for SPECT tumor studies are different than those used for dementia or seizures. The tumor tracers are 20ITI (more common) and 99mTc Sestamibi (less common). 20ITI is a potassium analog, that enters the cell via the Na/K pump. Inflammatory conditions will increase the uptake o f this tracer, but not as much as tumors. The higher the tumor grade, the more intense the uptake. Thallium can be thought o f as a marker o f viability, as it will localize in living tumor cells, and not necrosis. The control is the scalp (abnormalities will have greater uptake than the scalp). You can use Thallium in combination with perfusion tracers (HMPAO).

Answer 185

Thallium Hot, | HMPAO Cold

Answer 186

Thallium Cold, | HMPAO Cold

Answer 187

As discussed in the neuro chapter CNS lymphoma vs CNS Toxoplasmosis can be a diagnostic dilemma. Thallium has a role in helping to distinguish the two (Toxo Cold, Lymphoma Hot).

Answer 188

Ga-67 scintigraphy.

Answer 189

You are looking for the absence of intracerebral perfusion to confirm brain death. So that you don’t keep Grandma around as a piece of broccoli, you need to have a tourniquet on the scalp - otherwise you might think scalp perfusion is brain perfusion and say she’s still alive. You have to identify tracer in the common carotid - otherwise the study must be repeated. In the setting of brain death, tracer should stop at the skull base. The hot nose sign, is seen secondary to perfusion through the external carotid to the maxillary branches. As a point o f trivia - the hot nose sign cannot be used to call brain death , it is a “Secondary Sign.” Some institutions will say you have to image the kidneys (to prove adequate systemic circulation / perfusion) and the injection site (to prove the tracer didn’t extravasate).

Answer 190

brain death

Answer 191

There is no reason, ever, under any circumstances known to man, women, or beast to ever, ever use SPECT to diagnose stroke. Having said that, you can look at stroke with SPECT and will therefore likely be asked questions about it.

Answer 192

* Acute Stroke is Cold * Subacute Stroke can be warm - from luxury’ perfusion (blood flow is more than dead cells need) * Chronic Stroke is Cold

Answer 193

You can evaluate for cerebrovascular reserve by first giving acetazolamide (Diamox) - which is a vasodilator , followed by a perfusion tracer. Normally you should get a 3-4x increase in perfusion. However, in areas which have already maxed out their auto regulatory vasodilation (those at risk for ischemia) you will see them as relatively hypointense. These areas of worsening tracer uptake may benefit from some revascularization therapy.

Answer 194

Ischemic Tissue Looks WORSE (relatively) compared to surrounding tissue, after vasodilation (Diamox / Acetazolamide)

Answer 195

= Diamox = Acetazolamide... don’t just remember one. You don’t know which one they will use.

Answer 196

Worsening Uptake = Ischemia This might benefit from revascularization. Next Step = Angio

Answer 197

PET can assess perfusion (15O-H20) but typically it uses l8FDG to assess metabolism (which is analogous to perfusion). Renal clearance o f l8FDG is excellent, giving good target to background pictures. Resolution o f PET is superior to SPECT. It’s important to remember that external factors can affect the results; bright lights stimulating the occipital lobes, high glucose (>200) causes more competition for the tracer and therefore less uptake, e tc ...

Answer 198

The most common indication for FDG Brain PET is dementia imaging. Because blood flow mimics metabolism HMPAO, and ECD can also be used for dementia imaging and the patterns of pathology are the same.

Answer 199

The principle involved in imaging the CSF consists o f intrathecal administration that will safely follow CSF and remains in the CSF compartment until it is absorbed through the conventional pathways. The most common tracer used is IMln - labeled DTPA. So, you have to do an LP on the dude (it’s intrathecal).

Answer 200

* Time Zero - You do the LP * 2-4 hours it ascends and reaches the basal cisterns * 4 hours - 24 hours it flows around the sylvian fissures and interhemispheric cistern * At 24 hours it should clear from the basilar cisterns and be over the cerebral convexities

Answer 201

* Tracer in the lateral ventricles | * Failure to clear from the cisterns and localize over the convexities by 24 hours

Answer 202

Normal pressure hydrocephalus is wet, wacky, and wobbly (incontinent, confused, and ataxic) clinically, and demonstrates “ventricular enlargement out of proportion to atrophy” on CT. Since radiotracer shouldn’t normally enter the ventricles, a radionuclide cistemogram cannot be used to distinguish communicating from noncommunicating hydrocephalus. Historically (1930s) you could tell by injecting the material directly into the lateral ventricles.

Answer 203

• Early entry (4-6 hours) o f tracer into the lateral ventricles * Persistence o f tracer in the lateral ventricle > 24 hours ’ Delay in Assent to the parasagittal region > 24 hours

Answer 204

NPH vs Non Obstructive (Communicating) Hydrocephalus. | NPH will have a normal opening pressure on LP.

Answer 205

Persistent Tracer in the Ventricles > 24 Hours

Answer 206

You can use CSF tracers to localize a leak. The most common sites of CSF leak (fistulas) are between the cribriform plate and ethmoid sinuses, from the sella turcica into the sphenoid sinus and from the ridge of the sphenoid to the ear. The study is like a bleeding scan, in that the leak must be active during the test for you to pick it up.

Answer 207

You image around the time the CSF is at the basilar cisterns (1-3 hours) and also image pledgets (jammed up the nose prior to the exam). You compare tracer in the pledgets to serum (ratio greater than 1.5 is positive).

Answer 208

* Normal Test will show tracer in the peritoneum - shows distal end is patent. * You can manually occlude the distal limb to force tracer into the ventricles - shows proximal end is patent. If the tracer fails to reflux into the ventricles, or it does but then doesn’t clear, you can think proximal obstruction • If there is delayed tracer flow into the peritoneum (> 10 minutes = delayed), this can mean partial distal obstruction.

Answer 209

* Normal Test will show tracer in the peritoneum - shows distal end is patent. * You can manually occlude the distal limb to force tracer into the ventricles - shows proximal end is patent. If the tracer fails to reflux into the ventricles, or it does but then doesn’t clear, you can think proximal obstruction • If there is delayed tracer flow into the peritoneum (> 10 minutes = delayed), this can mean partial distal obstruction.

Answer 210

One sneaky way to test this would be related to the differences between solid food and liquid food curves. The main point is that solids have a “lag phase” in which the stomach helps grind up the food into smaller parts (liquids don’t have this). Lag Time can be increased in diabetic patients.

Answer 211

``` Another possible question is that “attenuation correction” plays a role in calculation of emptying times, as movement from the back of the stomach to the front can increase counts due to attenuation. ```

Answer 212

• Prokinetic drugs (which enhance gastric emptying) metoclopramide (Reglan), tegaserod (Zelnorm), erythromycin, and domperidone (Motilium) are stopped at least 2 days prior to the test. - this can cause a false negative exam. • Opiates (which delay gastric emptying) are stopped 2 days prior to the test. These can cause a false positive exam. • Anticholinergic/ Antispasmodic drugs such as Donnatal, Bentyl, Robinul, and Levsin, are stopped for 2 days prior to the test • Serotonin receptor antagonists - the classic one being Ondansetron (Zofran) are fine and can be given prior to the exam.

Answer 213

``` " 4 oz o f Egg Whites ■ 2 Slices o f White Bread - Strawberry Jam ■ Water ■ Tc Sulfur Colloid ```

Answer 214

Used (rarely) in the evaluation of esophageal motility disorders. The supposed advantage is the ability to give quantitative information. The patient is made to fast overnight, then fed Tc-99 sulfur colloid. Dynamic imaging is performed and transit time and /or residual esophageal activity is measured.

Answer 215

The goal of a GI bleeding scan is to localize the bleed (not to say there is one). Bleeding scan is sensitive to GI bleed rates as low as at 0.1 ml/min (Mesenteric angiography requires 1-1.5 ml/min bleeding). Before the Tc-99 can be tagged to a RBC (beta chain o f the hemoglobin)', it must first be reduced. This is accomplished with stannous ion (tin). This is referred to as “tinning.” There are 3 methods

Answer 216

GI bleed scan sensitivity — 0.1 ml/min Angiogram sensitivity = 1.0 ml/min

Answer 217

1. Tin (stannous ion) is injected into the patient 2. Then Tc-99m pertechnetate is injected 3. Tin binds to the hemoglobin then reduces the Tc (which then binds) Although the process is super simple, you only get about 60-80% of it bound. So you have a lot o f free Tc and a dirty image (poor target to background). Sometimes it fails miserably (via drug interaction - heparinized tubing, or recent IV contrast). The images are too crappy for cardiac wall motion studies, but can work for GI bleeding.

Answer 218

1. Tin (stannous ion) is injected into the patient 2. After 15-30 mins, you pull 3-5 cc o f blood out o f an IV line into a syringe with both Tc-99m pertechnetate and an anticoagulant 3. It’s then re-injected 10 mins later This one does a little better, binding close to 85%. Drug interactions (like heparin) are the most common cause o f failure.

Answer 219

Blood is withdrawn and added to a kit with both Tin (stannous ion) and Tc. It’s then reinjected. This method works the best (98% binding), but is the most expensive

Answer 220

Blood is withdrawn and added to a kit with both Tin (stannous ion) and Tc. It’s then reinjected. This method works the best (98% binding), but is the most expensive

Answer 221

GI bleeding scan is acquired with DYNAMIC imaging (as opposed to 5 min static, transmission, SPECT, or dual tracer protocol). This allows the detection of intermittent bleeds and better localization of the origin of the bleed.

Answer 222

(1) Tracer outside the vascular distribution (2) Tracer that Moves like bowel (can be antegrade or retrograde) (3) Tracer that Increases Intensity over time The distal colon is an exception to the rule of mobility — tracer here may not move.

Answer 223

No Abnormal Tracer Accumulation. Normal Uptake in Blood Pool, Liver, & Heart.

Answer 224

Abnormal Tracer accumulation at the Hepatic Flexure, increases over time. SMA territory 9could be anywhere or any territroy)

Answer 225

You can get faked out by a lot of stuff; renal or bladder excretion (possibly with hydro), transplant kidney (classic trick - but again it won’t move), varices or angiodysplasia (these shouldn’t move), a penis with blood in it (this will look like a penis), hemangioma (this will be over the liver or spleen - and not move), and the last trick - Free Tc in the stomach. It you see gastric uptake * next look at the salivary glands and thyroid to confirm it’s free Tc, and not an actual bleed.

Answer 226

* Celiac: Distal Esophagus, Stomach, 1st part of the Duodenum * SMA: 2nd - 4th Parts o f the Duodenum, the rest o f the small and large bowel to the transverse colon at the level o f the splenic flexure. * IMA: Distal 1/3 of the Transverse Colon to the Proximal Rectum

Answer 227

Back when dinosaurs roamed the earth, they used to do bleeding scans with Tc Sulfur Colloid. This had a variety of disadvantages: fast clearance (had to do scan in 30 mins), multiple blind spots (the stomach, splenic flexure, and hepatic flexures - as sulfur colloid goes to the liver and spleen normally). The only possible advantages are that it requires less prep and has good target to background

Answer 228

The Meckel Diverticulum is a remnant of the omphalomesenteric duct located near the distal ileum. These things can have ectopic gastric mucosa and present with painless bleeding in the pediatric population. Pertechnetate is used because it is taken up by gastric mucosal cells. So you are looking for tracer uptake in the pelvis (usually RLQ) around the same time as the stomach.

Answer 229

Only about 10-30% o f Meckels diverticulum will have eastric mucosa (these are the ones most likely to bleed).

Answer 230

* You need to do the study when the patient is NOT bleeding (if they are bleeding - then do a bleeding scan). * Pre-Treatment: You can use a bunch of different stuff to make the exam better: O Pentagastrin - enhances uptake o f pertechnetate by gastric mucosa (also stimulated GI activity) 0 H2 Blockers (Cimetidine and Ranitidine) block secretion of the pertechnetate out o f the gastric cells making it stick around longer. O Glucagon - slows gastric motility. * False Positive: Can occur from bowel irritation (recent scope, laxative use) * False Negative: Recent In vivo labeling of RBCs , Recent Barium Study (attenuated)

Answer 231

Function and integrity of the biliary system can be evaluated by using Tc-99m labeled tracers that mimic bilirubin’s uptake, transport, and excretion. All the tracers are basically analogs of this iminodiacetic acid stuff. Normally, the liver will have prompt tracer uptake (within 5 minutes), then you will have excretion into the ducts, then the bowel - pretty much the same time you see the gallbladder. If the gallbladder is sick (obstructed), it will still not have filled within 60 min. This is the basic idea.

Answer 232

You need higher doses o f tracer if the patient has hyperbilirubinemia

Answer 233

Prep for the test is diet control. You need to have not eaten within four hours (so your gallbladder is ready to fill), and have eaten within 24 hours (so your gallbladder isn’t so full, it can’t let any tracers in). If you haven’t eaten for over 24 hours, then CCK can be given.

Answer 234

makes teh GB contract

Answer 235

``` A curved area of increased activity along the gallbladder fossa (hot rim, or pericholecystic hepatic activity sign) suggests a more angry gallbladder - (supposedly seen in 20% of gangrenous cholecystitis). ```

Answer 236

This sign is seen with acute cholecystitis. The sign describes a nub of activity in the cystic duct, with the

Answer 237

The mechanism is the result o f inflammation causing regional hepatic hyperemia, with more radiopharmaceutical being delivered to this area o f hepatic parenchyma'.

Answer 238

This can be shown two ways; (1) delayed filling o f the GB (not seen at 1 hour, but seen at 4 hours), or (2) with a low EF (< 30%) with CCK stimulation. A reduced EF can also be seen in acute acalculous cholecystitis.

Answer 239

- The Dose o f CCK: 0.02 microgram/kg over 60 mins | - The Dose o f Morphine 0.02-0.04 mg/kg over 30-60 mins

Answer 240

The classic way to show this is a lack of visualization o f the biliary tree - sometimes call a “Liver Seem S ig n ” It’s caused by back pressure in an obstructed CBD.

Answer 241

Cholestatic jaundice can be drug induced. The classic offenders: Chlorpromazine, Erythromycin. Birth Control (Estrogens), Anabolic Steroids, and sometimes Statins. This can mimic biliary obstruction.

Answer 242

Cholestatic jaundice can be drug induced. The classic offenders: Chlorpromazine, Erythromycin. Birth Control (Estrogens), Anabolic Steroids, and sometimes Statins. This can mimic biliary obstruction.

Answer 243

If you see a hepatobiliary scan (HIDA) in a kid, for sure this is the indication. Apparently, these two things are hard to tell apart clinically. If you see tracer in the bowel it’s hepatitis, but just remember that it might be slow so you need super delays (24 hours if necessary). If you don’t see it in the bowel, you might still need to repeat the study if you didn’t charge up those hepatocytes with some phenobarb (up regulates the cytochrome system). In other words, a lot of places pre-medicate with phenobarbital to increase the utility o f the test. If you operate early (Kasai procedure) they do a lot better, so it’s important not to screw this up.

Answer 244

Dose of Phenobarb to prime the liver = 5 mg/kg x 5 days “5 fo r 5 keeps the liver alive ” Technically it ’s 2.5 mg/kg twice a day - but that doesn t rhyme

Answer 245

``` You can use HIDA tracer after trauma or surgery to look for bile leak. The trick is that you need delayed images, and look in the right paracolic gutter / pelvis. You can get tracer in the gallbladder fossa, mimicking a gallbladder. ```

Answer 246

``` Labeled bile may track superiorly into the peri-hepatic space and coat the surface of the liver. This can give the appearance o f paradoxically increasing activity in the liver after an initial decrease in activity from liver emptying into the bowel. ```

Answer 247

No Bowel Activity, Persistent Blood Pool = Hepatocyte Dysfunction (Hepatitis) No Bowel Activity, Blood Pool Goes Away Normally = Common Duct Obstruction No Gallbladder Activity x 4 hours (or 1 hour + morphine) = Acute Cholecystitis Abnormal GB emptying (EF < 30%) = Chronic Cholecystitis

Answer 248

Most people will say something like - “hold the morphine for at least 6 hours — or 3 half lives - prior to the HIDA scan.” Having said that narcotics alone should not prevent you from seeing the gallbladder. What narcotics can do is delay bowel visualization by triggering the sphincter of oddi to contract. This can mimic a biliary obstruction. Don’t get it twisted - morphine is not the devil - it is a tool. Remember you will give morphine to help promote visualization of the gallbladder in the scenario where there is dumping of the tracer into the small bowel, but no GB activity seen. Never inject CCK and morphine within 30 minutes of one another. Why Not ? It would be bad. Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light— Total protonic reversal.

Answer 249

``` Elevated bilirubin (total > 5mg/dl) will increase the number of non-diagnostic/inconclusive and false negative exams. ```

Answer 250

Increased renal activity can suggest elevated bilirubin

Answer 251

Alternative agents DISIDA and BROM1DA are preferred over HIDA in the setting of high levels of bilirubin

Answer 252

Not frequently done because of the modem invention of CT. Sulfur Colloid tagged with Tc is quickly eaten by the liver’s reticuloendothelial system. It can be used to see “hot” and “cold” areas in the liver. Classically, the multiple choice question is Focal Nodular Hyperplasia is Hot on sulfur colloid (although in reality it’s only hot 30-40% of the time).

Answer 253

``` Hepatic adenoma colid FNH 40% hot, 30% cold, 30% neutral Cavernous hemangioma cold (rbc scan hot) HCC cold (gallium hot) Cholangiocarcinoma cold mets cold abscess cold (gallium hot) focal fat cold (xe hot) ```

Answer 254

Particles for this scan need to be 0.1 - 1.0 micrometers. This is the right size for the liver to eat them. If they are too big the spleen will eat them, and if they are too small the bone marrow will eat them. Also, realize that if they were too big they would get stuck in the lungs like a VQ on the first pass through.

Answer 255

In a normal sulfur colloid scan, 85% of the colloid is taken up by the liver (10% spleen, 5% bone marrow). In the setting of diffuse hepatic dysfunction, portal hypertension, hypersplcnism, or bone marrow activation you can see change in uptake - shift to the spleen and bone marrow. The most specific causes of colloid shift are cirrhosis, diffuse liver mets, diabetes, and blunt trauma to the spleen.

Answer 256

This is not normal localization of sulfur colloid. This is non-specific and can be seen with a ton of things (most commonly diffuse liver disease), but the first thing you should think (on multiple choice) is excess aluminum in the colloid. It can also be seen in primary pulmonary issues (reflecting phagocytosis by pulmonary macrophages).

Answer 257

The most common cause is CHF (maybe due to decreased renal blood flow and'filtration pressure). Alternatively, in the setting of renal transplant - this can indicate rejection (due to colloid entrapment within the fibrin thrombi o f the microvasculature). Other more rare causes include coxsackie B viral infection, disseminated intravascular coagulopathy, and thrombotic thrombocytopenic purpura.

Answer 258

You can “prove” a liver lesion is a hemangioma with a Tc Labeled RBC scan.

Answer 259

You can “prove” a liver lesion is a hemangioma with a Tc Labeled RBC scan.

Answer 260

Using Tc labeled RBCs with anterior and posterior projection images . Delayed blood pool is typically done (30 mins - 3 hours).

Answer 261

“Small” is actually the most common reason for a false negative exam. You need the thing to be at least 1,5cm, otherwise your sensitivity really drops off. You could try SPECT but first you seriously need to consider what you are doing with your life.

Answer 262

You want to see marked HOT on delays, with no real hot spot on immediate flow or immediate pool. Angiosarcoma could be HOT on delays but would also be hot on flow. A partially fibrosed hemangioma may be a false negative.

Answer 263

You can use Tc Sulfur Colloid or heat damaged Tc labeled RBCs to localize to the spleen. A possible indication might be hunting ectopic spleen.

Answer 264

A fatty liver can alter the distribution o f several tracer. Examples: • Reduced uptake in the Liver on Tc Sulfur Colloid - including the possible reversal of normal liver > spleen uptake pattern (Colloid Shift). • There will be increased uptake in a fatty liver with Xenon 133. • Trivia - FDG-PET uptake in the liver is not altered by background steatosis.

Answer 265

Normal kidney function is 80% secretion and 20% filtration. Tracer choice is based on which o f these parameters you want to look at.

Answer 266

Almost all filtered and therefore a great agent for determining GFR. A piece of trivia is that since a small (5%) portion of DTPA is protein bound (and not filtered) you are slightly underestimating GFR. Critical organ is the bladder.

Answer 267

``` This agent is almost exclusively secreted and therefore estimates effective renal plasma flow (ERPF). It is cleared by the proximal tubules. Critical organ is the bladder. ```

Answer 268

This agent can be used for structural imaging (discussed later in this section), or functional imaging as it is filtered. Critical organ is the bladder.

Answer 269

(1) Differential Function (2) Suspected Obstruction, (3) Suspected Renal Artery Stenosis, (4) Suspected Complication from Rental Transplant, (5) Suspected Urine Leak.

Answer 270

Images are obtained posteriorly (anterior if patient has a transplant or horseshoe). Typically dynamic exams have 3 phases: blood flow phase, cortical phase, and clearance phase.

Answer 271

Filtered (GFR) Good For Native Kidneys with Normal Renal Function Critical Organ Bladder

Answer 272

Secreted (ERPF) Concentrated better by kidneys with poor renal function Critical Organ Bladder

Answer 273

Filtered Good for dynamic and cortical imaging. Critical Organ Bladder

Answer 274

Begins within 20 seconds o f injection. Flow will first be seen in the aorta. Then as it reaches the renal arteries, the kidneys should enhance symmetrically and about equal to the aorta (at that time).

Answer 275

Technical Error - poor bolus

Answer 276

``` Renal Artery Thrombosis Renal Vein Thrombosis Chronic High Grade Obstruction Acute Rejection Acute Pyelonephritis ```

Answer 277

Renal Artery Aneurysm

Answer 278

ATN, Interstitial Nephritis, and Cyclosporin toxicity | will all have normal perfusion/flow.

Answer 279

This is the most important portion of the exam (with regard to differential function). An area o f interest in drawn around the kidneys and a background area o f interest is also drawn (to correct for the background). This can be screwed up by drawing your background against the liver or spleen (which is not true background since they will take up some tracer). You want to measure this at a time when the kidney is really drinking that contrast, but not so late that it is putting it in the collection system. Most places use around 1 min. A steep slope is good.

Answer 280

Radiotracer will begin to enter the renal pelvis, collecting system, and bladder. In a normal patient, you will be down to half peak counts at around 7-10 mins. If you wanted to quantify retention of tracer you could look at a 20/3 or 20/peak ratio.

Answer 281

This is a method o f quantifying retention of radiotracer by comparing the peak count at 20 minutes with the peak count at 3 mins (normal < 0.8) or the peak count (normal 0.3).

Answer 282

The exam is performed the same as a standard dynamic exam (blood flow, cortical, and clearance), with a 30 minute wait after clearance. If there is still activity in the collecting system, a challenge is performed with Lasix. The idea is that a true obstruction will NOT respond to Lasix, whereas a dilated system will empty when overloaded by Lasix. The study can be done with MAG-3 or DTPA. MAG-3 does better with patients with poor renal function, and thus is used more commonly.

Answer 283

``` * No obstruction = tracer clears from collecting system without need for Lasix * No obstruction = Washout o f 50% of the tracer within 10 minutes of Lasix administration ```

Answer 284

``` Washout o f 50% of the tracer within 10-20 minutes of Lasix administration o The most common cause for this indeterminate result is a very dilated pelvis and subsequent “reservoir effect.” ```

Answer 285

Washout taking longer than 20 mins after Lasix administration

Answer 286

* Poor response to Lasix - secondary to bad renal function, or dehydration at baseline * “Reservoir Effect” - very dilated renal pelvis, delaying transit time Back Pressure Effects - Full or Neurogenic Bladder can generate back pressure and not let the kidneys empty (can be resolved with a foley catheter).

Answer 287

``` Remember this is a GFR tracer. A sick kidney will have decreased uptake and flow, because of loss of perfusion pressure. ```

Answer 288

``` Remember this is a Secreted tracer. A sick kidney will have marked tracer retention, with a curve similar to obstruction. ```

Answer 289

If it’s bilateral up or bilateral down, it’s not RAS. If the baseline study has asymmetrically poor function, that isn’t positive for RAS, you need to see it worsen (> 10%).

Answer 290

they need to stop their ACE inhibitor prior to the renal study (3-5 days if captopril). They should be NPO for 6 hours prior to the test (for PO ACE inhibitors).

Answer 291

No Difference Between Pre and Post

Answer 292

No Difference Between Pre and Post

Answer 293

The most common indication for nuclear medicine in the setting o f renal transplant is to differentiate rejection from ATN. ATN is usually in the first week after transplant, and is more common in cadaveric donors. There will be preserved renal perfusion with delayed excretion in the renal parenchyma (elevated 20/3 ratio, delayed time to peak). ATN usually gets better. There is an exception to this rule, but it will confuse the issue with respect to multiple choice, so I’m not going to mention it. Cyclosporin toxicity can also look like ATN (normal perfusion, with retained tracer) but will NOT be seen in the immediate post op period. Rejection will have poor perfusion, and delayed excretion. A chronically rejected kidney won’t really take up the tracer.

Answer 294

the nephrographic appearance is the same. Tracer in the cortex, and that s it.

Answer 295

Immediate Post OP (3-4 days post op) Perfusion Normal Excretion Delayed

Answer 296

Long Standing Perfusion Normal Excretion Delayed

Answer 297

Immediate Post OP Poor Perfusion Excretion Delayed

Answer 298

Fluid collections seen after a transplant include urinomas, hematomas, and lymphoceles. All 3 can cause photopenic areas on blood pool imaging.

Answer 299

Usually found in the first 2 weeks post op. Delayed imaging will show tracer between the bladder and transplanted kidney. The primary differential in this time period is the hematoma. A hematoma is not going to have tracer in it. O Urinoma = Hot with Tracer O Hematoma = No Tracer

Answer 300

Usually found 4-8 weeks after surgery. The cause is a disruption o f normal lymphatic channels during perivascular dissection. Most are incidental and don’t need intervention. If they get huge, they can cause mass effect. This will look like a photopenic area on the scan.

Answer 301

Timing - Early (< Month) Blood pool - COLD - No Tracer delay - COLD - No Tracer

Answer 302

Timing - Early (< Month) Blood pool - COLD - No Tracer delay - HOT with Tracer

Answer 303

Timing - Late (> Month) Blood pool - COLD - No Tracer delay - COLD - No Tracer

Answer 304

If you want to look at the renal cortex, you will want to use an agent that binds to the renal cortex (via a sulfhydryl group). You have two main options with regard to tracer.

Answer 305

This is the more commonly used tracer. It binds to the renal cortex and is cleared very slowly. Critical organ is the kidney (notice other renal tracers have the bladder as their critical organ).

Answer 306

This is less commonly used and although it binds to the cortex, it is also filtered and therefore can be used to assess renal flow, the collecting system, and the bladder. Critical organ is the bladder.

Answer 307

DMSA is the preferred cortical imaging agent in pediatrics, because it has a lower dose to the gonads (even though its renal dose is higher than TcGH).

Answer 308

Acute Pyelonephritis: Can appear as (a) fo ca l ill-defined area o f decreased uptake, (b) multifocal areas o f decreased uptake, (c) diffuse decreased uptake - in an otherwise normal kidney. ° Scarring and Masses can also appear as fo ca l areas o f decreased uptake - although scarring usually has volume loss.

Answer 309

Simply put, the mass will be cold. The Column o f Bertin | (normal tissue) will be take up tracer.

Answer 310

* Defects on DMSA with acute renal problems = pyelo. | * Defects on DMSA with chronic renal problems = scar (or mass).

Answer 311

* Defects on DMSA with acute renal problems = pyelo. | * Defects on DMSA with chronic renal problems = scar (or mass).

Answer 312

This hasn’t been done in the United States since 1968, therefore it is very likely to be on the test. The study is basically a blood flow study. The primary clinical question is testicular torsion vs other causes of pain (epididymitis). The tracer used is sodium pertechnetate (Na99mTc04). Oh, don’t forget to tape the penis out o f the way - tape it up, not down like is required for the male residents on mammography rotations.

Answer 313

Symmetric low level flow to the testicles

Answer 314

Focal absence o f flow to the affected side (“nubbin sign”).

Answer 315

Sometimes called a missed torsion. The appearance is a | halo of increased activity, with central photopenia.

Answer 316

Identical to delayed torsion - halo o f increased activity, with central photopenia.

Answer 317

Increased flow and blood pool to the affected side.

Answer 318

As mentioned before, 18-FDG is cyclotron produced and decays via beta positive emission to 18-0. The positron gets emitted, travels a short distance, then collides with an electron producing two 511 keV photons which go off in opposite directions. The scanner is a ring and when the two photons land 180 degrees apart at the same time the computer does math (which computers are good at) to localize the origin.

Answer 319

(1) Anatomy - so you can see what the hell you are looking at. (2) Attenuation Correction - Dense stuff will slow down the photons, and the CT allows for correction o f that. It also leads to errors, the classic one being a metallic pacemaker looks bright hot on the corrected image (the computer overcorrected). This is a classic question. The answer is look at the source images (uncorrected).

Answer 320

Some other technical trivia is that FDG enters the cell via a GLUT 1 transporter and is then phosphorylated by hexokinase to FDG-6-Phosphate. This locks it in the cell. Normal bio distribution is brain, heart, liver, spleen, GI, blood pool, salivary glands, and testes. The collecting system and bladder (critical organ) will also be full of it, because that’s where it’s getting excreted.

Answer 321

Muscles (classic forearm muscle uptake in the nervous chair squeezing patient). Breast and ovaries in females at certain stages o f the menstrual cycle. Thymus in younger patients. Lastly, brown fat around the neck, thorax, and adrenals (especially in a cold room).

Answer 322

Keep the room warm. Medications like | benzodiazepines or beta blockers.

Answer 323

Insulin: So why not just give the patient some insulin??? It will drive it all into the muscles. This is a classic trick. PET with diffuse muscle uptake = Insulin Administration

Answer 324

High Blood Glucose (> 150-200): The more glucose the patient has, the more competition is created for the FDG and you will have artificially low SUVs.

Answer 325

* Fat people will have HIGHER SUV values, because the fat takes up less glucose * You leave the house in high heels... and come back home in flip flops

Answer 326

Following therapy; an interval of 2-3 weeks for chemotherapy and 8-12 weeks for radiation is the way to go. This avoids “stunning” - false negatives, and inflammatory induced false positive.

Answer 327

The main utility is extent o f disease, and distal metastatic spread. Local invasion is tricky with a lot o f things. Usually straight up CT or MRI is better for local invasion and characterization.

Answer 328

The RV is not typically seen on PET unless it’s enlarged. | If you see the RV think about RVH.

Answer 329

FDG Concentration at time “T” / - (Dose / Body Weight)

Answer 330

``` BAC (Adeno In Situ) - Lung Cancer carcinoid rcc peritoneal/liver implants anything mucinous prostate ```

Answer 331

``` infection inflammation ovaries in follicular phase muscles brown fat thymus ```

Answer 332

Requires Further Workup - might be cancer, might be nothing

Answer 333

Most often Autoimmune (Hashimoto) Thyroiditis

Answer 334

RCC are COLD (usually), Oncocytomas are FIOT

Answer 335

COLD Ground Glass Nodule = Cancer, HOT Glass Nodule = Infection

Answer 336

The Reason HCC is often cold (60%) is that it has variable glucose-6- phosphatase and can’t trap the FDG

Answer 337

Testicular cancers skip right to the retroperitoneum. The trivia is the seminomatous CA is FDG hot, whereas non-seminomatous tends to be FDG COLD (or Luke Warm).

Answer 338

While it’s OK for ovaries to be hot in functional (ovulating) young people, Grandma should NOT have FDG up-take in her dried-up raisin ovaries. This is suspicious - next step Ultrasound.

Answer 339

Metformin is classic for causing false positive bowel uptake. The uptake is typically intense and diffuse. It tends to favor the colon (small bowel to a lesser extent).

Answer 340

mild uptake is normal. In general, an adrenal pathology is typically considered malignant if the uptake is higher than the liver (used as an internal control). Although this does not really hold up that well in my experience (especially since liver uptake is variable). For example, Adrenal Adenomas can have moderate uptake (still usually not super hot).

Answer 341

Most Lymphoma is Super Hot

Answer 342

Thymic Hyperplasia (or Rebound) can be “Warm” on PET, but recurrent Lymphoma should be HOT. Also, Rebound tends to maintain the normal thymus look (it sorta drapes over the heart). Lymphoma is round like a ball. A hot ball o f death, or a “great ball of fire”

Answer 343

Extranodal marginal zone lymphomas, including the mucosa-associated lymphoid tissue (MALT) marginal zone lymphoma, have been shown to have LOW Avidity for FDG

Answer 344

Two described peaks of FDG (1) Rag Week / Menstruation (first 4 days of cycle) and (2) Ovulation (~ day 14) and menstruation may mimic disease. Physiological uptake in the endometrium is usually diffuse. Cancer is usually more focal. You won’t see this in postmenopausal women

Answer 345

Seen during ovulation Typically appears as ovoid or a rim of activity with a photopenic center. You won’t see this in postmenopausal women

Answer 346

suspicious (next step ultrasound)

Answer 347

* Uterine Fibroids | * Benign Endometriotic Cysts

Answer 348

Focal uptake in the ureter or the bladder - if mapped incorrectly can simulate disease. Main strategy to reduce this artifact is to minimize the time between the PET and CT acquisitions

Answer 349

can falsely elevated SUV values by spilling urinary FDG excretion

Answer 350

Necrotic, Mucinous, Cystic, or Low-grade Cancers — you gotta correlate with US and/or MRI to avoid looking stupid. 50% of RCC may not be FDG avid

Answer 351

can be missed because they are small, can also be missed because the adjacent bowel (which has physiological uptake) masks them

Answer 352

can be missed because of | the high uptake in the adjacent bladder — look at source images (uncorrected)

Answer 353

Remember secondary osteosarcomas (the ones from Pagets. Radiation, Multiple Chondromas, e tc ....) are the bad mother fuckers. They have by far the worst outcome.

Answer 354

Back in the stone ages - if you got diagnosed with an osteosarcoma they assumed that 80% of the time you had distal mets. This was prior to effective chemotherapy for osteosarcoma... it was basically a death sentence. They do better now (little bit).

Answer 355

Typically mets go to (a) second bone sites, and (b) the lungs. Remember the classic vignette of a spontaneous pneumothorax in an osteosarcoma patient = lung met.

Answer 356

With the modem addition o f effective chemo, accurate staging and restaging actually matters - and this is why I’m rambling on about osteosarcoma. PET may/could actually play a key role in treatment and is therefore testable.

Answer 357

Average SUV is used at some institutions for describing tumor metabolism. Most literature says you should use the SUV Max for describing osteosarcoma - because it’s a very heterogenous tumor.

Answer 358

Multiple papers have shown a correlation between tumor grade and FDG uptake (SUV values). Higher SUV Max = Higher Tumor Grade.

Answer 359

Baseline SUV Max is an independent and significant predictor of overall survival (more = bad). Having said that PET is not typically used fo r baseline staging.

Answer 360

An important point is that especially with bone stuff, nukes is highly non-specific. Remember earlier in the chapter I said several B9 bones lesions are hot on Tc-MDP? Same thing with PET. Giant Cell is the classic example. Lots o f cases o f GCTs have higher SUV than sarcomas. Fibrous dysplasia is another classic that can be hot on PET.

Answer 361

There is no cutoff to tell the difference between a B9 bone lesion and a bone sarcoma. Same deal with infection. Osteomyelitis can have very high FDG uptake.

Answer 362

Important point = Because PET is so nonspecific, it is NOT used clinically to avoid biopsy.... but can sometimes guide biopsy.

Answer 363

The most important prognostic factor = response to preoperative (neoadjuvant) chemotherapy.

Answer 364

There is a proven positive correlation o f FDG uptake and viable tumor tissue. In other words, F,8-FDG PET can be used to evaluate the effectiveness of neoadjuvant chemotherapy.

Answer 365

11'In Pentetreotide is the most commonly used agent for somatostatin receptor imaging. The classic use is for carcinoid tumors, gastrinomas, paragangliomas, merkel cell tumors, lymphoma, small cell lung cancer, medullary thyroid cancer, and meningiomas.

Answer 366

Meningiomas take up Octreotide (and Tc MDP).

Answer 367

As a point o f trivia, there are 5 somatostatin receptors but " 'In Pentetreotide can only bind to two of them. The scan works because 80% o f neuroendocrine tumors express these two receptors.

Answer 368

Hot on Octreotide and Tc MDP

Answer 369

Normal uptake is in the thyroid, liver, gallbladder, spleen, kidneys, bladder, and GI tract. Imaging is done in early and delayed phase. The advantage o f the early phase (4 hours) is that the bowel activity is absent. The delayed is done to clarify that the abdominal tracer is o f GI origin.

Answer 370

Indium is produced in a cyclotron and decays with a 67 hour half life via electron capture. It produces two photopeaks at 173 keV and 247 keV. Just like Gallium, In"' in a liquid will carry a +3 valence and behaves like Fe+3, with the capability o f forming strong bonds with transferrin.

Answer 371

The most common application is to bind it to WBC, although it can also be hooked to octreotide, or DTPA for CNS imaging (cisternography). Basically, you can hook indium to almost anything if you hook it first to a strong chelator like DTPA. As a point of trivia, you need to isolate the WBCs prior to labeling because the transferrin in the blood binds with greater affinity and will out-compete them.

Answer 372

MIBG is an analog o f nor adrenalin and is therefore taken up by adrenergic tissue. MIBG is first line for tumors like pheochromocytoma, paraganglioma, and neuroblastoma. You can have MIBG with either 1-123 or I -131. 1-123 is better because it has better imaging quality. 1-131 is cheaper, and the long half life allows for delayed imaging.

Answer 373

The thyroid gland should be blocked, to prevent unintended radiation to the gland from unbound 1-123 or 1-131. This is accomplished with Lugol’s Iodine or Perchlorate. Sometimes you’ll see “SSKT' which is Super Saturated Potassium /odine

Answer 374

Normal in liver, spleen, colon, salivary glands. The adrenals may be faintly visible. Note the kidneys are NOT seen.

Answer 375

MIBG is superior to MDP bone scan for neuroblastoma bone mets. * I f you see a skeleton on MIBG the answer is diffuse bone mets.

Answer 376

MIBG is better for Pheo than In-111 Octreotide. MIBG is better than CT or MRI for the extra-adenral Pheos.

Answer 377

Certain medications interfere with the workings o f MIBG and must be held. Medications include calcium-channel blockers, labetalol (other beta-blockers have no effect), reserpine, tricyclic antidepressants and sympathomimetics.

Answer 378

``` What’s Different Between Patient “A” and “B” - who both recently got MIBG Scans? Patient B - Forgot to take her Lugol’s ! So, she ju s t cooked her thyroid. ```

Answer 379

Just like you can see it on FDG PET (around the shoulders / traps) you can also see it with MIBG. In fact, it’s the MOST COMMON variant in I123 MIBG bio distribution.

Answer 380

Apparently brown fat has sympathetic innervation.

Answer 381

The classic use for MIBG is Neuroblastoma. But.... if someone wanted to get sneaky they could also show you a pheochromocytoma, paraganglioma, or carcinoid on MIBG. Essentially any catecholamine producing tumor. See the chart on the next page for specifics.

Answer 382

Octreotide works as an analog to somatostatin and will bind to the same receptors as somastostain. Well... sorta. Technically, there are 5 subtypes of somatostatin receptors and Octreotide will only bind to 2 of them. As you can imagine, the sensitivity of the agent is going to depend on which receptors are expressed by the tumor. Fortunately, most tumors express those 2 receptors.

Answer 383

Some sources will say that Octreotide can trigger hypoglycemia in the setting of an insulinoma. What to do about this seems to vary a lot on who you ask and what you read. Some places will say to give them some IV solution with glucose before and during the administration o f Octreotide. Other places will just say have D50 ready just in case.

Answer 384

You will need to stop the treatment for 3 days prior to giving the labeled agent.

Answer 385

MIBG - Inferior (Sensitivity 50-70%) Octreotide - Superior (Sensitivity 80-90%) Misc - Octreotide and MIBG are similar for detection of Liver Mets

Answer 386

MIBG - Octreotide - SHIT (Sensitivity ~ 30%) Misc - Insulinoma is usually B9

Answer 387

MIBG - Octreotide - Good (Sensitivity ~ 85%) Misc -

Answer 388

MIBG - Crap (No Function, No Fleceptors) Octreotide - Crap (No Function, No Fleceptors) Misc - FDG PET is the test of choice.

Answer 389

MIBG - Superior For Non- Malignant (Adrenal) Types (which is like 90% of them) Octreotide - Superior For Malignant (Extra-Adrenal) Types (which is a minority of them 10%) Misc - FDG is also good - but Octreotide is cheaper - so people go that route first when malignancy is suspected

Answer 390

MIBG - Less Sensitive and Less Specific (*onty concentrates in the functional subtypes) Octreotide - Superior (Sensitivity ~ 95%) Misc -

Answer 391

MIBG - Inferior (Sensitivity 30 %) Octreotide - Superior - (Sensitivity 50-80%) Misc - Octreotide is still the first line as a nukes agent. If it’s negative (in the setting of rising calcitonin) the next step is FDG-PET.

Answer 392

MIBG - Superior (Sensitivity ~ 95%) Octreotide - Inferior (Sensitivity ~ 64%) Misc -

Answer 393

Gallium can be used for tumors. Remember, it’s very nonspecific with regard to infection, inflammation, or tumor.

Answer 394

During the Cretaceous Period (when many o f your attendings trained); Gallium was used to differentiate residual tumor vs fibrosis, scarring, necrosis etc... in patients with Hodgkin’s disease and Malignant Lymphoma

Answer 395

If you are going to use Gallium for treatment monitoring it’s important to have a pretreatment exam (to ensure that the tumor site is actually Gallium - avid).

Answer 396

11'In can be labeled to the antibody Capromab Pendetide (ProstaScint). Capromab is a monoclonal antibody which recognizes PSA membrane antigen “PSMA” - which is slightly different that PSA. Pendetide is the chelating agent. In my opinion, the exam is shit and doesn’t work well.

Answer 397

If you have a rising PSA and negative bone scan. The purpose o f the study is to look for mets outside the prostate bed (soft tissue mets). If they do not have distal mets, they can be offered salvage therapy (radiation to the surgical bed). It’s important to not obsess over the surgical bed, the real question is distal mets. Having said that, the prostate bed is best seen on the lateral between the bladder and penis.

Answer 398

ProstaScint will localize to soft tissue mets, NOT bone mets.

Answer 399

ProstaScint’s critical organ is the LIVER.

Answer 400

This confuses some people. Avoid this trap: Indium = WBC. It’s slang to say “Indium Scan” and people in Nukes just think tagged WBC with Indium. But.... Not all Indium is WBC. Remember that Octreotide is actually labeled with Indium, and so is a bunch o f other stuff.

Answer 401

Indium ProstaScint = Liver Indium WBC = Spleen Indium Octreotide = Spleen

Answer 402

A sentinel node is the node which receives afferent drainage directly from a primary cancer. Surgeons want to know where these are at; especially with melanoma and breast cancer. The agent used for lymphoscintigraphy is 10-50 nm Tc99m sulfur colloid.

Answer 403

Sentinel node mapping is done when you have a lesion between 1 mm-4 mm deep. Less than 1 mm you are typically safe. More than 4 mm you are totally screwed and it makes no difference. The utility o f the test is to go after the ones in that middle zone (between 1-4 mm). Intradermal injection in 4 spots around the lesion / excision scar and imaging is done.

Answer 404

Cancer drains to the internal mammary chain nodes about 3% o f the time. Knowing this, and which axillary node to go for first, can help avoid aggressive lymph node dissection. Injections can be done superficial or deep (into the pectoral muscle).

Answer 405

Yes and No. The idea is that particles have to be small enough to travel through the lymphatics. A particle that is 500 nm will not go anywhere. So any answer choice with 500 nm or larger for a lymph node study is universally incorrect. Now this is where you will read different stuff (and send me nasty emails). Some sources say < 200 nm. This will probably work, but you will be waiting all day for the study. The larger the particles the slower the study. More sources will say < 100 nm. This this will work, but again slow study. There is at least one paper out that advocates for using a 0.22 mm filter (available in most hospital pharmacies because it is commonly used for sterilization o f hyperalimentation solutions). If you do that you end up with particles that are 10-100 nm. If you use this 0.22 mm filter method you can routinely visualize lymphatic channels and sentinel nodes within 30 mins after administration.

Answer 406

How do you know what the question writer does at his/her institution? If it was me - 1 would pick a choice less than 100 nm. If forced to choose between 100 and 50 - 1 would pick 50, and there is literature to back you up (not that you’d have a chance to defend yourself), but practically most places do filter the particles and use small ones.

Answer 407

Lymphoscintigraphy < 0.2 microns (< 200 nm) VQ 10-100 microns (10,000 - 100,000 nm) Liver Spleen “Unfiltered” - so all sizes big and small

Answer 408

Tc99 Sestamibi will concentrate in a breast cancer 6 times more than normal background breast tissue. It does pretty well, with the sensitivity supposedly near 90%. The technique is to give 20-30 mCi o f Tc99 Sestamibi in the contralateral arm then image 20 mins later. A foot injection is often done if you are going to image both breasts. You are supposed to use a dedicated gamma camera that can mimic a mammogram and provide compression.

Answer 409

Nope. The distribution is homogeneous regardless of density. Having said that, hormonal fluctuation can increase the background uptake

Answer 410

Around mid-cycle in premenopausal women.

Answer 411

Fibroadenoma, fibrocystic change, or inflammation can give a false positive

Answer 412

Lesions that are small (< 1 cm), or deep. Lesions located in the medial breast, and/or those overlapping with heart activity.

Answer 413

You see lymph nodes on a “MIBI” scan - this is NOT normal, it is concerning for mets.

Answer 414

Tc Sestamibi and Tc Tetrofosmin are the most common tracers. They work by crossing the cell membrane and localizing in mitochondria (passive diffusion). They don’t redistribute (like Thallium), giving better flexibility.

Answer 415

Tetrofosmin is cleared from the liver more rapidly and decreases the chance of a hepatic uptake artifact.

Answer 416

This is historical with regard to cardiac imaging. It mimics potassium and crosses the cell membrane first by distribution related to blood flow - second by delayed redistribution (washout). Washout is delayed in areas with poor perfusion.

Answer 417

Tc studies (sestamibi and tetrofosmin) are done 30-90 mins after injection - allowing for clearance from background

Answer 418

old Crosses cell via Na/K pump redistributes Imaging must be done immediately after injection

Answer 419

newer Crosses cell via passive diffusion (localizes in mitochondria) Does NOT redistribute Imaging typically done 30-90 mins after injection to allow for background to clear

Answer 420

Only done with Thallium. If there is more uptake in the lungs, this correlates with multi-vessel disease or high grade LAD or LCX lesions.

Answer 421

You will see less perfusion distal to an area o f vascular obstruction (compared to normal myocardium). To improve sensitivity, the heart is stressed. Under stress you need about 50% stenosis to see a defect (it needs to be like 90% without stress).

Answer 422

Patient shouldn’t eat for 4 hours prior to imaging (decreases GJ blood flow). Patients should (ideally) stop beta-blockers, calcium channel blockers, and long-acting nitrates for 24 hours prior to the exam - as these meds mess with the sensitivity of the stress portion. There are reasons to keep people on these meds (they might be getting risk stratification on medical therapy) - but I’d say for the purpose of multiple choice just know that those medication classes mess with stress imaging sensitivity.

Answer 423

There are multiple ways to skin this particular cat. People will do two day exams; rest then stress. People will do one day exams stress then rest. The advantage to doing stress first is that you can stop if it’s normal. Typically the dosing is low for the rest and high for the stress.

Answer 424

If you can’t exercise, the modem trend is to give you Regadenoson (coronary vasodilator) - which is a specific adenosine receptor agonist. It’s specific to a certain receptor having less bronchospasm than conventional adenosine or dipyridamole. If they get bronchospasm anyway you need to give them albuterol.

Answer 425

known LBBB will make ECG stress testing non-diagnostic. So diagnostic imaging (radionuclide myocardial perfusion) is typically the way to go. The important trivia is: LBBB Classic Artifact Pharmaceutic Choice

Answer 426

``` = False Positive Reversible Perfusion Defect at the Septum (anteroseptal region). Supposedly this has something to do with the septum not relaxing correctly during diastolic coronary filling (because the rhythm is not totally coordinated with the left sided block). ```

Answer 427

= Adenosine or Dipyridamole is supposedly better for LBBB patients than Dobutamine. The reason is Dobutamine increases the HR more, and the more rapid the HR, the worse the septal relaxation stuff is. Dobutamine = More False Positives.

Answer 428

Fixed Defect (seen on stress and rest), Scar (prior infarct) Reversible Defect (seen on stress, better on rest), Ischemia Fixed Defect with Reversible Defect around it, Infarct with peri-infarct ischemia Transient Ischemic Dilation (LV cavity is larger on stress), From diffuse subendocardial hypoperfusion producing an apparent cavity dilation. Correlated with high risk disease (left main or 3 vessel). Fixed Cavity Dilation, Dilated cardiomyopathy Right Ventricular Activity on Rest, If has intensity similar to LV then think right ventricular hypertrophy Lots of splanchnic (liver and bowel) activity, Means you aren’t exercising hard enough - not shifting enough blood out of the gut.

Answer 429

This is the result of ischemia and reperfusion injury. It is an acute situation. The perfusion will be normal, but contractility will be crap. It will get better after a few weeks.

Answer 430

This is a more chronic process, and the result of severe CAD causing chronic hypoperfusion. You will have areas of decreased perfusion and decreased contractility even when resting (just like scar). Don’t get it twisted, this is not an infarct. This tissue will take up FDG more intensely than normal myocardium, and will also demonstrate redistribution of thallium.

Answer 431

Will take up less tracer (relative to other areas) on stress, and the same amount of tracer (relative to other areas) on rest. It’s not normal heart so it won’t contract well.

Answer 432

Won’t take up tracer on rest or stress (it’s dead Jim). It’s scar not muscle, so it won’t contract normally either.

Answer 433

The perfusion will be normal on both stress and rest, but the contractility is not normal.

Answer 434

Won’t take up tracer on rest or stress (it’s not dead,just asleep - like a bad soap opera plot). The difference between hibernating muscle and scar is that the hibernating muscle will take up FDG and redistribute thallium. The defect at rest will resolve / “redistribute” on delayed thallium imaging. Remember thallium works with the Na/K pump - so cells need to be alive to pump it in. A truly dead cell won’t have a functioning Na/K pump and therefore won’t be able to redistribute / resolve the defect.

Answer 435

This is an equilibrium radionucleotide angiogram with cardiac pool images taken after the tracer has equilibrated to the intravascular space. Drugs like Adriamycin and Doxorubicin can be cardiac toxic. Oncologists will alter treatment protocols when the LVEF drops (usually by 10%).

Answer 436

It’s an angiogram using tagged RBCs. You time (gate) the exam to get pictures that can be used to estimate the Ejection Fraction (and evaluate motion etc...)

Answer 437

These studies requires gating (the “G” in MUGA). The study is done using Tc 99 labeled RBCs, and the objective is to calculate an EF (MUGA is more accurate than myocardial perfusion for LVEF). Photopenic halo around the cardiac blood pool is a classic look for pericardial effusion. Regional wall motion abnormality on a resting MUGA is usually infarct (could be stunned or hibernating as well).

Answer 438

Screwed up LAO view can cause overlap of LV with LA or RV or even great vessels - causing a false low EF. Inclusion of the Left Atrium (which happens when it is enlarged) - the result of LA inclusion is inclusion of the LA counts — this falsely lowers the EF.

Answer 439

Wrong background ROI (over the spleen), will cause over subtraction of background and elevate the EF.

Answer 440

``` Left A nterior Oblique (LAO) is the “best septal view” - and the one usually used to measure the LVEF. A basic internal QA step when reading these studies is to confirm a good photopenic septum. ```

Answer 441

This is a potassium analog (mechanism is Na/K pump). This is similar to TI-201, and can be used as a similar agent. You can use it for PET myocardial perfusion, although it’s not used in most places because of cost limitations. Also, because o f the very short half life ( 75 seconds) it tends to give a dirtier image compared to PET o f NH?.

Answer 442

Tc99 and Rubidium. * Rubidium is the only PET agent made like this, so that instantly makes it a testable fact.

Answer 443

LAD and apex

Answer 444

between the LAD and RCA

Answer 445

Decreased activity in anterior wall (may also affect septal and lateral - depending on body habitus) Check for ECG changes and wall motion. If normal, then call it artifact. If not sure can repeat in prone position.

Answer 446

Decreased activity in inferior wall Check for ECG changes and wall motion. If normal, then call it artifact.

Answer 447

Increased activity in inferior wall, can mask true defect. Can also mess with “normalization” o f the ventricle and make the rest o f the LV look low. Liver Excretes Tc, so you see it in the liver and bowel. Little bit o f exercise can be used to reduce GI blood flow.

Answer 448

Causes all kinds o f problems You can repeat because tracer is fixed for around 2 hours

Answer 449

Causes all kinds o f problems

Answer 450

Reversible or Fixed Septal Defects , sparing the apex Seen more in exercise or dobutamine stress compared to vasodilators

Answer 451

Normal variant Look for matching stress and rest perfusion patterns with preserved wall function to show you this is normal (and not infarct)

Answer 452

Inhibits the breakdown of adenosine - which builds up. Adenosine is a potent vasodilator. No caffeine

Answer 453

Vasodilator No caffeine Side effects are worse than with dipyridamole. Rare side effect is AV block - which will get better when adenosine short half life runs out.

Answer 454

Selective A2A - causes fewer side effects No caffeine

Answer 455

Beta 1 agonist - acts like exercise by increasing heart rate and myocardial contraction. Patient Can NOT be on a beta blocker. Best used in patients who cannot have Adenosine or Dipyridamole. Better in patients with COPD or Asthma, or who have taken caffeine in the last 12 hours. Avoid with LBBB

Answer 456

Antidote for Adenosine Half life is shorter than Dipyridamole - so must continue to monitor.

Answer 457

There are currently three approved agents for bone pain associated with metastatic disease from breast and prostate cancer: (1) Sr89-Chloride, (2) Sm153 EDTMP, and (3) Ra223-dichloride.

Answer 458

Metastatic disease leads to a tumor derived factor that increases osteolytic activity. You end up with increased fracture risk, osteopenia, and hypercalcemia o f malignancy.

Answer 459

Yes, External radiation is not a contraindication and can be used with the therapy.

Answer 460

Pregnancy, Breastfeeding, and renal Failure (GFR < 30). Patients with extensive bony mets (superscan) maybe shouldn't be treated either * controversial - and therefore not likely tested.

Answer 461

It works by complexing with the hydroxyapatite in areas where bone turnover is the highest. It’s the oldest, and worst o f the three agents. It is a pure beta emitter. It has a high myelotoxicitiy, relative to newer agents and therefore isn’t really used.

Answer 462

This is probably the second best o f the three agents; “Samarium is a good Samaritan. ” It works by complexing with the hydroxyapatite in areas where bone turnover is the highest. It is a beta decayer. The primary method o f excretion is renal. Unlike Sr89, about 28% o f the decay is via gamma rays (103 kev) which can be used for imaging. Does have some transient bone marrow suppression (mainly thrombocytopenia and leukopenia), but recovers faster than Sr.

Answer 463

15-30% drops in platelet and WBC from preinjection 8-12 weeks needed for full recovery

Answer 464

40-50% drops in platelet and WBC from preinjection 6-8 weeks needed for full recovery

Answer 465

This is the most recent o f the three agents, and probably the best. The idea is that Ra223 behaves in a similar way to calcium. It is absorbed into the bone matrix at the sites o f active bone mineralization. Its primary mechanism is the emission o f 4 alpha particles, causing some serious double stranded DNA breaks.

Answer 466

(1) It’s an alpha emitter with a range shorter than Sr and Sm. This means less hematologic toxicity. (2) At least one trial actually showed a survival benefit in prostate CA. (3) It has a long half life (11.4 days), allowing for easy shipping.

Answer 467

The general population is safe, as the gamma effects are low. Soiled clothing and bodily fluids should be handled with gloves, and clothes should be laundered separately. A 6 month period o f contraception is recommended although none o f this is evidence based (as per usual).

Answer 468

Non-hematologic toxicities are generally more common than hematologic ones; diarrhea, fatigue, nausea, vomiting, and bone pain make the list.

Answer 469

Pure Beta Emitter Most Bone Marrow Toxicity (longest recovery). Renal excretion

Answer 470

Beta Emitter, with some imageable gamma rays Less Bone Marrow Toxicity Renal excretion

Answer 471

Alpha Emitter Least Bone Marrow Toxicity GI excretion Improves Survival (prostate mets)

Answer 472

This can be used as a radioembolization method for unresectable liver tumors. This is a pure Beta emitter that spares most of the adjacent normal liver parenchyma (as the maximum tissue penetration is about 10 mm).

Answer 473

Prior to treatment with Y-90 the standard is to do a 99mTc MAA hepatic arterial injection. The primary purpose of this injection is to look for a lung shunt fraction. This fraction needs to be < 10% under ideal circumstances. You can still use Y-90 for 10-20% shunts but you need to decrease the dose. Above 20% the risk of radiation pneumonitis is too large.

Answer 474

The optimal particle size is between 20-40 um, as this allows particles to trap in the tumor nodules, but large enough to get stuck without totally obstructing. If you create a true embolization the process actually doesn’t work as well because you need blood flow as a free radical generation source.

Answer 475

The dose is typically 100-1000 Gy delivered. The current thinking is that lesions require at least 70 Gy for monotherapy success.

Answer 476

There are 175 Kev and 185 keV emissions you can use to image

Answer 477

The average half life is 2.67 days.

Answer 478

Monoclonal antibodies can be used with Indium111 , such as ibritumomab tiuxetan (Zevalin) for refractory non-Hodgkin lymphoma treatment or as a first line treatment. The idea is that you can give the antibody labeled with Indium111 for diagnostic evaluation of the tumor burden and then if the biodistribution is ok you can give the antibody labeled with Y-90 for treatment.

Answer 479

The antibody binds to the CD-20 receptors on B-cells.

Answer 480

Don’t give to patients with platelets less than 100K

Answer 481

(1) Uptake in the lungs is more intense than the heart day one, or more intense than liver on day 2 & 3. (2) Uptake in the kidneys more than the liver on day 3. (3) Uptake in the bowel that is fixed, and/or more than the liver (4) Uptake in the bone marrow > 25%

Answer 482

Thrombocytopenia and neutropenia (about 90% of cases).

Answer 483

Dose to caretakers or persons near the patient is low, and they can be released to the general population after treatment. Although some things like sleeping apart, no kissing, etc... for about a week are still usually handed out.

Answer 484

You need to first give rituximab to block the CD20 receptors on the circulating B cells and those in the spleen to optimize biodistribution. Then you can give the In111 labeled antibody to assess for altered biodistribution. If you suspect altered distribution you should get delayed full body imaging at 90-120 hours. If altered you shouldn’t treat. If ok, then blast’em.

Answer 485

An organ that limits the dose of the radiopharmaceutical due to the increased susceptibility of the critical organ for cancer. This may or may not be the “Target Organ.”

Answer 486

This is the organ you want the tracer to accumulate in. It’s your organ of interest

Answer 487

If you are trying to figure it out, it’s the organ that the tracer is going to spend the most time in. For example, Gallium ends up in the bowel. Tc RBC scans are going to end up passing through the heart a lot, unless they are heat treated then the spleen eats them. Tc- MAG3s and DTPA is going to be the bladder, but DMSA (which sticks to the kidney) is going to be the kidney.

Answer 488

- In -P ro s taS c in t - M31 m ib g - S u lfur Colloid (IV)

Answer 489

* -O ctre otid e * -Damaged RBCs * -In-WBC

Answer 490

pertechnetate

Answer 491

• Thallium | . DMSA

Answer 492

* Sulfur Colloid (oral) | * Sestamibi

Answer 493

MAG 3 • I123 MIBG • MDP *some source say bone

Answer 494

Analog - Energy - “Low” - 140 Physical Half Life - 6 hours

Answer 495

Analog - Iodine Energy - “Low” - 159 Physical Half Life - 13 hours

Answer 496

Analog - Energy - “Low” - 81 Physical Half Life - 125 hours (biologic tl/2 30 seconds)

Answer 497

Analog - Potassium Energy - “Low” - 135 (2%), 167 (8%), use 71 MiHg daughter x-rays Physical Half Life - 73 hours

Answer 498

Analog - Energy - “Medium” - 173 (89%), 247 (94%) Physical Half Life - 67 hours

Answer 499

Analog - Iron Energy - Multiple; 93 (40%), 184 (20%), 300 (20%), 393 (5%) Physical Half Life - 78 hours

Answer 500

Analog - Iodine Energy - “High” - 365 Physical Half Life - 8 days

Answer 501

Analog - Sugar Energy - “High” -511 Physical Half Life - 110 mins

Answer 502

Strontium 89 50.5 DAYS (14 days in hone) Samarium 153 46 Hours Radium - 223 11 Days Yttrium 90 64 Hours

Answer 503

Rubidium 82 75 seconds | Nitrogen 13 10 mins

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