CTC Nucs Flashcards
1
Q
Hot spleen should make you think
A
Octreotide and WBC Scans
Sulfur colloid will have tracer in the spleen, but not as much as the liver.
2
Q
Cardiac activity with MIBG
A
Will see it with I-123 not with I-131
3
Q
High count study with no bones + liver + dark spleen + dark kidneys?
A
Octreotide
Images should be cleaner b/c of high counts.
4
Q
Difference between Tc and In WBC scans
A
Both will have hot spleens. Tc will have higher count and will look cleaner.
Tc WBC have to image at 4 and 24 hours. At 4 hours you get lung uptake. At 24 hours, the lungs are clearing up, but you start getting bowel uptake
Tc WBC = Renal and GI
In WBC = No Renal and No GI.
5
Q
How do you prepare MDP?
A
Kit which has MDP and stannous ion. Add free pertechnetate and the stannous ion reduces it so it will bind the MDP.
Don’t have enough stannous ion (or get air into the vial or syringe - that can cause oxidation) you might get free Tc (salivary gland, thyroid, stomach uptake).
Inject tracer (15-25 mCi) wait 2-4 hours to let tracer clear from soft tissues.
6
Q
How do you tell the difference between an F-18 vs Tc-MDP bone scan vs PET-FDG with marrow stimulation?
A
Tc-MDP will have bone and kidney uptake. Will be blurry and fuzzy.
F-18 will be high resolution and look like a MIP PET
FDG-PET with bone stimulation will look similar to F-18, but will have BRAIN uptake
F-18 not commonly done b/c expensive.
7
Q
Highest doses in MDP and F-18 bone scans?
A
MDP = bone
F-18 = Bladder
8
Q
What is normal uptake on a bone scan? What factors will affect tracer uptake?
A
Normal: Bone, kidney, bladder, breasts (esp in young women), soft tissues - low levels, epiphyses in kids
Factors: OsteoBLASTIC activity, blood flow.
9
Q
Marked uptake of skull sutures on bone scan?
A
Renal osteodystrophy
Normal to see some persistent visualization of skull sutures.
10
Q
Increased renal cortex activity in bone scan?
A
Supposed to see renal activity, but when renal cortex is hotter than the adjacent lumbar spine, think hemachromatosis.
Diffuse renal activity - seen in setting of chemotherapy, but can be seen with urinary obstruction.
11
Q
Diffuse renal uptake on a bone scan?
A
Seen in setting of chemotherapy, but can be seen with urinary obstruction
Increased renal cortex uptake can be seen with hemachromatosis - more than adjacent lumbar spine.
12
Q
Causes of liver uptake on bone scan?
A
Too much Aluminum contamination in the Tc
Cancer - either hepatoma or mets
Amyloidosis
Liver necrosis
13
Q
Cause of diffusely decreased skeletal uptake?
A
Free Tc
Bisphosphonate therapy
14
Q
What is Flair Phenomenon with bone scans?
A
Bone scan with good response to therapy will mimic a bad response.
Increased radiotracer uptake (both in number and size of lesions) seen 2 weeks to 3 months after treatment.
Lesion will be more sclerotic on plain film if flair.
Will improve after 3 months.
15
Q
Best bone tracer to use for neuroblastoma mets?
A
I-123 or I-131 MIBG
16
Q
How can Pagets be shown on bone scan?
A
Super hot enlarged femur
Super hot enlarged pelvis
Super hot skull
Expanded hot “entire” vertebral body - BOTH vertebral body and posterior elements.
Metabolic superscan - from widespread Pagets.
17
Q
What causes a metabolic superscan on bone scan?
A
hyperPTH
18
Q
How can Fibrous Dysplasia be shown on a bone scan?
A
Super hot mandible
Leg that looks similar to Pagets
19
Q
Lesions that are hot on bone scan?
A
Fibrous Dysplasia Giant Cell Tumor Aneurysmal Bone Cyst Osteoblastoma Osteoid Osteoma
Cold: Bone cyst without fracture
Variable: Hemangioma and multiple hereditary exostosis.
20
Q
Why do you image heterotopic ossification on bone scan?
A
See if it’s “mature” or not. If active it has a higher rate of recurrence if resected.
21
Q
How can you tell the difference between metabolic and malignant superscans?
A
Skull will be asymmetrically hot on a metabolic superscan.
Metabolic: hyperPTH, renal osteodystrophy, Pagets, or severe thyrotoxicosis.
22
Q
What to do for “equivocal lesions” on bone scan?
A
Plain film. If no lesion = MORE suspicious for mets = MRI.
23
Q
Bone scan with increased uptake on flow and blood pool with periarticular uptake on delayed phase?
A
Reflex Sympathetic Dystrophy
Often involves the entire extremity
24
Q
What is the fourth phase of a bone scan?
A
Sometimes done in diabetics due to reduced peripheral blood flow - may help distinguish between bone and delayed soft tissue clearance.
25
When should you consider Tc99 HMPAO instead of In-WBC for infection?
Kids - Tc99 will have a lower absorbed dose and shorter imaging time
Small parts- Tc99m does better in hands and feet.
Disadvantages of Tc99 HMPAO
Shorter half life -6 hrs- limits delayed imaging
Normal GI and GB activity which would obscure injection in those areas.
26
Tracers used for V/Q ventilation?
Xenon 133 -
Physical half life of 5.3 days, biological half life is 30 seconds - only can do one view.
Low energy (80 keV) - NEED TO DO FIRST
3 phases: 1. Wash in (single max inspiration and breath hold). 2. Equilibrium (breathing room air and xenon mix). 3. Wash out (breathing normal air).
Tc-99m -
Requires patient cooperation. Must do first.
27
When doing V/Q, what must be done first?
Ventilation must be first.
28
V/Q Tc99 MAA tracer in brain
Shunt - ASD, VSD, or pulmonary AVM.
29
How big are Tc99 MAA tracer particles?
10-100 micrometers
Capillary is about 10 micrometers. Need to stay in lung, so can't be smaller than that. Don't want too big so they block arterioles.
Reduce particle amount if you have fewer capillaries (children or 1 lung), if they have a R-L shunt (stroke), and pulm HTN.
Reducing particles does NOT reduce dose - just added to fewer particles.
Multiple focal scattered hot spots in lungs?
Clumped MAA - tech draws blood into the syringe prior to injection
30
What causes multiple focal scattered hot spots in the lungs on MAA perfusion?
Clumped MAA - tech draws blood into the syringe prior to injection.
31
Persistent pulmonary activity during washout of Xenon ventilation?
Air trapping - COPD
32
Accumulation of Xenon tracer over the RUQ during ventilation?
Fatty infiltration of liver - xenon is fat soluble.
33
What is the classification of a triple match in the lower lung fields on V/Q?
Intermediate
34
What is a Reverse Mismatch on V/Q?
Normal perfusion with abnormal ventilation - MC atelectasis.
Can be pleural effusion, pneumonia, cardiometaly, and partial bronchial obstruction.
35
What is Stripe Sign on V/Q?
Zone of normally preserved peripheral lung.
PE is peripherally based, makes PE unlikely, considered very low probability.
36
Cause of Solitary Lobar or Solitary Whole Lung Perfusion Defects
Hilar mass, hypoplastic pulmonary artery, or mediastinal fibrosis - uncommon for PE
37
MC cause of unilateral whole lung perfusion defect with normal ventilation?
Lung cancer.
38
How do pleural effusions fit in V/Q scans?
Small effusion causing matched defects = intermediate prob
Large effusion = low prob
Triple matched defects in the lower lobe (caused by any size effusion) = intermediate
*Triple matched defects in the middle and upper lobe = low probability
39
When to f/u high probability scan?
Do f/u in 3 months for new baseline.
40
What are quantitative lung perfusion scans done for?
Evaluate prior to lung resection or prior to transplant.
Quant is NOT possible if you use Tc99 DTPA aerosol. Can do it with combined Xe + Tc99 MAA b/c the Xe will not interfere with the Tc.
41
How does Gallium work?
Works like iron- binds to lactoferrin and concentrates in areas of inflammation, infection, and rapid cell division. Not very specific for infection or tumor.
Produced in cyclotron via bombardment of Zn68 and complexed with citrate to make Gallium Citrate. Half life of 3 days (78 hours).
Decays by electron capture - 4 photopeaks - 90, 190, 300, 390.
Do images at 24 hours b/c background is too high.
Target organ is the colon.
Liver, bone marrow, spleen, salivary glands, lacrimal glands, breast (if lactating or pregnant)
42
Characteristics of Gallium
Works like iron- binds to lactoferrin and concentrates in areas of inflammation, infection, and rapid cell division. Not very specific for infection or tumor.
Produced in cyclotron via bombardment of Zn68 and complexed with citrate to make Gallium Citrate. Half life of 3 days (78 hours).
Decays by electron capture - 4 photopeaks - 90, 190, 300, 390.
Do images at 24 hours b/c background is too high.
Target organ is the colon.
Liver, bone marrow, spleen, salivary glands, lacrimal glands, breast (if lactating or pregnant)
43
Non-infectious things Gallium can be used for?
Show early drug reaction from chemotherapy (Bleomycin) or other drugs (Amiodarone)
Elevated in IPF and can be used to monitor response to therapy.
44
What can Gallium be used for in immunocompromised patients?
PCP = Gallium hot - diffuse bilateral pulmonary uptake
Kaposi Sarcoma = Gallium negative, Thallium Positive
Bacterial Pneumonia = Intense lobar configuration w/o parotid or nodal uptake
45
Use In-111 WBC or Gallium with abdominal and pelvic infection?
In-111 WBC is superior.
Gallium has normal GI uptake
46
Use In-111 WBC or Gallium for spinal osteo?
Gallium
47
What are the two types of thyroid imaging?
Trapping - Transported into the gland - I-123, I-131, and Tc99 all do this
Organification - Analog is oxidized by thyroid peroxidase and bound to tyrosyl moiety. 123 and 131 do this. Tc does not and slowly washes out of the gland.
48
Pros and cons of I-131, I-123, and Tc-99m for thyroid imaging
I-131:
Pro: Cheap
Con: Long half life (8 days) and high energy (364 keV) = crappy images with 1/2 inch crystal. Ideal for therapy, not routine imaging. Contraindicated in kids and pregnant women.
I-123:
Pro: Shorter half life (13 hours) and ideal energy (159). Decays via electron capture = prettier images.
Con: Costs more
Tc-99m:
Trapped, but not organified. Background levels are higher b/c only 1-5% is taken up by thyroid.
Choose Tc over Iodine when recent thyroid blocker on board or iodinated contrast
49
When would you choose Tc-99m over an iodine agent for thyroid imaging?
Had a recent thyroid blocker
| Recent iodinated contrast.
50
Rules for breast feeding after thyroid imaging
Tc-99m: Resume in 12-24 hours
I-123: Resume in 2-3 days
I-131: Should not breast feed (not getting pregnant for 6-12 months).
51
How is an iodine uptake test done?
Give 5 mCi of I-131 or 10-20 mCi of I-123.
4-6 hours and 24 hours
Normals are 6-18% (4-6 hours) and 10-30% at 24 hours.
Correction for background is done for measurements prior to 24 hours.
Factors affecting uptake:
Renal function (increases stable iodine pool, reduces numbers)
Dietary Iodine - variable and controvercial
Medications - thyroid blockers, nitrates, IV contrast, Amiodarone
52
What factors can affect a thyroid uptake scan?
Factors affecting uptake:
Renal function (increases stable iodine pool, reduces numbers)
Dietary Iodine - variable and controvercial
Medications - thyroid blockers, nitrates, IV contrast, Amiodarone
53
What causes increased and decreased uptake on a thyroid scan?
```
Increased:
Graves
Early Hashimoto
Rebound after abrupt withdrawl of antithyroid meds
Dietary Iodine Deficiency
```
Decreased:
Primary or secondary causes of hypothyroidism
Renal Failure
Medications - thyroid blockers, nitrates, IV contrast, amiodarone
Dietary iodine overload
54
What is Plummer Disease?
Multi-nodular Toxic Goiter
Elderly woman with weight loss, anxiety, insomnia, and tachycardia.
Gland is heterogeneous, with uptake that is only moderately elevated. Nodules will be hot on the background of a cold gland.
55
How to tell the difference between a Toxic multi-nodular goiter vs a Non-toxic multi-nodular goiter?
Toxic goiter will have hot nodules on a background of cold thyroid.
Non-toxic will have warm/hot nodules on a normal background of the thyroid.
Graves = high uptake (70%), homogeneous
Toxic Multi-nodular goiter = uptake medium high: 40s, heterogeneous.
56
What is Hashimotos?
MC cause of goitrous hypothyroidism. Autoimmune disease that causes hyper first then hypothyroidism second as the gland burns out later. Usually hypo when its seen.
Increased risk of primary thyroid lymphoma.
Associated with Ab to thyroid peroxidase (TPO) and antithyroglobulin.
Hypothyroid = Inhomogeneous gland with focal cold areas.
Hyperthyroid (acute) = Looks like Graves.
57
Difference between Subacute Thyroiditis and Graves?
Both can have low TSH, high T3, and high T4.
Subacute thyroiditis will have low %RAU.
58
What kinds of nodules are more likely to be cancer?
Cold nodules when compared to functional (warm) nodules.
Most are cold and therefore most are benign (colloid, cysts, etc..). Colds nodules in a multi-nodular goiter are even less likely to be cancer compared to a single cold nodule.
59
What is a discordant nodule?
Hot on Tc99 but COLD on I-123.
B/c some cancers can maintain their ability to trap, but lose the ability to organify = can't be benign until you show that it's also hot on I-123.
60
What causes a thyroid that takes up Tc, but NOT Iodine on 24 hour imaging?
Congential enzyme deficiency that inhibits organification
Drug like PTU that blocks organification.
If just an iodine thyroid with low uptake on 24 hours, this is de Quervains, or a burned out Hashimotos.
61
MC subtype of thyroid cancer?
Papillary is popular. - does well with surgery plus I-131.
```
Medullary thyroid (MEN 2a and 2b) does not do well with I-131.
Occasionally (10%) take up Octreotide - cold on thyroid scan.
```
62
Things that make you treatment resistant for I-131?
Medullary subtype CA - will not take up tracer
History of prior I-131- easy gland has been killed off
History of Methamazole treatment -even if years ago.
63
What to do before thyroid therapy?
Tiny dose of I-131 to see how much thyroid they have left - <5% is ideal. More than 5% can be painful.
Get high TSH - like 50 (30 would be minimum).
Dosing is dependent on the stage of disease
100 for thyroid only
150 for thyroid + nodes
200 for distal
64
What are the possible side effects of I-131 treatment?
Pulmonary fibrosis if lung mets
Sjogrens have greater risk of salivary gland damage
Salivary gland damage is dose related - so cancer treatment patients have a greater.
65
What are absolute contraindications of I-131?
Uncontrolled thyrotoxicosis and pregnancy
66
Iodine scan with liver uptake =
ALWAYS a post treatment scan
67
What to do about iodine therapy with patient on dialysis?
Give I-131 immediately after dialysis to max time.
Decrease dose as there is limited (essentially no) excretion until next dialysis.
Dialysate can go down sewer. Tubing needs to stay in storage.
68
Dosing for hyperthyroid I-131 therapy?
Depends on etiology
15 mCi for graves (more vascular)
30 mCi for multinodular (harder to treat the capsule)
TSH must be high
By 3-4 months, should be clinical evidence.
No emergency, can use drugs to cool down
Standard med is Methimazole
PTU is recommended during pregnancy
69
What is the Wolff-Chaikoff Effect?
Reduction in thyroid hormone levels caused by ingestion of large amount of iodine.
Lasts several days (around 10) after which is followed by an "escape phenomenon"
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.
Also explains why hypothyroidism is sometimes produced in patients taking several iodine-containing drugs, including amiodarone.
70
What is Dual Tracer Technique for Parathyoid imaging?
Two different agents are used then subtraction is done.
First Tc99 Sestamibi or Thallium Chloride - goes to both thyroid and parathyroid. Second that only goes to the thyroid (I-123 or pertechnetate).
Subtraction is done, anything left hot could be a parathyroid adenoma.
Problems:
Motion
Stuff messing with thyroid tracers: recent iodinated contrast, etc...
71
False positives on a Sestamibi parathyoid scan
Thyroid Nodules
Head and neck cancers
LAD
Brown fat
72
Should you see LN on Mibi scans (parathyroid or heart)?
No. If seen they are suspicious - US to further evaluate them.
Focal breast uptake = cancer.
73
What are the CNS Spect agents?
HMPAO
Neutral and lipophilic
Accumulate in the cortex proportional to blood flow (gray matter > white matter)
Washout is FAST
Uptake favors frontal lobe, thalamus, and cerebellum
ECD
Neutral and lipophilic
Accumulate in the cortex proportional to blood flow (gray matter > white matter)
Washout is SLOW (more rapid clearance from blood pool)
Uptake favors the parietal and occipital lobes - makes comparison of HMPAO and ECD difficult
74
Difference in washout of HMPAO and ECD?
HMPAO washes out FAST
| ECD washes out SLOW - more rapid clearance from blood pool
75
Difference in uptake patterns for HMPAO and ECD?
```
HMPAO = frontal lobe, thalamus, and cerebellum
ECD = parietal and occipital lobes
```
Makes comparison of HMPAO and ECD difficult.
76
Key differences between HMPAO and ECD?
Both agents pass BBB and stick to gray matter proportional to CBF
HMPAO washes out faster
ECD washes out slower, has better background clearance, and does not demonstrate intracerebral redistribution.
77
What is Tc DTPA used for in CNS imaging?
Used for flow.
Does NOT cross the BBB - not used for parenchymal imaging - CANNOT DO SPECT.
Has advantage over HMPAO and ECD in that it can be repeated without delay.
78
Facts about Thallium
```
Produced in a Cyclotron
Decays by electron capture
Half life of 3 days (73 hours)
Major emissions - 69 and 81 keV.
Normally given as a chloride and will therefore rapidly be removed from the blood.
```
Behaves like Potassium, crossing cell membrane by active transport.
Tumors and inflammatory conditions will increase uptake of this tracer - Higher grade tumor = more uptake - can be thought of as a viability marker.
Normal distribution: Thyroid, salivary glands, lungs, heart, skeletal muscle, liver, spleen, bowel, kidneys, and bladder. Any muscle twitching.
If doing Gallium and Thallium scans - Do Thallium first b/c Gallium peaks will scatter over Thallium.
Toxoplasmosis infection is Thallium negative, lymphoma is thallium positive
Kaposi Sarcoma is thallium positive (Gallium negative)
Tumor is thallium positive, necrosis is thallium negative.
79
What SPECT tracers are used for tumor imaging?
Thallium and Sestamibi (less common)
Thallium is a potassium analog - Na/K pump. Inflammatory will increase uptake, but not as much as tumors - more intense in high grade tumors.
80
Telling tumor vs necrosis with Thallium and HMPAO
Thallium hot and HMPAO cold = tumor
| Thallium Cold and HMPAO cold = necrosis
81
Telling CNS lymphoma vs Toxoplasmosis
Thallium
Toxo = cold
Lymphoma = hot
82
What PET agent can be used to assess perfusion?
15O-H2O
F18-FDG assess metabolism, which is analogous to perfusion.
83
FDT PET Brain findings
Alzheimers - Low posterior temporoparietal cortical activity - Identical to Parkinson Dementia
Multi-Infarct - Scattered areas of decreased activity
Dementia with Lewy Bodies - Low in lateral occipital cortex - Preservation of the mid posterior cingulate gyrus (Cingulate Island Sign)
Picks/Frontotemporal - Low frontal lobe
Huntingtons - Low activity in caudate nucleus and putamen
84
What is the Cingulate Island Sign on Brain FDG PET?
Preservation of the mid posterior cingulate gyrus in Dementia with Lewy Bodies - Low in lateral occipital cortex.
85
How is CSF imaging done?
In-111 DTPA
Do LP
2-4 hours it ascends and reaches the basal cisterns
4-24 hours - flows around the sylvian and interhemispheric cistern
24 hours - should clear from the basilar cisterns and be over the cerebral convexities
Abnormal examination:
Tracer in the lateral ventricles
Failure to clear from the cisterns and localize over the convexities by 24 hours
86
What is an abnormal CSF imaging study?
Tracer in the lateral ventricles
| Failure to clear from the cisterns and localize over the convexities by 24 hours.
87
What does Communicating Hydrocephalus look like on CSF imaging?
Early entry (4-6 hours) of tracer into the lateral ventricles
Persistence of tracer in the lateral ventricle > 24 hours
Delay in assent to the parasagittal region >24 hours
Since radiotracer shouldn't normally enter the ventricles, a radionuclide cisternogram cannot be used to distinguish communicating from noncommunicating hydrocephalus. Could tell by injecting material directly into the lateral ventricles.
88
How to tell shunt patency with CSF imaging?
Tc99 DTPA or In111 DTPA directly into the tubing.
Normal will show tracer accumulation in the peritoneum - distal end is patent.
Manually occlude the distal limb to force tracer into the ventricles - proximal is patent.
If tracer fails to reflux into the ventricles, or it does but then doesn't clear you can think proximal obstruction.
Delayed tracer flow into the peritoneum (>10 min = delayed), this can mean partial obstruction.
89
Difference between the emptying curves of solids and liquids on gastric emptying?
Solids have "lag phase" where stomach helps grind up food into smaller parts
Lag time can be increased in diabetic patients.
90
What needs to be taken into account for gastric emptying studies?
Attenuation correction - movement from back of stomach to front.
91
Sensitivity of tagged RBC for GI bleed vs Angio?
```
RBC = 0.1 ml/min
Angiogram = 1 ml/min
```
92
How is RBC tagging done?
In Vivo
Tin (stannous ion) injected into the patient; Then Tc99m pertechnetate is injected; Tin binds to Hb then reduces the Tc (which then binds)
Only 60-80% bound - lots of free, dirty image. Can get drug interactions - heparinized tubing or recent IV contrast.
In Vivo - In Vitro (Modified Method)
Tin (stannous ion) is injected into the patient; After 15-30 min you pull 3-5 cc of blood out of IV line into a syringe with both Tc99 pertechnetate and an anticoagulant; Reinjected 10 min later
85% - Drug interactions (like heparin) are MC cause of failure.
In Vitro
Blood is withdrawn and added to a kit with both Tin (stannous ion) and Tc. It's then reinjected. 98% binding, but more expensive
93
What drug interactions can interfere with RBC binding?
Heparin
| IV contrast.
94
If you see free Tc in the stomach on a GI bleed scan what should you do next?
Look at salivary glands and thyroid to confirm free Tc and not GI bleed.
95
Pre-Treatment with Meckels Scan?
Pentagastrin - enhances uptake of pertechnetate by blocking gastric mucosa (also stimulated GI activity)
H2 blockers (Cimetidine and Ranitidine) block secretion of pertechnetate out of the gastric cells making it stick around longer
Glucagon - slows gastric motility.
False Positives: Bowel irritation (recent scope, laxative use)
False Negative: Recent in vivo labeling or RBCs. Recent barium study (attenuated).
96
How is chronic cholecystitis shown?
Delayed filling of the GB (not seen at 1 hour, but seen at 4).
Low EF (<30%) with CCK stimulation. Reduced EF can also be seen in acute acalculous cholecystitis.
Need higher doses of tracer if patient has hyperbilirubinemia.
97
Doses of CCK and Morphine for HIDA
CCK: 0.02 microgram/kg over 60 min
Morphine: 0.04 mg/kg over 30-60 min
98
Abnormal studies on HIDA
No bowel activity, persistent blood pool activity = Hepatocyte Dysfunction (hepatitis)
No bowel activity, blood pool goes away normally = CBD obstruction
No GB activity x 4 hours (or 1 hour + morphine) = Acute cholecystitis
Abnormal GB emptying (EF <30%) = chronic cholecystitis.
Dilantin (Chlorpromazine) and birth control pills can cause prompt tracer uptake and delayed clearance - mimic biliary obstruction.
99
What drugs can mimic biliary obstruction on HIDA?
Dilantin (Chlorpromazine) and birth control pills - can cause prompt tracer uptake and delayed clearance - can mimic biliary obstruction.
100
What is the reappearing liver sign on HIDA?
Bile leak - labeled bile may track superiorly into the perihepatic space and coat the surface of the liver - paradoxically increasing activity in the liver after initial decrease in activity from liver emptying into the bowel.
101
Liver lesions on Sulfur Colloid studies
```
Hepatic Adenoma = Cold
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)
```
102
What size to particles need to be for sulfur colloid liver scan?
0.1 to 1 micrometers
Too big the spleen will eat them. Too small bone marrow will eat them. Too big they would get stuck in lungs like VQ scan on first pass.
103
What is Colloid Shift?
Normal = 85% liver, 10% spleen, and 5% bone marrow
Diffuse hepatic dysfunction, portal HTN, hypersplenism, or bone marrow activation you can change uptake - shift to spleen from bone marrow.
Most specific causes of colloid shift are cirrhosis, diffuse liver mets, DM, and blunt trauma to spleen.
104
What causes renal uptake on a sulfur colloid scan mean?
CHF - may be due to decreased renal blood flow and filtration pressure.
Can be seen in renal transplant - can indicate rejection (due to colloid entrapment w/in the fibrin thrombi of the microvasculature).
Other: Coxsackie B viral infection, disseminated intravascular coagulopathy, and TTP.
105
What causes Diffuse Pulmonary Activity on Sulfur Colloid Scan?
Not normal localization. Non-specific, tons of things (MC diffuse liver disease).
First thing to think of should be ALUMINUM IN THE COLLOID.
Can be seen in primary pulmonary issues (reflecting phagocytosis by pulmonary macrophages).
106
What is a Hemangioma Scan?
Tc labeled RBCs. Delayed blood pool is typically done (30 min - 3 hours).
If small (<2 cm) need SPECT to localize it. Otherwise planar will show a hot focus.
Want to see marked HOT delays, with no real hot spot on immediate flow or immediate pool.
Angiosarcoma would be HOT on delays but would also be hot on flow.
Partially fibrosed hemangioma may be a false negative.
107
Tracers used for kidney imaging?
Tc-DTPA: Almost all filtered = GFR. Small amount (5%) is protein bound (and not filtered), so GFR is slightly underestimated. Critical organ is bladder.
Tc-MAG3: Almost exclusively secreted - estimates effective renal plasma flow (ERPF). Cleared by proximal tubules. Critical organ is the bladder.
Tc-GH (Glucoheponate): Used for structural or functional imaging. Critical organ is bladder.
108
How does Tc-GH (Glucoheponate) work for renal imaging?
Filtered
Good for dynamic and cortical imaging.
Critical organ is bladder.
109
Differences between DTPA and MAG 3 for renal imaging?
DTPA:
Filtered (GFR)
Good for native kidneys with normal renal function
MAG3:
Secreted (ERPF)
Concentrated better by kidneys with poor renal function
110
What will ATN, interstitial nephritis, and cyclosporin toxicity look like on perfusion images?
Normal perfusion/flow.
111
What is normal clearance on a renal scan?
Excreted - normally will go down to half peak counts by 7-10 min.
Want to quantify retention of tracer - look at 20/3 or 20/peak ratio.
Compare peak at 20 min with peak at 3 min (normal <0.8) or the peak count (normal 0.3)
112
What are the 20/3 or 20/peak ratios?
Method of quantifying retention of radiotracer by comparing the peak count at 20 min with peak count at 3 min (normal <0.8) or the peak count (normal 0.3)
113
What is a Lasix Renogram?
For suspected obstruction. Performed as standard dynamic exam - blood flow, cortical, and clearance with a 30 min wait after clearance. Still activity in the collecting system - give Lasix. True obstruction won't respond.
No obstruction = washout of 50% of tracer w/in 10 min after Lasix
Intermediate = Washout of 50% of the tracer w/in 10-20 min of Lasix - MC cause is very dilated pelvis and subsequent "reservoir effect"
Obstructed = washoutu taking longer than 20 min after Lasix
114
Results of a Lasix Renogram
No obstruction = washout of 50% of tracer w/in 10 min after Lasix
Intermediate = Washout of 50% of the tracer w/in 10-20 min of Lasix - MC cause is very dilated pelvis and subsequent "reservoir effect"
Obstructed = washoutu taking longer than 20 min after Lasix
115
Causes of False Positive for Obstruction on Lasix Renogram?
Poor response to Lasix - Bad renal lfunction, 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 (Foley).
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How does the selection of tracer vary the appearance of a renal artery stenosis study?
DTPA = GFR tracer. Sick kidney will have decreased uptake and flow b/c of loss of perfusion pressure.
MAG3 = Secreted tracer. Sick kidney will have marked tracer retention, with a curve similar to obstruction.
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How to tell ATN vs Rejection on renal scan?
ATN is usually first week after transplant - more with cadaveric donors.
Will be preserved renal perfusion with delayed excretion in the renal parenchyma (elevated 20/3 ratio, delayed time to peak). ATN usually gets better.
Cyclosporin toxicity can also look like ATN (normal perufsion, with retained tracer) but will NOT be seen in the immediate post op period.
Rejection will have poor perfusion and delayed excretion.
Chronically rejected kidney won't really take up the tracer.
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Difference between ATN, Cyclosporin Toxicity, and Acute Rejection on renal scans
ATN - Immediate post op (3-4 days post op) - Perfusion Normal - Excretion Delayed
Cyclosporin Toxicity - Long standing - Perfusion normal - delayed excretion
Acute Rejection - Immediate Post Op - POOR perfusion - Excretion delayed.
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Uses for renal cortical imaging?
DMSA and Glucoheptonate (also filtered and can assess renal flow, collecting system, and bladder - critical organ is bladder).
Acute Pyelo - focal ill defined decreased uptake, multifocal areas of decreased uptake, diffused decreased uptake
Scarring and masses can appear as focal areas of decreased uptake - scarring usually has some volume loss. (Scarring vs Pyelo = History).
Column of Bertin vs Mass - Mass will be cold.
120
What is testicular imaging done for?
Blood flow study - torsion vs other causes of pain (epididymitis).
Sodium pertechnetate.
Acute (early) torsion - focal absence of flow to the affected side ("nubbin sign")
Delayed (late) torsion - missed torsion - halo of decreased activity with central photopenia.
Testicular Abscess - identical to delayed torsion - halo of increased activity with central photopenia.
Acute epididymitis - increased flow and blood pool to the affected side.
121
What does 18-FDG break down to?
18-O
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Tumors that are PET COLD
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BAC (Adeno in situ) - Lung cancer
Carcinoid
RCC
Peritoneal Bowel/Liver Implants
Anything mucinous
Prostate
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123
Not cancer but PET HOT
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Infection
Inflammation
Ovaries in follicular phase
Muscles
Brown fat
Thymus
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124
Calcuation of SUV?
(Measured activity x body weight)/Administered activity
125
What effect does being fat have on SUV?
HIGHER SUV b/c fat takes up less glucose
126
RCCs vs Oncocytoma on PET?
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RCC = cold
Oncocytoma = HOT
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127
Ground glass nodules on PET
COLD GGN = Cancer
| Hot GGN = Infection
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Why is HCC cold on PET?
Has variable glucose-6-phosphatase and can't trap FDG.
129
What is Indium 111?
Cyclotron produced
67 hour half life
Electron capture
Two photopeaks - 173 and 247 keV
Like Gallium, has +3 valence and behaves like Iron and binds to transferrin.
WBC, octreotide, or DTPA for CNS imaging (cisternography)
Thyroid, liver, GB, spleen, kidneys, bladder, and GI tract.
Early (4 hours) and delayed phases - eary = absent bowel activity. Delays shows that accumulation is of GI origin.
130
Meningiomas can take up which tracers?
Octreotide and Tc-MDP
131
What is MIBG?
Analog of noradrenalin - taken up by adrenergic tissue - pheochromocytoma, paraganglioma, and neuroblastoma.
I-123 or I-131- need to block thyroid for unbound 123 or 131.
Liver, spleen, colon, salivary glands. Adrenals may be faintly visible. KIDNEYS ARE NOT SEEN.
MIBG is superior to MDP for neuroblastoma mets.
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What medications can interact with MIBG?
CCB, labetalol (other BBs ok), resperine, TCAs, and sympathomimetics.
133
What is Prostascint?
In-111 labeled Ab Capromab (Prostacint) - monoclonal Ab to PSA antigen.
Use with a rising PSA and negative bone scan. Looking for mets outside the prostate bed (soft tissue mets). If no distal mets, can be offered salvage therapy (radiation to surgical bed).
Real question is distal mets - don't care about prostate bed.
Will localize to soft tissue mets, NOT bone mets.
134
Particle sizes used for Lymphoscintigraphy, V/Q, and Liver-spleen scans?
Lymphoscintigraphy - <0.2 microns (< 200 nm)
VQ - 10-100 microns
Liver-spleen - "Unfiltered"
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Facts about Breast Specific Gamma Imaging
Tc99 Sestamibi
Sensitivity near 90%.
Does breast density affect uptake/distribution? No. Distribution is homogeneous regardless of density. Hormone fluctuation can increase background uptake.
When will background activity be lowest?
Mid-cycle.
What are causes of false positives?
Fibroadenoma, fibrocystic change, or inflammation.
Causes of false negatives?
Small (<1 cm) or deep. Lesions located in the medial breast, and/or those overlapping with heart activity.
What if you see lymph nodes?
Should not be seen. Concerning for METS.
136
Tracers used for Myocardial perfusion/SPECT?
Tc-Sestamibi and Tc-Tetrofosmin - both localize in mitochondria proportional to flow
Tertrofosmin is cleared from the livier more rapidly and decreases change of hepatic uptake artifact.
137
What is the lung/heart ratio with cardiac imaging?
Only done with Thallium.
If more uptake in the lungs, correlates with multi-vessel disease or high grade LAD or LCX lesions.
138
What does lots of splanchnic (liver and bowe) activity on cardiac study mean?
Aren't exercising hard enough - not shifting enough blood out of the gut.
139
What is stunned myocardium?
Ischemia and reperfusion injury. Acute situation.
Perfusion will be normal, but contractility will be bad.
140
What is hibernating myocardium?
More chronic process, severe CAD causing chronic hypoperfusion.
Decreased perfusion and decreased contractility even when resting. Not an infarct. Tissue will take up FDG more intensely than normal myocardium, and will also demonstrate redistribution of thallium.
141
What is MUGA?
Equilibrium radionucleotide angiogram with cardiac pool images take after tracer equilibrated to the intraventricular space.
Requires gating. Done with Tc99 RBCs - calculates EF.
Photopenic halo around cardiac blood pool is classic look for pericardial effusion.
142
Causes of false low and high EFs on MUGA?
False Low EF: Screwed up LAO view can cause overlap of LV with LA or RV or even great vessels
False High EF: Wrong background ROI (over the spleen), will cause over subtraction of background and elevate EF.
143
What is Rubidium 82?
Potassium analog - like Thallium.
PET myocardial perfusion.
Short 75 second half life = dirtier image.
Made by generator.
144
Tracers made by generator?
Tc99 and Rubidum.
145
What is Balanced Ischemia?
Miss 3 vessel disease when comparing stress and rest images. Won't see areas of cold relative to the rest of the heart b/c the entire heart is cold.
Look to a quantitative answer using PET perfusion agents (Rubidium and N13 Ammonia).
146
What is the antidote for Adenosinen?
Aminophylline
Half life is shorter so must continue to monitor.
147
What are the treatments for bone pain from metastatic disease?
Breast and prostate
Strontium-89
Samarium-153
Radium-223
Absolute contraindications (for Sr and Sm): Pregnancy, breastfeeding, and renal failure (GFR <30)
148
What is Strontium-89?
Metastron - complexes with hydroxyapatite in areas of bone turnover is highest.
Pure beta emitter. High myelotoxicity - older and isn't really used.
149
What is Samarium-153?
Quadramet - 2nd best of the 3 bone treatment agents. Complexes with hydroxyapatite in areas where bone turnover is highest.
Beta decay. 28% is via gamma rays (103 keV) which can be used for imaging. Primary method of excretion is renal.
Does have some transient bone marrow suppression (mainly thrombocytopenia and leukopenia), but recoverse faster than Strontium.
150
What is Radium-223?
Xofigo - best of the three bone treatment agents. Behaves in a similar way to calcium - absorbed into the bone matrix at the sites of active bone mineralization.
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Alpha emitter (4 alpha particles) causing DNA damage.
Shorter range than Sr and Sm. Less hematologic toxicity.
Long half life (11.4 days) allowing for easy shipping.
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151
Differences between Sr-89, Sm-153, and Ra-223 for bone treatment?
Sr-89
Pure beta emitter
Most bone marrow toxicity (longest recovery)
Renal excretion
Sm-153
Beta emitter, with some imageable gamma rays
Less bone marrow toxicity
Renal excretion
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Ra-223
Alpha emitter
Least bone marrow toxicity
GI excretion
Improves survival (prostate cancer)
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152
What is Yttrium-90?
Radioembolization of unresectable liver tumors.
Pure beta emitter that spares most of the adjacent normal liver parenchyma as the maximum tissue penetration is about 10 mm.
Need to do a Tc99 MAA hepatic artery injection to look for lung shunt fraction. Needs to be <10%. Can still do 10-20%, but need to decrease dose. Above 20% increases risk of radiation pneumonitis.
Particle size is 20-40 um- allows particles to trap in tumor, but large enough to get stuck w/o totally obstructing. Need blood flow as a free radical generation source.
Has 175 and 185 keV emissions you can image.
2.67 day half life.
153
What is Radioimmune Therapy?
Monoclonal Ab used with Indium-111 ibritumomab tiuxetan (Zevalin) for refractory non-Hodgkin lymphoma treatment or a first line treatment.
Give Ab labeled with In-111 for diagnostic evaluation of tumor burden and then if biodistribution is okay give Ab labeled with Y-90 for treatment.
Ab binds to Cd-20 receptors on B-cells.
154
What is considered altered distribution for Zevalin?
Ab treatment for NHL.
Uptake in lungs that is more intense than heart on day one, more intense than the liver on day 2 and 3.
Uptake in the kidneys more than the liver on day 3.
Uptake in the bowel that is fixed, and/or more than the liver
Uptake in the bone marrow >25%.
155
Side effects and MC side effect of Zevalin?
Don't give to patients with platelets <100 K
MC side effect: Thrombocytopenia and neutropenia.
156
What is the Zevalin protocol?
Give Rituximab to block Cd20 receptors on the circulating B cells and those in the spleen to optimize bio-distribution.
Then can give In-111 labeled Ab to assess altered biodistribution. If suspected altered biodistribution you should get delayed full body imaging at 90-120 hours. If altered you shouldn't treat. If ok, treat.
