CORE - Nucs Flashcards
Medications administered prior to Meckel’s scan
cimetidine/ranitidine, pentagastrin, glucagon
MAG3 is preferred to DTPA in…
moderate or severe renal failure, immature kidneys (peds), transplant kidneys
Syndromes associated with pheochromocytoma
NF1, VHL, MEN 2, Carney’s triad
Whole body tracer distribution: liver > spleen, bones, salivary glands
Ga-67
Whole body tracer distribution: liver = spleen, bones, no salivary glands
Tc-99m sulfur colloid
Whole body tracer distribution: spleen > liver, bones
In-111 WBC or Tc-99m HMPAO WBC
Whole body tracer distribution: salivary glands, cardiac, thyroid, parathyroid
Tc-99m sestamibi
Whole body tracer distribution: liver > spleen, no bones, salivary glands
I-123/I-131 MIBG; NO renal uptake (important to see pheo and neuroblastoma)
Whole body tracer distribution: spleen > liver, no bones, kidneys
In-111 pentetreotide (octreotide scan)
Whole body tracer distribution: liver, spleen, kidneys, cardiac, bowel
thallium-201
Whole body tracer distribution: gastric, salivary glands, thyroid
free pertechnetate or I-123/I-131
Tracers with cardiac activity
sestamibi, tetrofosmin, MIBG (low), thallium-201, F-18 FDG
Breast uptake on Ga-67 scan
mild uptake is normal in pregnant or lactating women
Thyroid uptake on MIBG scan
forgot to give Lugol’s (aqueous iodine)
Adrenal uptake on MIBG scan
normal adrenal uptake of MIBG is seen in some patients
SNR and spatial resolution with higher energy radiotracers
lower SNR and spatial resolution with high energy tracers (relative to low energy tracers)
Is I-123 or I-131 MIBG more likely to have cardiac activity?
I-123 MIBG
Causes of free pertechnetate
insufficient stannous ions or air in vial/syringe
Tc-99m HDP is used for which study?
bone scan
Difference between NaF bone scan vs. FDG PET with marrow stimulation?
F-18 NaF bone scan will not have brain uptake
Diffuse marrow uptake on FDG PET DDx
G-CSF, post-chemotherapy, EPO, myelodysplastic syndromes, thalassemia, CML, severe anemia, diffuse mets (less likely)
Focal uptake in shoulder on bone scan
consider arthritis (also in hip or knee)
Segmental focal rib uptake on bone scan
rib fractures
Prominent skull sutures on bone scan
renal osteodystrophy
Focal breast uptake on bone scan
breast cancer; mild diffuse uptake is normal (especially in younger women)
Prominent renal cortical uptake on bone scan
hemochromatosis
Diffusely increased renal uptake on bone scan (greater than spine on posterior projection)
chemotherapy, ATN; urinary obstruction is not a cause (Core Review)
Liver uptake on bone scan
aluminum contamination, amyloidosis, mets (or primary HCC), liver necrosis, metastatic calcification
Splenic uptake on bone scan
auto-infarcted spleen in sickle cell (patchy hot and cold areas)
Lung uptake on bone scan
osteosarcoma mets, metastatic calcification, alveolar microlithiasis, Wegener’s, berylliosis, sarcoidosis
How often is a solitary lesion on bone scan benign?
80% are benign
Solitary sternal focus of uptake on bone scan
breast cancer met
Increased sacral uptake on bone scan
insufficiency fracture (especially if H-shaped)
Diffusely decreased skeletal uptake on bone scan
free pertechnetate or bisphosphonate therapy
Benign vs. malignant vertebral body fractures (bone scan)
linear = benign; involvement of posterior elements = malignant
Flare phenomenon (bone scan)
good response mimics a bad one; increased size and number of lesions on bone scan <3 months after treatment
Signs of flare phenomenon
lesions becoming more sclerotic on plain film, lesions improve on bone scan >3 months after treatment
Cold mets on bone scan
RCC, thyroid, myeloma, +/- lymphoma
Spinal hemangioma on bone scan
cold
Active heterotopic ossificaton
hot on bone scan (mature is cold); increased risk of recurrence if resected
Long bone periosteal uptake on bone scan + NEXT STEP
hypertrophic osteoarthropathy; next step is CXR or chest CT
Paget’s in spine on bone scan
involves both vertebral body and posterior elements (classically), may also expand vertebral body
Bone scan uptake for AVN
cold (early) => hot => cold (late)
3-phase hot on bone scan DDx
osteomyelitis, osteoid osteoma, reflex sympathetic dystrophy, fracture, septic arthritis, neuropathic joint, active Paget’s
Increased mandible uptake on bone scan
fibrous dysplasia (young), Paget’s (old)
Benign lesions hot on bone scan
fibrous dysplasia, GCT, ABC, osteoblastoma, osteoid osteoma
Benign lesions cold on bone scan
simple bone cyst (without fracture)
Causes of metabolic superscan
hyperparathyroidism, renal osteodystrophy, osteomalacia, myelofibrosis, Paget’s; HOT skull on metabolic superscan
Equivocal lesion on bone scan - NEXT STEP
plain film (if that’s also equivocal, get an MRI)
Periarticular uptake on delayed phase of bone scan
reflex sympathetic dystrophy
Septic arthritis on bone scan
3-phase hot on both sides of joint
Shin splints vs. stress fracture (bone scan)
shin splints hot on delayed phase only, while stress fracture is 3-phase hot
Indication for sulfur colloid + WBC study
evaluate for osteomyelitis near prosthesis or fracture (photopenic on sulfur colloid)
Why is sulfur colloid + WBC no good for spine?
In-111 WBC gives false positives in spine (use Ga-67 instead)
Diffuse peri-prosthetic uptake on bone scan DDx
normal for cemented arthroplasty <1 year and cementless arthroplasty <2 year; also may be infection or less likely loosening
Prosthetic loosening on bone scan (hip)
focal uptake along stem and lesser trochanter (infection would be diffuse); both are excluded by a negative bone scan
When to use Tc-99m HMPAO WBC?
peds (lower absorbed dose and shorter half-life), imaging hands/feet
Indications for V/Q scan
contrast allergy or low GFR with concern for PE
Probability of PE with a normal perfusion study
none; normal perfusion study excludes PE
Xe-133 vs. Tc-99m DTPA differences
Xe only has anterior and posterior projections and has wash-in, equilibrium, and wash out phases; Tc-99m DTPA allows for multiple projections, but has only a single phase, may also see clumping in airways
Brain or renal uptake on MAA scan
right-to-left shunt
Particle size for MAA
10-100 micrometers
Indications to half MAA dose
peds, right-to-left shunt, pulmonary HTN, pregnant; ~100,000 particles (normal is 200k to 500k)
Focal “hot spots” in lungs on MAA scan
blood was drawn back into the syringe => clumping
Persistent pulmonary activity on washout phase of Xe-133 study
COPD
Hepatic uptake on Xe-133 study
hepatic steatosis if diffuse, focal fat if focal
Lung shunt fraction study
performed with Tc-99m MAA; <10% is normal, 10-20% needs a decreased Y-90 dose, >20% is at risk for radiation pneumonitis
Entire single lung is photopenic on MAA scan + NEXT STEP
mass, fibrosing mediastinitis, or central PE; need to get CT or MRI of chest
Ga-67 uptake in lungs
sarcoidosis, PCP, IPF, lymphangitic carcinomatosis, military TB, fungal infection
Ga-67/Tl-201 uptake - Kaposi sarcoma
Ga-67 cold, Tl-201 hot
Radiotracer to use for suspected abdominal infection
In-111 WBC (no bowel uptake)
Meningioma is hot on…
Tc-99m MDP and In-111 pentetreotide
Malignant otitis externa findings
hot on Ga-67 and bone scan
Radiotracer that “traps but does not organify” (thyroid imaging)
Tc-99m pertechnetate (slowly washes out of thyroid); I-123/I-131 are organified
Radiotracers used for thyroid uptake quantification
I-123 or I-131 (NOT Tc-99m pertechnetate)
Hot caudate sign
Budd-Chiari; increase caudate uptake on sulfur colloid scan
High probability on V/Q scan
2+ large mismatched segmental defects (without assoc. radiographic abnormality); “large” = >75% of segment; may involve contiguous segments (confluent appearance)
Very low probability on V/Q scan (4)
solitary triple-matched defect in mid-to-upper lung, non-segmental lesion, stripe sign, 1-3 small segmental defects
Indications for Tc-99m pertechnetate for thyroid scan (over I-123/I-131)
recent thyroid blocker, recent iodinated contrast; Tc-99m pertechnetate slowly washes out of thyroid
Normal RAIU (radioactive iodine uptake) values
5-15% at 4 hours, 10-30% at 24 hours; only with I-123 or I-131; thigh used for background correction
Medications causing decreased RAIU (radioactive iodine uptake)
thyroid blockers (PTU/MZ), nitrates, amiodarone, iodinated contrast
Increased RAIU (radioactive iodine uptake) DDx
Graves, multinodular goiter, early Hashimoto’s, dietary iodine deficiency, rebound (after cessation of PTU/MZ), lithium
Decreased RAIU (radioactive iodine uptake) DDx
late Hashimoto’s, subacute thyroiditis, renal failure, iodine load (Wolff-Chaikoff effect), thyroid hormone replacement, ectopic thyroid hormone, PTU/MZ (does not block Tc-99m uptake)
Visualization of pyramidal lobe (thyroid scan)
Graves disease; also seen in 10% of normal patients
RAIU (radioactive iodine uptake) in Graves and multinodular goiter
> 50% and >30%, respectively (Core Review; Prometheus says >70% and >40%)
Plummer disease
multinodular goiter or thyroid adenoma associated with hyperthyroidism
Panda sign DDx
Ga-67 scan; sarcoidosis, Sjogren’s, treated lymphoma
Clinical hyperthyroidism with decreased RAIU (radioactive iodine uptake)
subacute thyroiditis (a.k.a. de Quervain’s or granulomatous); viral etiology
Discordant nodule (thyroid scan)
lesion traps (Tc-99m hot), but does not organify (I-123/131 cold); suspicious => biopsy indicated
Thyroid cancer types which respond poorly to I-131 therapy
medullary, anaplastic, Hurthle cell
Diffuse Tc-99m pertechnetate uptake, but no I-123/131 uptake (thyroid)
congenital enzyme deficiency inhibiting organification or taking PTU (blocks organification)
Things that make patient I-131 treatment resistant
medullary, anaplastic, or Hurthle cell subtype, prior I-131 treatment (need 50% higher dose), prior MZ treatment
Ideal TSH prior to I-131 treatment
goal is 30-50 mU/L; stop levothyroxine or give recombinant TSH (thyrogen)
I-131 treatment dosing
100 mCi if cancer confined to thyroid, 150 mCi if nodal mets, 200 mCi if distant mets; 30 mCi for multinodular goiter or toxic adenoma, 15 mCi for Graves
I-131 treatment + lung mets
risk of pulmonary fibrosis
I-131 treatment + Sjogren’s
salivary gland damage (higher dose => more damage)
I-131 scan with liver uptake
post-treatment scan (always)
Contraindications to I-131 treatment
severe thyrotoxicosis (use PTU/MZ to calm down first), pregnancy
Lab test to monitor for thyroid cancer recurrence
thyroglobulin; after thyroidectomy anything >0 is abnormal (but trend is most important)
Wolff-Chaikoff effect
ingestion of large amount iodine => decreased thyroid hormone; can be used to calm down hyperthyroidism
Most common cause of hyperparathyroidism
hyperfunctioning adenoma > hyperplasia
Dual-phase parathyroid scan technique
Tc-99m sestamibi; imaging at 10 minutes and 3 hours; depends on mitochondrial density and blood flow
Tc-99m sestamibi scan with lymph node uptake
suspicious for cancer; next step is ultrasound (or other imaging modality)
Tc-99m sestamibi scan with breast uptake
suspicious for breast cancer; next step is mammogram
Lipophilic CNS tracers
Tc-99m HMPAO, Tc-99m ECD; cross BBB, used to assess perfusion (parenchymal uptake)
CNS tracer with slow washout
Tc-99m ECD, while Tc-99m HMPAO has fast washout
CNS studies using DTPA tracer
cisternogram and CSF leak studies use In-111 DTPA; shunt and brain death studies use Tc-99m DTPA (shorter half-life)
Ictal vs. inter-ictal seizure focus radiotracer uptake
ictal is hot, inter-ictal is cold
Which tracer is used first in Tl-201 + Ga-67 comparison study?
Tl-201 should be used first (otherwise downscatter from Ga-67 peaks)
CNS Tl-201+Ga-67: lymphoma vs. infection (e.g. toxo, abscess, crypto, TB)
all will be hot on Ga-67 portion, but only lymphoma will be hot on Tl-201