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129 Cards in this Set
- Front
- Back
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What is a superscan?
Where do you look to differentiate metabolic from metastatic superscans? |
Osseous uptake with sparing of soft tissues and relative sparing of kidneys
Metastatic superscans SPARE the distal humeri and femora (mets go to hematopoetic marrow which is found proximally) |
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Main DDx of a superscan?
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Diffuse Paget's dz
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When does a metastatic superscan not spare the distal extremities?
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Young patients (more red marrow) e.g. neuroblastoma
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Absent soft tissue uptake is more important for the diagnosis of a metastatic or metabolic superscan?
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Metabolic; the metastatic superscan appearance with its char- acteristically increased uptake of the axial skeleton and cold, more distal appendicular skeleton should be confidently called even in the absence of a significantly appreciable decrease in soft-tissue/renal radiotracer uptake (unlike a metabolic superscan, which should be considered only with a decrease in soft tissues)
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Cold thyroid nodule risk for malignancy?
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15 to 20%
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Radiotracers used for thyroid uptake?
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I123, sometimes Tc99m pertech
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Hyperthyroidism: 3 DDx?
If pyramidal lobe is seen, which is more likely? |
Graves (70%) elevated RAIU
Thyroididits (20%) very low RAIU Toxic Nodule (10%) assoc. with pyramidal lobe Rarely Hashimotos toxicosis |
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Dose range for I131 tx of hyperthyroidism
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5 to 30 mCi
RAIU, weight of gland |
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Total annual effective radiation dose to a worker? General public?
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The annual total effective dose limit for a radiation worker is 5 rem (50 mSv); general public 0.1 rem (1 mSv)
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Annual exposure limit for any organ? Lens? Extremity?
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Organ-specific annual exposure limits also apply:
- 50 rem (500 mSv) to any organ except the lens of the eye: deep dose equivalent (DDE) 1 committed dose equivalent (CDE) - 15 rem (150 mSv) to the lens of the eye: lens dose equivalent (LDE) - 50 rem (500 mSv) to the extremities: shallow dose equivalent (SDE) |
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Occupational dose limit for minors is what fraction of adults?
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1/10; 10%
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Define TEDE, DDE, CEDE, SDE, LDE
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TEDE: represents total risk from external and internal exposures (DDE + CEDE)
DDE: external whole-body exposure at a tissue depth of 1.0 cm Committed effective dose equivalent (CEDE): provides an estimate of the lifetime radiation dose to an individual from radioactive material taken into the body through either inhalation or ingestion SDE: external exposure to the skin or extremity at a tissue depth of 0.007 cm LDE: external exposure to the lens of the eye at a tissue depth of 0.3 cm |
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How can you tell apart ischemia from hibernating myocardium?
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Both will have stress induced defects and normal distribution on delays, but ischemia will show a normal rest image, whereas the rest image won't be completely normal in the areas of concern for hibernating (needs more time to achieve normal distribution); hibernating myocardium probably also has wall motion defects
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Redistribution imaging (delays) requires what radiotracer?
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Thallium 201, can be performed up to 3 days later due to 3 day half life of Thallium
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Scar vs. Hibernating, which PET radiotracer?
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FDG; rubidium 82 will show defect for both
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What can cause a physiologic atypical distribution of FDG on PET?
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Hyperinsulinemia
Brown fat (not extremities) Myositis/exercise (not diffuse) |
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Biodistribution of Gallium?
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Physiologic liver, spleen, colon, bone, and lacrimal gland uptake
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What tumor(s) is Gallium avid?
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Lymphoma, also melanoma, sarcoma (not Kaposi's), lung Ca, HCC; don't forget sarcoid
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Difference between Gallium and WBC scan (Tc99m-WBC or In111-WBC)
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Similar but...
Gallium has salivary gland activity WBC scans: Spleen more than Liver (makes sense) Colon activity seen with Gallium and Tc99m-WBCs, not Indium111 |
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If growth plates are hot, what radiotracer?
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Tc99m MDP or Gallium (poor man's bone scan)
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If liver, spleen and bone marrow are hot, what radiotracer?
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Gallium or WBC, look to see if salivary glands are hot (Gallium)
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When do you use Gallium over WBC and vice versa?
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Gallium: Spine, lung
WBC: abdomen |
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DDx of Meckel's diverticulum?
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Ectopic gastric mucosa in duplication cyst
Ectopic renal pelvis |
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What extra view can help visualize a Meckel's?
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Lateral, usually anterior to bladder
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Matched vent/perf defects are what prob for PE?
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Low; Xe133 can be seen in liver if fatty
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What Tc ventilatory agent is also used?
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Tc99m DTPA
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What is the HIDA "nubbin" sign?
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Acute cholecystitis with dilation of the proximal cystic duct that appears like a small gallbladder producing a false negative study
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In what instance can there be gallbladder filling with acute cholecystitis?
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Acute acalculous cholecystitis rarely can have GB filling. In this case you would give CCK to see if the EF is decreased, which would confirm cholecystitis.
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DDx for HPO?
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Venous stasis - lower ext only
Shin splints - tibia only Paget's - not diffuse/symmetric HPO is upper/lower, diffuse, symmetric, medial and lateral cortex (tram trackings) |
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MIBG, I131 and Octreotide are similar, how are they different?
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MIBG - cardiac activity (not blood pool; ddx MIBI)
I131 - no cardiac activity Octreotide - intense spleen and kidney uptake For WB scans, if normal skeletal activity is absent , the study is probably an MIBG scan, an I131 WB scan, or OctreoScan |
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Why give KI prior to MIBG scanning?
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MIBG uptake in thyroid is blocked, decrease radiation dose
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What is preferred for adrenal neuroendocrine imaging?
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MIBG is preferable to octreotide for adrenal neuroendo - crine tumors, given the normally intense adjacent renal cortical uptake of the latter
Octreotide is used for islet tumors |
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What are two renal parenchymal imaging agents?
Two flow imaging agents? |
DMSA; Glucohepnotate. Bind to cortex so you can see pyelo, masses etc
DTPA; MAG 3. Used for assessing function (DMSA can also) |
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What agent is used to image the parathyroid glands?
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Tc99m MIBI (remember this has cardiac activity!)
TETRO and dual isotope imaging is also possible |
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Parathyroid uptake is most commonly adenoma rather than hyperplasia or carcinoma, but what is multiple foci are detected?
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If multiple present then hyperplasia is more likely
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What is the definition of dedifferentiated thyroid carcinoma?
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Papillary and follicular CA is commonly hot on I131
Post therapy imaging in the setting of elevated TG should produce abn foci if there is recurrence unless the tumor has become anaplastic May only show up on PET/CT |
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How do we image Medullary thyroid CA?
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Octreotide or MIBG
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Where does free pertech accumulate?
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Stomach, thyroid
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Which is more efficient, in vivo or in vitro labelling of Tc99m pertech to RBCs?
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In vitro
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Where should you look if you suspect free pertech?
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Thyroid; Any Tc99m-labeled study can have free pertechnetate artifact (e.g., bone scans with gastric uptake). Other recent Tc99m studies performed within 24 hours can cause free pertechnetate artifact (e.g., MUGA scan followed by bone scan).
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What are two findings of Paget's dz in the spine?
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Osteoporosis circumscripta (picture frame)
Involvement of entire vertebral body (mickey mouse ears) |
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What is the salient difference between mets and Paget's dz?
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PD is CORTICAL. Unlike metastases, PD is not red marrow based and thus can often involve the more distal appendicular skeleton.
Both can cause superscans |
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You suspect Brain Death on a Tc99m HMPAO. What are the other possibilities you should consider before making the call?
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Infiltrated bolus
Diffuse cerebral edema Massive infarct Severe b/l ASVD of carotids...get delayed images to be sure...beware of venous collaterals |
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What is the minimum amount of MAA that can injected for a perfusion study? What scenarios would you reduce the number?
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100,000 particles; pregnancy, kids, right to left shunts, PAH
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When is the stomach imaged and how much radiotracer can be left to call gastric emptying delay?
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Imaged at 0, 1, 2 and 4 hours; should be less than 10% at 4 hours
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What agents are used for dynamic renal scintigraphy? What situations do we use one over the other? What artifactual uptake may be present?
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Tc99m DTPA and MAG3
MAG3 is secreted (not filtered) so can be used during renal dysfunction MAG3 uptake in Gallbladder and later in bowel, shouldn't be confused with leak |
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For a MAG3 scan, when do we measure split function? When do we give Diuretics? Why do we give Diuretics?
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Function is determined at 1-3 minutes, prior to accumulation in collecting system and prior to diuretic administration
We give Diuretics after split function if we see counts in the collecting system so that it can wash into the bladder |
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What is the bone scan appearance of shin splints?
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Hot only on delays. Stress fractures are hot on all three.
Shin splints involve the posterior medial tibia due to pulling of muscle tendons on the cortex |
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What is the difference between a hot and warm thyroid nodule? Are they benign?
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Hot nodule: toxic adenoma, suppresses background thryoid, causes hyperthyroidism
Warm nodule: hyperfunctioning, but no hyperthyroidism These are benign if imaged with radioactive iodine If imaged with Tc99m pertech then RAIU is needed (20% malignancy in discordant nodules) |
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How much Moly99 is allowed per mCi of Tc99m pertech?
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less than 0.15 uCi
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How is the radioNUCLIDE purity of Tc99m pertech measured?
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Dose calibrator
Dose is placed in lead pig that shields energy of Tc (140 KeV) so that Moly can be measured. Then the dose in the lead pig is measured and a ratio is calculated) |
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How is radioCHEMICAL purity of Tc99m measured? Who sets the limits?
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Thin layer chromatography
Tc99m pertech must be greater than 95% (free tech seen on GI bleeding studies in stomach and thyroid) Most other Tc99m studies need >90% U.S. Pharmacopeia, not the NRC |
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How is chemical purity measured? What are the limits?
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Colorimetry; not mandated by NRC states
typically worried about Aluminium must be less than 10ppm |
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How do we image diabetic feet for osteomyelitis?
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Dual bone scan/WBC scan imaging looking for concordant uptake in osteomyelitis is most specific to avoid false-positives from neuropathic joints (on bone scan) or cellulitis (with WBC alone).
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Why is gallium not used for abdominal infections?
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GI excretion
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What are three chemotherapeutics used for metastatic bone pain?
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Samarium (beta and gamma emitter, can be imaged using a gamma camera)
Strontium 89 (beta emitter only) Phosphate 32 (beta emitter only) |
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How often can Sm67 be given?
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q3-6 months if there is a response to therapy
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What is the adverse side effect of bone pain chemo?
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Myelosuppresion
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What are the lipophilic brain tracers?
What are the CBF radiotracers? |
Lipophilic: Tc 99m HMPAO, ECD - adv don't need a bolus, assess cerebellum/BS also
CBF: Tc 99m DTPA or pertech - need bolus, only looks at ICA circulation |
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What do the angiographic and blood pool phases look like in a normal brain, brain damage but not death, brain death?
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Normal
Angiographic phase: Early arterial visualization of both anterior (seen together) and middle cerebral arteries - "TRIDENT SIGN" Blood pool phase: Visualization of venous sinuses, but not brain Brain damaged but not brain death Angiographic phase: May see asymmetrical flow or incomplete trident Blood pool phase: May see uptake in epidural hematoma, choroid plexus (pertechnetate) or areas of blood brain barrier breakdown Brain death Angiographic phase: Absence of trident, "empty light bulb sign", "hot nose sign" due to shunting to ECA Blood pool phase: May visualize venous sinuses from centrally draining scalp perforators |
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Radiotracer used for cavernous hemangiomas...
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Tagged RBC
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Radiotracer used for splenosis...
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Heat damaged RBCs
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Radiotracer used for pheochromocytoma...
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MIBG more sensitive than Octreotide
Image quality of Octreotide is better |
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Radiotracer used for Islet cell tumors, carcinoid...
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Octreotide
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Radiotracer used for inflammatory bowel dz?
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Tc 99m HMPAO WBC scan
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Radiotracer used for pre-Y-90 therapy...
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Tc 99m MAA
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What radiotracer is exclusively filtered by glomeruli?
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DTPA, used for GFR estimation
MAG3 exclusively secreted by tubules, used for ERPF |
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Free pertechnitate is seen in...
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Stomach and thyroid
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Bone radiotracer uptake in the stomach, lungs and myocardium represents...
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hypercalemia such as in renal failure
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What are the criteria to dx biliary atresia on HIDA? What confounders may be present?
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No bowel activity at 24 hours with clearing of blood pool
Gallbladder may be present with radiotracer uptake noted Vicarious excretion of tracer into the kidneys shouldn't be confused with bowel activity. Liver can be primed with phenobarbitol |
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AVN appearance on bone scan acutely? Subacute/chronic?
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Photopenic on all three phases
Increased activity on delayed phases in epiphyses (but this can also be normal so you need to evaluate for asymmetry) Splenic uptake + osseous lesions suggests sickle cell dz (cause of AVN) |
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What erroneously elevates spleen activity for PET?
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G-CSF
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Normal or increased liver uptake on Sulfur Colloid scan means...
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Tumor is unlikely (including hepatic adenoma)
Could represent FNH Caudate lobe - Budd Chiari Quadrate lobe - SVC obstruction |
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How soon must delivered packages be inspected? What is the procedure?
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WIthin 3 hrs of the day or next working day if after hours;
Package needs to be inspected for damage (leaked radiation) and dose on the package surface/at 1 meter distance |
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The delivery company, RSO, and Nuclear Regulatory Commission (NRC) must be notified by telephone if:
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Activity is greater than 200 mrem/h (2 mSv/h) at surface or greater than 10 mrem/h (0.1 mSv/h) at 1 m
Removable surface contamination for & emitters is > 22 disintegrations per minute/cm 2 |
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How does the department of US transportation define radiation levels of packages
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White I radioimmunoassay kits
Yellow II radiopharmaceuticals Yellow III generators |
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Triple match V/Q, CXR finding in a lower lobe would represent...
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Intermediate prob for acute PE, worrisome for infarct
If this were in the upper 1/3 of the lung it would be very low prob for acute PE |
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What is the etiology behind most matched V/Q defects?
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Vasoconstriction from lack of ventilation - low prob for acute PE
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1 to 3 moderate mismatched V/Q defects is...
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Intermediate prob for acute PE (most common scenario)
One large defect = 2 moderate |
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Why is there pseudo uptake of FDG PET for higher density materials?
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The CT coefficients for correcting CT energies to that of PET's energies cause an overcorrection for metals...
Stand alone PETs don't have this problem...no CT coefficient necessary |
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What agents are used to assess cardiac perfusion with PET
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Rubidium 82 or N13 ammonia
Viability is tested with FDG |
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Why can you see liver during a sentinal node SC injection?
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Venous injection
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Using a sheet source during imaging is called a...
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Transmission scan; both emission and transmission scans are used during sentinal LN evaluation
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What is the advantage of Bexxar over Zevalin
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NHL therapies - imaging performed to evaluate for rare altered biodistribution to lung or liver, which precludes therapy
Bexxar can be used for imaging and therapy - thyroid blocking is needed Zevalin needs to be attached to a radiotracer for imaging, then can be given therapeutically - plastic syring needed Both need to be given cold rituximab prior to decrease crossfire effects |
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What are contrainidcations to Bexxar or Zevalin therapy?
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>25% malignant bone marrow, platelets < 100,000; <1,500 ANC; allergy to rituximab
myelosuppression can occur with therapy |
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What radiotracer can be used to identify meningiomas?
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Octreotide; they all express somatostatin receptors
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What is the role of Thallium in heart imaging?
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Best redistribution agent, so used during stress imaging only to assess viability...higher radiation dose than MIBI or TETRO
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What is the issue with MPI for three vessel dz? What can help you identify its presence?
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MPI assesses relative perfusion, so three vessel dz may look normal on stress and rest
Look for transient ischemic LV dilation or increased RV uptake as clue. Lung uptake can also suggest resting or stress induced LV dysfunction vs. inflammation of the lung |
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DDx whole body scan with absent skeletal activity...
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No skeletal, think the endocine group
Octreotide, MIBG, Iodine 131 |
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What numbers are used as threshold for major/minor spills?
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1 mCi for big hitters (I 131)
10 mCi for medium hitters (Gallium, Indium) 100 mCi for small hitters (Tc, Thal) |
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DDx whole body scan with skeletal activity...
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Bone scan
Gallium (poor man's bone scan) WBC (gallium's counterpart) Antibody |
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DDx whole body scan with salivary gland activity...
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Gallium
Radioiodine MIBG |
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Whole body scan with dominant spleen activity? Liver? Kidneys/Spleen?
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Spleen - WBC
Liver - antibody, all go to blood pool then accumulates in liver Kidneys/Spleen - Pentetreotide |
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DDx whole body scan with elevated growth plate activity...
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Gallium and bone scan
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What is the neck star artifact?
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After thyroid surgery, the residual thyroid tissue will accumulate a large amount of I-131, which causes penetration of the lead septa in a medium energy collimator creating a star artifact
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What are the three types of radiation detectors?
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Safety - Survey meter, monitors, personal dosimeters
Verify dose - Dose calibrator Measure dose post tx - Well counter, thyroid uptake probe, scinitillation camera, SPECT, PET |
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How often must survey meters be tested for accuracy?
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Annually
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What test does a well counter use for quality control?
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Chi-Square test
Also tested annually but after repair too |
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How often is Dose Calibrator Accuracy tested? Constancy? What radioisotope is used? Linearity?
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Annually; Daily; Cs-137
Linearity is tested quarterly |
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Frequency of tests for Thyroid and intra operative probes?
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Daily, specifically the Anger camera
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Describe Compton scatter...
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Photon displaces an electron
Atom is now ionized Photon reflects/scatters at the scatter angle and now has lower energy than before Discharged electron has more energy and may even ionize something else |
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Describe photoelectric effect...
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Photon displaces an electron, giving it all its energy
Atom is now ionized Discharged electron may have enough energy to ionize something else |
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Gamma camera is made up of a Scintillation detector and photo multiplier tube, what does each do?
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Scintillation camera converts gamma rays into visible photons using Compton scatter and photoelectric effect
PMT converts photons into electrical signal |
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In an Anger detector, what happens if you lose a PMT?
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Cresentic defect (bite out of the cookie)
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What is the scintillation material in a gamma camera?
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NaI
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What happens if the scintillation crystal is cracked?
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Linear areas of decreased activity
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What is the utility of a pinhole collimator?
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Magnification of small objects like the thyroid or small bones
It will distort larger objects |
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Sensitivity and spacial resolution are best when the patient, detector and collimator are...
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Close together
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Collimators set the max energy level, what is the max energy for High energy collimators? LEAP? Medium?
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511 keV for PET/High energy
150 keV for LEAP (all purpose) 400 keV for medium |
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What daily check is performed for gamma cameras? Weekly?
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Uniformity using a Co-57 flood source
Weekly...geometry, spatial resolution |
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What are the annual tests of a gamma camera?
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Dead time test, rotational uniformity
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What is the sequence involved with gamma ray detection?
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Tc99m gives off a gamma ray, the NaI crystal scintillator converts the gamma ray to visible light, the PMT detects the visible light and creates an electrical signal
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Using a thicker scintillation crystal does what to sensitivity?
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Increases it, but decreases spatial resolution
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What is the photopeaks of different positron emitters?
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They are all 511 KeV
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What are the half lives of different positron emitters?
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RONC
1 min, 2 min, 10 min, 20 min |
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What must be considered when there is MDP uptake in the arm?
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Breast disease such as mastitis, tumor, lymphedema
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When PET only scanner is used, what is the source of the transmission scan?
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Germanium 68
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Tc 99m MAA hot spots result from...
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blood clots, drawing back on syringe
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What prob does the stripe sign confer?
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Low
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What agent in addition to In 111 - WBCs is used to image IBD? When is In 111 usually imaged and when is it imaged for IBD?
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Tc 99m HMPAO; imaged quickly (2 hrs) due to HB clearance
With In 111 WBCs, we usually image at 24 hrs, but at 4 hrs for IBD |
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DIffuse lung uptake on bone scan suggests...
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Metastatic caclification...
Renal failure, hyperparathyroidism, lung mets If joints are hot, think secondary hyperpara from renal failure |
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What is the acceptable rad dose in pregnancy? Children?
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5 mSv for gestation
Children can get 10% of adults, so occupational exposure is 10% of 50 mSv or 5 mSv |
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Which is more efficacious, in vivo or in vitro labeling of RBCs?
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In vitro
In vivo is cheaper |
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What projection is used for a MUGA?
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LAO
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If background isn't subtracted in a MUGA the EF will...If please is included the EF will...
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Falsely decrease
Falsely increase |
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Decreased washout/air trapping of radiotracer in the lower lobes suggests
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alpha 1 antitrypsin def
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Diffuse liver uptake in MDP bone scan suggests...
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Aluminum breakthrough
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What is the appearance of metastatic calcification on bone scan?
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Stomach, intense kidneys and lungs
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Gamma cammer QC: intrinsic resolution is tested with collimator on or off?
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Off
extrinisic - collimator on |
