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What function that is common to the liver and spleen is used in nuclear medicine for imaging those organs?
What is the most commonly used agent for liver/spleen nuclear imaging?
99 - Tc sulfur colloid
What cells take up sulfur colloid particles in the liver?
How long does it take for the liver to take up adequate sulfur colloid in patients with normal versus abnormal hepatic function?
5 - 10 minutes in normal patients
20 - 30 minutes in patients with compromised hepatic function
What type of collimator is used for liver/spleen scans?
What is the most common right liver lobe shape variant?
Long, thin right lobe (Riedel's lobe)
What are the most common liver lobe variant shapes?
Prominent quadrate lobe
What size defects can be detected on gamma camera?
How much radiotracer usually accumulates in liver vs spleen?
What uptake pattern is seen in pelvic insufficiency fractures?
What effect do vertebral compression fractures have on the measurement of bone mineral density?
More bone in smaller volume > overestimation of bone mineral density
How does gamma x-ray emission occur?
The positron reacts with the electron causing annhilation
Release of two 511 keV photons
How much demineralization needs to occur for a lytic lesion to be visualized on radiographs?
30-50% is needed to be visualized on plain film
What type of malignancy is much more likely to produce a false-negative bone scan?
Skeletal survey is test of choice for these patients
What tumors have a propensity to metastasize to bone?
When is a single focus of increased activity associated with metastatic disease?
Single sternal lesion in patient with breast cancer
80% are metastatic lesions
What is the expected response on bone scan after initiation of successful chemotherapy?
Increased uptake by focal bone metastases
What is the differential diagnosis of diffuse symmetric increased uptake in bone with diminished activity in the kidneys?
Metastatic disease (prostate)
Metabolic disease (hyperparathyroidism)
What is the typical appearance of malignant versus benign bone lesions on initial and early blood pool images?
Malignant tumors > hyperemic
Benign tumors > Little radiopharmaceutical uptake
What types of fracture location may not show any activity on bone scan even by 14 days?
Which types of fracture show delayed increase in activity?
By 3 days, only 30% of these fratures have increased activity
What are the findings in shin splints?
Normal angiographic phase
Normal blood pool phase
Increased linear activity along posteromedial tibial cortex on delayed phase
What is the half life of Technetium 99?
What is the half life of Thallium 201?
What are the two main methods by which radioisotopes are produced?
Mother daughter system - longer half life mother decays into shorter half life daughter
What is the photon energy emitted from Technetium-99?
What are the energy peaks for Thallium?
69 to 81 KeV
What is the difference in physical vs biologic half lives of Xenon-133?
Physical half life - 5 days
Biologic half life - Seconds to minutes
What is the energy peak for Xenon?
What are the energy peaks seen in Gallium citrate?
What is the half life of Gallium citrate?
78 hour half life
What types of collimators are useful for tracking small targets?
What types of foods/drinks can interfere with coronary vasodilator agents?
Caffeine (xanthine compounds)
How does one identify sentinel node(s) on lymphoscintigraphy?
These nodes are the first to be visualized on this study
What is the most common perfusion defect seen in patients with left bundle branch block?
Reversible defect in Septum
Prior to Yttrium 90 microsphere treatment, what type of nuclear medicine study needs to be performed?
- Intra-arterial Injection of Tc-99 MAA particles into hepatic artery branch
- Lung or GI tract shunting
>20% lung shunting - contraindication to treatment
GI tract shunting > may need to embolize
What types of 24 hour iodine uptake values are seen in patients with hyperthyroidism due to Graves disease versus toxic multinodular goiter?
Graves disease - very high iodine uptake (>60%)
Multinodular goiter - mildly elevated (20-30%)
What is the difference in thyroid gland processing of Tc-99-pertechnetate versus I-123 or I-131?
I-123 and I-131 are taken up by the thyroid gland (trapping), and then are bound to tyrosine moieties (organification) to eventually form T3 and T4
Tc-99-pertechnetate - undergoes TRAPPING but no organification.
How does I-131 decay versus I-123?
Beta emission for I-131
Electon capture for I-123
What is the half life of I-131 versus I-123?
8 days for I-131
13 hours for I-123
What is the principle energy emission of Iodine-131 vs I-123?
364 keV for I-131
159 keV for I-123
What is the difference between physical half life and biological half life?
Physical half life - amount of time required for half of the material to decay via radioactive decay
Biological half life -amount of time for half of the material to be removed by body clearance mechanisms.
How does one distinguish Alzheimer's from Lewy body disease on PET?
Both - Decreased uptake in parietal and temporal lobes
Lewy body disease - Occipital lobe involvement (+/- hallucinationss)
What is the most common inherited cause of neonatal cholestasis?
Alpha-1 antitrypsin deficiency
What are the mechanisms by which gallium accumulates in inflammatory tissues?
- 1) Iron compounds (Lactoferrin, Transferrin)
- 2) Taken up by bacteria
What type of nuclear medicine study to initially evaluate for fever of unknown origin?
Labeled leukocyte study - 1/3 of infections are in the abdomen and gallium has lots interfering bowel activity
In an immunocompromised patient with a mass on CXR, what does a normal gallium scan suggest?
In an immunocompromised patient, what does bilateral diffuse uptake of gallium suggest?
Pneumocystis carinii pneumonia (PCP)
What does increased nodal uptake suggest in a patient with AIDS suggest?
Lambda sign in chest
Panda sign in parotid/salivary/lacrimal glands
What type of metastases can have increased uptake on a bone scan?
Mucin producing adenocarcinomas
Decreased parietal / temporal metabolism
Focal nodular hyperplasia
Disorganized hepatocytes have Kupffer cells that take up sulfur colloid
- "Hot nose sign"
- Decreases perfusion to internal carotid arteries, increased perfusion to the external carotid arteries
What are radionuclides?
Isotopes attempting to reach stability by emitting radiation
What occurs in alpha decay?
Emission of helium nucleus (two protons and two neutrons)
Describe beta minus decay
To achieve more optimal stability of number of neutrons vs protons, an electron (B-) is emitted from the nucleus along with an an anti-neutrino. A neutron is converted into a proton.
Describe beta plus decay
Because of an excess of protons, a beta plus particle is emitted consisting of a positron and neutrino. A proton is converted into a neutron.
Describe electron capture
Neutron deficient nuclide - capture of one of the inner orbital electrons by proton in the nucleus > formation of neutron and neutrino
Always accompanied by gamma emission
How do generator systems work versus cyclotrons?
Generator - radionuclide parent (ex. 99 Mo) with long half life is fixed to ion exchange column. Parent isotope decays to radioactive daughter (ex. 99 Tc) with shorter half life. Daughter is periodically washed off and used clinically.
Cyclotron - Irradiation of target elements with neutrons or charged particles to produce an unstable isotope
What is the physical half life of fluorine-18 (F-18)?
2 hours (110 minutes)
What are the photopeaks for Indium-111?
What is the half life for Indium-111?
What are the half lives of Strontium 89 vs other treatment radionuclides (Samarium-153 and Yttrium-90)?
Strontium 89 - Very long (50.5 days, 14 days in bone)
- Samarium-153 - 46 hours
- Yttrium-90 - 64 hours
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