Nuclear Medicine Flashcards

Question

Diagnosis? Cause? Differential?

Answer 1

**Hypertrophic osteoarthropathy**. Can be primary (rare, pachydermoperiostosis) or secondary (HPOA, secondary to tumors involving the pleura or inflammatory pleural disease. Can also be secondary to inflammatory GI/liver disease- IBD, celiac, PBC). Also get clubbing of fingers/toes, skin thickening, painful joints. May regress after underlying disease treated. Shin splints (confined to mid-distal tibia), venous stasis (typically below the knees).

Answer 2

**Tc99m-MIBI** _early and delayed imaging_. Tracer binds to increased mitochondria in abnormal parathyroid glands. Tracer also binds to normal thyroid early; it washes out of the thyroid late but persists in abnormal parathyroids. More sensitive for parathyroid adenoma than hyperplasia. _Note- MIBI is a nonspecific tracer_. Focal uptake can represent parathyroid adenoma, parathyroid carcinoma, thyroid adenoma, thyroid carcinoma, mets, lymphoma, or infection/inflammation. Clinical history important.

Answer 3

Dedifferentiated thyroid carcinoma may not be I131 avid, but would be seen on PET/CT. (although these sometimes still respond to high dose I131 therapy) Low-grade papillary and follicular cancers, on the other hand, may be non-FDG avid, but radioiodine-avid. Medullary thyroid cancer is also not iodine avid, but can be seen with octreotide or MIBG. Note: TSH levels should be \> 30 microU/mL before doing any studies. Can pre-treat with Thyrogen instead to avoid hypothyroid state if necessary, but will not be quite as sensitive.

Answer 4

Immediate uptake in the stomach, salivary glands, and thyroid. 2 strep process. 1) Provide an intercellular reducing agent (cold tin) then 2) introduce Tc99m to bind to hemoglobin. These steps can each be performed in a test tube (in vitro) or in vivo. Test tube provides better labeling efficiency.

Answer 5

**Brain death** (hot nose sign due to preferential ECA flow and no ICA flow). Note - can see some venous activity in the transverse or sagittal sinus due to scalp collaterals, even when no ICA flow. Can use almost any tracer labeled with **Tc99m**. HMPAO and ECD (Neurolite) are brain-specific, allowing delayed imaging to ensure no cerebral flow. Other agents (pertechnetate, DTPA, glucoheptonate) can be used for dynamic angiographic images.

Answer 6

Artifact of upright Tc99m-MAA injection. If symmetric and no matched (Xe133 or Tc99m-DTPA aerosol) ventilation defect. PE- if no matched ventilation defect. Typically not symmetric, usually includes lower lobes as well (lower lobes receive the most blood flow). Asthma/COPD- commonly demonstrates symmetric uper lobe perfusion abnormalities, but you should see a matched ventilation abnormality.

Answer 7

90% must be 10-90 micrometers, with no particle \>150. Injection of 200,000-600,000 particles is typical, which occludes about 0.1% of pulmonary capillaries temporarily. This particle number can be decreased in patients with pulmonary arterial HTN, pregnancy (minimum 100,000). Note- always perform ventilation images before perfusion.

Answer 8

MAG3 is better for collecting system evaluation because of its unique excretion pathway- active tubular secretion (vs glomerular filtration with DTPA). Also, MAG3 activity can be seen in the gallbladder.

Answer 9

To "wash" tracer from the collecting system into the bladder. Following diuretic a half-time renal pelvic washout of \<10 minutes is normal, \>20 minutes is obstructed. 10-20 min is indeterminate.

Answer 10

After elution of the generator. This is the fraction of the total radioactivity that is from Tc99m. The allowable limit is **\< 0.15 μCi of Mo99 per mCi of Tc99m at the time of administration** (ratio changes over time due to longer half life of Mo99). Checked by placing it in a lead pig that allows the penetration of the higher activity Mo99 (739/778 keV), check that level then check all activity. Record ratio.

Answer 11

_Infected jt prosthesis_: discordant increased In111-WBC uptake, normal Tc99m-SCOL uptake. For _loosening_, will see normal, equal uptake on both due to marrow packing. No increased uptake. (Activity is increased on a Tc99m MDP bone scan for both infection and loosening.) _Osteomyelitis_: concordant increased In111-WBC and Tc99m-SCOL uptake.

Answer 12

They are all B- emitting agents for the treatment of widespread osteoblastic metastatic bone pain. Only Samarium 153 can be imaged because it also emits gama rays. Side effect from all- thrombocytopenia and leukopenia (temporary).

Answer 13

**Right to left shunt** (ASD, PDA, pulmonary AVM, cirrhosis) with Eisenmenger physiology- elevated right heart pressures. In this case, you will see activity in the brain. **Free pertechnetate**. Activity in the kidneys and/or thyroid, but not in the brain. Recent prior nuclear study. No brain activity, history.

Answer 14

Intrinsic- collimator OFF. Measure the performance of the crystal and electronics. Done weekly. Extrinsic- collimator ON. Measures performance of the entire system. Done daily before clinical use. Note- the source must be at a distance at least 5x the useful field of view of the camera head to ensure uniform distribution of energy across the head.

Answer 15

Lytic mets- renal, thyroid. Plasmacytoma or multiple myeloma. Acute bone infarcts (usually increased uptake when subacute-chronic due to healing). Prior external-beam radiation.

Answer 16

**Obstructive communicating hydrocephalus** (NPH is a subtype of this but can't distinguish w/o LP). This is an _indium-111 DTPA_ scan. Normally, should see migration over the convexities by 24 hours, no later than 48 hours, and should never see activity in the ventricles. MRI may help for defining who will respond to shunting. Look for CSF flow void in the cerebral aqueduct and 3rd ventricles, and ventricular dilation out of proportion to sulcal atrophy. _Type 4_ benefits from shunting. This is based on the cisternogram- poor clearance and persistent ventricular activity.

Answer 17

Thyroid cancer- only 15-20% but needs to be excluded. Most common- papillary, follicular, followed by medullary, Hurthle cell, and anaplastic. Most are benign- colloid nodule, simple cyst, hypofunctioning thyroid adenoma. But if not completely cystic on ultrasound, it needs to be biopsied.

Answer 18

Papillary- regional mets. Follicular- distant hematogenous mets. Medullary thyroid Ca- elevated calcitonin levels. Arise from C cells (parafollicular).

Answer 19

Granulocyte colony stimulating factor (G-CSF) therapy, post chemotherapy, erythropoietin therapy. Myelodysplatstic syndromes, beta thalassemia, chronic myeloid leukemia (CML), interleukins in pyrexic states, cytokines in tumours, diffuse marrow metastases (less likely), severe anemia (hyperplastic marrow).

Answer 20

After the 10th week.

Answer 21

Probably octreoscan, MIBG scan, or iodine-131 scan.

Answer 22

Neuroendocrine tumors- most islet cell tumors (except insulinomas not as well), pituitary adenomas, pheochromocytomas. Also can be positive with: small-cell lung cancers, meningiomas, astrocytomas, some breast cancers and lymphomas.

Answer 23

Thyroid bed remnant: 30-100 mCi. Local lymph node mets: 150 mCi. Lung mets: 175 mCi. Bone mets: 200 mCi. Orally administered- the patient needs to have elevated TSH at the time of administration. A patient can be released from the hospital if the projected dose to an individual member of the public doesn't exceed 5 mSv based on dose calculations, with instructions if exposure likely to exceed 1 mSv.

Answer 24

If in the lower longs, it's intermediate probability for PE. If in the mid/upper lungs, it's low probability. (A "stripe sign" on V/Q- preserved peripheral perfusion with a more central defect- is very low probability.)

Answer 25

To determine whether or not renal artery stenosis is the cause of hypertension- **renovascular hypertension**. Do a MAG3 or DTPA renal study with and without an ACE inhibitor (like captopril). Look for decreased renal function in patients with RVH, on the side of the stenosis. If function stays normal, it excludes RVH. If both kidneys decrease it could be bilateral RVH, but make sure it's not transient hypotension from the ACE inhibitors.

Answer 26

For all therapeutic radiopharmaceuticals and for diagnostic doses of I-131 \> 30 μCi. _Recordable_: \>20% error, whole body dose \<5 rem (50 mSv). **Reportable**: \>20% error and whole body dose \>5 rem (50mSv) or single organ dose \>50rem (500 mSv).

Answer 27

**Gallium scan** (iron analogue, nonspecific uptake in some tumors esp lymphoma and melanoma, and active inflammation). Do delayed images (48-72 hours) because there is some initial renal and lung uptake that can be normal, but normal activity should clear out within the first 24 hours. Diagnosis: **Sarcoid**. ("Lambda sign" = due to symmetric mediastinal and hilar uptake. "Panda sign" = due to involvement of the lacrimal, parotid, and salivary glands) Other considerations would be lypmhoma, other infectious process.

Answer 28

**Heat-damaged RBC scan.** Still has some blood pool and liver activity, but lower than on non-damaged RBC scan, and has _increased affinity for splenic tissue_. Could also use sulfur colloid scan, however the target to background ratio is not as high.

Answer 29

Hypercalcemia. Diffuse uptake in stomach, lungs, myocardium, and renal parenchyma.

Answer 30

Could do FDG-PET... recurrence will have uptake greater than the white matter (doesn't need to be as high as grey matter), radiation necrosis will not have uptake.

Answer 31

**Biliary atresia**. Prenatal biliary inflammation leading to fibrosis and atresia. NO bowel activity at 24 hours (seeing any in bowel excludes BA). 25% of patients have a gallbladder, so can see activity there. Main differential is _neonatal hepatitis_. Would typically see some bowel activity at 24 hours and delayed blood pool clearance due to hepatocyte dysfunction, but not necessarily. Treatment- surgical. Kasai procedure (portoenterostomy) to eliminate atretic portion and bring the duodenum closer to the liver.

Answer 32

**Subacute thyroiditis.** Markedly decreased thyroid radioiodine uptake (normal 10-30% at 24 hours). Most common subtype is DeQuervain (granulomatous), also includes postpartum. Self-limited. Painless etiologies of hyperthyroidism with low thyroid uptake include _thyrotoxicosis factitia_, _struma ovarii_, and _iodine or amiodarone induced thyrotoxicosis_. Primary or secondary hypothyroidism would also have low uptake, but these patients would present with hypothyroid.

Answer 33

PE- multiple mismatched, wedge-shaped segmental and subsegmental perfusion defects. Microembolic disease: multiple linear mismatched perfusion defects outlining the periphery of segments. "Segmental contouring" or "contour mapping" sign. See pic below.

Answer 34

**Lingual thyroid**- failure of descent of the embryologic thyroid anlage from the posterior tongue. Often _hypothyroid_. May present with obstruction to breathing or swallowing with larger lesions. Other (rare) locations for thyroid ectopy- submandibular glands, trachea, cervical lymph nodes. On unenhanced CT, it will be higher attenuation because it is iodine-rich. Keep in mind that any disease that can affeect the normal thyroid can affect a lingual thyroid, so you can get ca here. Also, avoid biopsy because of risk for hemorrhage and precipitation of thyroid storm.

Answer 35

The US DOT defines radiation levels as: **White I**: \<0.5 mrem/h at package surface and 0 at 1 m. (Radioimmunoassay kits usually shipped as white 1) **Yellow II**: \<50 mrem/h at package surface *and* \< 1 mrem/h at 1 m. (Radiopharmaceuticals are shipped as yellow 2) **Yellow III**: \> 50 mrem/h at package surface *or* \> 1 mrem/h at 1 m. (Generators shipped as yellow 3) **Procedure**: Must be opened w/in 3 hours. Wear gloves, inspect package for signs of damage, monitor external radiation levels at surface and 1 m, wipe test, open and check packing slip, inspect radioactive material container, deface all radioactive labels before discarding packaging. Make a record of package receipt and _keep for at least 3 years_. Must notify the delivery company, RSO, and NRC if activity of a package is \> 200 mrem/h at surface or \> 10 mrem/h at 1 m.

Answer 36

Hot quadrate- due to SVC obstruction (with upper extremity tracer injections). Hot caudate- due to hepatic vein thrombosis (Budd-Chiari) as a consequence of separate and unaffected venous drainage from the caudate lobe directly into the IVC.

Answer 37

Normal flow with normal extraction, but _severe cortical retention with minimal excretion into the collecting system_. The most common causes of ATN include ischemia, sepsis, and renal toxic drugs. In acute transplant rejection, there is delayed flow/extraction.

Answer 38

Defect on all 3 - ventilation, perfusion, and x-ray (xray defect must be smaller than perfusion defect). If in lower 1/3 of lungs, it's intermediate probability for PE. Upper, it's very low probability. The other way to be intermediate probability (more common) is 1-3 moderately sized mismatched perfusion defects.

Answer 39

_Pertechnetate is trapped_ by the thyroid, _radioiodine is organifie_d by the thyroid (oxidized and incorporated into tyrosine). In an _organification defect_, which can be congenital or acquired (chronic thyroiditis), the patient is hypothyroid. Pertechnetate scan will be normal, radioiodine will show very low 24 hour uptake. The recovery phase of thyroiditis can have this same appearance, when trapping has returned to normal but organification is still inhibited.

Answer 40

Either with **delayed thalium201 SPECT **(potassium analogue, marker of cell membrane integrity, will distribute to hibernating, not infarct) or **cardiac viability PET** (uptake in hybernating, not infarct).

Answer 41

**Complex regional pain syndrome** (Reflex sympathetic dystrophy). CT/plain film: periarticular osteopenia. **MRI** can demonstrate soft-tissue edema and enhancement, skin thickening, and muscle atrophy. **Bone scan** will demonstrate increased blood flow, blood pool, and delayed phase periarticular uptake. In the chronic "burned-out" phase, all 3 stages can be down.

Answer 42

**Tc99m-DTPA** (often used for VP shunt studies, quicker study, less expensive, less radiation). or **Indium111-DTPA** (better for leak studies when delayed imaging may be necessary b/c of longer half life).

Answer 43

**Indium 111 labeled capromab pendetide**, an antibody targeted to prostate-specific membrane antigen (PMSA), which is over-expressed in prostate cancer. For detecting _soft tissue recurrence/mets_. Image 4-6 days following injection. Rarely, other tumors can be avid too. See blood pool, _intense liver_, bone marrow, and bowel activity.

Answer 44

Most centers use Tc99m labeled MIBI or TETRO at rest and thallium 201 or Tc99m-MIBI/TETRO at stress. Thallium is a higher dose and lower quality images, but can be used for redistribution imaging if there is a resting perfusion defect. Can use dobutamine or adenosine/regadenason. Adenosine is contraindicated with active bronchospasm and heart block, and it's effects are inhibited by caffeine (can lead to false negatives).

Answer 45

Calculated from the _perfusion_ images. Multiply current FEV1 by the percentage of perfusion to the lung that is going to be remaining post-op (based on an old ACCP recommendation). A post-operative FEV1 \> 800 mL is considered adequate.

Answer 46

Tc99m, Tl201: 100 mCi. Ga67, In111: 10 mCi. I131: 1 mCi. Notify radiation safety officer for all spills. **Minor spill:** notify personnel, cover with absorbant paper, clean while wearing protection, place cleaning materials etc in a bag marked "caution: radioactive material," monitor for residual contamination. **Major spill:** clear area/evacuate others, cover with absorbant paper, shield around source if possible, close and secure room, mark the area with caution signs, decontaminate involved personnel. Note- for xenon gas spill, everyone should leave the room immediately and the door should be closed for (precalculated) amount of time based on activity.

Nuclear Medicine Flashcards

(70 cards)