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132 Cards in this Set
- Front
- Back
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Gallium-67 dose? Gamma energies? Half-life? Time to imaging?
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Dose:
5 mCi (inflam). 10 mCi (tumor). Gamma Energies: 93, 184, 296, 388 keV. T1/2: 78 hrs. Time to Imaging: 6, 24 (inflam). 48-72 (tumor). |
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Gallium-67 mechanism of uptake?
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Fe analog via transferrin.
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Gallium-67 Normal distribution?
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Liver > spleen, marrow, bone. Variable: breast, bowel, salivary glands, lacrimal glands.
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I-131 dose? Gamma energies? Half-life? Time to imaging?
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2 mCi. 364 keV. half-life 8 days. 48 hrs.
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I-131 mechanism of uptake?
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Iodine. Thyroid uptake,TSH-mediated
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I-131 Normal distribution?
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1. Stomach
2. GI 3. Bladder. Variable: salivary, nasopharynx, |
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I-131 MIBG dose? Gamma energies? Half-life? Time to imaging?
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Dose: 2 mCi.
Gamma Energy: 364 keV. Beta Energy: 606 keV T1/2: 8 days Imaging: 48 hrs. |
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I-131 MIBG mechanism of uptake?
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- Guanethidine analog.
- Norepinephrine reuptake. |
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I-131 MIBG normal distribution?
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Liver > spleen. Variable: salivary, lung, GI, bladder, skeletal muscle, heart.
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I-123 MIBG dose? Gamma energies? Half-life? Time to imaging?
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1-10 mCi. 159 keV. 13 hrs. 24 hrs.
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I-123 MIBG normal distribution?
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Liver > spleen. Variable: salivary, lung, GI, bladder, skeletal muscle, heart.
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In-111 octreoscan dose? Gamma energies? Half-life? Time to imaging?
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6 mCi. 172, 247 keV. 67 hrs. 4, 24 hrs.
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Octreoscan mechanism of uptake?
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Somatostatin analog. Neuroendocrine tumors.
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In-111 octreoscan normal distribution?
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Intense renal cortex. Spleen, liver, pituitary, salivary, GI, bladder. Variable: breast, thyroid.
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FDG-PET dose? Gamma energies? Half-life? Time to imaging?
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10-15 mCi. 511 keV. 2 hrs. 1 hr.
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FDG-PET mechanism of uptake?
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Glucose analog. Active transport into cell. Phosphorylated and trapped.
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FDG-Pet normal distribution
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Intense urinary activity and cerebral cortex. GU, liver, spleen, marrow. Variable: thyroid, cardiac, GI, muscle.
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In-111 WBC dose? Gamma energies? Half-life? Time to imaging?
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Dose: 0.5 mCi.
Energies: 172, 247 keV. T1/2: 67 hrs. Imaging Time: 24 hrs. |
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In-111 WBC mechanism of uptake?
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WBC localized at infection.
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In-111 WBC normal distribution?
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Spleen >> Liver > marrow. No renal or GI activity.
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Tc-99 WBC dose? Gamma energies? Half-life? Time to imaging?
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20 mCi. 140 keV. 6 hrs. 1-4, 24 hrs.
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Intense cardiac activity radiotracer?
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MIBG. PET.
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Intense spleen activity radiotracer?
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WBC.
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Intense renal activity radiotracer?
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Octreotide.
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With which radiotracer do you see lacrimal activity?
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Gallium-67.
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For about __ months after hip replacement surgery, the bone around the prosthesis is expected to have increased osteoblastic activity.
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6 months.
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Refers to a hot spot at the tip of a prosthesis and two areas of increased uptake at the proximal end.
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Toggle sign. Prosthetic loosening.
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Three phases of bone scan osteomyelitis?
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1. First phase: Early arterial flow, seconds after injection.
2. Second phase: Blood pool, few minutes after injection. 3. Third phase: Bone labeling, 3 or more hours after injection. All three positive in infection. |
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Contraindications to perfusion lung scanning include
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Severe pulmonary hypertension. Allergy to human serum albumin products.
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Common indication for V/Q scans
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1. Suspected PE.
2. Preoperative estimates of lung function. 3. To evaluate right-to-left shunts. 4. Serial assessment of inflammatory lung disease. |
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When should a V/Q scan be ordered over CTA?
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1. Low clinical probability.
2. CXR is normal. 3. Pregnant patient. 4. Contraindication to iodinated contrast. |
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Normal ventilation scans
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Homogeneous radiopharmaceutical distribution throughout both lungs on all three phases: Initial breath. Equilibrium. Washout.
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Retention (trapping) of xenon in the lungs in a focal or diffuse pattern is an indication of
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Obstructive lung disease.
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Normal perfusion scans
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Well-defined margins of both lungs on all views. Sharply defined costophrenic angles.
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Hampton hump
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Wedge-shaped, pleural-based infarct on CXR.
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Westermark sign
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Wedge-shaped area of oligemia.
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Most common but nonspecific CXR finding of PE
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Atelectasis or opacities in the region of emboli. Elevated diaphragm, small pleural effusion, and/or prominent hilum are also frequently seen.
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Two moderate (25-50%) or four small (<25%) perfusion defects are equivalent to
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Full-segment defect.
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Perfusion defect that demonstrates normal ventilation is termed a
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Mismatched defect.
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Perfusion defects that match ventilation and CXR abnormalities in size and location are called
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Triple match defects.
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Stripe sign.
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Central perfusion defects with a rim or stripe of increased activity around them. Less than 10% probability of PE.
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V/Q scan PIOPED categories?
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High (2 or more mismatched perfusion segments). Intermediate. Low. Very low. Normal.
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Ventilation scan signs in COPD?
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Delayed wash-in and delayed washout.
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Perfusion defects that are significantly larger than the CXR abnormality are
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Higher probability for PE.
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Three principle coronary artery distributions of the LV
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Left anterior descending artery (LAD). Left circumflex artery (LCX). Posterior descending artery (PDA).
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Pharmocologic stress agents in myocardial perfusion imaging?
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Adenosine. Dipyridamole (if bronchospasm may give dobutamine).
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At what percent stenosis can pharmocologic agents not dilate effectively?
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> 50% stenosis.
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Tc-99m Sestamibi is taken up by perfused myocardium by
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Passive diffusion. Bound in myocyte, mostly within myocardial mitochondria.
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Hibernating Myocardium
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- Severe ischemia with high-grade stenosis may be slow to reverse on Tl-201 rest imaging after stress.
- Respond to revascularization procedures. - Perfusion-metabolism mismatch. |
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Stunned Myocardium
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Temporarily damaged cells around infarct. Generally is hypokinetic or akinetic. Will not uptake Tl-201 until recovery several weeks later. Normal perfusion.
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Solitary palpable thyroid nodules are best evaluated initially
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FNA.
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Discordant thyroid nodule
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Increased Tc-99m-O4 uptake but decreased I-123 uptake (lost ability to organify iodine). Increased risk of malignancy.
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Measurement of the RAIU is usually indicated for one of three reasons:
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1. Differentiation of Graves disease (uptake high, usually >35% at 24 hours) from subacute or factitious hyperthyroidism (uptake usually < 2%).
2. Calculation of radioactive iodine dose for treatment of Graves disease. 3. Assessment of suspected toxic multinodular goiters. |
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Lingual thyroid pediatric patients are at high risk of developing
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Hypothyroidism, with an estimated risk of ~30%.
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Causes of hyperthyroidism?
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1. Graves disease (diffuse toxic goiter) is most common.
2. Subacute or painless thyroiditis. 3. Toxic nodular goiter. 4. Factitious hyperthyroidism. |
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Substernal goiter imaging?
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- I-123.
- Due to large blood pool, Tc-99m-O4 is not useful with substernal goiters. |
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Multinodular goiter
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- Clinical term for adenomatous hyperplasia.
- Multiple, discrete hot nodules on a background of normal or cool parenchyma. - Photopenic regions should be palpated. |
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All types of thyroiditis are characterized by
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- Rapid, asymmetric glandular enlargement with or without nodularity.
- Subacute viral patients have a very low RAIU. |
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Graves disease
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Most common cause of hyperthyroidism. Autoimmune disorder, thyroid-stimulating antibodies cause hyperplasia and hyperfunction of thyroid gland.
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Acute (suppurative) thyroiditis
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- Bacterial infections caused by Streptococcus, Staphylococcus, or Pneumococcus.
- Fever, severe sore throat, and asymmetric swelling. - May result in sepsis from hematogenous spread or extend into mediastinum via fascial planes. |
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Subacute (viral) thyroiditis (de Quervain or granulomatous thyroiditis).
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- Thyroid pain and hyperthyroidism following upper respiratory infection.
- Disrupted gland releases thyroid hormone. - Iodine uptake is usually decreased or absent in acute stages. |
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Hashimoto thyroiditis
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Most common cause of goiter and primary hypothyroidism in adults in developed countries. Autoimmune disorder with circulating antithyroid antibody.
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Riedel thyroiditis
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Rare inflammatory fibrosiS that involves thyroid and commonly extends into neck. Radionuclide uptake is absent (cold) in involved areas.
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Secondary hyperthyroidism may develop in patients with
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Hydatidiform moles or choriocarcinoma (secrete HCG). Subunit of HCG is similar to TSH, which may directly stimulating thyroid.
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Single cold nodules have a _______ incidence of malignancy, whereas malignancy is exceedingly rare in hot nodules.
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10% to 15%.
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Thyroid nodule differential
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Follicular adenoma. Adenomatous hyperplasia. Thyroid cysts. Hemorrhagic cyst.
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Most common benign neoplasm of the thyroid and represents about 20% of thyroid nodules.
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Follicular adenoma.
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Adenomatous nodules, also called ________, are not true neoplasms but are the result of cycles of hyperplasia and involution of a thyroid lobule.
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Colloid nodules.
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Signs Suggesting Benign Etiology of Thyroid Nodules
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Extensive cystic component. Multiple nodules. Hot on radionuclide scan. Peripheral calcification. Shrinkage in size following levothyroxine suppression hormone therapy. Sudden onset. Female gender. Older patient.
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Signs Suggesting Malignancy of Thyroid Nodules
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Solid nodule. Cold on radionuclide scan. Irregular contour. Poor margination. Size >4 to 5 cm.
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Thyroid malignancies
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Papillary carcinoma. Follicular carcinoma. Medullary thyroid carcinoma. Anaplastic carcinoma.
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This thyroid malignancy does not take up I-131?
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Medullary thyroid carcinoma.
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Most authorities agree with postthyroidectomy ablation in primary thyroid tumors that are > _____ cm?
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> 1.5 cm.
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The patient should be hypothyroid with a serum TSH greater than_______ prior to whole body I-131 imaging or ablation,
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40 IU/Ml.
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Radioiodine therapy side effects?
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Sialoadenitis. Xerostomia. Pulmonary fibrosis. Leukemia.
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Ectopic locations for abnormal parathyroid tissue include:
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Thymus (10% to 15%). Posterior mediastinum (5%). Retroesophageal (1%). Within carotid sheath (1%). Parapharyngeal (0.5%).
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Sestamibi and Tetrofosmin Imaging of parathyroid adenoma?
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Immediate and delayed images of neck and mediastinum. May be cold on initial imaging. Hot on delayed (1-2 hours) imaging. Normal thyroid gland washes out.
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Which parathyroid glands are more commonly ectopic?
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Inferior parathyroid glands (from third branchial pouch along with thymus). Usually within mediastinum.
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Positive GI bleeding studies demonstrate three cardinal findings:
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1. Focal activity appears out of nowhere.
2. Activity persists and may increase with time. 3. Activity moves with peristalsis antegrade, retrograde, or in both directions. |
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Meckel Scan
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Tc-99mO4. Activity concentrates within right lower quadrant or mid abdomen in synchrony with stomach (ectopic gastric mucosa).
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Liver/Spleen Scan
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Tc-99m-radiolabeled albumin or sulfur colloid. RES cells phagocytize colloid particles.
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FNH sulfur colloid scan features
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Isointense or hotter than liver parenchyma.
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Heat-Damaged Red Blood Cell Scan
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Tc-99m-labeled heat damaged red blood cells are preferentially extracted from circulation by splenic tissue. Useful for: Polysplenia. Splenosis. Accessory splenic tissue.
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Normal HIDA scan (Tc-mebrofenin)
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Activity should be seen in major extrahepatic ducts, gallbladder, and small bowel within 1 hour.
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Hallmark of acute cholecystitis by cholescintigraphy is
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Nonvisualization of gallbladder at both 1- and 4-hour intervals or 30 minutes after morphine administration.
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Chronic cholecystitis scintigraphy features
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Gallbladder is not visualized at 1 hour but is seen by 4 hours.
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Rim sign on hepatobiliary scan images
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Band of increased activity around gallbladder fossa. Represents poor excretion of radiotracer from inflamed hepatocytes. Usually associated with gangrenous cholecystitis
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Normal gallbladder ejection fraction is greater than
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35%.
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Acalculous biliary disease
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Chronic acalculous cholecystitis. Cystic duct syndrome. Gallbladder dyskinesis.
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CCK-assisted cholescintigraphy in acalculous biliary disease demonstrates
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Decreased gallbladder contraction. Decreased gallbladder ejection fraction.
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Which scintigraphy study is used in diagnosing liver cavernous hemangiomas?
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Tc-99m-labeled red blood cells using an in vitro labeling technique.
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________ is the agent of choice for imaging kidneys in moderate to severe renal failure.
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Tc-99m-MAG3.
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Agent of choice for renal cortical imaging?
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Tc-99m-DMSA has minimal urinary excretion (<5%) and high cortical binding (50%).
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Radiotracers used to assess GFR and ERPF (plasma flow)?
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1. GFR with Tc-99m-DTPA.
2. ERPF with Tc-99m-MAG3. |
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Renal vein thrombosis scintigraphic findings?
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Decreased perfusion of enlarged kidney with prolonged cortical retention of tracer.
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Renal transplant complication timeline?
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1st week: ATN
2nd-4th week: Acute rejection Early: Urinoma Several Weeks: Lymphoceles Later: Chronic rejection |
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ACEi effect on RAS?
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Angiotensin II causes constriction of efferent arteriole. ACEi blocks Angiotensin II. In RAS ACEi causes relaxation of constricted efferent arteriole, decreasing GFR.
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Ga-67 imaging is the radionuclide procedure of choice in what patient population?
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Immunocompromised patients. Patients with FUO.
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_________ is the radionuclide procedure of choice for diagnosing osteomyelitis.
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Three-phase bone scintigraphy.
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Three-phase bone scan findings in osteomyelitis?
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Focal hyperperfusion. Focal hyperemia. Focally increased bony uptake on delayed (2 to 4 hours postinjection).
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Can all produce a positive three-phase bone scan, even in the absence of infection.
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Fractures. Orthopedic hardware. Neuropathic joint.
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Pores of Kohn
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Connect adjacent alveoli.
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Canals of Lambert
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Connect alveoli with respiratory, terminal, and preterminal bronchioles.
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Typical V/Q scan finding for PE
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Mismatched segmental or subsegmental distribution pattern, usually peripheral and wedge shaped in nature.
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Xenon-133 properties
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Half-life of 5.3 days. Beta emitter. Photon energy 81 keV. Trachea is critical organ. Should be performed before perfusion lung scans due to Compton scatter from Tc-99m.
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Patients who should receive fewer particles of Tc-99m-MAA?
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Pulmonary hypertension. Right to left shunts. Children.
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Standard cisternogram features
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- Intrathecal indium-111-DTPA.
- Ascends to basilar cisterns in about 4 hours. - Flows over convexities within 24 hours in normals. |
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NPH cisternogram features
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Early localization of activity within lateral ventricles persisting beyond 24 hours. Delayed clearance over convexities.
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Procedure of choice for CSF leak
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Cisternogram.
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Classic findings in PET brain imaging of Alzheimer's disease
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Bilateral temporoparietal defects.
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PET brain imaging basics of brain tumors
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High-grade tumors are hypermetabolic. Low-grade tumors are hypometabolic (except juvenile pilocystic astrocytoma).
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FDG activity in gallbladder bed suggests
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Acute or chronic cholecystitis. Gallbladder cancer. Adjacent liver tumor.
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Common brown fat location?
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Symmetric uptake in paraspinal regions, mediastinum, neck, and supraclavicular area.
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Most malignant tumors have an SUV of
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2.5 to 3.0.
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Physiologic activity usually has an SUV of
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0.5 to 2.5.
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PET is utilized in oncology for three major indications:
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Initial staging. Evaluation of response to treatment. Assessment for recurrence.
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Malignant pulmonary nodule at PET imaging
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SUV greater than 2.5 is considered indicative of malignancy. SUV under 1.5 is considered a benign nodule.
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With small nodules less than _______cm, the partial volume averaging effect may falsely lower the SUV below 2.5, even though the nodule is malignant.
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less than 1.5 cm
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PET false-positives for malignant pulmonary nodule
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1. Tuberculosis, Fungal infections.
2. Sarcoidosis. |
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Pulmonary nodule false-negative cases are usually hypometabolic malignancies, such as
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Bronchoalveolar carcinoma. Carcinoid tumor.
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Radiation pneumonitis is metabolically active in the first ___ months following radiotherapy, making detection of tumor recurrence by PET difficult
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6 months
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PET false positives for lymphoma search
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Hypermetabolic sarcoidosis. Tuberculosis. Pyogenic abscesses. Histoplasmosis and other fungal infections. Discitis.
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Diffuse splenic activity greater than that of _______ is consistent with diffuse lymphomatous infiltration of the spleen.
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Liver activity.
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Preferred diagnostic modality for melanoma region lymph node involvement
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Sentinel lymph node mapping.
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Benign causes of distal esophagus PET activity
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1. Distal esophagitis.
2. Gastric reflux. 3. Barrett's esophagus. 4. Hiatal hernia. 5. Retained saliva. |
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Tumor activity more than ____ times that of white matter or more than ____ times that of gray matter has very high sensitivity and specificity for malignancy
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1.5 times white matter. 0.6 times gray matter.
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PET features of Alzheimer disease
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Bilateral hypometabolism of temporal and parietal lobes. Sparing of visual and motor cortices.
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PET features of Pick disease
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Hypometabolic areas involving both frontal and anterior temporal lobes.
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PET features of Multi-infarct dementia
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Multiple defects throughout brain parenchyma without sparing of visual and motor cortices.
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PET features of Parkinson disease
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High FDG activity in lentiform nuclei and thalami related to lack of dopaminergic inhibition. Caudate nuclei are spared.
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PET features of CNS lymphoma versus toxoplasmosis
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1. CNS lymphoma is hypermetabolic.
2. Toxoplasmosis shows little or no FDG activity. |
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Malignant Tumors with Low PET Uptake
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1. Lobular breast carcinoma.
2. Low-grade lymphoma. 3. Salivary gland neoplasms. 4. Necrotic primary tumors and lymph nodes. |
