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