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 (<25%) perfusion defects are equivalent to
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 < 2%). Calculation of radioactive iodine dose for treatment of Graves disease. Assessment of suspected toxic multinodular goiters."
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."