Free Nuclear Medicine Exam Questions That Helps Candidates Pass

Comprehensive and Detailed Explanation: The daily constancy test uses a long-lived sealed source measured under identical geometry each day. The reading is compared with the decay-corrected expected value and must fall within institutional limits (commonly ±5 % or ±10 %). This rapid check detects electronic drift, chamber contamination, or other sudden changes that could cause incorrect patient doses. Linearity, geometry, and accuracy tests are performed less frequently. Failure requires the calibrator to be removed from service until corrected. Documentation of daily results is a required quality-control record.

Comprehensive and Detailed Explanation: Regulations require periodic physical inventory of all sealed sources (dose-calibrator reference sources, marker sources, calibration sources, etc.). The inventory confirms that each source is present in its assigned location and that records of identity and activity are accurate. Missing sources must be reported immediately. Inventory is performed in addition to, not instead of, leak testing. Technologists often assist the radiation safety officer with the inventory. Accurate source control prevents loss of radioactive material and is a standard item examined during regulatory inspections.

Comprehensive and Detailed Explanation: Flood-field uniformity testing assesses whether the camera responds evenly across the entire field of view. An intrinsic flood (without collimator, using a point source at a distance) or an extrinsic flood (with collimator and a sheet source) is acquired. Visual inspection and quantitative calculation of integral and differential uniformity are performed. Non-uniformities can arise from PMT gain differences, crystal defects, or electronics problems and, if uncorrected, produce artifacts in clinical images, especially SPECT. Daily floods are standard practice. Correction matrices generated from high-count floods are applied during acquisition. Technologists must recognize acceptable versus unacceptable uniformity and know when to take a camera out of service.

Comprehensive and Detailed Explanation: Hepatobiliary scintigraphy using Tc-99m IDA derivatives (e.g., mebrofenin or disofenin) is primarily indicated for the diagnosis of acute cholecystitis, evaluation of biliary obstruction, assessment of bile leaks, and measurement of gallbladder ejection fraction. Non-visualization of the gallbladder after adequate hepatic uptake and excretion is the classic finding in cystic-duct obstruction. Morphine augmentation or delayed imaging may be used when the gallbladder is not seen on early images. Renal studies use different agents (MAG3, DTPA). Lung perfusion uses MAA. Lymphoma staging is typically performed with FDG PET/CT. Proper patient preparation (NPO for several hours) and knowledge of interfering medications (opioids, etc.) are important for accurate results. Technologists must time the imaging sequence correctly and recognize when pharmacologic intervention is required.

Comprehensive and Detailed Explanation: Technetium-99m emits a principal gamma photon of 140.5 keV (commonly rounded to 140 keV). This energy is ideal for Anger-camera imaging because it provides good tissue penetration while being efficiently stopped by the NaI(Tl) crystal and low-energy collimators. The 69–80 keV x-rays are characteristic of thallium-201, 364 keV of iodine-131, and 511 keV of positron annihilation. Correct knowledge of photon energy is essential for selecting the proper energy window, collimator, and attenuation-correction parameters.