Free Nuclear Medicine Exam Questions That Helps Candidates Pass

Comprehensive and Detailed Explanation: Most Tc-99m kits contain stannous (tin II) chloride as the reducing agent. Pertechnetate (Tc-99m in the +7 oxidation state) does not readily bind to most ligands. Stannous ion reduces technetium to a lower oxidation state (typically +4 or +5), allowing chelation with the ligand (e.g., MDP, DTPA, sestamibi). Excess stannous ion must be carefully controlled; too little results in free pertechnetate, while excessive amounts can cause colloidal formation or instability. Ascorbic acid is sometimes used as an antioxidant or secondary reducing agent but is not the primary reductant in standard kits. Sodium pertechnetate is the starting material eluted from the generator. Aluminum oxide is the column material in the Mo-99/Tc-99m generator. Proper kit preparation technique, including correct volume of eluate, mixing, and incubation time, is critical for radiochemical purity and patient safety.

Comprehensive and Detailed Explanation: Indium-111 has a physical half-life of approximately 67 hours (2.8 days). It decays by electron capture and emits two principal gamma photons (171 keV and 245 keV), making it suitable for labeling leukocytes, antibodies, and peptides with imaging performed at 24 hours or later. The half-life is long enough for delayed imaging yet short enough to limit radiation dose compared with longer-lived radionuclides. Technologists must account for this half-life when scheduling studies, calculating residual activity, and planning waste storage. Medium-energy collimators are required because of the higher photon energies.

Comprehensive and Detailed Explanation: Hepatobiliary scintigraphy with Tc-99m IDA derivatives (mebrofenin or disofenin) is used to differentiate biliary atresia from neonatal hepatitis. In biliary atresia, no activity reaches the bowel even on delayed images up to 24 hours, whereas in hepatitis some excretion is usually seen. Phenobarbital pretreatment is often used to enhance excretion. Sulfur colloid, MDP, and MAA are not appropriate for this indication. Technologists must obtain delayed images as needed, maintain careful positioning of small patients, and coordinate with the clinical team regarding pretreatment. Accurate technique is critical because the scan results directly influence the decision for timely surgical intervention.

Comprehensive and Detailed Explanation: Even a properly functioning gamma camera exhibits small residual variations in sensitivity across the field of view caused by differences in PMT gain, light collection, and electronics. A high-count flood is used to generate a correction matrix that is applied to every subsequent clinical image, equalizing the response. The map must be acquired with the same collimator and energy settings used clinically and must be updated when significant changes occur. Without an accurate, current uniformity map, SPECT reconstructions develop ring artifacts and planar images may show subtle hot or cold areas. Technologists are responsible for ensuring that the correct map is loaded before patient studies begin.

Comprehensive and Detailed Explanation: Patients released after I-131 therapy must receive written instructions explaining how to keep doses to other individuals as low as reasonably achievable. Typical instructions cover distance from others (especially children and pregnant women), sleeping arrangements, personal hygiene, handling of bodily fluids, and the duration of restrictions. Providing and documenting these instructions is a regulatory requirement. The written directive authorizes the administration; the instruction sheet protects the public after release. Technologists often review the instructions verbally with the patient to ensure understanding before discharge.