NMTCB Positron Emission Tomography (PET) Practice Exam 2025 - Free PET Practice Questions and Study Guide

The photopeak energy of an isotope used for calibrating a well-counter is significant for accurate measurements in nuclear medicine. The isotope typically used for this purpose is Cesium-137 (Cs-137), which has a primary gamma emission energy of approximately 662 keV. This energy level is optimal for calibrating the detection equipment, as it aligns well with the energies typically encountered in the detection of gamma radiation in clinical settings.

The well-counter, being a device designed to measure radiation from sources of varying activity, requires a standard reference point for calibration to ensure accuracy in measuring radiopharmaceutical doses and patient dosimetry. Using 662 keV from Cs-137 allows technicians to ensure consistent performance across different measurements due to its stable emission characteristics.

When calibrating, it's important to use a gamma source that is well-characterized and widely accepted in the field, which is why Cs-137 is commonly selected. This choice enables healthcare professionals to maintain high standards for measurement accuracy and reliability in nuclear medicine applications.