Intercomparison of instrumentation systems for verification of ¹²⁵I brachytherapy source strength for use in radioactive seed localization procedures

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Two different radiation detection instruments, both commonly found in nuclear medicine clinics, were investigated for potential use in ¹²⁵I brachytherapy seed source strength verification. The goal of this investigation was to determine if either or both of these instruments could replace the air-communicating well-type ionization chamber (standard source strength verification instrument) when the ¹²⁵I seed is used for radioactive seed localization procedures instead of brachytherapy. In radioactive seed localization, the ¹²⁵I seed merely localizes the tissue of interest and does not deliver a therapeutic dose to the patient. The ¹²⁵I seeds are inserted into nonpalpable lesions, which are then removed for biopsy within 5 days. Dose calculations and patient modeling are not performed. As a result of this, stringent source strength accuracy tolerances are not necessary. The accuracy, precision, and reproducibility of an activity calibrator and an ionization chamber survey meter were assessed and compared to regulatory requirements.