Performance tests of the B-RAD survey meter and portable γ-spectrometer in a clinical environment

Introduction This note describes performance test of B-RAD, a commercial γ-survey meter/portable γ-spectrometer designed to operate in strong magnetic field. The instrument consists of an active probe housing a cylindrical LaBr3 crystal, and a central unit connected by a cable. Methods The measurements were performed at an MR-Linac Elekta Unity (1.5 T) and a Philips Ingenia (3 T) MRI system, by measuring the H *(10) rate and the gamma energy distributions using two certified radioactive sources of 57Co and 137Cs providing a reference irradiation while the detector was exposed to increasing values of the magnetic field. Measurements were performed in various configurations, with probe and central unit either kept close together or separate, and either aligned or orthogonal to the magnetic field. Results The results outline stable H *(10) rates and gamma spectrometry performances in the entire magnetic field range. The device’s performance is unaffected when only the probe is exposed to the static magnetic field while the central unit is in a lower field zone. When the latter is exposed to a strong field, the loss in dose rate remains within 10% for all configurations tested. Conclusion The results demonstrate the potential application of the instrument for operational and decommissioning measurements at MRI-Linac and PET-MRI systems.