Developing a protocol for Y-90 bremsstrahlung imaging after Transarterial Radioembolization

Yttrium-90 (Y-90) is an almost pure beta emitter used in Transarterial Radioembolization (TARE). Post-TARE Y-90 bremsstrahlung imaging is employed for quantification of the delivered dose. Y-90 bremsstrahlung imaging is the most challenging issue in nuclear medicine because of the low photon yield, the continuous and non-pronounced peak of the bremsstrahlung spectrum. GATE Monte Carlo code was employed to find the most proper imaging protocol for Y-90 bremsstrahlung imaging. Images were acquired using Medium-Energy Medium-Resolution (MEMR) and High-Energy Medium-Resolution (HEMR) in nine energy windows widths (50 to 500 keV). The quality of images was evaluated using contrast, resolution, sensitivity, Signal-to-Background Ratio (SBR), percentage of total counts in useful field of view, and Contrast-to-Noise Ratio (CNR). The HEMR collimator performed better than the MEMR collimator on all imaging criteria except for the sensitivity. The CNR values were equal in both collimators. Based on the measured parameters, images acquired by the HEMR collimator with the energy window of 50-200 keV are the best protocol for Y-90 bremsstrahlung imaging. The findings in this study suggest the imaging protocol for Y-90 bremsstrahlung imaging that can be practically used in the clinic.