90Y bremsstrahlung emission computed tomography using gamma cameras

Objective  This study demonstrates images obtained by ⁹⁰Y bremsstrahlung emission computed tomography (BECT), and characterizes the system performance of gamma cameras. Methods   ⁹⁰Y BECT images of phantoms were acquired using a gamma camera equipped with a medium energy general purpose parallel-hole collimator. Three energy window widths of 50% (57–94 keV) centered at 75 keV, 30% (102–138 keV) at 120 keV, and 50% (139–232 keV) at 185 keV were set on a ⁹⁰Y bremsstrahlung spectrum. The images obtained with three energy windows were reconstructed using filtered back projection (FBP) and ordered subsets expectation maximization (OSEM) methods. The images of the sum window were obtained by fusing the images of the 75, 120, and 185 keV windows. Results  The OSEM method improved the full width at half maximum by 20% and the standard deviation by 9% compared with the FBP method. BECT displayed ⁹⁰Y biodistribution and quantified ⁹⁰Y activity. BECT images obtained with OSEM method using the 120 keV window showed the highest resolution and lowest uncertainty. The sum window showed the highest sensitivity, while its resolution was 10% inferior to that of the 120 keV window. One whole-body image can be taken over 100 min using the sum window. An absorber to cover the body surface reduced background by 30%. Conclusions   ⁹⁰Y BECT imaging can be used for patient assessment without modifying current treatment procedures.