Use of digital front-end electronics for optimization of a modular PET detector

The sensitivity and resolution of a new 3D modular BGO detector system for positron emission tomography (PET) was examined in terms of its effect on the signal to noise ratio in the final image. The detector system uses custom hardware and firmware to adjust sensitivity and resolution to achieve optimum performance. This system utilizes lookup up tables (LUT) containing individually tailored positioning and energy windows to assure that events are correctly distributed among the detector elements. Without customizing the LUT, and for a common energy window, sensitivity was found to vary as much as a factor of 3.5 and resolution as much as 50% from center to edge within a single detector module. Eight different LUT configurations were tested, varying both energy window and positioning criteria. Typical intrinsic resolutions and sensitivities of the detector elements were determined in all configurations. The effect of nonuniformity of sensitivity of the detector system on image noise was evaluated by imaging uniform cylinders over a wide range of accumulated events. The effect of counting statistics in the measurement of detector sensitivities for the normalization of sinogram data was determined independently. The best of the LUT configurations provided an 16% improvement in effective sensitivity, while also providing a 10% improvement in the average intrinsic spatial resolution relative to the default configuration of the PET system.