PET camera performance design evaluation for BGO and BaF₂ scintillators (non-time-of-flight)

Bismuth germanate (BG0) and barium fluoride (BaF₂) scintillators are presently used in positron emission tomography (PET) cameras. This study evaluates the important PET performance parameters of image resolution, true sensitivity, scatter background, accidental background, and realistic maximum radioactivity in the field of view for both BGO and BaF₂ in an identical non-time-of-flight, whole-body camera configuration. These performance parameters are evaluated for three phantoms simulating (a) the head, (b) whole-body cross-section and (c) heart/kidney. This study finds that the high stopping power of BGO yields higher sensitivity, higher resolution, less vignetting, better immunity from scattered gamma, and lower accident/true ratio at any dose level. The faster BaF₂ timing acceptance window is traded off by its vulnerability to noncoincidental scatter-gamma which increases accidental coincidences. The BGO is found to be a better choice for non-time-of-flight systems especially with large objects which produce a lot of noncoincidental scatter-gammas. This study also found that the practical diminishing return maximum activity within the field-of-view is ~20-25 mCi for existing conventional cameras.