A Macintosh-based multi-energy data acquisition system for gamma cameras

A multi-energy data acquisition system based on the Macintosh II computer and a commercial ADC subsystem has been developed to allow the application of sophisticated Compton-scatter correction procedures. The system digitizes position and energy signals from the camera to 12 bits, bins the data into images, and transfers the data via an Ethernet interface to a computer network for reconstruction and analysis. The system also provides the necessary gantry control signals for tomographic acquisition. In a preliminary application, the system has been used along with polynomial nonlinear spectral fitting, which can account for shifts in the energy spectrum, to estimate scatter fractions for a hot, off-axis sphere in a cold, cylindrical phantom. The radioisotope was ^99mTc. The resultant scatter fractions displayed the expected symmetry with camera angle, and dependence on the amount of scattering material between the source and camera