Use of a Germanium Detector to Optimize Scatter Correction in SPECT

A collimated germanium detector with an energy resolution of 1 keV full width at half maximum at 140 keV was used to measure the energy spectrum of radiation emitted from a test object containing an asymmetric distribution of 99mTc and nonuniform attenuation. Energy spectra were recorded from 24 positions around the object and convolved with Gaussian functions to simulate data that would have been acquired with a scintillation camera. The scatter fraction was computed from the convolved spectra in conjunction with a scatter-free reference spectrum. After adding appropriate Poisson noise, a technique based on maximizing the signal to noise ratio was developed to optimally subtract the scatter fraction from the recorded counts. SPECT imaging of the test object was performed to evaluate the correction technique.