Simultaneous estimation of SPECT activity and attenuation distributions from measured phantom data using a differential attenuation method

The Differential Attenuation Method (DAM) simultaneously estimates SPECT activity and attenuation distributions from emission data. In this work, we extend the investigation of DAM to measured data and compare the results obtained with FBP without compensating for attenuation, and Penalized Weighted Least Squares (PWLS) with uniform and no attenuation. An anthropomorphic torso phantom with a heart insert containing a myocardial defect filled with ¹¹¹In is used to acquire data on a GE VG tomograph. An accurate scatter correction before reconstruction is crucial. Scatter is subtracted with an Energy Window Based Subtraction method (EWBS), with positions and widths of the energy windows selected using Monte Carlo simulated source distributions. The results show the potential benefits of DAM as the activity estimate has fewer artifacts and is more accurate than FBP without compensating for attenuation or PWLS with uniform attenuation. However, artifacts remain and additional constraints on the allowed attenuation values were required to produce acceptable images