The modeling of multiple order Compton scatter in SPECT

In our previous work, an efficient slice-by-slice blurring model was develo ped based on the Klein-Nishina formula to model first order Compton scatter in both parallel beam and converging beam SPECT. The first order Compton s catter projection was generated by first forming an effective scatter sourc e imaging (ESSI) corresponding to first order Compton scatter and then forw ard-projecting the ESSI to the detector surface. using a projector that mod eled both the non-uniform attenuation effect and the depth-dependent detect or response effect. In this work, the technique was exetended to model mult iple order Compton scatter. At each scattering voxel, first order Compton s cattered photons combined in a scattering cone which was determined by the energy window used for emission projection acquisition were used as the sou rce for second order Compton scatter. The effective scatter source image (E SSI) corresponding to die second order Compton scatter was then obtained us ing the slice-by-slice blurring model. Forward-projecting this ESSI to the detector gave the second order Compton scatter projection. For a point sour ce in a non-uniform scattering object for fan beam geometry. the second ord er Compton scatter point responses generated using the proposed method matc hed well with those using Monte Carlo Simulations at the Peak region, but n ot as well at the tails. This work proposed an efficient method to model mu ltiple order Compton scatter in both parallel beam and converging beam SPEC T.