Selfwrited point spread function (PSF changes according to the incident angle)

Dear CASToR Users and Developers,

We design a small-caliber PET system that has serious DOI parallactic error. With the help of CASToR, right now I reconstructed 7 point sources placed in different offsets which showed in the attachment. Obviously, the point on the far right deteriorated seriously. Since I used 0.79mm(crystal size) FWHM isotropic Gaussian kernel function as PSF in castor-recon command, detector responses caused by different incident angles are not considered. So I need to design a dynamic PSF with single-photon incidence response instead of Static symmetric Gaussian distribution as the PSF to generate the system matrix on the fly.
Does anyone know how I can make this? Because I just find out how to change the standard normal distribution into another static distribution function, fail to relate the current LOR to the distribution function. Any reply will be appreciated.

Thank you a lot,

Zhao Xin