Effect of scattering angle uncertainty compensation in Compton camera reconstruction

In Compton cameras, the uncertainty of measured scattering angle is of problem especially at low incident gamma-ray energy, since it degrades the spatial resolution of reconstructed images. M. Hirasawa and T. Tomitani extended their analytical reconstruction algorithm to compensate for the uncertainty. Their two algorithms, those with and without compensation for the angular uncertainty, were tested on the projection with scattering angular spread. The relation between spatial resolution (FWHM of PSF) and statistical noise (relative variance of reconstructed angular distribution from isotropic radioactivity density) were analyzed. The algorithm with compensation can attain better spatial resolution at a cost of statistical noise enhancement. The noise enhancement depends much on the magnitude of the scattering angular uncertainty to be compensated. The noise increases as the incident gamma-ray energy decreases and as the scattering angular uncertainty increases. Since the noise enhancement is pronounced at low incident gamma-ray energy, we must make a compromise between the spatial resolution and statistical noise.