Filtered Backprojection in Compton Imaging Using a Spherical Harmonic Wiener Filter With Pixelated CdZnTe

Filtered backprojection is an image reconstruction technique for Compton imaging that provides reasonably high resolution at much lower computational costs when compared to iterative methods. This work applies a Wiener filter that has been derived for spherical harmonics on Compton imaging using the OrionUM pixelated CdZnTe imaging spectrometer. To regularize the filter, an investigation is made into the power spectral density of the signal and noise to develop an appropriate spectral signal-to-noise ratio model for the restoration process. Experimental measurements were conducted with two Th-228 sources placed 30 degrees apart. The resulting filtered image of the two sources has an average full-width-at-half-maximum (FWHM) of 9.8 degrees or 7.5 degrees when using a mean squared error and structural similarity optimization approach, respectively, an improvement from the 29.0 degrees FWHM image when using simple backprojection.

Automated summary

Filtered backprojection is an image reconstruction technique for Compton imaging that provides reasonably high resolution at much lower computational costs when compared to iterative methods. By investigating the power spectral density of the signal and noise, an appropriate spectral signal-to-noise ratio model for the restoration process is developed. Experimental results demonstrate that the use of filtered backprojection significantly improves image quality and resolution.