Application of spherical harmonic filtering to 4π gamma imaging

Abstract

4π gamma imaging with sensitivity in all directions is useful for determining the incident direction of the gamma-ray to the detector. In this study, a spatial filter with a spherical harmonic function was proposed for 4π gamma imaging to reduce statistical noise in lower-event data. The application of the filtered 4π imaging for finding a point radiation source was investigated. In the filtered 4π images, the linearity and root mean squared error of the image improved with a small number of events. Furthermore, the finding of a 137Cs point source based on the filtered gamma imaging was demonstrated, and the accuracy of the estimated source location and activity was improved using lower-event data.