High positioning accuracy coded aperture gamma camera based on monolithic CeBr3 crystal.

Abstract

A monolithic CeBr3 crystal was utilized in a coded aperture camera system instead of the traditional array-type crystal, leading to enhanced energy resolution and improved accuracy in determining the angular position of the radiation source, particularly for the detection of single-point sources. The dimensions of the monolithic CeBr3 crystal are 26 × 26 × 10 mm3, and it is coupled to an 8 × 8 SiPM array. The coded aperture mask is constructed from tungsten blocks (1.7 × 1.7 × 8 mm3) arranged on a photosensitive resin frame, following a 2 × 2 mosaic of the rank 11 MURA pattern. By utilizing a convolutional neural network, we achieved a spatial resolution of ∼1.2 mm and a depth resolution of ∼2 mm in the CeBr3 crystal. Imaging experiments were conducted using Co-57, Na-22, Cs-137, and Co-60 sources to evaluate the performance of the gamma camera system. With the application of position-segmented energy calibration, we obtained an energy resolution better than 5% @662 keV. The methods of balanced decoding following fine sampling and the weighted averaging after depth of interaction stratification were employed to enhance the positioning accuracy of the radiation source, ultimately attaining an image angular resolution of 5.2° and an angular accuracy of 3.44° with a field of view of 44°.