Stduy on Induced Signal Compensation and Filtering Methods and Spatial Resolution Ability of Pixel-Type CdZnTe Compton Imaging System

To realize the application of semiconductor cadmium zinc telluride (CdZnTe) detectors in high-energy ray imaging fields such as nuclear safety monitoring, proton and heavy ion radiotherapy range assessment and verification, the pixel-type CdZnTe imaging detectors were used for Compton imaging research. The 2× 2 Compton imaging system consists 4 CdZnTe pixel detectors with 2 mm pixel size. The spatial resolution of the Compton imaging system was 2 mm× 2 mm× 1 mm. The data used for Compton imaging was corrected for incompletely charge collection according to the depth of interaction (DOI) and the initial gamma energy. The characteristic energy of
¹³⁷
Cs,
¹³³
Ba, and
¹⁵²
Eu were used to calculate the energy compensation. The corrected data was filtered by four necessary conditions before imaging reconstruction. The reconstructed events are filtered from the four aspects: the sum of the energy of the two events, the DOI, the calculated scattering angle, and the distance between the two events. The
¹³⁷
Cs dual-source imaging experiment was delivered to verify the imaging ability of the CdZnTe Compton imaging detector. The two sources were arranged in the same plane that parallel to the electrode plane, which were 60 mm (P
1
) and 70 mm (P
2
) from the anode of the detector, respectively. The Simple Back-Projection (SBP) method was used for image reconstruction. The reconstructed image could reconstruct the relative position of the two
¹³⁷
Cs radioactive sources, with the reconstructed distance of 15.6 mm and 15 mm for P
1
and P
2
, respectively., and the best spatial resolution of the reconstruction image was 29 mm. The research results shown that the CdZnTe Compton imaging system based on CdZnTe pixel detectors has excellent relative positional resolution ability.