DOI PET Imaging Study Based On Sub-Millimeter Cross-Strip 3D CdZnTe Semiconductor Detectors

Positron emission tomography(PET)devices are important tools for clinical disease diagnosis and basic medical research.With the continuous advancement of research in time-of-flight(TOF)technology,image reconstruction algorithms,and other areas,PET imaging performance has made significant progress.However,depth-of-interaction(DOI)correction,which accounts for the effect of radiation penetration depth,remains an important aspect of current PET research.In this paper,two submillimeter-resolution cross-strip cadmium zinc telluride(CZT)detectors are designed,and a CZT-based three-dimensional position calculation method using signal waveforms is proposed.This method enables accurate measurement of the 3-D position coordinates of gamma ray interactions within the CZT detector,thereby achieving gamma ray DOI detection.The paper also successfully uses CZT semiconductor detectors with yttrium lutetium oxyorthosilicate scintillation detectors for PET imaging experiments,obtaining submillimeter high-resolution PET imaging results.This validates the feasibility of utilizing submillimeter-resolution cross-strip CZT detectors for high-resolution DOI-PET imaging.This paper focuses on a high-speed digital waveform acquisition system based on the micro-TCA architecture.The PET imaging algorithm design and verification are accomplished by programming the on-board Xilinx V6 FPGA.Signal processing modules such as baseline restoration,signal identification and peak finding,and coincidence logic are implemented using MATLAB/Simulink and Sys gen programming environments.Digital signal processing modeling and simulation are performed,and a fast-slow coincidence imaging technique combining cadmium zinc telluride(CZT)semiconductor detectors and yttrium lutetium oxyorthosilicate scintillation detectors is developed.Signal waveforms are acquired,and the anode output signals from CZT detectors are used for event classification.Single anode events,neighboring anode charge sharing events,and non-neighboring anode Compton events are reconstructed.The three-dimensional positions of 511 ke V annihilation radiation are calculated using a three-dimensional coordinate formula,and the obtained positions show good agreement with those obtained through neural network algorithms.The 1.0 mm cross-strip cadmium zinc telluride(CZT)detector achieves an energy resolution of 2.7% for single anode events.The energy resolution for neighboring anode charge signal summation spectra is 5.8%,and for non-neighboring anode Compton events,it is 6.3%.The 0.4 mm ultra-high-resolution CZT detector is designed with 0.3 mm anode strips and 0.9 mm cathode strips,with an electrode gap of 0.1 mm.The detector’s electric field and weighting potential are analyzed using Comsol software,confirming the small pixel effect of the 0.4 mm detector with smaller anode strips.The energy resolutions for single anode events,neighboring anode events,and non-neighboring anode events in the 0.4 mm CZT detector are6.5%,4.6%,and 8.5% respectively.The good energy resolution for single anode events in the 0.4 mm CZT detector demonstrates the success of the cross-strip design.The neighboring anode signal summation spectra show excellent energy resolution,and the distribution of charge sharing between neighboring anodes displays a clear linear pattern,providing important basis for signal interpolation in CZT detector PET imaging.To evaluate the PET imaging performance of the CZT detectors,this paper conducted PET coincidence imaging using a 1.0 mm yttrium lutetium oxyorthosilicate scintillation detector,a 1.0 mm CZT detector,and a 0.4 mm CZT detector.A rotating platform was used to perform PET tomography imaging of a 3 mm diameter Na-22 point source.The results showed that the 1.0 mm CZT detector PET imaging achieved good differentiation between two Na-22 point sources separated by 7 mm.The reconstructed image resolution for single anode events was 3.1 mm full width at half maximum(FWHM),and for neighboring anode events,it was 3.2 mm FWHM.The introduction of neighboring anode events in PET image reconstruction improved the sensitivity of the CZT PET imaging system by 1.7 times.The 0.4 mm CZT detector exhibited improved PET imaging of the Na-22 point source.The reconstructed image resolution for single anode events was 3.0 mm FWHM,and for neighboring multiple anode events,it was 3.1 mm FWHM.The image resolution significantly increased,and the introduction of neighboring multiple anode events improved the system sensitivity by 1.8 times.This paper successfully conducted PET imaging experiments using submillimeter high-resolution three-dimensional cross-strip CZT detectors.It demonstrated the feasibility of utilizing CZT semiconductor detectors for high-resolution DOI-PET imaging and laid the foundation for the development of CZT semiconductor PET devices.