TY - JOUR T1 - <strong>Development of 3D HEXITEC CdZnTe detector - A large area high-resolution </strong><strong>γ-</strong><strong>ray imaging camera for future SPECT imaging</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1770a LP - 1770a VL - 59 IS - supplement 1 AU - Jiajin Zhang AU - Elena Maria Zannoni AU - Matthew Wilson AU - Ling-Jian Meng Y1 - 2018/05/01 UR - http://jnm.snmjournals.org/content/59/supplement_1/1770a.abstract N2 - 1770aObjectives: We will present the design and preliminary performance of a large-area γ-ray imaging camera, the 3D HEXITEC detector[1], for use in future clinical SPECT imaging. The 3D HEXITEC hybrid pixelated CdZnTe camera is designed to offer an ultrahigh sub-pixel spatial resolution (~150μm), an unprecedented energy resolution of 0.8 keV for 140 keV γ rays, an wide dynamic range of 5 to 600 keV. And with a compact modular detector array of 13 cm x 13 cm active area, this SPECT imaging camera is ready to be packed closely to form large area imaging systems for future clinical imaging. Methods Basic designs for the camera and readout system: The structure design of each HEXITEC detector is shown in Fig.1-A1 and Fig.1-A2. It is composed of one piece of 2.5 cm×2.5 cm, 5 mm thick CdZnTe crystal and one piece of readout ASIC. The crystal and ASIC is connected together through a well-designed fan-out board. Every 5×5 CdZnTe detectors are connected on a PCB, constituting a 13 cm×13 cm large area γ-ray imaging camera, as shown in Fig.1-A3. This camera can work in three modes: (1)Coincidence-trigged cathode waveform readout and the depth of interaction(DOI) estimation based on FPGA firmware; (2)Energy-over-threshold ultrahigh speed data readout; (3)Enabling data readout in specific area on detector surface, which are all shown in Fig.1-B. Data processing techniques for charge-sharing correction and sub-pixel resolution: To extract the precise energy and spatial information for γ-ray interactions, we carried out detailed analysis of charge sharing and charge loss effects, as well as correlated behavior between adjacent pixels. These allow us to build up a detailed response function, which is then used to compensate for the incomplete charge collection and its effect on energy resolution, and to achieve sub-pixel spatial resolution of around 150 μm for 140 keV γ rays[2-5]. Experimental evaluation: In the experimental study, we will evaluate the energy resolution and spatial resolution of HEXITEC SPECT camera in different readout modes. Radioisotopes with different characteristic γ-ray energy peaks will be used to measure the hyperspectral energy resolution. 57Co and Tc-99m are used to analog the energy peak distance between Tc-99m and 123I (energy peak: 57Co:122 keV Tc-99m:140 keV 123I:159 keV). We will use well-collimated 10μm x-ray pencil beam to scan camera surface at different positions to carry out estimations on the positions of interaction, as shown in Fig.1-D1. Pencil beams with different angles of incidence will be used to estimate DOI based on cathode waveforms[6]. Preliminary Results Measured multi-isotope energy resolution: Multi-isotope energy spectrum is shown in Fig.1-C, in which photon peaks of 57Co and Tc-99m are clearly discriminated. Current energy resolution of HEXITEC camera is improved to be 0.75 ± 0.02 keV FWHM @ 122 keV(57Co) and 0.80 ± 0.02 keV @ 140 keV(Tc-99m). Sub-pixel spatial resolution demonstration: Camera response is shown in Fig.1-D2 when using 10 μm x-ray beam to scan camera surface. Scanning step size is controlled to be 100μm (half-pixel level). Due to charge sharing, CdZnTe camera shows different response patterns at different beam positions. Based on these distinguishable response patterns, we can utilize estimation methods to achieve sub-pixel spatial resolution. Conclusions and Future Results The 3-D CdZnTe HEXITEC detector array will be a novel hyperspectral SPECT imaging camera. With specific geometry structure, charge sharing-loss estimation algorithm and well-designed readout system, this compact detector array will be able to work in three different readout modes and assure excellent resolution for wide dynamic range γ-ray imaging. We will present more detailed experimental results of sub-pixel spatial resolution as well as the 3D position of interaction readout. Providing these attractive features, this HEXITEC camera modular design will provide promising advantages for future SPECT imaging research. ER -