# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2017, Vol. 28 ›› Issue (4): 47

• NUCLEAR ELECTRONICS AND INSTRUMENTATION •

### How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

Hojjat Mahani1,2, Gholamreza Raisali1, Alireza Kamali-Asl3, Mohammad Reza Ay2,4

1. Radiation Application Research School, Nuclear Science and Technology Research Institute, Tehran, Iran
Research Center for Molecular and Cellular Imaging, Tehran University of Medical Science, Tehran, Iran Radiation Medicine Department, Shahid Beheshti University, Tehran, Iran
Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Science, Tehran, Iran
• Received:2016-02-17 Revised:2016-06-08
• Supported by:

Supported by Research Center for Molecular and Cellular Imaging (RCMCI), Tehran University of Medical Sciences (No. 29885).

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Hojjat Mahani, Gholamreza Raisali, Alireza Kamali-Asl, Mohammad Reza Ay. How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?.Nuclear Science and Techniques, 2017, 28(4): 47
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Abstract:

It is well known that inter-crystal scattering and penetration (ICS–P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated
crystal. In this study, the effect of ICS–P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation. A 99mTc pencil-beam toward central crystal element was utilized. Beam incident angle was assumed to vary from 0 to 45 in 5 steps. The effects of various crystal configurations such as pixel-size, pixel-gap, and crystal material were studied. The influence of photon energy on the crystal identification (CI) was also investigated. Position detection accuracy (PDA) was defined as a factor indicating performance of the crystal. Furthermore, a set of 99mTc point-source simulations was performed in order to calculate peak-to-valley (PVR) ratio for each configuration. The results show that the CsI(Na) manifests higher PDA than NaI(Tl) and YAP(Ce). In addition, as the incident angle increases, the crystal becomes less accurate in positioning of the events. Beyond a crystal-dependent critical angle, the PDA monotonically reduces. The PDA reaches 0.44 for the CsI(Na) at 45 beam angle. The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations. In addition, the PVRs derived from flood images linearly correlate their corresponding PDAs. In conclusion, quantitative assessment of ICS–P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.