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Truncation compensated 3D-OSEM reconstruction in pinhole SPECT

¹ National Cardiovascular Center Research Institute, Suita, Osaka, Japan; ² University of Tsukuba, Tsukuba, Japan; ³ Kuopio University Hospital, Kuopio, Finland

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Objectives: Pinhole SPECT can provide high resolution with reasonable sensitivity when a collimator is close to an object, but truncation causes artifact and decreases quantitative accuracy. Defrise et al proposed new reconstruction theory to prevent overestimation due to truncation, and validated the theory by simulation with 2D X-ray CT. In this study, we expanded this method to truncation-compensated 3DOSEM reconstruction (TC-3DOSEM) for pinhole SPECT. Simulation and rat studies were performed to validate TC-3DOSEM.

Methods: According to Defrise theory, two conditions are assigned. First, field of view contains null or background counts, namely, a known value. Second, reconstruction space is defined large enough to contain the whole of object. This is held in 3D domain in our pinhole SPECT. TC-3DOSEM was validated by simulation and rat studies using microSPECT and Tl-201. A target of imaging was rat heart and the surrounding was truncated. Additionally, to evaluate for larger truncated area, we artificially generated data with the different amounts (22% and 48%) of truncation from rat experimental data. TC-3DOSEM and conventional method were compared.

Results: In simulation, myocardial counts were overestimated about 20% by conventional method, and were almost consistent with original counts by TC-3DOSEM. In rat study, conventional method significantly overestimated the counts along with the amount of truncation. TC-3DOSEM eliminated overestimation and the counts were consistent across all data sets with different amount of truncation (error of 0.7%).

Conclusions: These studies demonstrated that TC-3DOSEM compensated systematic errors attributed to truncation in pinhole SPECT reconstruction, while conventional method caused significant overestimation.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Zeniya, T. Articles by Iida, H. PubMed Articles by Zeniya, T. Articles by Iida, H.