量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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Objectives: The X'tal cube is the PET detector we have developed. It consists of a scintillation crystal block segmented into cubes and multi-pixel photon counters (MPPCs) which are coupled onto all six surfaces of the crystal block. A MPPC is a small semiconductor photo-detector. Recently, we achieved 1 mm isotropic spatial resolution in this structure by identifying 1 mm cubic crystals which composed the crystal block. As a part of the X'tal cube development, we have studied laser processing technique for easier crystal segmentation instead of composing the crystal block with such fine crystals. Because the laser processing has difficulty in the depth direction of a thick crystal block, as the first trial, we made segmentation of 3 mm intervals in each three direction of an 18 mm cubic monolithic crystal. Performance of the X'tal cube with the processed crystal block (laser-X'tal) was evaluated and compared in case the crystal block was composed of 3 mm cubic crystals (array-X'tal).
\nMethods: Performance of crystal segment identification was evaluated with the 3-dimensional position histogram in which the results of Anger-type calculation of the MPPC signals in each three dimension were plotted. Each segment makes corresponding response in the histogram.
A 137Cs point source was used for the measurement. For the crystal and a MPPC, we used LYSO and S10931-50P (Hamamatsu Photonics K.K., sensitive area; 3 x 3 mm2, micro cell; 50 um2), respectively.
\nResults: Obtained position histograms showed sufficient segment identification performance of both the X'tal cubes. Average energy resolutions were 8.4 % and 10.4 % for the laser- and array-X'tals, respectively.
\nConclusions: We showed that laser processing is feasible enough for easy and precise segmentation of the crystal block. In the next stage, we will try finer segmentation of 2 mm intervals.
\nResearch Support: Funds from Japan Science and Technology Agency (JST) Development of Systems and Technology for Advanced Measurement and Analysis.
Performance evaluation of the X'tal cube PET detector using a monolithic scintillator segmented by laser processing
