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 and Radiological Science and Technology.
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X'tal cube is the PET detector we have developed and it has the capability of getting depth of interaction (DOI) information about radiation detected position in the detector. Fig. 1 illustrates the structure of the X'tal cube. It is composed of a scintillation crystal block and a number of multi-pixel photon counters (MPPCs) on the crystal block surfaces. A MPPC is thin and small enough not to interfere in radiation detection. The crystal block is segmented 3-dimensionally into small cubes. There is no reflector between the crystal segments so that scintillation light originating in a radiation detected segment spreads to all 6 surfaces and detected by all MPPCs. Simple Anger-type calculation can be used in position calculation for segment identification. By expressing results of the calculation with the all MPPC signals in a 3-dimensional (3D) position histogram, we get response corresponding to each crystal segment.
In the first stage, we composed of the crystal block by fabricating a 3D array with small cubic crystal segments (array-XC). Later, we newly developed the laser processing technique to segment inside of a monolithic crystal block 3-dimensionally (laser-XC). In both ways, we have already confirmed that small segments such as 1.0 mm x 1.0 mm x 1.0 mm segments can be identified in the X'tal cube structure. Meanwhile, in a basic study, we found that scintillation light spreads in different manners between the array and laser-XCs due to different condition of optical discontinuity between crystal segments. Because different light distribution among MPPCs should result in different segment response positioning in the 3D position histogram, we reconsidered about the weight of Anger-type calculation to improve segment identification performance for the array and laser- XCs.
Development of a DOI-PET detector X'tal cube: optimal position calculation for each optical condition in the scintillation crystal block
