A depth-of interaction (DOI) PET detector is a detector which provides a detected radiation location 3-dimensionally. The DOI information is important to ensure the PET scanner has both high resolution and high sensitivity. We have successfully developed a 4-layer DOI detector which is composed of four layers of scintillation crystal arrays optically coupled to a position sensitive photomultiplier tube. Scintillation light spread in the crystal arrays is utilized for the crystal identification in the 4-layer DOI crystal arrays. As a new trial in our further investigation about scintillation light spread in a crystal array, we used scintillation crystals cut as a triangular prism (triangular crystal) with the expectation that the crystal shape would cause different light behavior compared with rectangular crystals generally used for a PET detector. As an application of the triangular crystals, we developed a 3-layer DOI detector with Lu(2x)Gd(2(1-x))SiO(5) (LGSO) crystals in dimensions of an equilateral triangle of 3.0 mm one side in cross section and 10.0 mm long. The detector performance evaluation showed sufficient crystal identification performance and energy resolution of 9 - 12% was also obtained.第5回日韓医学物理会
