Basic study of the PET detector

The X\u27tal cube is a PET detector we have developed. It has the new structure, which consists of a monolithic scintillation crystal block segmented 3-dimensionally into cubes and semiconductor photo-detectors are coupled on all sides of the crystal block. The crystal segment originating scintillation light can be identified by a simple position calculation with the photo-detector signals. Determination of the crystal segment provides radiation detected location inside the crystal block including depth of interaction (DOI) information which is necessary for a PET scanner to have both high sensitivity and high spatial resolution. We have already showed sufficient performance of the X\u27tal cube with the prototype using multi-pixel photon counters (MPPCs) for the photo-detectors and a 3-dimensional (3D) array of cubic crystals for the crystal block (array-X\u27tal cube). Because we newly succeeded to fabricate the 3D array by applying laser processing to a monolithic crystal for easy and reliable assembly, in this study, we evaluated performance of the X\u27tal cube using the monolithic crystal as the crystal block (laser-X\u27tal cube). The results showed high crystal identification performance and average energy resolution of 8.6 % for all crystal segments, which are superior to the array-X\u27tal cube performance.第6回日韓医学物理学術合同大会（JKMP

Feasibility study for a PET detector integrated with a RF coil for PET-MRI

We are developing a PET system integrated with a birdcage RF coil for the PET-MRI. The proposed integrated system is intended to realize a convenient and highly sensitive PET system for simultaneous measurements. The integrated system can be easily replaced to other RF coils for other MRI study. In addition, a small ring diameter of the PET is applied for high sensitivity. In the presented system, PET detectors are placed close to the objective to achieve high sensitivity. Each element of the RF coil is inserted between scintillation crystal blocks inside of the shielding material. We carried out a feasible study for the PET detector integrated with the bird cage RF coil. The prototype PET detector consisted of a LGSO crystal (Hitachi Chemical) and a multi-pixel photon counter array (S11064 series, Hamamatsu Photonics K.K.). The detector and its electrical circuit were packaged in an aluminum shielding box. Experiments were carried out with 1.5T MRI (Phillips, INTERA 1.5T Master) and a birdcage type RF-coil. The shielding boxes, with the detector and circuit, were placed in the gap of the RF-coils. In order to reduce noise contamination from outside the MRI room, a band pass filter was applied on the power line of the MPPC. First, influence on the PET detector from MRI was evaluated by comparing energy spectra obtained before and during MRI measurement. Simultaneously, influences on the MRI image from the PET detector were evaluated. Next, the influences of the shielding material for the PET detectors on the magnetic field and RF pulse of MRI were evaluated. Dummy detectors which were simply copper shielding boxes were placed at all gaps of the RF coil and MRI images were evaluated. As a result, the PET detector worked in simultaneous measurements the same as it did when the MRI was not operated. The MRI images also were obtained as usual even though the PET detector and the shielding materials was positioned close to the RF coil.IEEE 2011 NSS MIC RTS