@misc{oai:repo.qst.go.jp:00070878,
 author = {Yoshida, Eiji and Tashima, Hideaki and Nishikido, Fumihiko and Hirano, Yoshiyuki and Inadama, Naoko and Murayama, Hideo and Yamaya, Taiga and 吉田 英治 and 田島 英朗 and 錦戸 文彦 and 平野 祥之 and 稲玉 直子 and 村山 秀雄 and 山谷 泰賀},
 month = {Sep},
 note = {The detection of depth-of-interaction (DOI) is essential to achieve both high spatial resolution and high sensitivity for positron emission tomography (PET), since DOI information will reduce the parallax error due to the crystal penetration. In particular, performance of a small bore PET scanner is improved for dedicated human brain, human breast, and small animal imaging. We developed a novel, general purpose isotropic-3D PET detector X'tal cube by effective readout of scintillation photons from six sides of the crystal block. The X'tal cube is composed of the 3D crystal block with isotropic resolution and arrays of multi pixel photon counters (MPPCs). We have shown that the X'tal cube can achieve 1.9 mm uniform spatial resolution using the one pair prototype of the X'tal cubes with 3D grids of 2 mm pitch. Fig. 1 (a) shows the illustration of the X'tal cube with 3D grids of 2 mm pitch. In this work, we investigate spatial resolution of a PET scanner based on the X'tal cube using Monte Carlo simulations for predicting resolution performance in smaller 3D grid. The PET scanner of 15.6 cm in diameter was simulated. This PET scanner consisted of 24 X'tal cube detectors. For spatial resolution evaluation, a point source emitting 511 keV photons was simulated with all the physical processes involved during emission and interaction of positrons using the GATE. The interacted 3D grid is determined by finding the centroid which is weighted by each interaction intensity. These simulations were repeated, varying the radial offset of the point source to demonstrate the spatial resolution at different locations across the field-of-view (FOV). The simulated data were projected to the sinogram and reconstructed using the 2D filtered backprojection on each axial plane. Fig. 1 (b) shows average spatial resolutions for the X'tal cubes with 3D grids of several pitches. For all types of the X'tal cube, these detectors obtained uniform spatial resolution over the FOV. Also, as the 3D grid pitch was small, spatial resolution was improved adequately. The average spatial resolution of the X'tal cube with grids of 2 mm pitch was equal to the experimental data. Also, the average spatial resolution of the X'tal cube with 3D grids of 0.5 mm pitch was 0.7 mm. The X'tal cube along with excellent spatial resolution would lead to PET scanners with uniform spatial resolution across the FOV., 2012 World Molecular Imaging Congress},
 title = {Estimating the spatial resolution limits for isotropic-3D PET detector},
 year = {2012}
}