@misc{oai:repo.qst.go.jp:00069056,
 author = {Kobayashi, Tetsuya and 小林 哲哉},
 month = {Jul},
 note = {This paper investigates the benefit of depth-of-interaction (DOI) information in a time-of-flight (TOF) positron emission tomography (PET). TOF measurement, generally, has advantages to large bore scanners, and it improves signal-to-noise ratio of reconstructed images. On the other hand, DOI measurement has advantages to small bore scanners such as dedicated brain PET scanners or small animal PET scanners. DOI measurement provides uniform spatial resolution in the field-of-view (FOV) by minimizing resolution loss due to a parallax error. Therefore PET imaging using both TOF and DOI information has not investigated to date. We simulated two dimensional whole-body PET scanners with one-layer (i.e. non-DOI) and four-layer DOI capability using the GATE (Geant4 Application for Emission Tomography). The length of a short side of the crystal element was 2.9mm, and total thickness of the detector block of both scanners was 20mm. These scanners were assumed to have 200ps, 400ps and 800ps timing resolution. We developed a histogram based ordered-subsets expectation-maximization with accurate modeling of detector response and TOF kernel. Two simulations were performed to evaluate spatial resolution and contrast recovery. The results show that the spatial resolution, contrast recovery and their uniformity in the FOV degrades greatly with a parallax error of the non-DOI scanner; however the DOI scanner provides uniform resolution of approximately 2mm full width at half maximum in the whole FOV of 60cm diameter. Reconstruction with improved timing resolution provides higher contrast recovery at the low background noise level., Fully Three-Dimensional Image Reconstruction Meeting in Radiology and Nuclear Medicine},
 title = {Improvement of PET image quality using DOI and TOF information.},
 year = {2007}
}