title: Performance evaluation for 120 four-layer DOI block detectors of the jPET-D4.
abstract: The jPET-D4 is a brain positron emission tomography (PET) scanner that we have developed to meet user demands for high sensitivity and high spatial resolution. For this scanner, we developed a four-layer depth-of-interaction (DOI) detector. The four-layer DOI detector is a key component for the jPET-D4, its performance has great influence on the overall system performance. Previously, we reported the original technique for encoding four-layer DOI. Here, we introduce the final design of the jPET-D4 detector and present the results of an investigation on uniformity in performance of the detector. The performance evaluation was done over the 120 DOI crystal blocks for the detectors, which are to be assembled into the jPET-D4 scanner. We also introduce the crystal assembly method, which is simple enough, even though each DOI crystal block is composed of 1,024 crystal elements. The jPET-D4 detector consists of four layers of 16 x 16 Gd(2)SiO(5) (GSO) crystals and a 256-channel flat-panel position-sensitive photomultiplier tube (256ch FP-PMT). To identify scintillated crystals in the four-layer DOI detector, we use pulse shape discrimination and position discrimination on the two-dimensional (2D) position histogram. For pulse shape discrimination, two kinds of GSO crystals that show different scintillation decay time constants are used in the upper two and lower two layers, respectively. Proper reflector arrangement in the crystal block then allows the scintillated crystals to be identified in these two-layer groupings with two 2D position histograms. We produced the 120 DOI crystal blocks for the jPET-D4 system, and measured their characteristics such as the accuracy of pulse shape discrimination, energy resolution, and the pulse height of the full energy peak. The results show a satisfactory and uniform performance of the four-layer DOI crystal blocks; for example, misidentification rate in each GSO layer is <5% based on pulse shape discrimination, the averaged energy resolutions for the central four crystals of the first (farthest from the FP-PMT), second, third, and 4th layers are 15.7 +/- 1.0, 15.8 +/- 0.6, 17.7 +/- 1.2, and 17.3 +/- 1.4%, respectively, and variation in pulse height of the full energy peak among the four layers is <5% on average.
authors.affiliation: Molecular Imaging Center, National Institute of Radiological Sciences, Inage-ku, Chiba-shi, Chiba, Japan. inadama@nirs.go.jp
authors.forename: Naoko
authors.initials: N
authors.lastname: Inadama
authors.forename: Hideo
authors.initials: H
authors.lastname: Murayama
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ono
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tsuda
authors.forename: Manabu
authors.initials: M
authors.lastname: Hamamoto
authors.forename: Taiga
authors.initials: T
authors.lastname: Yamaya
authors.forename: Eiji
authors.initials: E
authors.lastname: Yoshida
authors.forename: Kengo
authors.initials: K
authors.lastname: Shibuya
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nishikido
authors.forename: Kei
authors.initials: K
authors.lastname: Takahashi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kawai
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology; D001927:Brain Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D005682:Gadolinium / Q000737:chemistry; D006801:Humans; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012588:Scintillation Counting; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry
chemical_list: D012822:Silicon Dioxide; D005682:Gadolinium
references.citation: Science. 2000 Mar 31;287(5462):2451-6
references.pmid: 10741958