@article{81b689a25c31493595271c5257be79e9,
title = "Collection of Scintillation Light from Small BGO Crystals",
abstract = "We propose to develop a high resolution positron emission tomography (PET) detector designed for animal imaging. The detector consists of a 2-D array of small bismuth germanate (BGO) crystals coupled via optical fibers to a multi-channel photomultiplier tube (MC-PMT). Though this approach offers several advantages over the conventional BGO block design, it does require that a sufficient number of scintillation photons be transported from the crystal, down the fiber and into the PMT. In this study we use simulations and experimental data to determine how to maximize the signal reaching the PMT. This involves investigating factors such as crystal geometry, crystal surface treatment, the use of reflectors, choice of optical fiber, coupling of crystal to the optical fiber and optical fiber properties. Our results indicate that using 2 x 2 x 10 mm BGO crystals coupled to 30 cm of clad optical fiber, roughly 50 photoelectrons are produced at the PMT photocathode for a 511 keV interaction. This is sufficient to clearly visualize the photopeak and provide adequate timing resolution for PET. Based on these encouraging results, a prototype detector will now be constructed.",
author = "Cherry, {Simon R.} and Yiping Shao and Tornai, {Martin P.} and Stefan Siegel and Ricci, {Anthony R.} and Phelps, {Michael E.}",
note = "Funding Information: I. INTRODUCTION We are attempting to develop high resolution detectors suitable for use in a 3D PET scanner designed for imaging small laboratory animals. Since spatial resolution in PET is strongly dependent on the size of the detector elements, it is important to use the smallest elements possible. The block design used in most commercial PET tomographs [ 1-31 suffers from several drawbacks which may limit its application to very high resolution PET systems. First, light sharing is used to determine the position of an event, leading to statistical uncertainty which can result in mispositioning. Second, only -44% of the 5 11 keV gamma rays interact photoelectrically, thus many of the detected events are scattered in the block. If all or most of the energy is ultimately deposited, the block detector has no way of discriminating between photoelectric events and events which undergo one or more Compton scatters. It has been suggested that the combination of these two effects adds 2 mm to the resolution one would obtain using single scintillator/PMT configurations [4]. A third problem is due to the finite width of the saw cuts. As the block elements decrease in size, the cuts become a significant fraction of the detection surface, quickly reducing efficiency. Finally, there are the engineering difficulties related to reliably cutting fine divisions in a block of BGO. For these reasons, it is worthwhile examining new approaches to improve the spatial resolution of PET detectors. This work was supported by a grant from The Whitaker Foundation Our design overcomes many of these problems by returning to what is effectively a one-to-one coupling between scintillator element and photodetector. We propose to use 2-D arrays of small BGO crystals, coupled via short lengths of optical fiber, to a MC-PMT (Fig. l), such as the Philips XP1700 series. This PMT was designed for reading out fiber arrays and has 64 or 96 independent channels with low crosstalk [5].",
year = "1995",
month = aug,
doi = "10.1109/23.467749",
language = "English (US)",
volume = "42",
pages = "1058--1063",
journal = "IEEE Transactions on Nuclear Science",
issn = "0018-9499",
publisher = "Institute of Electrical and Electronics Engineers Inc.",
number = "4",
}