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Title: Image blurring due to light-sharing in PET block detectors

Abstract

The spatial resolution in PET is poorer than that of CT or MRI. All modern PET scanners use block detectors, i.e., clusters of scintillation crystals coupled to four photomultiplier tubes. Some of the loss of spatial resolution in PET is attributed to the use of block detectors, because a photon that interacts with one crystal in the cluster may be incorrectly positioned, resulting in blurring of the reconstructed image. This is called the ''block effect.'' The block effect was measured for detectors from the CTI HR+ scanner, and the GE Advance scanner; two popular clinical PET scanners. The effect of changing the depth of first interaction of a gamma ray in the scintillation crystals was also studied to determine if it may be a contributor to the block effect. The block effect was found to be 1.2{+-}0.5 mm for the central crystals and negligible for the edge crystals in the CTI HR+ block. It was 0.9{+-}0.3 mm in the central crystals of the GE Advance detector, and 0.7{+-}0.3 mm in the edge crystals of the GE Advance detector. In the CTI HR+ detector, a depth dependence on the positioning of the event was observed, as was a dependence on themore » crystal location (edge versus center). In the GE Advance detector events that occurred at different interaction depths were positioned consistently. The percentage of events that may be positioned inaccurately was also calculated for both detectors. In the CTI HR+ detector as many as 16% of all events in the block detector may be positioned incorrectly. In the GE Advance detector as many as 13% of all events in the block detector may be positioned inaccurately. These results suggest that the depth of interaction of an annihilation photon may contribute to the block effect in detectors that use crystals cut from a single scintillation crystal (pseudodiscrete crystals), and is less dominant a factor for detectors that use discrete crystals with light sharing between the crystals. Investigating the effect of changing photon interaction depth in PET detectors can lead to better detector design, and an intuitive explanation of what sources of blurring may exist in the detector examined.« less

Authors:
;  [1]
  1. Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4 (Canada)
Publication Date:
OSTI Identifier:
20775066
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 33; Journal Issue: 2; Other Information: DOI: 10.1118/1.2161406; (c) 2006 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ANNIHILATION; GAMMA DETECTION; GAMMA RADIATION; IMAGE SCANNERS; IMAGES; NMR IMAGING; PHOTOMULTIPLIERS; POSITRON COMPUTED TOMOGRAPHY; SCINTILLATIONS; SOLID SCINTILLATION DETECTORS; SPATIAL RESOLUTION

Citation Formats

St James, Sara, and Thompson, Christopher J. Image blurring due to light-sharing in PET block detectors. United States: N. p., 2006. Web. doi:10.1118/1.2161406.
St James, Sara, & Thompson, Christopher J. Image blurring due to light-sharing in PET block detectors. United States. doi:10.1118/1.2161406.
St James, Sara, and Thompson, Christopher J. Wed . "Image blurring due to light-sharing in PET block detectors". United States. doi:10.1118/1.2161406.
@article{osti_20775066,
title = {Image blurring due to light-sharing in PET block detectors},
author = {St James, Sara and Thompson, Christopher J.},
abstractNote = {The spatial resolution in PET is poorer than that of CT or MRI. All modern PET scanners use block detectors, i.e., clusters of scintillation crystals coupled to four photomultiplier tubes. Some of the loss of spatial resolution in PET is attributed to the use of block detectors, because a photon that interacts with one crystal in the cluster may be incorrectly positioned, resulting in blurring of the reconstructed image. This is called the ''block effect.'' The block effect was measured for detectors from the CTI HR+ scanner, and the GE Advance scanner; two popular clinical PET scanners. The effect of changing the depth of first interaction of a gamma ray in the scintillation crystals was also studied to determine if it may be a contributor to the block effect. The block effect was found to be 1.2{+-}0.5 mm for the central crystals and negligible for the edge crystals in the CTI HR+ block. It was 0.9{+-}0.3 mm in the central crystals of the GE Advance detector, and 0.7{+-}0.3 mm in the edge crystals of the GE Advance detector. In the CTI HR+ detector, a depth dependence on the positioning of the event was observed, as was a dependence on the crystal location (edge versus center). In the GE Advance detector events that occurred at different interaction depths were positioned consistently. The percentage of events that may be positioned inaccurately was also calculated for both detectors. In the CTI HR+ detector as many as 16% of all events in the block detector may be positioned incorrectly. In the GE Advance detector as many as 13% of all events in the block detector may be positioned inaccurately. These results suggest that the depth of interaction of an annihilation photon may contribute to the block effect in detectors that use crystals cut from a single scintillation crystal (pseudodiscrete crystals), and is less dominant a factor for detectors that use discrete crystals with light sharing between the crystals. Investigating the effect of changing photon interaction depth in PET detectors can lead to better detector design, and an intuitive explanation of what sources of blurring may exist in the detector examined.},
doi = {10.1118/1.2161406},
journal = {Medical Physics},
number = 2,
volume = 33,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}