Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors

Craig S. Levin, Martin P. Tornai, Simon R Cherry, Lawrence R. MacDonald, Edward J. Huffman

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

To improve spatial resolution, positron emission tomography (PET) systems are being developed with finer detector elements. Unfortunately, using a smaller crystal size increases intercrystal Compton scatter and X-ray escape crosstalk, causing positioning errors that can lead to degradation of image contrast. We investigated the use of extremely thin (<300 /urn) lead strips for passive shielding of this intercrystal crosstalk. Using annihilation gamma rays and small (2- and 3-mm wide) Bismuth Germanate (BGO) crystal detectors in coincidence, crosstalk studies were performed with either two small adjacent crystals [(one-dimensional) (1-D)] or one crystal inside a volume of BGO [(two-dimensional) (2-D)J. The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D one, with a 300 (ISO)-4m-thick lead strip in between the crystals and a 300-700-keV energy window in both crystals. We could not measure a reduction in bismuth X-ray crosstalk with the use of lead septa due to the production of lead X-rays of similar energy. The full-width at half-maximum (FWHM) of the coincident point-spread function (CPSF) was not significantly different for the 1- and 2-D studies, with or without the different septa in place. However, the FWTM was roughly 20% smaller with the 300-jum lead shielding in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution at FWHM, but does affect the tails of the CPSF. Thus, without introducing any additional dead area, an insertion of very thin lead strips can reduce the extent of positioning errors. Reducing the intercrystal crosstalk in a high-resolution PET detector array could potentially improve tomographic image contrast in situations where intercrystal crosstalk plays a significant role in event mispositioning. -.

Original languageEnglish (US)
Pages (from-to)218-224
Number of pages7
JournalIEEE Transactions on Nuclear Science
Volume44
Issue number2
DOIs
StatePublished - 1997

Fingerprint

septum
Positron emission tomography
Crosstalk
crosstalk
positrons
tomography
Detectors
X rays
Crystals
high resolution
detectors
crystals
x rays
positioning
strip
Optical transfer function
image contrast
point spread functions
Full width at half maximum
Bismuth

Keywords

  • Compton scatter
  • Detector crosstalk
  • Intercrystal septa
  • PET detectors
  • Scintillation crystals
  • X-ray escape

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Nuclear Energy and Engineering

Cite this

Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors. / Levin, Craig S.; Tornai, Martin P.; Cherry, Simon R; MacDonald, Lawrence R.; Huffman, Edward J.

In: IEEE Transactions on Nuclear Science, Vol. 44, No. 2, 1997, p. 218-224.

Research output: Contribution to journalArticle

Levin, Craig S. ; Tornai, Martin P. ; Cherry, Simon R ; MacDonald, Lawrence R. ; Huffman, Edward J. / Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors. In: IEEE Transactions on Nuclear Science. 1997 ; Vol. 44, No. 2. pp. 218-224.
@article{5eb7a2e9862247a4add2e8c955c76faa,
title = "Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors",
abstract = "To improve spatial resolution, positron emission tomography (PET) systems are being developed with finer detector elements. Unfortunately, using a smaller crystal size increases intercrystal Compton scatter and X-ray escape crosstalk, causing positioning errors that can lead to degradation of image contrast. We investigated the use of extremely thin (<300 /urn) lead strips for passive shielding of this intercrystal crosstalk. Using annihilation gamma rays and small (2- and 3-mm wide) Bismuth Germanate (BGO) crystal detectors in coincidence, crosstalk studies were performed with either two small adjacent crystals [(one-dimensional) (1-D)] or one crystal inside a volume of BGO [(two-dimensional) (2-D)J. The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D one, with a 300 (ISO)-4m-thick lead strip in between the crystals and a 300-700-keV energy window in both crystals. We could not measure a reduction in bismuth X-ray crosstalk with the use of lead septa due to the production of lead X-rays of similar energy. The full-width at half-maximum (FWHM) of the coincident point-spread function (CPSF) was not significantly different for the 1- and 2-D studies, with or without the different septa in place. However, the FWTM was roughly 20{\%} smaller with the 300-jum lead shielding in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution at FWHM, but does affect the tails of the CPSF. Thus, without introducing any additional dead area, an insertion of very thin lead strips can reduce the extent of positioning errors. Reducing the intercrystal crosstalk in a high-resolution PET detector array could potentially improve tomographic image contrast in situations where intercrystal crosstalk plays a significant role in event mispositioning. -.",
keywords = "Compton scatter, Detector crosstalk, Intercrystal septa, PET detectors, Scintillation crystals, X-ray escape",
author = "Levin, {Craig S.} and Tornai, {Martin P.} and Cherry, {Simon R} and MacDonald, {Lawrence R.} and Huffman, {Edward J.}",
year = "1997",
doi = "10.1109/23.568809",
language = "English (US)",
volume = "44",
pages = "218--224",
journal = "IEEE Transactions on Nuclear Science",
issn = "0018-9499",
publisher = "Institute of Electrical and Electronics Engineers Inc.",
number = "2",

}

TY - JOUR

T1 - Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors

AU - Levin, Craig S.

AU - Tornai, Martin P.

AU - Cherry, Simon R

AU - MacDonald, Lawrence R.

AU - Huffman, Edward J.

PY - 1997

Y1 - 1997

N2 - To improve spatial resolution, positron emission tomography (PET) systems are being developed with finer detector elements. Unfortunately, using a smaller crystal size increases intercrystal Compton scatter and X-ray escape crosstalk, causing positioning errors that can lead to degradation of image contrast. We investigated the use of extremely thin (<300 /urn) lead strips for passive shielding of this intercrystal crosstalk. Using annihilation gamma rays and small (2- and 3-mm wide) Bismuth Germanate (BGO) crystal detectors in coincidence, crosstalk studies were performed with either two small adjacent crystals [(one-dimensional) (1-D)] or one crystal inside a volume of BGO [(two-dimensional) (2-D)J. The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D one, with a 300 (ISO)-4m-thick lead strip in between the crystals and a 300-700-keV energy window in both crystals. We could not measure a reduction in bismuth X-ray crosstalk with the use of lead septa due to the production of lead X-rays of similar energy. The full-width at half-maximum (FWHM) of the coincident point-spread function (CPSF) was not significantly different for the 1- and 2-D studies, with or without the different septa in place. However, the FWTM was roughly 20% smaller with the 300-jum lead shielding in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution at FWHM, but does affect the tails of the CPSF. Thus, without introducing any additional dead area, an insertion of very thin lead strips can reduce the extent of positioning errors. Reducing the intercrystal crosstalk in a high-resolution PET detector array could potentially improve tomographic image contrast in situations where intercrystal crosstalk plays a significant role in event mispositioning. -.

AB - To improve spatial resolution, positron emission tomography (PET) systems are being developed with finer detector elements. Unfortunately, using a smaller crystal size increases intercrystal Compton scatter and X-ray escape crosstalk, causing positioning errors that can lead to degradation of image contrast. We investigated the use of extremely thin (<300 /urn) lead strips for passive shielding of this intercrystal crosstalk. Using annihilation gamma rays and small (2- and 3-mm wide) Bismuth Germanate (BGO) crystal detectors in coincidence, crosstalk studies were performed with either two small adjacent crystals [(one-dimensional) (1-D)] or one crystal inside a volume of BGO [(two-dimensional) (2-D)J. The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D one, with a 300 (ISO)-4m-thick lead strip in between the crystals and a 300-700-keV energy window in both crystals. We could not measure a reduction in bismuth X-ray crosstalk with the use of lead septa due to the production of lead X-rays of similar energy. The full-width at half-maximum (FWHM) of the coincident point-spread function (CPSF) was not significantly different for the 1- and 2-D studies, with or without the different septa in place. However, the FWTM was roughly 20% smaller with the 300-jum lead shielding in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution at FWHM, but does affect the tails of the CPSF. Thus, without introducing any additional dead area, an insertion of very thin lead strips can reduce the extent of positioning errors. Reducing the intercrystal crosstalk in a high-resolution PET detector array could potentially improve tomographic image contrast in situations where intercrystal crosstalk plays a significant role in event mispositioning. -.

KW - Compton scatter

KW - Detector crosstalk

KW - Intercrystal septa

KW - PET detectors

KW - Scintillation crystals

KW - X-ray escape

UR - http://www.scopus.com/inward/record.url?scp=0031122154&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031122154&partnerID=8YFLogxK

U2 - 10.1109/23.568809

DO - 10.1109/23.568809

M3 - Article

AN - SCOPUS:0031122154

VL - 44

SP - 218

EP - 224

JO - IEEE Transactions on Nuclear Science

JF - IEEE Transactions on Nuclear Science

SN - 0018-9499

IS - 2

ER -