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The relationship between radiation-induced chemical processes and transverse relaxation times in polymer gel dosimeters

Lepage, M; Whittaker, A K; Rintoul, L; Bäck, Sven LU and Baldock, C (2001) In Physics in Medicine and Biology 46(4). p.1061-1074
Abstract
The effects of ionizing radiation in different compositions of polymer gel dosimeters are investigated using FT-Raman spectroscopy and NMR T2 relaxation times. The dosimeters are manufactured from different concentrations of comonomers (acrylamide and N,N'-methylene-bis-acrylamide) dispersed in different concentrations of an aqueous gelatin matrix. Results are analysed using a model of fast exchange of magnetization between three proton pools. The fraction of protons in each pool is determined using the known chemical composition of the dosimeter and FT-Raman spectroscopy. Based on these results, the physical and chemical processes in interplay in the dosimeters are examined in view of their effect on the changes in T2. The precipitation... (More)
The effects of ionizing radiation in different compositions of polymer gel dosimeters are investigated using FT-Raman spectroscopy and NMR T2 relaxation times. The dosimeters are manufactured from different concentrations of comonomers (acrylamide and N,N'-methylene-bis-acrylamide) dispersed in different concentrations of an aqueous gelatin matrix. Results are analysed using a model of fast exchange of magnetization between three proton pools. The fraction of protons in each pool is determined using the known chemical composition of the dosimeter and FT-Raman spectroscopy. Based on these results, the physical and chemical processes in interplay in the dosimeters are examined in view of their effect on the changes in T2. The precipitation of growing macroradicals and the scavenging of free radicals by gelatin are used to explain the rate of polymerization. The model describes the changes in T2 as a function of the absorbed dose up to 50 Gy for the different compositions. This is expected to aid the theoretical design of new, more efficient dosimeters, since it was demonstrated that the optimum dosimeter (i.e, with the lowest dose resolution) must have a range of relaxation times which match the range of T2 values which can be determined with the lowest uncertainty using an MRI scanner. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physics in Medicine and Biology
volume
46
issue
4
pages
1061 - 1074
publisher
IOP Publishing
external identifiers
  • wos:000168210700012
  • scopus:0035041897
ISSN
1361-6560
DOI
language
English
LU publication?
yes
id
80aeaed1-b63d-4727-959b-d8cbf679120c (old id 1297230)
date added to LUP
2009-07-15 09:34:55
date last changed
2018-05-29 10:16:25
@article{80aeaed1-b63d-4727-959b-d8cbf679120c,
  abstract     = {The effects of ionizing radiation in different compositions of polymer gel dosimeters are investigated using FT-Raman spectroscopy and NMR T2 relaxation times. The dosimeters are manufactured from different concentrations of comonomers (acrylamide and N,N'-methylene-bis-acrylamide) dispersed in different concentrations of an aqueous gelatin matrix. Results are analysed using a model of fast exchange of magnetization between three proton pools. The fraction of protons in each pool is determined using the known chemical composition of the dosimeter and FT-Raman spectroscopy. Based on these results, the physical and chemical processes in interplay in the dosimeters are examined in view of their effect on the changes in T2. The precipitation of growing macroradicals and the scavenging of free radicals by gelatin are used to explain the rate of polymerization. The model describes the changes in T2 as a function of the absorbed dose up to 50 Gy for the different compositions. This is expected to aid the theoretical design of new, more efficient dosimeters, since it was demonstrated that the optimum dosimeter (i.e, with the lowest dose resolution) must have a range of relaxation times which match the range of T2 values which can be determined with the lowest uncertainty using an MRI scanner.},
  author       = {Lepage, M and Whittaker, A K and Rintoul, L and Bäck, Sven and Baldock, C},
  issn         = {1361-6560},
  language     = {eng},
  number       = {4},
  pages        = {1061--1074},
  publisher    = {IOP Publishing},
  series       = {Physics in Medicine and Biology},
  title        = {The relationship between radiation-induced chemical processes and transverse relaxation times in polymer gel dosimeters},
  url          = {http://dx.doi.org/},
  volume       = {46},
  year         = {2001},
}