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Modelling of energy-dependent spectral resolution for SPECT Monte Carlo simulations using SIMIND

Morphis, Michaella ; van Staden, Johan A. ; du Raan, Hanlie and Ljungberg, Michael LU (2021) In Heliyon 7(2).
Abstract
Monte Carlo (MC) modelling techniques have been used extensively in
Nuclear Medicine (NM). The theoretical energy resolution relationship (∝1/E−−√),
does not accurately predict the gamma camera detector response across
all energies. This study aimed to validate the accuracy of an energy
resolution model for the SIMIND MC simulation code emulating the Siemens
Symbia T16 dual-head gamma camera.MethodsMeasured
intrinsic energy resolution data (full width half maximum (FWHM)
values), for Ba-133, Lu-177, Am-241, Ga-67, Tc-99m, I-123, I-131 and
F-18 sources in air, were used to create a fitted model of the energy response of the gamma camera. Both the fitted and theoretical... (More)
Monte Carlo (MC) modelling techniques have been used extensively in
Nuclear Medicine (NM). The theoretical energy resolution relationship (∝1/E−−√),
does not accurately predict the gamma camera detector response across
all energies. This study aimed to validate the accuracy of an energy
resolution model for the SIMIND MC simulation code emulating the Siemens
Symbia T16 dual-head gamma camera.MethodsMeasured
intrinsic energy resolution data (full width half maximum (FWHM)
values), for Ba-133, Lu-177, Am-241, Ga-67, Tc-99m, I-123, I-131 and
F-18 sources in air, were used to create a fitted model of the energy response of the gamma camera. Both the fitted and theoretical models
were used to simulate intrinsic and extrinsic energy spectra using
three different scenarios (source in air; source in simple scatter
phantom and a clinical voxel-based digital patient phantom).ResultsThe results showed the theoretical model underestimated the FWHM values at energies above 160.0 keV up to 23.5 keV. In contrast, the fitted model
better predicted the measured FWHM values with differences less than
3.3 keV. The I-131 in-scatter energy spectrum simulated with the fitted model
better matched the measured energy spectrum. Higher energy photopeaks,
(I-123: 528.9 keV and I-131: 636.9 keV) simulated with the fitted model, more accurately resembled the measured photopeaks. The voxel-based digital patient phantom energy spectra, simulated with the fitted and theoretical models, showed the potential impact of an incorrect energy resolution model when simulating isotopes with multiple photopeaks.ConclusionModelling of energy resolution with the proposed fitted model
enables the SIMIND user to accurately simulate NM images. A great
improvement was seen for high-energy photon emitting isotopes (e.g.
I-131), as well as isotopes with multiple photopeaks (e.g. Lu-177, I-131
and Ga-67) in comparison to the theoretical model. This will result in accurate evaluation of radioactivity quantification, which is vital for dosimetric purposes. (Less)
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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Energy resolution, Energy spectrum, Monte Carlo simulation, Multiple photopeak isotope
in
Heliyon
volume
7
issue
2
article number
e06097
publisher
Elsevier
external identifiers
  • scopus:85100719884
  • pmid:33659726
ISSN
2405-8440
DOI
10.1016/j.heliyon.2021.e06097
language
English
LU publication?
yes
id
0a514a9a-f532-4923-ab60-6aed978dadd9
date added to LUP
2021-03-02 09:10:51
date last changed
2024-06-28 11:58:03
@article{0a514a9a-f532-4923-ab60-6aed978dadd9,
  abstract     = {{Monte Carlo (MC) modelling techniques have been used extensively in <br>
Nuclear Medicine (NM). The theoretical energy resolution relationship (∝1/E−−√),<br>
 does not accurately predict the gamma camera detector response across <br>
all energies. This study aimed to validate the accuracy of an energy <br>
resolution model for the SIMIND MC simulation code emulating the Siemens<br>
 Symbia T16 dual-head gamma camera.MethodsMeasured<br>
 intrinsic energy resolution data (full width half maximum (FWHM) <br>
values), for Ba-133, Lu-177, Am-241, Ga-67, Tc-99m, I-123, I-131 and <br>
F-18 sources in air, were used to create a <em>fitted model</em> of the energy response of the gamma camera. Both the <em>fitted</em> and <em>theoretical models</em><br>
 were used to simulate intrinsic and extrinsic energy spectra using <br>
three different scenarios (source in air; source in simple scatter <br>
phantom and a clinical voxel-based digital patient phantom).ResultsThe results showed the <em>theoretical model</em> underestimated the FWHM values at energies above 160.0 keV up to 23.5 keV. In contrast, the <em>fitted model</em><br>
 better predicted the measured FWHM values with differences less than <br>
3.3 keV. The I-131 in-scatter energy spectrum simulated with the <em>fitted model</em><br>
 better matched the measured energy spectrum. Higher energy photopeaks, <br>
(I-123: 528.9 keV and I-131: 636.9 keV) simulated with the <em>fitted model</em>, more accurately resembled the measured photopeaks. The voxel-based digital patient phantom energy spectra, simulated with the <em>fitted</em> and <em>theoretical</em> models, showed the potential impact of an incorrect energy resolution model when simulating isotopes with multiple photopeaks.ConclusionModelling of energy resolution with the proposed <em>fitted model</em><br>
 enables the SIMIND user to accurately simulate NM images. A great <br>
improvement was seen for high-energy photon emitting isotopes (e.g. <br>
I-131), as well as isotopes with multiple photopeaks (e.g. Lu-177, I-131<br>
 and Ga-67) in comparison to the <em>theoretical model</em>. This will result in accurate evaluation of radioactivity quantification, which is vital for dosimetric purposes.}},
  author       = {{Morphis, Michaella and van Staden, Johan A. and du Raan, Hanlie and Ljungberg, Michael}},
  issn         = {{2405-8440}},
  keywords     = {{Energy resolution; Energy spectrum; Monte Carlo simulation; Multiple photopeak isotope}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{Elsevier}},
  series       = {{Heliyon}},
  title        = {{Modelling of energy-dependent spectral resolution for SPECT Monte Carlo simulations using SIMIND}},
  url          = {{http://dx.doi.org/10.1016/j.heliyon.2021.e06097}},
  doi          = {{10.1016/j.heliyon.2021.e06097}},
  volume       = {{7}},
  year         = {{2021}},
}