Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy

Taewoong Lee, Changyeon Yoon, Won Ho Lee

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × ε mm3, where ε is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.

Original languageEnglish
Pages (from-to)1745-1750
Number of pages6
JournalJournal of the Korean Physical Society
Volume64
Issue number11
DOIs
Publication statusPublished - 2014 Jan 1

Fingerprint

therapy
cameras
optimization
detectors
photons
scattering
angular resolution
dosage
radiation therapy
zinc tellurides
cadmium tellurides
sequencing
tungstates
figure of merit
cadmium
point sources
scintillation counters
scintillation
Monte Carlo method
energy

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy. / Lee, Taewoong; Yoon, Changyeon; Lee, Won Ho.

In: Journal of the Korean Physical Society, Vol. 64, No. 11, 01.01.2014, p. 1745-1750.

Research output: Contribution to journalArticle

@article{d2607a1982584df5931f580cb99ce0e9,
title = "Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy",
abstract = "During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × ε mm3, where ε is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.",
keywords = "Compton camera, Semiconductor detector, Uncertainty factor",
author = "Taewoong Lee and Changyeon Yoon and Lee, {Won Ho}",
year = "2014",
month = "1",
day = "1",
doi = "10.3938/jkps.64.1745",
language = "English",
volume = "64",
pages = "1745--1750",
journal = "Journal of the Korean Physical Society",
issn = "0374-4884",
publisher = "Korean Physical Society",
number = "11",

}

TY - JOUR

T1 - Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy

AU - Lee, Taewoong

AU - Yoon, Changyeon

AU - Lee, Won Ho

PY - 2014/1/1

Y1 - 2014/1/1

N2 - During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × ε mm3, where ε is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.

AB - During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × ε mm3, where ε is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.

KW - Compton camera

KW - Semiconductor detector

KW - Uncertainty factor

UR - http://www.scopus.com/inward/record.url?scp=84902973871&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84902973871&partnerID=8YFLogxK

U2 - 10.3938/jkps.64.1745

DO - 10.3938/jkps.64.1745

M3 - Article

VL - 64

SP - 1745

EP - 1750

JO - Journal of the Korean Physical Society

JF - Journal of the Korean Physical Society

SN - 0374-4884

IS - 11

ER -