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Title: SU-C-201-04: Noise and Temporal Resolution in a Near Real-Time 3D Dosimeter

Abstract

Purpose: To characterize the performance of a real-time three-dimensional scintillation dosimeter in terms of signal-to-noise ratio (SNR) and temporal resolution of 3D dose measurements. This study quantifies its efficiency in measuring low dose levels characteristic of EBRT dynamic treatments, and in reproducing field profiles for varying multileaf collimator (MLC) speeds. Methods: The dosimeter prototype uses a plenoptic camera to acquire continuous images of the light field emitted by a 10×10×10 cm{sup 3} plastic scintillator. Using EPID acquisitions, ray tracing-based iterative tomographic algorithms allow millimeter-sized reconstruction of relative 3D dose distributions. Measurements were taken at 6MV, 400 MU/min with the scintillator centered at the isocenter, first receiving doses from 1.4 to 30.6 cGy. Dynamic measurements were then performed by closing half of the MLCs at speeds of 0.67 to 2.5 cm/s, at 0° and 90° collimator angles. A reference static half-field was obtained for measured profile comparison. Results: The SNR steadily increases as a function of dose and reaches a clinically adequate plateau of 80 at 10 cGy. Below this, the decrease in light collected and increase in pixel noise diminishes the SNR; nonetheless, the EPID acquisitions and the voxel correlation employed in the reconstruction algorithms result in suitable SNR valuesmore » (>75) even at low doses. For dynamic measurements at varying MLC speeds, central relative dose profiles are characterized by gradients at %D{sub 50} of 8.48 to 22.7 %/mm. These values converge towards the 32.8 %/mm-gradient measured for the static reference field profile, but are limited by the dosimeter’s current acquisition rate of 1Hz. Conclusion: This study emphasizes the efficiency of the 3D dose distribution reconstructions, while identifying limits of the current prototype’s temporal resolution in terms of dynamic EBRT parameters. This work paves the way for providing an optimized, second-generational real-time 3D scintillation dosimeter capable of highly efficient and precise dose measurements. The presenting author is financially supported by an Alexander-Graham Bell doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC).« less

Authors:
 [1];  [2];  [2];  [2];  [3]; ;  [1];  [2];  [2];  [4]
  1. Department of physics, engineering physics and optics, Universite Laval, Quebec City, QC (Canada)
  2. (Canada)
  3. Radiation oncology department, CHU de Quebec, Quebec City, QC (Canada)
  4. Center for optics, photonics and lasers, Universite Laval, Quebec City, Quebec (Canada)
Publication Date:
OSTI Identifier:
22624309
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 60 APPLIED LIFE SCIENCES; ALGORITHMS; COLLIMATORS; DOSEMETERS; ITERATIVE METHODS; PLASTIC SCINTILLATORS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; SIGNAL-TO-NOISE RATIO; SPATIAL RESOLUTION

Citation Formats

Rilling, M, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, Center for optics, photonics and lasers, Universite Laval, Quebec City, Quebec, Goulet, M, Beaulieu, L, Archambault, L, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, and Thibault, S. SU-C-201-04: Noise and Temporal Resolution in a Near Real-Time 3D Dosimeter. United States: N. p., 2016. Web. doi:10.1118/1.4955544.
Rilling, M, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, Center for optics, photonics and lasers, Universite Laval, Quebec City, Quebec, Goulet, M, Beaulieu, L, Archambault, L, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, & Thibault, S. SU-C-201-04: Noise and Temporal Resolution in a Near Real-Time 3D Dosimeter. United States. doi:10.1118/1.4955544.
Rilling, M, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, Center for optics, photonics and lasers, Universite Laval, Quebec City, Quebec, Goulet, M, Beaulieu, L, Archambault, L, Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Radiation oncology department, CHU de Quebec, Quebec City, QC, and Thibault, S. 2016. "SU-C-201-04: Noise and Temporal Resolution in a Near Real-Time 3D Dosimeter". United States. doi:10.1118/1.4955544.
@article{osti_22624309,
title = {SU-C-201-04: Noise and Temporal Resolution in a Near Real-Time 3D Dosimeter},
author = {Rilling, M and Centre de recherche sur le cancer, Universite Laval, Quebec City, QC and Radiation oncology department, CHU de Quebec, Quebec City, QC and Center for optics, photonics and lasers, Universite Laval, Quebec City, Quebec and Goulet, M and Beaulieu, L and Archambault, L and Centre de recherche sur le cancer, Universite Laval, Quebec City, QC and Radiation oncology department, CHU de Quebec, Quebec City, QC and Thibault, S},
abstractNote = {Purpose: To characterize the performance of a real-time three-dimensional scintillation dosimeter in terms of signal-to-noise ratio (SNR) and temporal resolution of 3D dose measurements. This study quantifies its efficiency in measuring low dose levels characteristic of EBRT dynamic treatments, and in reproducing field profiles for varying multileaf collimator (MLC) speeds. Methods: The dosimeter prototype uses a plenoptic camera to acquire continuous images of the light field emitted by a 10×10×10 cm{sup 3} plastic scintillator. Using EPID acquisitions, ray tracing-based iterative tomographic algorithms allow millimeter-sized reconstruction of relative 3D dose distributions. Measurements were taken at 6MV, 400 MU/min with the scintillator centered at the isocenter, first receiving doses from 1.4 to 30.6 cGy. Dynamic measurements were then performed by closing half of the MLCs at speeds of 0.67 to 2.5 cm/s, at 0° and 90° collimator angles. A reference static half-field was obtained for measured profile comparison. Results: The SNR steadily increases as a function of dose and reaches a clinically adequate plateau of 80 at 10 cGy. Below this, the decrease in light collected and increase in pixel noise diminishes the SNR; nonetheless, the EPID acquisitions and the voxel correlation employed in the reconstruction algorithms result in suitable SNR values (>75) even at low doses. For dynamic measurements at varying MLC speeds, central relative dose profiles are characterized by gradients at %D{sub 50} of 8.48 to 22.7 %/mm. These values converge towards the 32.8 %/mm-gradient measured for the static reference field profile, but are limited by the dosimeter’s current acquisition rate of 1Hz. Conclusion: This study emphasizes the efficiency of the 3D dose distribution reconstructions, while identifying limits of the current prototype’s temporal resolution in terms of dynamic EBRT parameters. This work paves the way for providing an optimized, second-generational real-time 3D scintillation dosimeter capable of highly efficient and precise dose measurements. The presenting author is financially supported by an Alexander-Graham Bell doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC).},
doi = {10.1118/1.4955544},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
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