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Title: SU-E-T-161: Characterization and Validation of CT Simulator Hounsfield Units to Relative Stopping Power Values for Proton Treatment Planning

Abstract

Purpose: To develop a calibration curve that includes and minimizes the variations of Hounsfield Unit (HU) from a CT scanner to Relative Stopping Power (RSP) of tissues along the proton beam path. The variations are due to scanner and proton energy, technique, phantom size and placement, and tissue arrangement. Methods: A CIRS 062 M phantom with 10 plugs of known relative electron density (RED) was scanned through a 16 slice GE Discovery CT Simulator scanner. Three setup combinations of plug distributions and techniques clinically implemented for five treatment regions were scanned with energies of 100, 120, and 140 kV. Volumetric HU values were measured for each plug and scan. The RSP values derived through the Bethe-Bloch formula are currently being verified with parallel-plate ionization chamber measurements in water using 80, 150, and 225 MeV proton beam. Typical treatment plans for treatment regions of brain, head-&-neck, chest, abdomen, and pelvis are being planned and dose delivered will be compared with film and Optically Stimulated Luminescence (OSL) measurements. Results: Percentage variations were determined for each variable. For tissues close to water, variations were <1% from any given parameter. Tissues far from water equivalence (lung and bone) showed the greatest sensitivity to changemore » (7.4% maximum) with scanner energy and up to 5.3% with positioning of the phantom. No major variations were observed for proton energies within the treatment range. Conclusion: When deriving a calibration curve, attention should be placed to low and high HU values. A thorough verification process of calculated vs. water-phantom measured RSP values at different proton energies, followed by dose validation of planned vs. measured doses in phantom with film and OSL detectors are currently being undertaken.« less

Authors:
;
Publication Date:
OSTI Identifier:
22545286
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ANIMAL TISSUES; BRAIN; COMPUTERIZED TOMOGRAPHY; ELECTRON DENSITY; HEAD; IONIZATION CHAMBERS; NECK; PELVIS; PHANTOMS; PLANNING; PROTON BEAMS; SIMULATORS; STOPPING POWER

Citation Formats

Schnell, E, Ahmad, S, and De La Fuente Herman, T. SU-E-T-161: Characterization and Validation of CT Simulator Hounsfield Units to Relative Stopping Power Values for Proton Treatment Planning. United States: N. p., 2015. Web. doi:10.1118/1.4924523.
Schnell, E, Ahmad, S, & De La Fuente Herman, T. SU-E-T-161: Characterization and Validation of CT Simulator Hounsfield Units to Relative Stopping Power Values for Proton Treatment Planning. United States. https://doi.org/10.1118/1.4924523
Schnell, E, Ahmad, S, and De La Fuente Herman, T. 2015. "SU-E-T-161: Characterization and Validation of CT Simulator Hounsfield Units to Relative Stopping Power Values for Proton Treatment Planning". United States. https://doi.org/10.1118/1.4924523.
@article{osti_22545286,
title = {SU-E-T-161: Characterization and Validation of CT Simulator Hounsfield Units to Relative Stopping Power Values for Proton Treatment Planning},
author = {Schnell, E and Ahmad, S and De La Fuente Herman, T},
abstractNote = {Purpose: To develop a calibration curve that includes and minimizes the variations of Hounsfield Unit (HU) from a CT scanner to Relative Stopping Power (RSP) of tissues along the proton beam path. The variations are due to scanner and proton energy, technique, phantom size and placement, and tissue arrangement. Methods: A CIRS 062 M phantom with 10 plugs of known relative electron density (RED) was scanned through a 16 slice GE Discovery CT Simulator scanner. Three setup combinations of plug distributions and techniques clinically implemented for five treatment regions were scanned with energies of 100, 120, and 140 kV. Volumetric HU values were measured for each plug and scan. The RSP values derived through the Bethe-Bloch formula are currently being verified with parallel-plate ionization chamber measurements in water using 80, 150, and 225 MeV proton beam. Typical treatment plans for treatment regions of brain, head-&-neck, chest, abdomen, and pelvis are being planned and dose delivered will be compared with film and Optically Stimulated Luminescence (OSL) measurements. Results: Percentage variations were determined for each variable. For tissues close to water, variations were <1% from any given parameter. Tissues far from water equivalence (lung and bone) showed the greatest sensitivity to change (7.4% maximum) with scanner energy and up to 5.3% with positioning of the phantom. No major variations were observed for proton energies within the treatment range. Conclusion: When deriving a calibration curve, attention should be placed to low and high HU values. A thorough verification process of calculated vs. water-phantom measured RSP values at different proton energies, followed by dose validation of planned vs. measured doses in phantom with film and OSL detectors are currently being undertaken.},
doi = {10.1118/1.4924523},
url = {https://www.osti.gov/biblio/22545286}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}