SUFT73: Experimental Determination of the Effective Point of Measurement in Electron Beams Using a Commercial Scintillation Detector
Abstract
Purpose: The aim of this work was to determine experimentally the effective point of measurement (EPOM) in clinical electron beams for three cylindrical ionization chambers using a commercial scintillation detector as a reference detector. Methods: Percent depth dose (PDD) curves were measured using an Exradin W1 scintillation detector and were used as a representative PDD to water. Depth dose curves were measured with the Exradin A18, A1SL, and A28 ionization chambers. The raw ionization chamber curve data were corrected by the chamber fluence perturbation correction factor and restricted mass collisional stopping power ratio at each depth to obtain a percent depth dose curve to the gas volume (PDDGV) of the detector. Ratios of the W1 PDD to the ion chamber PDDGV were calculated for each measurement depth. The W1 PDD curve was shifted by small depth increments, Δz, until the ratio of the W1 PDD to the ion chamber PDDGV was depthindependent (optimal Δz). A MATLAB routine was developed to determine the optimal Δz value. Results: The optimal Δz shift was used as an estimate of the EPOM for each chamber. The average calculated EPOM shifts (expressed as a fraction of the chamber cavity radius) for the A18, A1SL, andmore »
 Authors:
 University of Wisc Madison, Madison, WI (United States)
 Publication Date:
 OSTI Identifier:
 22642321
 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; CORRECTIONS; CYLINDRICAL CONFIGURATION; DEPTH DOSE DISTRIBUTIONS; ELECTRON BEAMS; IONIZATION CHAMBERS; PERTURBATION THEORY; PHOSPHORS; SCINTILLATION COUNTERS; SCINTILLATIONS; SIMULATION; STOPPING POWER
Citation Formats
Simiele, E, Smith, B, and Culberson, W. SUFT73: Experimental Determination of the Effective Point of Measurement in Electron Beams Using a Commercial Scintillation Detector. United States: N. p., 2016.
Web. doi:10.1118/1.4956209.
Simiele, E, Smith, B, & Culberson, W. SUFT73: Experimental Determination of the Effective Point of Measurement in Electron Beams Using a Commercial Scintillation Detector. United States. doi:10.1118/1.4956209.
Simiele, E, Smith, B, and Culberson, W. 2016.
"SUFT73: Experimental Determination of the Effective Point of Measurement in Electron Beams Using a Commercial Scintillation Detector". United States.
doi:10.1118/1.4956209.
@article{osti_22642321,
title = {SUFT73: Experimental Determination of the Effective Point of Measurement in Electron Beams Using a Commercial Scintillation Detector},
author = {Simiele, E and Smith, B and Culberson, W},
abstractNote = {Purpose: The aim of this work was to determine experimentally the effective point of measurement (EPOM) in clinical electron beams for three cylindrical ionization chambers using a commercial scintillation detector as a reference detector. Methods: Percent depth dose (PDD) curves were measured using an Exradin W1 scintillation detector and were used as a representative PDD to water. Depth dose curves were measured with the Exradin A18, A1SL, and A28 ionization chambers. The raw ionization chamber curve data were corrected by the chamber fluence perturbation correction factor and restricted mass collisional stopping power ratio at each depth to obtain a percent depth dose curve to the gas volume (PDDGV) of the detector. Ratios of the W1 PDD to the ion chamber PDDGV were calculated for each measurement depth. The W1 PDD curve was shifted by small depth increments, Δz, until the ratio of the W1 PDD to the ion chamber PDDGV was depthindependent (optimal Δz). A MATLAB routine was developed to determine the optimal Δz value. Results: The optimal Δz shift was used as an estimate of the EPOM for each chamber. The average calculated EPOM shifts (expressed as a fraction of the chamber cavity radius) for the A18, A1SL, and A28 ionization chambers were 0.21 ± 0.04, 0.10 ± 0.05, and 0.22 ± 0.03, respectively. Conclusion: The experimentally determined EPOM values for the A18 and A1SL in this work agreed with the simulated values of Muir and Rogers (MedPhys 2014). The results also indicate that the Exradin W1 scintillator is water equivalent for electron energies of 6 MeV, 9 MeV, 12 MeV, and 16 MeV. In addition, we confirmed that the AAPM TG51 recommended EPOM shift of 0.5 times the cavity radius is not accurate for the A18 and A1SL chambers.},
doi = {10.1118/1.4956209},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}

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