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Title: Measurement of Gamma Knife registered helmet factors using MOSFETs

Abstract

The relative dose rate for the different Gamma Knife registered helmets (4, 8, 14, and 18 mm) is characterized by their respective helmet factors. Since the plateau of the dose profile for the 4 mm helmet is at most 1 mm wide, detector choices are limited. Traditionally helmet factors have been measured using 1x1x1 mm{sup 3} thermoluminescent dosimeters (TLDs). However, these are time-consuming, cumbersome measurements. This article investigates the use of metal-oxide-semiconductor field effect transistors (MOSFETs) (active area of 0.2x0.2 mm{sup 2}) as a more accurate and convenient dosimeter. Their suitability for these measurements was confirmed by basic characterization measurements. Helmet factors were measured using both MOSFETs and the established TLD approach. A custom MOSFET cassette was designed in analogy to the Elekta TLD cassette (Elekta Instruments AB) for use with the Elekta dosimetry sphere. Although both dosimeters provided values within 3% of the manufacturer's suggestion, MOSFETs provided superior accuracy and precision, in a fraction of the time required for the TLD measurements. Thus, MOSFETs proved to be a reasonable alternative to TLDs for performing helmet factor measurements.

Authors:
;  [1];  [2];  [2];  [3]
  1. Department of Physics, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba R3B 2E9 (Canada)
  2. (Canada)
  3. (Canada) and Department of Physics and Astronomy, University of Manitoba, Winnipeg MB R3E 0V9 (Canada)
Publication Date:
OSTI Identifier:
20951090
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 3; Other Information: DOI: 10.1118/1.2437282; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; DOSE RATES; DOSIMETRY; MOSFET; RADIATION DOSES; RADIOTHERAPY; SEMICONDUCTOR MATERIALS; THERMOLUMINESCENT DOSEMETERS

Citation Formats

Kurjewicz, Laryssa, Berndt, Anita, Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9, Winnipeg Centre for Gamma Knife Surgery, Health Sciences Centre, Winnipeg Regional Health Authority, Winnipeg MB R3E 0V9, and Section of Neurosurgery, Department of Surgery, Department of Radiology, University of Manitoba, Winnipeg MB R3E 0V9. Measurement of Gamma Knife registered helmet factors using MOSFETs. United States: N. p., 2007. Web. doi:10.1118/1.2437282.
Kurjewicz, Laryssa, Berndt, Anita, Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9, Winnipeg Centre for Gamma Knife Surgery, Health Sciences Centre, Winnipeg Regional Health Authority, Winnipeg MB R3E 0V9, & Section of Neurosurgery, Department of Surgery, Department of Radiology, University of Manitoba, Winnipeg MB R3E 0V9. Measurement of Gamma Knife registered helmet factors using MOSFETs. United States. doi:10.1118/1.2437282.
Kurjewicz, Laryssa, Berndt, Anita, Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9, Winnipeg Centre for Gamma Knife Surgery, Health Sciences Centre, Winnipeg Regional Health Authority, Winnipeg MB R3E 0V9, and Section of Neurosurgery, Department of Surgery, Department of Radiology, University of Manitoba, Winnipeg MB R3E 0V9. Thu . "Measurement of Gamma Knife registered helmet factors using MOSFETs". United States. doi:10.1118/1.2437282.
@article{osti_20951090,
title = {Measurement of Gamma Knife registered helmet factors using MOSFETs},
author = {Kurjewicz, Laryssa and Berndt, Anita and Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 and Winnipeg Centre for Gamma Knife Surgery, Health Sciences Centre, Winnipeg Regional Health Authority, Winnipeg MB R3E 0V9 and Section of Neurosurgery, Department of Surgery, Department of Radiology, University of Manitoba, Winnipeg MB R3E 0V9},
abstractNote = {The relative dose rate for the different Gamma Knife registered helmets (4, 8, 14, and 18 mm) is characterized by their respective helmet factors. Since the plateau of the dose profile for the 4 mm helmet is at most 1 mm wide, detector choices are limited. Traditionally helmet factors have been measured using 1x1x1 mm{sup 3} thermoluminescent dosimeters (TLDs). However, these are time-consuming, cumbersome measurements. This article investigates the use of metal-oxide-semiconductor field effect transistors (MOSFETs) (active area of 0.2x0.2 mm{sup 2}) as a more accurate and convenient dosimeter. Their suitability for these measurements was confirmed by basic characterization measurements. Helmet factors were measured using both MOSFETs and the established TLD approach. A custom MOSFET cassette was designed in analogy to the Elekta TLD cassette (Elekta Instruments AB) for use with the Elekta dosimetry sphere. Although both dosimeters provided values within 3% of the manufacturer's suggestion, MOSFETs provided superior accuracy and precision, in a fraction of the time required for the TLD measurements. Thus, MOSFETs proved to be a reasonable alternative to TLDs for performing helmet factor measurements.},
doi = {10.1118/1.2437282},
journal = {Medical Physics},
number = 3,
volume = 34,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}