open access

Vol 10, No 6 (2005)
Original Paper
Published online: 2005-01-01
Submitted: 2005-01-31
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MOSFET detectors as a tool for the verification of therapeutic doses of electron beams in radiotherapy

Marcin Dybek, Włodzimierz Łobodziec, Aneta Kawa-Iwanicka, Tomasz Iwanicki
DOI: 10.1016/S1507-1367(05)71103-2
·
Rep Pract Oncol Radiother 2005;10(6):301-306.

open access

Vol 10, No 6 (2005)
Original Paper
Published online: 2005-01-01
Submitted: 2005-01-31

Abstract

Aim

To examine the characteristics of MOSFET (Metal – Oxide Semiconductor Field Effect Transistor) detectors for the purpose of electron beam dose determination in in vivo radiotherapy.

Materials/Methods

Indications of MOSFET detectors were recorded from phantom measurements, including: dose values of electron beams, the environmental temperature of the detectors, the incidence direction of an electron beam on the detector, the size of the irradiated field.

The change in sensitivity of the detectors when under the effects of accumulated doses was also tested.

Because of the very small dimensions of the detectors, they were placed in specially designed aluminium capsules – to ensure electron equilibrium (δ electrons) during the dose measurement. The detector indications were compared to those seen in a Markus type ionization chamber with a calibration certificate. The measurements were made for electron beams with energies of 6, 9, 12, 15, 18 and 21 MeV.

Results

The following were established experimentally: There is a linear relationship between detector indications and the dose value. A drop in detector sensitivity is associated with increased environmental temperature (as much as 6% as temperatures rise from 22°C to 42°C). There is a non-linear drop in detector sensitivity with accumulated dose. Detector indications are not affected by changes in incident beam angles within the range of –70° to +70°. The dependency of detector indications on the size of the irradiated field conform with those recorded in the ionization chamber, with variations of up to 1.5%. The dependencies and correction coefficients determined in this study allow measurement of electron beam doses with an accuracy of 2.2%.

Conclusions

MOSFET detectors are a useful tool for verification of the entrance doses in electron beam radiotherapy.

Abstract

Aim

To examine the characteristics of MOSFET (Metal – Oxide Semiconductor Field Effect Transistor) detectors for the purpose of electron beam dose determination in in vivo radiotherapy.

Materials/Methods

Indications of MOSFET detectors were recorded from phantom measurements, including: dose values of electron beams, the environmental temperature of the detectors, the incidence direction of an electron beam on the detector, the size of the irradiated field.

The change in sensitivity of the detectors when under the effects of accumulated doses was also tested.

Because of the very small dimensions of the detectors, they were placed in specially designed aluminium capsules – to ensure electron equilibrium (δ electrons) during the dose measurement. The detector indications were compared to those seen in a Markus type ionization chamber with a calibration certificate. The measurements were made for electron beams with energies of 6, 9, 12, 15, 18 and 21 MeV.

Results

The following were established experimentally: There is a linear relationship between detector indications and the dose value. A drop in detector sensitivity is associated with increased environmental temperature (as much as 6% as temperatures rise from 22°C to 42°C). There is a non-linear drop in detector sensitivity with accumulated dose. Detector indications are not affected by changes in incident beam angles within the range of –70° to +70°. The dependency of detector indications on the size of the irradiated field conform with those recorded in the ionization chamber, with variations of up to 1.5%. The dependencies and correction coefficients determined in this study allow measurement of electron beam doses with an accuracy of 2.2%.

Conclusions

MOSFET detectors are a useful tool for verification of the entrance doses in electron beam radiotherapy.

Get Citation

Keywords

MOSFET detectors; in vivo dosimetry of electrons

About this article
Title

MOSFET detectors as a tool for the verification of therapeutic doses of electron beams in radiotherapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 10, No 6 (2005)

Pages

301-306

Published online

2005-01-01

DOI

10.1016/S1507-1367(05)71103-2

Bibliographic record

Rep Pract Oncol Radiother 2005;10(6):301-306.

Keywords

MOSFET detectors
in vivo dosimetry of electrons

Authors

Marcin Dybek
Włodzimierz Łobodziec
Aneta Kawa-Iwanicka
Tomasz Iwanicki

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