open access

Vol 23, No 3 (2018)
Original research articles
Published online: 2018-05-01
Submitted: 2017-08-24
Get Citation

Uncertainty in positioning ion chamber at reference depth for various water phantoms

Naoki Kinoshita, Hiroshi Oguchi, Toshiki Adachi, Hiroki Shioura, Hirohiko Kimura
DOI: 10.1016/j.rpor.2018.03.001
·
Rep Pract Oncol Radiother 2018;23(3):199-206.

open access

Vol 23, No 3 (2018)
Original research articles
Published online: 2018-05-01
Submitted: 2017-08-24

Abstract

Background

Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type.

Aim

We evaluated the uncertainty in the positioning of a cylindrical chamber at a reference depth for reference dosimetry of high-energy photon beams and the resulting uncertainty in the chamber readings for 6- and 10-MV photon beams. The aim was to investigate major contributions to the positioning uncertainty to reduce the uncertainty in calibration for external photon beam radiotherapy.

Materials and methods

The following phantoms were used: DoseView 1D, WP1D, 1D SCANNER, and QWP-07 as one-dimensional (1D) phantoms for a vertical-beam geometry; GRI-7632 as a phantom for a fixed waterproofing sleeve; and PTW type 41023 and QWP-04 as 1D phantoms for a horizontal-beam geometry. The uncertainties were analyzed as per the Guide to the Expression of Uncertainty in Measurement.

Results

The positioning and resultant uncertainties in chamber readings ranged from 0.22 to 0.35[[ce:hsp sp="0.25"/]]mm and 0.12–0.25%, respectively, among the phantoms (using a coverage factor k[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1 in both cases). The major contributions to positioning uncertainty are: definition of the origin for phantoms among users for the 1D phantoms for a vertical-beam geometry, water level adjustment among users for the phantom for a fixed waterproofing sleeve, phantom window deformation, and non-water material of the window for the 1D phantoms for a horizontal-beam geometry.

Conclusion

The positioning and resultant uncertainties in chamber readings exhibited minor differences among the seven phantoms. The major components of these uncertainties differed among the phantom types investigated.

Abstract

Background

Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type.

Aim

We evaluated the uncertainty in the positioning of a cylindrical chamber at a reference depth for reference dosimetry of high-energy photon beams and the resulting uncertainty in the chamber readings for 6- and 10-MV photon beams. The aim was to investigate major contributions to the positioning uncertainty to reduce the uncertainty in calibration for external photon beam radiotherapy.

Materials and methods

The following phantoms were used: DoseView 1D, WP1D, 1D SCANNER, and QWP-07 as one-dimensional (1D) phantoms for a vertical-beam geometry; GRI-7632 as a phantom for a fixed waterproofing sleeve; and PTW type 41023 and QWP-04 as 1D phantoms for a horizontal-beam geometry. The uncertainties were analyzed as per the Guide to the Expression of Uncertainty in Measurement.

Results

The positioning and resultant uncertainties in chamber readings ranged from 0.22 to 0.35[[ce:hsp sp="0.25"/]]mm and 0.12–0.25%, respectively, among the phantoms (using a coverage factor k[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1 in both cases). The major contributions to positioning uncertainty are: definition of the origin for phantoms among users for the 1D phantoms for a vertical-beam geometry, water level adjustment among users for the phantom for a fixed waterproofing sleeve, phantom window deformation, and non-water material of the window for the 1D phantoms for a horizontal-beam geometry.

Conclusion

The positioning and resultant uncertainties in chamber readings exhibited minor differences among the seven phantoms. The major components of these uncertainties differed among the phantom types investigated.

Get Citation

Keywords

Positioning uncertainty; Ionization chamber; Water phantom; External photon beam radiotherapy; Calibration

About this article
Title

Uncertainty in positioning ion chamber at reference depth for various water phantoms

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 3 (2018)

Pages

199-206

Published online

2018-05-01

DOI

10.1016/j.rpor.2018.03.001

Bibliographic record

Rep Pract Oncol Radiother 2018;23(3):199-206.

Keywords

Positioning uncertainty
Ionization chamber
Water phantom
External photon beam radiotherapy
Calibration

Authors

Naoki Kinoshita
Hiroshi Oguchi
Toshiki Adachi
Hiroki Shioura
Hirohiko Kimura

Important: This website uses cookies. More >>

The cookies allow us to identify your computer and find out details about your last visit. They remembering whether you've visited the site before, so that you remain logged in - or to help us work out how many new website visitors we get each month. Most internet browsers accept cookies automatically, but you can change the settings of your browser to erase cookies or prevent automatic acceptance if you prefer.

By "Via Medica sp. z o.o." sp.k., ul. Świętokrzyska 73, 80–180 Gdańsk, Poland
tel.:+48 58 320 94 94, fax:+48 58 320 94 60, e-mail: journals@viamedica.pl