open access

Vol 15, No 6 (2010)
Published online: 2010-11-01
Submitted: 2010-03-16
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The influence of the bolus-surface distance on the dose distribution in the build-up region

Martyna Sroka, Jakub Reguła, Włodzimierz Łobodziec
DOI: 10.1016/j.rpor.2010.09.003
·
Rep Pract Oncol Radiother 2010;15(6):161-164.

open access

Vol 15, No 6 (2010)
Published online: 2010-11-01
Submitted: 2010-03-16

Abstract

Aim

The aim of the paper is to examine the relation between the increase of the photon dose in water in the region of electronic disequilibrium – so-called build-up region – and the distance of the bolus from the water surface for the applied parameters of X-ray beams.

Materials and methods

PDD measurements were carried out using the plane-parallel ionization chamber Markus in the automatic water phantom IBA BluePhantom with OmniPro-Accept V7 (IBA Dosimetry GmbH, Schwarzenbruck, Germany). All measurements were performed for different field sizes and for 6[[ce:hsp sp="0.25"/]]MV and 15[[ce:hsp sp="0.25"/]]MV X-ray beams, respectively. A water-equivalent RW3 slab (Goettingen White Water) produced by PTW was used as a bolus.

Results

Placing a bolus in an irradiated field changes the shape of the PDD curve in the build-up region in comparison with the one obtained for an open field. All results has been inserted in tables and figures.

Conclusion

The closer the bolus is to the water surface, the smaller the depth of the maximum dose in the phantom for all investigated fields and energies. The changes in the build-up region are important, even if the bolus does not touch the surface of the water phantom. The influence of the bolus can be ignored when the bolus-surface distance equals 25[[ce:hsp sp="0.25"/]]cm for 6MV X-ray beams and 39[[ce:hsp sp="0.25"/]]cm for 15[[ce:hsp sp="0.25"/]]MV X-ray beams.

Abstract

Aim

The aim of the paper is to examine the relation between the increase of the photon dose in water in the region of electronic disequilibrium – so-called build-up region – and the distance of the bolus from the water surface for the applied parameters of X-ray beams.

Materials and methods

PDD measurements were carried out using the plane-parallel ionization chamber Markus in the automatic water phantom IBA BluePhantom with OmniPro-Accept V7 (IBA Dosimetry GmbH, Schwarzenbruck, Germany). All measurements were performed for different field sizes and for 6[[ce:hsp sp="0.25"/]]MV and 15[[ce:hsp sp="0.25"/]]MV X-ray beams, respectively. A water-equivalent RW3 slab (Goettingen White Water) produced by PTW was used as a bolus.

Results

Placing a bolus in an irradiated field changes the shape of the PDD curve in the build-up region in comparison with the one obtained for an open field. All results has been inserted in tables and figures.

Conclusion

The closer the bolus is to the water surface, the smaller the depth of the maximum dose in the phantom for all investigated fields and energies. The changes in the build-up region are important, even if the bolus does not touch the surface of the water phantom. The influence of the bolus can be ignored when the bolus-surface distance equals 25[[ce:hsp sp="0.25"/]]cm for 6MV X-ray beams and 39[[ce:hsp sp="0.25"/]]cm for 15[[ce:hsp sp="0.25"/]]MV X-ray beams.

Get Citation

Keywords

PDD; Bolus; Depth of the dose maximum; Build-up region

About this article
Title

The influence of the bolus-surface distance on the dose distribution in the build-up region

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 15, No 6 (2010)

Pages

161-164

Published online

2010-11-01

DOI

10.1016/j.rpor.2010.09.003

Bibliographic record

Rep Pract Oncol Radiother 2010;15(6):161-164.

Keywords

PDD
Bolus
Depth of the dose maximum
Build-up region

Authors

Martyna Sroka
Jakub Reguła
Włodzimierz Łobodziec

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