open access

Vol 24, No 6 (2019)
Original research articles
Published online: 2019-11-01
Submitted: 2018-09-12
Get Citation

Measurement of percentage dose at the surface for a 6MV photon beam

O.O. Galván De la Cruz, M.A. Rodríguez-Ávila, T. Rivera-Montalvo, O.A. García Garduño
DOI: 10.1016/j.rpor.2019.09.007
·
Rep Pract Oncol Radiother 2019;24(6):585-592.

open access

Vol 24, No 6 (2019)
Original research articles
Published online: 2019-11-01
Submitted: 2018-09-12

Abstract

Aim

To evaluate if a radiochromic film (RF) Gafchromic EBT3 is suitable for surface dose measurements of radiotherapy treatments performed with a 6MV linear accelerator. Two aspects of RF were analyzed, beam energy dependence and surface dose determination.

Background

The measurements done at the surface or near the radiation source are done without charged electronic equilibrium and also have contribution of electron contamination. The detectors used for these measurements should not alter the dose to the target. To counteract these dosimetric problems it is proposed to do the measurements with radiochromic films which are thin detectors and have tissue equivalent properties.

Materials and Methods

The measurements were done using a Novalis linear accelerator (LINAC) with nominal energy of 6MV. To determine the surface dose, the total scatter factors (TSF) of three different field sizes were measured in a water phantom at 5cm depth. Energy dependence of EBT3 was studied at three different depths, using a solid water phantom. The surface measurements were done with the RF for the same field sizes of the TSF measurements. The value of the percentage depth dose was calculated normalizing the doses measured in the RF with the LINAC output, at 5cm depth, and the TSF.

Results

The radiochromic films showed almost energy independence, the differences between the curves are 1.7% and 1.8% for the 1.5cm and 10cm depth, respectively. The percentage depth doses values at the surface measured for the 10cm×10cm, 5cm×5cm and 1cm×1cm were 26.1±1.3%, 21.3±2.4% and 20.2±2.6%, respectively.

Conclusions

The RF-EBT3 seems to be a detector suitable for measurements of the dose at the surface. This suggests that RF-EBT3 films might be good candidates as detectors for in vivo dosimetry.

Abstract

Aim

To evaluate if a radiochromic film (RF) Gafchromic EBT3 is suitable for surface dose measurements of radiotherapy treatments performed with a 6MV linear accelerator. Two aspects of RF were analyzed, beam energy dependence and surface dose determination.

Background

The measurements done at the surface or near the radiation source are done without charged electronic equilibrium and also have contribution of electron contamination. The detectors used for these measurements should not alter the dose to the target. To counteract these dosimetric problems it is proposed to do the measurements with radiochromic films which are thin detectors and have tissue equivalent properties.

Materials and Methods

The measurements were done using a Novalis linear accelerator (LINAC) with nominal energy of 6MV. To determine the surface dose, the total scatter factors (TSF) of three different field sizes were measured in a water phantom at 5cm depth. Energy dependence of EBT3 was studied at three different depths, using a solid water phantom. The surface measurements were done with the RF for the same field sizes of the TSF measurements. The value of the percentage depth dose was calculated normalizing the doses measured in the RF with the LINAC output, at 5cm depth, and the TSF.

Results

The radiochromic films showed almost energy independence, the differences between the curves are 1.7% and 1.8% for the 1.5cm and 10cm depth, respectively. The percentage depth doses values at the surface measured for the 10cm×10cm, 5cm×5cm and 1cm×1cm were 26.1±1.3%, 21.3±2.4% and 20.2±2.6%, respectively.

Conclusions

The RF-EBT3 seems to be a detector suitable for measurements of the dose at the surface. This suggests that RF-EBT3 films might be good candidates as detectors for in vivo dosimetry.

Get Citation

Keywords

Radiochromic film EBT3; Energy independence; Surface dose

About this article
Title

Measurement of percentage dose at the surface for a 6MV photon beam

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 24, No 6 (2019)

Pages

585-592

Published online

2019-11-01

DOI

10.1016/j.rpor.2019.09.007

Bibliographic record

Rep Pract Oncol Radiother 2019;24(6):585-592.

Keywords

Radiochromic film EBT3
Energy independence
Surface dose

Authors

O.O. Galván De la Cruz
M.A. Rodríguez-Ávila
T. Rivera-Montalvo
O.A. García Garduño

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