On the Use of Optically Stimulated Luminescent Dosimeter for Surface Dose Measurement during Radiotherapy.

Fasihah Hanum Yusof,Vincent Chee Ee Phua,Kwan Hoong Ng,Jeannie Hsiu Ding Wong,Siew Ping Heng,Wei Loong Jong,Ngie Min Ung,Vannyat Ath,Chih-Hsin Tang

doi:10.1371/journal.pone.0128544

Fasihah Hanum Yusof, Vincent Chee Ee Phua + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0128544

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Journal: PloS one	Publication Date: Jun 8, 2015
Citations: 69	License type: CC BY 4.0

Affiliation: University of Malaya, Hospital Kuala Lumpur

Abstract

This study was carried out to investigate the suitability of using the optically stimulated luminescence dosimeter (OSLD) in measuring surface dose during radiotherapy. The water equivalent depth (WED) of the OSLD was first determined by comparing the surface dose measured using the OSLD with the percentage depth dose at the buildup region measured using a Markus ionization chamber. Surface doses were measured on a solid water phantom using the OSLD and compared against the Markus ionization chamber and Gafchromic EBT3 film measurements. The effect of incident beam angles on surface dose was also studied. The OSLD was subsequently used to measure surface dose during tangential breast radiotherapy treatments in a phantom study and in the clinical measurement of 10 patients. Surface dose to the treated breast or chest wall, and on the contralateral breast were measured. The WED of the OSLD was found to be at 0.4 mm. For surface dose measurement on a solid water phantom, the Markus ionization chamber measured 15.95% for 6 MV photon beam and 12.64% for 10 MV photon beam followed by EBT3 film (23.79% and 17.14%) and OSLD (37.77% and 25.38%). Surface dose increased with the increase of the incident beam angle. For phantom and patient breast surface dose measurement, the response of the OSLD was higher than EBT3 film. The in-vivo measurements were also compared with the treatment planning system predicted dose. The OSLD measured higher dose values compared to dose at the surface (Hp(0.0)) by a factor of 2.37 for 6 MV and 2.01 for 10 MV photon beams, respectively. The measurement of absorbed dose at the skin depth of 0.4 mm by the OSLD can still be a useful tool to assess radiation effects on the skin dermis layer. This knowledge can be used to prevent and manage potential acute skin reaction and late skin toxicity from radiotherapy treatments.

Highlights

External beam radiotherapy (EBRT) is a treatment technique using high energy ionizing radiation which is used mainly for the treatment of cancers
We investigated the use of optically stimulated luminescence dosimeter (OSLD) for surface dose measurement
The water equivalent depth (WED) of the OSLD was determined by substituting the percentage of normalized surface dose to the dose at dmax measured by the OSLD into the equation by the percentage depth dose (PDD) graph of Markus ionization chamber’s measurements

Summary

Introduction

External beam radiotherapy (EBRT) is a treatment technique using high energy ionizing radiation which is used mainly for the treatment of cancers. The skin is at risk of skin toxicity such as erythema, necrosis, desquamation, dermal lymphatic and basal-cell carcinoma [2,3,4] This is because while delivering a lethal dose to the tumour at a certain depth in tissue is of utmost importance, it is often done at the expense of the risk of developing skin reactions. Understanding of the surface dose delivered to the surface of the skin may be useful in providing better clinical management of potential acute skin reactions This can be done via invivo measurements, i.e with the dosimeter placed on the surface of skin, whreby the dose to a point inside the patient can be derived [6]. Surface dose measurements can serve as a form of treatment verification to ensure the correct dose is being delivered during radiotherapy, in line with AAPM TG 40 recommendation

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