Protocol determination for OSL in vivo measurements of absorbed dose in the oral mucosa in oral cancer patients: A pilot study

Abstract

Radiation-induced oral mucositis (RIOM) is one of the major oral complications caused by radiotherapy (RT), and can lead a negative impact on patients’ quality of life. Considering that there is no specific radiation therapy dose constraint for oral mucosa, the need to study the correlation between absorbed dose and effect in this area is crucial. This pilot study aims to report in vivo OSL dosimetry protocol to investigate the dose distribution in the oral mucosa in patients with oral cancer using Intraoral customised Stent (IOS). For measurements, aluminium oxide nanoDot dosimeters and a microStar ii OSL reader from Landauer Inc. were used. The OSL dosimetry system was calibrated with a 6 MV photon beam using an Elekta Synergy linear accelerator and solid water phantoms following the recommendations of the AAPM TG 191 protocol. The dose distribution in the oral mucosa using seven OSL dosimeters fixed on the intraoral stent was evaluated and compared with the dose distribution available from the RT planning for the patient. Our experimental results showed the expected linearity response of the nanoDot dosimeters from 20 to 200 cGy. The repeatability of readings was better than 1.0% in all commissioning measurements. The uncertainty budget of the commissioning analysis resulted in an overall type An uncertainty of ∼3.4% at the 1-sigma level for dose calculation, compatible with the TG 191 protocol. The dose distribution in the oral mucosa was assessed and dose deviations up to 35% can be found in high dose gradient regions of the treatment planning. This type of deviation may impact on the development and progression of RIOM, as analysed in this protocol. It is feasible to establish this procedure in vivo dosimetry for a patient undergoing RT using a multidisciplinary approach. Additionally, intraoral customised stents can decrease radiation doses in the oral mucosa, and the understanding of the dose distribution in the oral mucosa may help to minimise damages from radiation.