ESTRO 2024 - Abstract Book

S3413

Physics - Dose calculation algorithms

ESTRO 2024

121

Digital Poster

Analysis of the dose impact of dental fillings using multiple alghoritms

Roxana E Zaharia 1 , Elena C Gheara 1,2

1 The Oncology Institute "Prof. dr. Ion Chiricuta", Radiotherapy, Cluj-Napoca, Romania. 2 "Babes-Bolyai" University, Faculty of Physics, Cluj-Napoca, Romania

Purpose/Objective:

Head and neck cancers are frequently treated with radiation therapy (RT), sometimes in combination with surgery or chemotherapy. RT employs high-energy radiation to target and eliminate cancer cells in a specific region, while striving to minimize harm to healthy tissues. Nonetheless, RT can lead to various short-term and long-term side effects in the head and neck area. One factor that can influence the precision and effectiveness of RT is the presence of dental fillings, which may create artifacts that affect the visualization of the patient's anatomy and critical structures when seen on computed tomography (CT) images. Moreover, the algorithms responsible for calculating the distribution of radiation dosage in treatment planning systems can introduce inaccuracies due to the high density of these fillings.The accuracy of dose calculation algorithms relies on several variables, including the type of radiation beam, the configuration of the treatment field, and the tissue's variations in density. The existence of dental fillings can introduce notable inaccuracies in dose calculations, potentially jeopardizing the safety and efficacy of the treatment. In this study, we investigated the effects of dental fillings on dose distribution using three different algorithms: analytical anisotropic algorithm (AAA), Acuros (AXB) and Collapse Cone Convolution (CCC) for a 6 MV photon beam. We used three types of commercial dental fillings: pure titanium, Ni-Cr alloy and zirconium. We inserted the fillings in phantoms made from bolus material in order to reproduce soft tissue. We created multiple treatment plans using volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques. For each filling and algorithm, we performed three dose calculations: one without overriding the densities of the filling and the CT artifact, one with overriding only the density of the filling, and one with overriding both the density of the filling and the CT artifact. The density we used were the ones provided by the productor. We performed the measurements on two machines: a Varian ClinacIX and a Radixact X7. Using an Exradin® A1SL Ion Chamber (Standard Imaging), we assessed the dose at three specific locations: anterior, posterior, and in close proximity to the implant. To ensure accurate chamber placement, we relied on 2D and 3D images obtained from the integrated imaging systems on both devices. In the case of Radixact, we utilized MVCT images, while for Varian, we employed KV images captured at angles of 0 and 270 degrees. We repeated the measurements for each combination of artifact and algorithm and compared the results against the TPS calculated values. Material/Methods:

Results: