Journal of Clinical and Diagnostic Research. 2018 Nov, Vol-12(11): XC05-XC10 5 5 DOI: 10.7860/JCDR/2018/36733.12258 Original Article Oncology Section Verification of Radiation Fluence using Stack Film in HDR Brachytherapy with Heterogeneity Algorithm INTRODUCTION In High Dose Rate (HDR) brachytherapy, applicators are identified using either 2Dimensional (2D) orthogonal radiograph or Computed Tomography (CT) images. Treatment plans are optimised by altering the dwell times with respect to the anatomical point or volume subjected to the normal tissue constraints. These treatment plans are verified before delivery which was not of common practice worldwide [1]. However, verification of planned dose distribution pose a thought provoking task due to nature of high range doses, steep dose gradients and small spatial distributions [2]. Therefore, need of the hour is to find a method to verify dose distribution which was a common practice in external beam radiotherapy [3]. The commercially available Treatment Planning Systems (TPS) employ dose calculation algorithms which do not take into account heterogeneities present in the patient and the applicators shielding effects used in the treatment. This suggests a mismatch between the planned and real delivered dose to the tumour and organs at risk [4]. A number of experimental and Monte Carlo (MC) studies have been reported in literature representing the influence of inhomogeneity in brachytherapy treatments [5-8] and the shielding effect created by the applicators [9,10]. Brachytherapy treatments are currently undergoing a period of significant innovation and rapid transformation, together with a fundamental shift away from the use of traditional pre-determined dose distributions and alteration from 2Dimensional (2D) to 3Dimensional (3D) viewpoints of the entire treatment process. It is essential that quality assurance techniques need to be in line with progresses in brachytherapy treatment planning and delivery to ensure an appropriate level of dosimetric accuracy and quality. Modern 3D-based brachytherapy which requires multi-dimension verification measurements of the planned dose with clinical treatment applicator in-situ and the potential of significant patient-specific dose distribution optimisation [11]. Radiochromic film dosimetry is often employed for dose distribution measurement in radiotherapy, with significant advantage compared to other dosimetry methods, including high spatial resolution, low energy dependence, and near water equivalence [12-15] and relative ease of signal readout with a desktop scanner [16,17]. The independent 3D brachytherapy dosimetry audit needs a development of practical measurement and analysis technique [11]. Advancement in brachytherapy procedures has increased the need for three dimensional dosimeters to verify dose calculation algorithms and treatment deliveries. Development of a stable, easy to analyse 3D dosimeter is essential and could result in broader clinical implementation of 3D dosimetry [18]. Hence, the study was carried out to validate the model based dose calculation algorithm. MATERIALS AND METHODS The study was piloted in order to effectively commission the new algorithm for clinical use. The traditional method of testing newer algorithm is to do simulation study on tissue equivalent phantom which was carried out for six months in the medical physics laboratory. The materials used in this study are: •฀ HDR฀ Brachytherapy฀ unit฀ (Gammamed฀ Plus฀ iX)฀ with฀ Acuros TM BV algorithm, •฀ Titanium฀ applicators฀ viz.฀ ring฀ with฀ tandom฀ set,฀ vaginal฀ mould฀ with partial shielded (Tungsten), stainless steel interstitial needles, •฀ Tissue฀equivalent฀material, •฀ RW3฀water฀equivalent฀slab฀phantom, •฀ EBT2฀Gafchromic฀flm฀with฀EPSON฀10000XL฀scanner, •฀ Film฀QA฀Pro฀software฀for฀flm฀analysis, •฀ IBM฀SPSS฀software฀21.0฀version฀for฀statistical฀analysis. Descriptive analytical study was carried out to effectively commission the new algorithm for calculating the brachytherapy dose in clinical use. A 192Ir brachytherapy treatment planning MOUROUGAN SINNATAMBY 1 , VIVEKANANDAN NAGARAJAN 2 , REDDY SATHYANARAYANA KANIPAKAM 3 , GUNASEELAN KARUNANIDHI 4 , VIJAYAPRABHU NEELAKANDAN 5 , SARAVANAN KANDASAMY 6 Keywords: Acuros TM ฀BV,฀Fluence,฀Gamma,฀High฀dose฀rate,฀Stack฀flm ABSTRACT Introduction: It is essential that Quality Assurance (QA) need to be in line with progresses in HDR brachytherapy treatment planning and delivery to ensure an appropriate level of dosimetric accuracy and quality. Aim: To verify radiation fluence using stack films in HDR brachytherapy with heterogeneity algorithm. Materials and Methods: Gafchromic EBT2 films were stacked in different experimental setup and each film acted as dosimeter to validate Acuros TM BV algorithm in HDR brachytherapy. These films were read using Epson expression 10000 XL flatbed scanner, calibrated against the standard value and analysed with Film QA Pro 2015 software. Different criterion were set for gamma analysis which include Dose Difference (DD)/Distance- To-Agreement (DTA); 2%/1 mm, 5%/1 mm, 10%/1 mm. Results: In order to validate the point doses calculated using model based dose calculation algorithm (Acuros TM BV), a virtual phantom created in the TPS, which agreed with MC based calculation mostly within 2%. The results of each plane were analysed in all the experimental setup. In the gamma pass criteria of 2% and 1 mm, 92% passed, in 5% and 1 mm criteria 96% passed and with 10% and 1 mm criteria, almost 100% passing rate was achieved. Conclusion: Methods provide a comprehensive verification for commissioning the MBDCA-Acuros TM BV and are recommended to use stack film for QA program in HDR brachytherapy.