ESTRO 37 Abstract book

S953

ESTRO 37

EP-1774 Utilization Of Osld As The Quality Control Indicator For In-Vivo Measurements In Tbi Treatment K. V 1 , S. Osman 2 , K. Jassal 2 , B. Sarkar 2 , S. Singh 2 , U.K. Giri 2 , G. T 2 1 Apollo Hospital, Radiation Oncology, Bangalore, India 2 Fortis Memorial Research Institute, Radiation Oncology, Gurgaon, India Purpose or Objective The In vivo dosimetry involves a measurement of the dose delivered to the patient in the treatment conditions to detect a possible deviation between the prescribed and the delivered dose. The advent of the optically stimulated luminescence dosimeters (OSLD), particularly in the Nano Dots form, is a very appropriate tool for its size, ease of handling, accurate and fast reading. This study investigate the application of OSLD for the quality control of Total Body Irradiation (TBI) treatment. Material and Methods In-vivo dose measurements using OSLD nanoDots (LANDAUER, Glenwood, Illinois) were done in a total of 24 patients who treated with 6 MV & 15 MV. To provide a uniform dose to the entire patient length, the treatment was split into 2 lateral fields. In this technique, the patient is kept inside the TBI box which is filled with rice filled muslin bags and irradiated using bilateral parallel opposed beams of 40×40 cm 2 size with 45° collimator rotation at an SSD of 333.5 cm in an Elekta Synergy Platform linear accelerator (Elekta AB, Stockholm, Sweden). All patients received a dose of 2 Gy in single fraction as conditioning regimen. The beams were equally weighted at the centre of the box which lies exactly at mid-line plane of the patient. The nanoDots were placed at both medially and laterally including forehead, right and left neck, right and left lung, umbilicus, right and left abdomen, upper right of thigh, and right knee. Results Measurement values of doses with nanoDots were found for medial sites forehead, umbilicus, and knee were, 2.19±9.66, 2.12±6.35, 2.16±8.1 Grey respectively. Lateral sites right and left neck, right and left lung, right and left abdomen were 2.17±8.75, 2.12±6.37, 2.15±7.81, 2.16±8.42, 2.21±5.35, and 2.17±8.66 Grey respectively. For medially placed nanoDots measurement D mean was 2.16±9.66 Grey and laterally D mean was 2.16±8.75 Grey. Conclusion The results demonstrate that nanoDot can be potentially used for TBI verification in various levels on Patients body, with a high degree of accuracy and precision. In addition OSLD exhibit better dose reproducibility with standard deviation of 0.6%. The dose response was also linear for both medial and lateral fields. This can help with time saving and work efficiency in the clinic. EP-1775 The feasibility study of clinical high accuracy QA system for treatment planning using Monte Carlo B. Lee 1 , H. Kim 1 , S. Jeong 2 , S. Jung 1 , E. Shin 1 , H. Park 1 , D. Lim 1 , J. Lee 3 , J. Chung 4 , M. Yoon 2 , Y. Han 1 1 Samsung Medical Center, Radiation Oncology, SEOUL, Korea Republic of 2 Korea University, Bio-convergence Engineering, SEOUL, Korea Republic of 3 Konkuk University, Radiation Oncology, SEOUL, Korea Republic of 4 Seoul National University Bundang Hospital, Radiation Oncology, SEONGNAM, Korea Republic of Purpose or Objective This study was carried out to manage and construct the accuracy of commercialized Treatment Planning system(TPS) and a system for accurate dose calculation. The configured QA system was programmed to verify or study the clinical QA results of the dose calculation program.

Material and Methods The modeling of the linear accelerator was performed primarily to take into account the accuracy for the dose calculation of the system. The linear accelerators are modeled on Truebeam(Varian Medical System) and HD120, which are currently used on our site. The Monte Carlo simulation for accurate dose calculation uses open- source GATE(v8.0) platform based on the GEANT4(v10.3) toolkit. We have verified 4 MV, 6 MV, 10 MV, 6FFF, and 10FFF energy that are currently used in clinical practice. The percentage depth dose and profile of Monte Carlo and measured beam data was compared with at various depths(D max , 5cm, 10cm, 20cm) according to the field size(secondary collimator, multileaf collimator) at each energy. The modeled Monte Carlo calculation LINAC system is used in the QA system. The QA system analyzes the treatment plan file generated by the RTP, checks the information required for the treatment, and generates the files in QA system. The files generated by the program are sent to the compact cluster for dose calculation and analyzation. The QA system proceeds in the following order. The 3D-CRT and VMAT plan are arbitrarily selected and the plan is calculated in the solid water phantom. We compare the results of the dose distribution in TPS and the results of QA system using Monte Carlo calculation. We compare the results of dose distribution in RTP and QA system in the same way in random patient CT data. Results The commissioning for linear accelerator was analyzed by PDD and profile according to secondary collimator and MLC. The comparisons between the Monte Carlo calculation and the RTP beam data measured using CC13 ion chamber were within an average of 2%. The treatment plan for the clinical validation using gamma index was analyzed by 3D-CRT and VMAT using solid water phantom and arbitrary patient data. The gamma evaluation results were calculated as 99.1% and 93.0% in 3D-CRT and VMAT plan using solid water phantom at 3% and 3mm, respectively. In the case of 3D-CRT and VMAT using CT data of the patient, 95.9% and 93.2% were The results of our study show that the most accurate dose calculation system using Monte Carlo QA system can be constructed and applied to clinical practice. The proposed QA system will be used for verification of clinical TPS such as SRS planning using small field, dose distribution for VMAT and secondary cancer risk which is difficult to verify dose calculation in TPS. EP-1776 Verification of the NCS Code of Practice Report 24 for VMAT QA using a high-resolution detector. F. Matar 1 , D. Wilkinson 2 , J. Davis 1 , T. Causer 2 , I. Fuduli 1 , A. Ceylan 2 , M. Carolan 2 , P. Metcalfe 1 , M. Petasecca 1 , A.B. Rosenfeld 1 1 University of Wollongong, Centre For Medical Radiation Physics, Wollongong NSW, Australia 2 Wollongong Hospital, Illawarra Cancer Care Centre, Wollongong, Australia Purpose or Objective This work aims to design and optimize a high spatial resolution silicon detector placed in the accessory tray of the linac to verify gantry angle and rotation speed, dose rate accuracy and synchronicity as suggested by the recommendations of the Code of Practice for VMAT QA published by the NCS Report 24. Material and Methods The VMAT CAP plan (Customer Acceptance Procedure) is designed to evaluate the synchronisation between gantry speed and dose rate during arc delivery. 10 sectors, each with a different MU weightings are generated for a Varian 21EX Clinac operating at 6 MV. The plan was customized calculated. Conclusion