Program Information
Dose Calculation of a Low Energy X-Ray Intra-Operative Radiotherapy System IntraBeam
T Dai1*, K Mao2 , Z Wang3 , Q Wei4 , (1) China-Japan Friendship Hospital, Beijing, Beijing, (2) China-Japan Friendship Hospital, Beijing, Beijing, (3) University of Science and Technology Beijing, Beijing, Beijing, (4) University of Science and Technology Beijing, Beijing, Beijing
Presentations
SU-I-GPD-T-50 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The intra-operative radiotherapy system IntraBeam utilizes 50 kV low energy X-rays to provide single fractional high dose irradiation to tumor bed, and has been applied for the treatment of breast/brain/skin cancer, etc. The accuracy of surface dose calculation is crucial to the prescription; well the three-dimensional dose distribution is necessary for evaluation. However, direct measurement of surface dose is technically not possible, and the system does not provide planning system. This abstract reports the dose curve fitting and Monte Carlo simulation method for the dose calculation.
Methods: We have carried out a series of depth-dose measurement based on the plate ion chamber in water tank for the probe source and sphere/flat/surface applicators with different sizes. By studies on fitting methods and analysis of physical processes, different fitting methods are tested and compared with the measurement data. In order to get the dose distribution, the probe source (x-ray tube) and typical applicators were modeled and simulated by Monte Carlo platform GATE, and rotational symmetry was used to improve calculation efficiency.
Results: For the depth-dose-curve (DDC) fitting, a combination of function of quadratic distance law and three functions of Lambert-Beer absorption law has good fitting accuracy for DDC of probe source, and composite functions with exponential and power function could be qualified for fitting the applicator’s transfer function. The dose distribution of MC simulation based on GATE has good agreement with the measured depth-dose, and the system modeling is validated.
Conclusion: We have studied and provided fitting method for DDC of IntraBeam system, which could give accurate surface dose for prescription. The MC simulation we have implemented could provide dose distribution for evaluation.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by National Natural Science Foundation of China (No.11505300,11605008).
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