Paper Title
Radiobiological Plan Evaluation Parameters for the Fractionated High-Dose Rate GYN Brachytherapy

Abstract
Radiobiological plan evaluation parameters such as Equivalent Uniform Dose (EUD), Normal Tissue Complication Probability (NTCP), and Tumor Control Probability (TCP) are used as assessment methods of high-dose rate Brachytherapy treatment plans in endometrial cancer. This retrospective study aims to calculate and evaluate the EUD and EUD-based NTCP for organs at risk, such as bladder and rectum using retrospective Dose Volume Histogram (DVH) data from repetitive CT scans during fractionated high-dose-rate Brachytherapy treatments. MATLAB was employed to calculate Niemierko’s EUD-based NTCP model[1], and also a 3D point-cloud rigid registration method was utilized to calculate the applicator displacement. The evaluations were performedfor118 HDR treatment plans for30 patients by registration of the subsequent treatment plans into the initial CT-image guided plan. Dose fractionation regimens were varied from 4Gy to 7Gy per fraction and 1 or 2 fractions per week, depending on the cancer staging. Our results demonstrated that no significant radiobiological impacts on organs at risks (OAR)are found from different fractions for 30 patients’ retrospective treatment plans. Keywords - Radiation therapy, HDR Brachytherapy, Normal Tissue Complication Probability (NTCP), Radiobiological parameters.