Author: Palanisamy Karunanithi, Karthikeyan Perumal, Siva Subramanian Vadivel 👨🔬
Affiliation: Dr. Kamakshi Memorial Hospital 🌍
Purpose:
Recent advancements in high dose-rate (HDR) brachytherapy include the image guidance, new applicators, and dose calculation algorithms. Brachytherapy has steep dose gradient, hence relatively distant normal structures and surface doses are neglected in brachytherapy. The purpose of this study was to elucidate computed tomography (CT) based volumetric calculations of radiation doses to the normal tissues other than bladder and rectum in patients with carcinoma of the cervix treated with high-dose-rate (HDR) intracavitary brachytherapy (ICT).
Methods: 14 treatment plans delivering HDR dose of 7 Gy by ICT using tandem and ovoids and post-implant CT scans were studied. Apart from ICRU bladder and rectum point doses along with 4 additional rectal points, radiation doses to right and left femur, surface dose over pubic symphysis, right and left side of femur were recorded. The DVHs for all the normal tissues detailed above were calculated and the minimum doses to the highest irradiated 2cc volume were recorded (D2cc) for individual fraction.
Results: Dose received by individual organs are given as Mean±Standard Deviation (Range). Bladder dose was 5.25±1.96 Gy (Range: 2.6954-9.4942); Rectum dose was 4.64±0.84 Gy (Range: 3.5627-6.1107); Right Femur dose was 1.25±0.265 Gy (Range: 0.9595-1.7599); Left Femur dose was 1.32±0.25 Gy (Range: 0.8313-1.7853), Sigmoid dose was 2.66±0.84 Gy (Range: 0.548-3.6552); Right Hip was 0.26±0.30 Gy (Range: 0.14-1.26); Left Hip was 0.25±0.16 Gy (Range: 0.14-0.7); Symphysis was 0.61±0.10 Gy (Range: 0.4323-0.7493).
Conclusion: Doses assessed by volumetric calculations indicate non-negligible dose to the normal structures and surface. More data and real time data is needed for better understanding of normal tissue dosimetry.