Program Information
Dosimetric Study of Co60source Step Size in Intracavitary HDR Brachytherapy
A Shukla1*, N Singh2 , S Kumar3 , B Rana4 , I Sandhu5 , (1) IK Gujral Punjab Technical University (PTU), Jalandhar, Punjab, Jalandhar, Punjab, (2) IK Gujral Punjab Technical University (IKGPTU), Jalandhar, Punjab, Jalandhar, Punjab, (3) Department of Physics, G.G.D.S.D. College, Sector-32 C, Chandigarh, Chandigarh, Chandigarh, (4) Department of Radiotherapy, PGIMER, Chandigarh., Chandigarh., Chandigarh., (5) Chitkara University, Rajpura, Punjab, Rajpura, Punjab, Punjab
Presentations
SU-I-GPD-T-29 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To compare different step sizes of cobalt60 HDR miniature source for intracavitary brachytherapy treatment.
Methods: The Computed tomography (CT) scan was done of 15 patients of carcinoma of uterine cervix using 3 mm slice thickness. The contouring of bladder and rectum was done in axial planes with the help of sagittal and coronal planes in Treatment Planning System (TPS). Dose prescription was done on Point A. Volumetric parameters D0.1cc ,D1cc ,D2cc ,D5cc ,ICRU reference points for bladder and rectum, Overall treatment time and volume of prescribed dose were calculated for 1mm, 5mm and 10 mm step sizes and compared with standard 2.5 mm step size.
Results: Study shows that the maximum difference with 2.5 mm step size in D0.1cc ,D1cc ,D2cc ,D5cc and ICRU reference point dose of bladder are -2.32 % to maximum 3.06% for 1mm to 5mm while for it goes to +8.79% for 10 mm step size. Similarly maximum difference with 2.5 mm step size in D0.1cc ,D1cc ,D2cc ,D5cc and ICRU reference point dose in rectum are -5.30% to maximum 7.72% while it goes to +21.04% for 10 mm step size. Treatment time varies from -2.40% to +4.04% for 1mm and 5 mm respectively while for 10 mm it varies up to +11.07% compared to 2.5 mm step size. Prescribed dose volume varies from -4.03% to +6.52% for 1mm and 5 mm respectively while for 10 mm it increases to +17.66% compared to 2.5 mm step size.
Conclusion: This work shows that as the step size increases doses to the bladder and rectum also increases that leads to increase in toxicity. As the step size increases the total treatment time also increases that leads to patient discomfort. It is concluded that step size more than 5mm should not be used for HDR brachytherapy treatment.
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