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Turkish Journal of Cancer
2007, Volume 37, Number 2, Page(s) 059-065
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Comparison of high and low energy treatment plans by evaluating the dose on the surrounding normal structures in conventional radiotherapy
1Pakistan Institute of Engineering and Applied Sciences, Department of Physics and Applied Mathematics, Islamabad
2Karachi Institute of Radiotherapy and Nuclear Medicine, Department of Radiotherapy, Karachi-Pakistan

The aim of this study was to quantitatively compare treatment plans of high (15 MV) and low energy photon (6 MV) beams in pelvic sites (Bladder, Prostate, Cervix and Femur heads) for conventional radiation therapy. A total of 13 patients were studied. X-ray simulation was performed on Shimadzu treatment simulator. Patient contours were acquired using a conformator type contour plotter. Optimal treatment plans were prepared with the help of Decision Support System (DSS by Multidata). In all cases three field (3-F) technique was compared for high and low energy photons, except for cervix and femur heads where in addition to 3-F technique box technique was compared as well. The parameters analyzed for the effectiveness of a treatment plan were; Quality Index, Global maximum dose, Doses to Organs at Risk (OAR), dose uniformity with in the tumor and entrance doses. The entrance doses from anterior side for 15 MV photons in case of bladder and prostate were reduced by 20% and 19.2% respectively. Where as the dose to rectum (OAR) for 15 MV photons, was reduced by 300 cGy and 210 cGy for bladder and prostate patients respectively. A 26% reduction in entrance dose from the anterior aspect was observed for 15 MV photons in Cervix patients (3-F technique). The dose to bladder and rectum were reduced by 810 cGy and 255 cGy respectively for 15 MV photons in cervix (3-F). Dose to left femur head for 6 MV increased by 16% as compared to 15 MV photons. For right femur head the dose for 6 MV photons was 16.5% higher as compared to 15 MV photons. The major conclusion was that patient re-planning was necessary in case of pelvic sites; otherwise very high doses were received by OAR. [Turk J Cancer 2007;37(2):59-65]

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