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Abstract Cancer in prostate is a widespread malignant disease. Recently, external beam radiotherapy has been used extensively for treating a large number of prostate cancer patient. Radiotherapy must be accurate by delivering the maximum target dose while sparing the surrounding normal tissue. There are many radiotherapy techniques used. One of these important techniques is Intensity Modulated Radiotherapy (IMRT). Intensity Modulation Radiotherapy (IMRT) is a more advanced technique of Three-Dimensional Conformal Radiotherapy (3D-CRT). IMRT applied by using gantry machine that moves remotely around the patient from all direction 360 degrees as it delivers radiation dose. Additionally can shaping the fields and directing the radiating field at the prostate from different angles, the fields intensity can be modified to control the doses of radiation sparing from surrounding critical organs. This also allows oncologist to give the tumor the highest radiation dose while sparing organs at risk. Since the introduction of IMRT, this technique has been widely used for prostate cancer treatment. IMRT can be used for delivering conformal dose distributions by the selection of an appropriate energy and MLC for performing a proper therapeutic plan and for delivering high-quality treatment through a treatment planning system (TPS). The Purpose of this Study The study’s objective was to compare between 6MV and 10MV energies and assess the impact of 160 MLC versus 58 MLC on prostate cancer treatment and sparing critical organs (OARs) such as; rectum, urine bladder, penile bulb, head of left femur and head of right femur by using Intensity Modulated Radiotherapy (IMRT). Chapter6: SUMMARY AND CONCLUSION 58 Study Preparation and Description The present study included fifteen cases confirmed prostate cancer and prescribed for RT treatment. Xio Treatment Planning System (TPS) with software version 4.64.02 was used to design the plans for each case. Three different intensity modulated radiotherapy plans with the same parameters dose 72Gy, 7 fields, and same dose constrains were designed as follow: plan1: 6MV, 58 MLC with 1cm width, Plan 2: 6MV, 160 MLC with 0.5 cm width and plan3: 10 MV, 160MLC with 0.5cm width to evaluate the dose distributions relating to PTV coverage, Homogeneity and Uniformity Indexes, and organs at risk doses. The three different IMRT plans were evaluated to detect the most suitable plan to be used later for the treatment of prostate patients according to achieving more homogeneous doses to the tumor volume and more sparing to the critical organs surrounding. The Results of this Study Showed the Following: The results of this study showed that, variations in dosimetry founded by the intensity modulated radiotherapy plans using 6MVenergy, the PTV dose percentage differences for D2%, D 5% and D 50% were the same tumor coverage without any significant differences between 1cm vs. 0.5 cm MLC leaves. Dose percentage of D95% and D98% indicated that 160 MLC, 0.5cm width leads to a better PTV coverage than 58 MLC, 1cm width with significant differences (p = 0.001), regardless of the energy used. No distinctive differences between Uniformity Index for both leaves width were reported while, Homogeneity Index of the target showed that, 160 MLC, with 0.5 widths enhanced homogeneity index than in IMRT plans using 58 MLC, with 1cm width. With regard to OAR, 6 MV,160 MLC with 0.5cm spared rectum, bladder and penile bulb in high-dose regions V60Gy V65Gy and V70Gy more than 6 MV,58MLC with 1cm, although without Chapter6: SUMMARY AND CONCLUSION 59 any significant differences. Also, the present work investigated the outcome of 6Megavolt and 10 Megavolt energies on the quality of IMRT plans for patients with prostate cancer. Results showed that, There were only minor distinctions in (D95%) of planning target volume, homogeneity and Uniformity index and organs at risk between 6Megavolt and 10Megavolt energies and there were insignificant variation between them. Conclusions The 6 MV energy dose distributions with 160MLC leaf with 0.5cm width for the PTV coverage and homogeneity generated by using treatment planning calculations were more better than, those generated by using the 6 MV energy beams with 58MLC leaf with 1 cm. The 6 MV energy dose with 160MLC leaf with 0.5cm width spared critical organs, such as the rectal wall, the urinary bladder, the femoral head and penile bulb more accurately than, those generated by using the 6 MV energy beams with 58MLC leaf with 1 cm. No relevant advantage on PTV coverage, homogeneity and Uniformity index or dose reduction at OAR was noticed between 6-MV and 10-MV. |