The Number of Beams and Their Arrangement in The Intensity Modulated Radiotherapy for Prostate Cancer

Document Type : Original Article


THIS STUDY presents a certain set of optimal physical parameters applied to the prostate cancer cases treated with the intensity-modulated radiotherapy (IMRT) technique. Generally, the physical parameters include the beam energy, number of beams, beam arrangement and the optimal segmentation. In this work, we focused on the role of the number of beams and the beam arrangement applied to enhance the IMRT plan. Three prostate cases with different PTV volume and Precise Elekta® planning were studied and 33 plans with a different number of beams and different angles were applied to identify the starting point in the optimal parameters. The obtained results had shown that in prostate cancer cases the D98 of prescribed PTV dose can be achieved with up to nine beams with accepted D30 of the rectum and accepted Dmean of femoral heads. The odd number of beams has an advantage over the even numbers of beams for getting a lower dose in the organs at risk, (OARs). The odd number of the beam with equally spaced angles showed achievable results better than that when these beams were arranged with un-equally spaced angels while in the case of the even number the results were different.