Evaluation of Intensity-Modulated Radiation Therapy (IMRT) Treatment Plans Using Various Numbers of Beams in Pelvic Cases

Objective: To evaluate the better plan for pelvic tumors in which achieving high target coverage dose and low normal tissues tolerance dose by using variable number of radiation beams in Intensity-Modulated Radiation Therapy (IMRT) technique . Materials and method: thirty pelvic cancer patients were included and four treatment plans contain different number of beams (5, 7, 9 and 11 beams) in each case were planned. The cross-sectional clinical study conducted in Al-Amal National Hospital for Radiotherapy and Nuclear Medicine, Baghdad, Iraq. The patients are delineated by oncologists according to Radiation Therapy Oncology Group RTOG 1005 protocol and prepare for radiation planning by MONACO 5.1 treatment planning system (TPS) with an X-ray photon beam of 6 MV energy using ‎ELEKTA‏’‏s Agility linear accelerator. Results: Significant differences between the treatment plans, after the comparison, it was found that the 7-beams treatment plan and 9-beam treatment plan achieved the optimal results among the treatment plans, it achieved adequate coverage of the tumor, sparing of organ at risk, homogeneity index and conformity index. As for the treatment plans of the 11 and 5 beams, they did not achieve good results in terms of coverage, sparing of organ at risk, homogeneity index, and conformity index. Conclusion: This analysis showed that increased beam count was associated with better dose formation of PTV. However, there was no noticeable improvement with the use of more than nine beams.