effect of field number on intensity modulated radiation therapy plan quality in head and neck cancer

Background: Radiotherapy of head and neck cancer is a difficult process because of the complex anatomy and close proximity of various organs at risk (OARs). This study aimed to assess the impact of field number of intensity modulated radiation therapy (IMRT) technique on the quality of the treatment of the head and neck cancer patient.. Methods and materials: The CT scans of thirteen head and neck cancer patients were selected at the Zhianawa Cancer Center (ZCC). The Monaco treatment planning system (TPS) V5.51.10 with the Monte Carlo (XVMC) algorithm V1.6 were utilized to generate nine and eleven field IMRT plans, all plans were carried out on an ELEKTAMLCi2 linear accelerator. The effect of field number was assessed by planning target volume (PTV) coverage, homogeneity index (HI), conformity index (CI), OARs dose, the monitor units (MUs), and delivery time. Results: The 11F-IMRT had improved tumor coverage and better spared ipsilateral and contralateral optic nerves, on the contrary the doses to the were above acceptance limit value. The CI of 11F-IMRT was better than 9F-IMRT, while the HI was similar. The 9F-IMRT had a reduced treatment time by 37.7 %, although increased MUs by 12.8%.