Comparison of intensity modulated radiation therapy (IMRT) vs. intensity modulated arc therapy (IMAT) in head-and-neck cancer radiotherapy

In this study, 5, 7, 9 field IMRT and 1 and 2 arc IMAT plans were performed for 12 patients with head and neck cancer. Plans were normalized to improve % 95 PTV coverage. PTV and critical structure maximum and mean doses were analyzed by using DVH. Comparisons were made among IMRT and IMAT priorities; 5, 7 and 9 field IMRT plans; 1 and 2 arc IMAT plans; 7 field IMRT and 2 arc IMAT plan. Higher doses to PTV for plans with IMRT priorities and to critical structures for plans with IMAT priorities were seen. When a comparison were made between 5, 7 and 9 field IMRT plans, higher doses were seen for 5 field IMRT. The most homogeneous dose distributions were seen for 7 field IMRT plans. Higher doses were seen for 1 arc IMAT plans, compared to 2 arc plans. When IMRT and IMAT plans were compared, higher doses were seen by 2 arc IMAT plans. As body contour inhomogeneities are more effective for IMAT plans which use whole body contour compared to fıxed gantry fields used at 7 field IMRT plans. IMRT plans use more MU in proportion to the number of fields. IMAT plans show significantly lower number of MU. There is no significant increase between MU values of 1 and 2 arcs. However, 2 arc IMAT plans have more homogeneous dose distribution and lower critical structure doses compare to 1 arc plan.