Potential advantages of volumetric arc therapy in head and neck cancer

Intensity-modulated radiation therapy (IMRT) uses solid compensators or multileaf collimators to modulate the intensity of radiation in each field, delivering highly conformal dose distributions. This technique allows treating volumes with concave shapes when the target is close to a critical structure. The movement of multileaf collimator under computer control can modulate the dose in 3 main ways: IMRT with static field with segments, IMRT with dynamic delivery, and IMRT rotational therapy. Volumetric modulated arc therapy (VMAT) is a novel radiation technique that creates conformal distributions with variable gantry speed, dynamic movements of multileaf collimator, and variations in dose rate. The purpose of this study was to review the basis of VMAT, highlighting the differences with other IMRT techniques.