Split X-jaw Planning Technique of Volumetric Modulated Arc Radiotherapy

Abstract

This brief communication article examines the constraints posed by the Varian linear accelerator machine’s volumetric-modulated arc therapy (VMAT) due to the maximum extent of the multileaf collimator (MLC) in the x-jaw direction. The MLC leaves within this machine are capable of extending up to 15 cm in the x-jaw direction. However, when VMAT is employed with excessive extension, modulation level decreases, leading to compromised target dose distribution, and the protection of critical organs. The existing VMAT techniques involve open and limited x-jaw approaches, but these methods present avenues for enhancement. One innovative approach is the split x-jaw planning technique, which involves segmenting the open field into two distinct fields with some overlap. This strategy yields four treatment arcs that comprehensively cover the planning target volume (PTV). Enhancing modulation and conformity can be achieved by restricting each field’s size to 15 cm. Consequently, this technique demonstrates improved target dose distributions, heightened plan conformity, and more effective sparing of organs at risk compared to the limited and open methodologies. Initial dosimetric studies suggest that the split X-jaw technique holds promise as a superior planning solution for larger PTVs that exceed the MLC’s maximum x-jaw extent.