Improved Methodology of Static HDMLC Virtual Cone based Rapid Arcs for Stereotactic Ablative Radiotherapy

Physical cones equipped on GammaKnife, Cyberknife, and C-arm linacs have been the standard practice in Stereotactic Ablative Radiotherapy (SART) for small intracranial lesions, such as treating trigeminal or glossopharyngeal neuralgia targets. The advancement of high-definition multi-leaf collimators (HDMLC), treatment planning systems, and small field dosimetry now allows for treatment without the need for an auxiliary mounted physical cone. This treatment type uses the “virtual cone”, a permanent high-definition MLC, arrangement to deliver “very small fields” with comparable spherical dose distributions to physical cones. The virtual cone therapy, on a Varian Edge™ linac using multiple non-coplanar arcs with static HDMLCs, is a comparable technique that can be used to treat small intracranial neuralgia or other small lesions.
In this investigation, two flattening filter free (FFF) photon beams, 6MV FFF and 10MV FFF, were tested for optimal delivery and safety conditions for treating intracranial lesions. The virtual cone method on a Varian Edge™ Linear accelerator using rapid arc stereotactic radiosurgery was used to treat cranial neuralgia for chronic pain for six patients. Absolute dose, relative dose measurements, and monitor units were the main characteristics that were examined to decide which energy was the best for treatment. Source-to-axis distances (SAD) of 100cm measurements were taken at depths of 10cm and 5cm, respectively.