Purpose/Objective: Volumetric modulated arc therapy (VMAT) with a single-isocenter setup has been used for patients with multiple brain lesions undergoing stereotactic radiosurgery (SRS). This retrospective study presents the results of the image-guided target localization and dosimetry associated with this technique.Material/Methods: Fifteen patients with 3 to 5 intracranial lesions (59 lesions total) treated with single-isocenter VMAT SRS were analyzed retrospectively. Each VMAT plan employed 3 to 5 arcs and treatment planning was performed in Eclipse. Conformity index, maximum dose, and coverage were calculated for each lesion. The total volume of brain tissue encompassed by isodose lines of 5 Gy (V5) and 12 Gy (V12) were calculated for each patient. For treatment delivery, each patient was set up with a target localizer initially. Rotational and translational corrections were then made using kilovoltage x-ray images from an ExacTrac system and 6D couch. 3D cone-beam CT (CBCT) images were used for final target localization to ensure that all the lesions were matched simultaneously with the planning CT.Results: Among the 59 lesions, the conformity index ranged from 1.0 to 1.7 with a mean and standard deviation of 1.2 ± 0.2. The maximum dose (relative to prescription dose) was 118.1% ± 8.6%, and coverage was 99.7% ± 0.3%. Mean V5 and mean V12 were 163.2 ± 148.0 and 20.5 ± 15.9 cc, respectively. The mean rotational corrections were 0.6 ± 0.6, 0.7 ± 0.5 and 0.6 ± 0.6 degrees for pitch, roll and couch rotation. The mean translational corrections from ExacTrac were 1.3 ± 0.8, 1.4 ± 1.7 and 0.8 ± 0.9 mm along the lateral, longitudinal and vertical direction. Additional corrections based on CBCT images were 0.8 ± 1.1, 0.8 ± 0.6 and 0.9 ± 0.5 mm along the lateral, longitudinal and vertical directions, and 0.7 ± 0.5 degrees for couch rotation.Conclusions: Single-isocenter multiple-arc VMAT can be an efficient treatment technique for intracranial SRS with multiple lesions provided that image guidance is used to localize and correct the position of all the lesions simultaneously. The treatment time for a patient with 3 ~ 5 lesions can be reduced from 2 ~ 4 hours to 1 hour by using this technique.
Wang, Z,
Volumetric Modulated Arc Therapy for Intracranial Stereotactic Radiosurgery with Multiple Lesions: Image Guidance and Dosimetric Analysis. Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL.
http://archive.rsna.org/2013/13042287.html
