The design, physical properties and clinical utility of an iris collimator for robotic radiosurgery

• Published in: Physics in medicine & biology 2009-09, Vol.54 (18), p.5359-5380
• Main Authors: Echner, G G, Kilby, W, Lee, M, Earnst, E, Sayeh, S, Schlaefer, A, Rhein, B, Dooley, J R, Lang, C, Blanck, O, Lessard, E, Maurer, C R, Schlegel, W
• Format: Article
• Language: English
• Subjects: Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Radiosurgery - methods; Reproducibility of Results; Robotics - instrumentation; Sensitivity and Specificity; Surgery, Computer-Assisted - methods
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/54/18/001

Robotic radiosurgery using more than one circular collimator can improve treatment plan quality and reduce total monitor units (MU). The rationale for an iris collimator that allows the field size to be varied during treatment delivery is to enable the benefits of multiple-field-size treatments to be realized with no increase in treatment time due to collimator exchange or multiple traversals of the robotic manipulator by allowing each beam to be delivered with any desired field size during a single traversal. This paper describes the Iris variable aperture collimator (Accuray Incorporated, Sunnyvale, CA, USA), which incorporates 12 tungsten-copper alloy segments in two banks of six. The banks are rotated by 30 degrees with respect to each other, which limits the radiation leakage between the collimator segments and produces a 12-sided polygonal treatment beam. The beam is approximately circular, with a root-mean-square (rms) deviation in the 50% dose radius of