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A New Physical Phantom for Routine Quantitative QA of Gamma Knife ICON HDMM System

C Wu

C Wu*, M Radevic , J Glass , S Skubic , Sutter Medical Foundation, Sacramento, CA


SU-I-GPD-T-229 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To design, manufacture, and test a novel physics phantom for quantitative QA of a Gamma Knife ICON HDMM system.

Methods: A physical phantom (named “Sutter HDMM Phantom” or “SH phantom”) was created and tested to enable quantitative QA of the Gamma Knife ICON HDMM system. The SH phantom design enables a known small shift of the HDMM reflector along any single axis (superior-inferior, anterior-posterior, or lateral), or along any combination of axes, thereby allowing us to quantitatively evaluate the accuracy of the shifts reported by the HDMM camera. The design consists of a base with a void, a top column that fits into the void (a HDMM reflector is placed on one side of this column), and three 1 mm/2 mm thin slices that can be inserted in order to create corresponding shifts. The design was implemented using TinkerCAD software online. The CAD design was then converted to STL files for subsequent 3D printing. A high end commercial 3D printer (mean printing accuracy less than 0.15 mm) was used to manufacture the SH phantom with its proprietary solid material. An immobilization head rest was made to conform to the SH phantom so that it can be used on the mask holder of the Gamma Knife ICON. The SH phantom was tested and evaluated by a group of four physicists on our ICON unit.

Results: By using the SH phantom, individual small shifts along each axis, all possible combinations of small shifts along any two axes, and one example composite shift along all three axes were tested and the designated shifts were compared against the HDMM readout.

Conclusion: The SH phantom is found to be a very useful tool to help quantitatively evaluate the accuracy of a Gamma Knife ICON HDMM system.

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