A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery.

A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery.
J Appl Clin Med Phys. 2016;17(4):6295
Authors: Brezovich IA, Popple RA, Duan J, Shen S, Wu X, Benhabib S, Huang M, Cardan RA
Abstract
Stereotactic radiosurgery (SRS) places great demands on spatial accuracy. Steel BBs used as markers in quality assurance (QA) phantoms are clearly visible in MV and planar kV images, but artifacts compromise cone-beam CT (CBCT) isocenter localization. The purpose of this work was to develop a QA phantom for measuring with sub-mm accuracy isocenter congruence of planar kV, MV, and CBCT imaging systems and to design a practical QA procedure that includes daily Winston-Lutz (WL) tests and does not require computer aid. The salient feature of the phantom (Universal Alignment Ball (UAB)) is a novel marker for precisely localizing isocenters of CBCT, planar kV, and MV beams. It consists of a 25.4mm diameter sphere of polymethylmetacrylate (PMMA) containing a concentric 6.35mm diameter tungsten carbide ball. The large density difference between PMMA and the polystyrene foam in which the PMMA sphere is embedded yields a sharp image of the sphere for accurate CBCT registration. The tungsten carbide ball serves in finding isocenter in planar kV and MV images and in doing WL tests. With the aid of the UAB, CBCT isocenter was located within 0.10 ± 0.05 mm of its true positon, and MV...

Source: Journal of Applied Clinical Medical Physics - July 28, 2016 Category: Physics Authors: Brezovich IA, Popple RA, Duan J, Shen S, Wu X, Benhabib S, Huang M, Cardan RA Tags: J Appl Clin Med Phys Source Type: research