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

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 pha...

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Autores principales: Brezovich, Ivan A., Popple, Richard A., Duan, Jun, Shen, Sui, Wu, Xingen, Benhabib, Sidi, Huang, Mi, Cardan, Rex A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690062/
https://www.ncbi.nlm.nih.gov/pubmed/27455506
http://dx.doi.org/10.1120/jacmp.v17i4.6295
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author Brezovich, Ivan A.
Popple, Richard A.
Duan, Jun
Shen, Sui
Wu, Xingen
Benhabib, Sidi
Huang, Mi
Cardan, Rex A.
author_facet Brezovich, Ivan A.
Popple, Richard A.
Duan, Jun
Shen, Sui
Wu, Xingen
Benhabib, Sidi
Huang, Mi
Cardan, Rex A.
author_sort Brezovich, Ivan A.
collection PubMed
description 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 25.4 mm diameter sphere of polymethylmetacrylate (PMMA) containing a concentric 6.35 mm 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 [Formula: see text] of its true positon, and MV isocenter was pinpointed in planar images to within [Formula: see text]. In clinical morning QA tests extending over an 18 months period the UAB consistently yielded measurements with sub‐mm accuracy. The average distance between isocenter defined by orthogonal kV images and CBCT measured [Formula: see text]. In WL tests the central ray of anterior beams defined by a [Formula: see text] MLC field agreed with CBCT isocenter within [Formula: see text] in the lateral direction and within [Formula: see text] in the longitudinal direction. Lateral MV beams approached CBCT isocenter within [Formula: see text] in the vertical direction and within [Formula: see text] longitudinally. It took therapists about 10 min to do the tests. The novel QA phantom allows pinpointing CBCT and MV isocenter positions to better than 0.2 mm, using visual image registration. Under CBCT guidance, MLC‐defined beams are deliverable with sub‐mm spatial accuracy. The QA procedure is practical for daily tests by therapists. PACS number(s): 87.53.Ly, 87.56.Fc
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spelling pubmed-56900622018-04-02 A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*) Brezovich, Ivan A. Popple, Richard A. Duan, Jun Shen, Sui Wu, Xingen Benhabib, Sidi Huang, Mi Cardan, Rex A. J Appl Clin Med Phys Radiation Oncology Physics 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 25.4 mm diameter sphere of polymethylmetacrylate (PMMA) containing a concentric 6.35 mm 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 [Formula: see text] of its true positon, and MV isocenter was pinpointed in planar images to within [Formula: see text]. In clinical morning QA tests extending over an 18 months period the UAB consistently yielded measurements with sub‐mm accuracy. The average distance between isocenter defined by orthogonal kV images and CBCT measured [Formula: see text]. In WL tests the central ray of anterior beams defined by a [Formula: see text] MLC field agreed with CBCT isocenter within [Formula: see text] in the lateral direction and within [Formula: see text] in the longitudinal direction. Lateral MV beams approached CBCT isocenter within [Formula: see text] in the vertical direction and within [Formula: see text] longitudinally. It took therapists about 10 min to do the tests. The novel QA phantom allows pinpointing CBCT and MV isocenter positions to better than 0.2 mm, using visual image registration. Under CBCT guidance, MLC‐defined beams are deliverable with sub‐mm spatial accuracy. The QA procedure is practical for daily tests by therapists. PACS number(s): 87.53.Ly, 87.56.Fc John Wiley and Sons Inc. 2016-07-08 /pmc/articles/PMC5690062/ /pubmed/27455506 http://dx.doi.org/10.1120/jacmp.v17i4.6295 Text en © 2016 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Radiation Oncology Physics
Brezovich, Ivan A.
Popple, Richard A.
Duan, Jun
Shen, Sui
Wu, Xingen
Benhabib, Sidi
Huang, Mi
Cardan, Rex A.
A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title_full A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title_fullStr A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title_full_unstemmed A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title_short A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery(*)
title_sort novel phantom and procedure providing submillimeter accuracy in daily qa tests of accelerators used for stereotactic radiosurgery(*)
topic Radiation Oncology Physics
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690062/
https://www.ncbi.nlm.nih.gov/pubmed/27455506
http://dx.doi.org/10.1120/jacmp.v17i4.6295
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