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Commissioning and quality assurance of an optically guided three‐dimensional ultrasound target localization system for radiotherapy
Author(s) -
Tomé Wolfgang A.,
Meeks Sanford L.,
Orton Nigel P.,
Bouchet Lionel G.,
Bova Francis J.
Publication year - 2002
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1494835
Subject(s) - imaging phantom , isocenter , quality assurance , radiation treatment planning , coordinate system , medical imaging , computer science , ultrasound , medical physics , image guided radiation therapy , computer vision , biomedical engineering , nuclear medicine , artificial intelligence , radiation therapy , medicine , radiology , external quality assessment , pathology
Recently, there has been proliferation of image‐guided positioning systems for high‐precision radiation therapy, with little attention given to quality assurance procedures for such systems. To ensure accurate treatment delivery, errors in the imaging, localization, and treatment delivery processes must be systematically analyzed. This paper details acceptance tests for an optically guided three‐dimensional (3D) ultrasound system used for patient localization. While all tests were performed using the same commercial system, the general philosophy and procedures are applicable to all systems utilizing image guidance. Determination of absolute localization accuracy requires a consistent stereotactic, or three‐dimensional, coordinate system in the treatment planning system and the treatment vault. We established such a coordinate system using optical guidance. The accuracy of this system for localization of spherical targets imbedded in a phantom at depths ranging from 3 to 13 cm was determined to be (average ± standard deviation) AP = 0.2 ± 0.7 mm, Lat = 0.9 ± 0.6 mm, Ax = 0.6 ± 1.0 mm. In order to test the ability of the optically guided 3D ultrasound localization system to determine the magnitude of an internal organ shift with respect to the treatment isocenter, a phantom that closely mimics the typical human male pelvic anatomy was used. A CT scan of the phantom was acquired, and the regions of interest were contoured. With the phantom on the treatment couch, optical guidance was used to determine the positions of each organ to within imaging uncertainty, and to align the phantom so the plan and treatment machine coordinates coincided. To simulate a clinical misalignment of the treatment target, the phantom was then shifted by different precise offsets, and an experimenter blind to the offsets used ultrasound guidance to determine the magnitude of the shifts. On average, the magnitude of the shifts could be determined to within 1.0 mm along each axis.