title: A quality assurance program for the on-board imagers.
abstract: To develop a quality assurance (QA) program for the On-Board Imager (OBI) system and to summarize the results of these QA tests over extended periods from multiple institutions. Both the radiographic and cone-beam computed tomography (CBCT) mode of operation have been evaluated. The QA programs from four institutions have been combined to generate a series of tests for evaluating the performance of the On-Board Imager. The combined QA program consists of three parts: (1) safety and functionality, (2) geometry, and (3) image quality. Safety and functionality tests evaluate the functionality of safety features and the clinical operation of the entire system during the tube warm-up. Geometry QA verifies the geometric accuracy and stability of the OBI/CBCT hardware/software. Image quality QA monitors spatial resolution and contrast sensitivity of the radiographic images. Image quality QA for CBCT includes tests for Hounsfield Unit (HU) linearity, HU uniformity, spatial linearity, and scan slice geometry, in addition. All safety and functionality tests passed on a daily basis. The average accuracy of the OBI isocenter was better than 1.5 mm with a range of variation of less than 1 mm over 8 months. The average accuracy of arm positions in the mechanical geometry QA was better than 1 mm, with a range of variation of less than 1 mm over 8 months. Measurements of other geometry QA tests showed stable results within tolerance throughout the test periods. Radiographic contrast sensitivity ranged between 2.2% and 3.2% and spatial resolution ranged between 1.25 and 1.6 lp/mm. Over four months the CBCT images showed stable spatial linearity, scan slice geometry, contrast resolution (1%; <7 mm disk) and spatial resolution (>6 lp/cm). The HU linearity was within +/-40 HU for all measurements. By combining test methods from multiple institutions, we have developed a comprehensive, yet practical, set of QA tests for the OBI system. Use of the tests over extended periods show that the OBI system has reliable mechanical accuracy and stable image quality. Nevertheless, the tests have been useful in detecting performance deficits in the OBI system that needed recalibration. It is important that all tests are performed on a regular basis.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA. sua.yoo@duke.edu
authors.forename: Sua
authors.initials: S
authors.lastname: Yoo
authors.forename: Gwe-Ya
authors.initials: GY
authors.lastname: Kim
authors.forename: Rabih
authors.initials: R
authors.lastname: Hammoud
authors.forename: Eric
authors.initials: E
authors.lastname: Elder
authors.forename: Todd
authors.initials: T
authors.lastname: Pawlicki
authors.forename: Huaiqun
authors.initials: H
authors.lastname: Guan
authors.forename: Timothy
authors.initials: T
authors.lastname: Fox
authors.forename: Gary
authors.initials: G
authors.lastname: Luxton
authors.forename: Fang-Fang
authors.initials: FF
authors.lastname: Yin
authors.forename: Peter
authors.initials: P
authors.lastname: Munro
mesh_terms: D019544:Equipment Failure Analysis / Q000379:methods / Q000592:standards; D011785:Quality Assurance, Health Care / Q000379:methods / Q000458:organization & administration*; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000592:standards*; D013813:Therapy, Computer-Assisted / Q000295:instrumentation* / Q000592:standards*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000592:standards*; D014481:United States