Verification of cone-beam CT functions for Varian Clinac IX linear accelerator

OBJECTIVES: The On-Board Imager (OBI) system is designed to correct for motion and setup errors in patients undergoing radiation therapy. The OBI system provides three imaging modes: radiographic and fluoroscopic image acquisition and three-dimensional cone-beam computed tomography (CBCT) acquisition. The use of this new technology necessitates a comprehensive quality assurance (QA) program. In this study, we describe the procedures of test items included in the QA program and present the results of measurements. METHODS: We used Catphan 600 phantom for CBCT image quality tests. We verified density resolution, spatial linearity measurement, image uniformity measurements, and high resolution and low contrast resolution. RESULTS: All measured values were in accordance with acceptance and limit values. CONCLUSION: Use of the tests over extended periods showed that the OBI system has stable image quality. While the results of the measurements were not exactly the same, they were observed to be in acceptable limits.