Quality Assurance of X-ray Computer Tomography

Quality assurance (QA) of computed tomography (CT) scanners is motivated by three primary performance endpoints: safety, mechanical, and image quality. As with any machine that could potentially injure a patient during operation, CT scanners typically have a number of emergency interlocks in place to reduce the risk to the patient. Mechanical QA for CT primarily concerns the table and the lasers used for patient setup and localization. Laser QA concerns not only the positional accuracy of the lasers but also their relation to the imaging plane. Image quality QA is important for both diagnostic scanners, where image artifacts and distortions can lead to an incorrect diagnosis and subsequent mistreatment, and CT simulators used in therapy, where good image quality is critical for both dosimetry and target identification. For CTs used only for diagnosis, this tolerance may be too tight whereas radiation oncology departments that make heavy use of stereotactic body radiation therapy may wish to obtain tighter tolerances.