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MPPG Report 2.b - AAPM MEDICAL PHYSICS PRACTICE GUIDELINE 2.b.: Commissioning and quality assurance of X-ray-based image-guided radiotherapy systems (2021)

Category: MPPG Report

Image-guided radiation therapy (IGRT), in its many forms, is an important tool in improving the effectiveness of clinical radiation oncology. IGRT involves the use of patient images to localize and reposition the patient or delivery system prior to treatment to ensure that the therapeutic beam is correctly directed toward the target. IGRT imaging strategies have utilized X-rays, ultrasound, and other means. In particular, IGRT has been most commonly facilitated using X-rays, beginning with the use of megavoltage (MV) portal and/or orthogonal setup images some decades ago. These images provide a means of evaluating the position of the treatment isocenter and field edges relative to the patient's position. Due to the poor low-contrast resolution of MV images, bony anatomy may be taken as a surrogate of the target volume, which is frequently soft tissue equivalent and not clearly visible within the image. However, as many studies have shown, the target volume can exhibit a different relative location to bony anatomy than expected. One solution to clinical scenarios in which improved soft tissue targeting is desired was the introduction of in-room kilovoltage (kV) imaging systems. Such systems have included computed tomography (CT) scanners located within the treatment room (e.g., "CT-on-rails") and kV imaging systems affixed to the floor/ceiling or to the linear accelerator gantry itself. These systems have provided improved the low-contrast localization of soft tissue targets and—in the case of in-room CT scanners and gantry-mounted imaging systems—allowed for the acquisition of pretreatment volumetric images.

Journal of Applied Clinical Medical Physics

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Keywords: AAPM, IGRT QA, image guidance, MPPG, radiotherapy quality assurance

Steven P. McCullough, Hassaan Alkhatib, Kyle J. Antes, Sarah Castillo, Jonas D. Fontenot, Andrew R. Jensen, Jason Matney, Arthur J. Olch

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