Image-guided radiation therapy (IGRT) is the use of daily imaging during a course of radiation therapy for the purpose of improving the precision and accuracy of the treatment setup and delivery.

IGRT can be accomplished with special imaging technology that allows the physician to image the tumor immediately before or even during the time radiation is delivered, while the patient is positioned on the treatment table. These imaging  technologies include Computed Tomography (known as CBCT), MRI, X-ray, and Ultrasound (US) in order to visualize the boney or soft-tissue anatomy used for setup. Using specialized computer software, these images are then compared to the reference images taken during simulation. Any necessary adjustments are then made to the patient's position and/or radiation beams in order to more precisely target radiation to the tumor and avoid healthy surrounding tissue. Some of the imaging technologies  use fiducials or implanted markers that show up on the images to further “match” the initial setup and positioning that was captured at the time of simulation. Other methods for IGRT use markers placed on the patient's body surface or markers implanted within the patient's body that emit a radiofrequency.

Arch Cancer Care utilizes the technology of the Clarity Patient Positioning System (ultrasound) to image the prostate and bladder daily for setup accuracy without the use of fiducial or implanted markers. Ultrasound does not emit radiation nor add additional dose to the patient’s treatment. Ultrasound images are acquired at the time of simulation allowing the physician to create  normal tissue and target volumes on the those images which are then compared and  “matched” with the daily acquired images  for setup by the therapists before radiation treatments. The combination of the Clarity Patient Positioning System and the state of the art Varian Clinac 2100ix, produces sub millimeter setup accuracy for the daily treatment of prostate cancer delivered with IMRT technology.