Implementation of daily image-guided radiation therapy using an in-room CT scanner for prostate cancer isocentre localization

Full text: The Tattersall's Cancer Centre has been performing image-guided radiation therapy (IGRT) using an in-room CT on rails since 2003 to verify accurate patient setup position (relative to bony anatomy) immediately prior to treatment delivery for prostate cancer patients. While the concept of online correction for bony anatomy is well established, the use of an in-room CT scanner also enables the collection and offline analysis of soft tissue volumetric data. Although initially IGRT was implemented under a research protocol, in-room CT verification has continued to be used to measure and correct for patient setup variations for all patients undergoing intensity modulated radiation therapy (IMRT) treatments. The present paper outlines the protocol that was used to implement IGRT using an in-room CT scanner at the Tattersall's Cancer Centre. Online corrections that minimize patient setup uncertainties allow confidence in delivering dose escalation as well as decreasing the margins required around the target volume. With improvements in auto-contouring tools, IGRT will also have the ability to measure and correct for variations in target and critical structure positioning online, rather than the current offline methods utilized.