An assessment of OAR delineation by the radiation therapist

Introduction: Role expansion of the radiation therapist into areas such as organ at risk (OAR) delineation is currently being discussed. Any role expansion into this area, however, must be carefully monitored and evaluated before it should occur. OAR delineation is a vital link in an effective Image Guided Radiation Therapy (IGRT) and Intensity Modulated Radiation Therapy (IMRT) program. The uniformity of OAR delineation must be proven between radiation therapists and with their radiation oncologist colleagues before role expansion can occur. Methods: Six radiation therapists were required to contour prostate, bladder and rectum on three CT datasets twice before undertaking a radiation oncologist guided education session. After this education intervention the process was repeated. Variance between the six radiation therapists (inter-observer) was calculated and also a comparison made to the radiation oncologist derived 'gold standard'. Results: There was little uniformity between the radiation therapist derived volumes for prostate, bladder and rectum. The education intervention had minimal impact on the variance between radiation therapist derived contours. When compared to the 'gold standard' there was minimal consistency shown by the radiation therapist led OAR delineation. Conclusion: The introduction of an education intervention had minimal impact on the variance in OAR delineation between individual radiation therapists (inter-observer) and in comparison with the gold standard. Role expansion of the radiation therapist into this area will need to be a framework of continuous education and evidence-based practise.