Measurement of Anatomy Contouring in EPI Review: A Practical Method for use in Radiation Therapy Departments

Abstract

ABSTRACTRadiation therapy treatment verification can be performed using hard copy portal films or digital Electronic Portal Images (EPI) of the treatment field, acquired at the time of treatment. This paper describes a practical method of assessing the accuracy of reference anatomy outlining, for treatment sites involving the pelvis, breast and lumbar spine. Seven original bone anatomy outlines contoured onto verification images of five patients, were printed on transparency sheets and reference points were marked at equal distances along the anatomy curves. Two sample anatomy contour sets were created by two independent radiation therapists who outlined visible bone anatomy on the same seven digitally reconstructed radiographs (DRR) and hard copy outlines were obtained. Three independent observers with differing levels of experience, assessed the discrepancies between the original anatomy contours and the sample sets on two occasions one week apart, by measuring the distances between the original and sample set contours (absolute values in mm). The degree of agreement between the same assessor on two occasions (intra‐rater reliability) and between assessors (inter‐rater reliability) was analysed using parametric analysis for levels of relationship and significant differences. This simple method of reference anatomy outline measurement was shown to be highly reliable within assessors and between assessors (r > 0.87 and r2 > 0.75 for both intra‐ and inter‐rater comparisons). This measurement process may be a suitable method, for undertaking quality assurance activities in image verification within radiation therapy departments.