Inter-observer Variability of Prostate Delineation on Cone Beam Computerised Tomography Images

Prostate delineation variability for five observers with resulting variability in isocentre placement for one subject.

Demonstration of the subject with maximum variability. One delineated volume is placed much superior to the others.

A clinical example of large systematic set-up error with cone beam computerised tomography image guidance. The intended set-up is shown on the left. The actual set-up is shown on the right, where a small-volume bladder has been misidentified as the prostate on the cone beam computerised tomography images.