Assessment of consistency in contouring of normal-tissue anatomic structures.

The purpose of this work is to estimate the uncertainty in the manual contouring of normal anatomical structures. The heart, esophagus, and spinal cord were contoured manually on six sets of computed tomography images by six dosimetrists whose experience ranged from 1 year to over 15 years. To determine the differences between inter- and intraobserver variations, each data set was contoured by one of the dosimetrists five times and once each by the five other dosimetrists.