Consequently, in this study, we assess dosimetric differences from the observed RGFP966 clinical baselines in each region rather than from absolute values. In this analysis, the four volumetric measures of
agreement (see Table 1) between the Raw TES CTVs (created by radiation therapists) and the RO-reviewed TES CTVs were computed for 140 randomly selected retrospective cases (40 cases seen between January 2009 and April 2009 and 100 cases seen between January 2010 and September 2010). This analysis indicates how satisfied the physicians were with the results of the algorithm and which regions required the most modifications. We refer the readers to our earlier work (17) for a comparison of the above volumetric evaluation (on 40 cases) with inter- and intraobserver variability in manual contouring. The aim of the dosimetric evaluation is to examine the clinical impact of planning using Raw TES contours. This helps to put differences in volumetric coincidence in perspective because if such differences do not result in a significant degradation in dosimetry when a Raw TES-derived plan is used to treat a reference contour, then
it is reasonable to suppose that the TES and reference contour are of equivalent selleck kinase inhibitor utility for planning purposes. To investigate this, 41 anonymized consecutive patients (seen between January 2009 and April 2009) had treatment plans generated using their Raw TES PTVs as described in the “Patient characteristics
why and treatment planning” section. The aforementioned dose parameters for these plans were calculated for the PTV and the nine sectors and used as the observed clinical baselines. These plans were then overlaid on the reference (RO-reviewed TES) contours and the resulting dose parameters calculated for the PTV and the nine sectors. The distribution of paired differences in the dose parameters was calculated (i.e., dose parameter of the plan generated using Raw TES PTVs and overlaid on RO-reviewed TES PTVs minus the observed clinical baseline values). Although the impact of TES-based planning is readily calculated, establishing a sensible threshold for the acceptable amount of dosimetric degradation below which the adoption of TES-based planning is unacceptable is challenging. For example, a plan with a whole PTV V100 below 97% would not be accepted for implant at our institution, so it may seem natural to set this as a target for TES-based planning. However, the patient might have been seen by any number of oncologists, none of whose plans are explicitly required to meet the 97% criterion on the contours of their colleagues. To avoid a double standard, the evaluation of any automatic contouring algorithm cannot ignore the implicitly accepted differences in dosimetry, which arise from the endemic variability in target definition between observers.