ESTRO 2022 - Abstract Book

S411

Abstract book

ESTRO 2022

section of the workflow, alleviating the presence of the doctor. To facilitate this, a RTT prostate and seminal vesicles (SVs) contouring training programme was developed. We investigated whether RTT contours were within the inter-observer range of the doctors’ contours. Materials and Methods Five RTTs and five doctors contoured the prostate and SVs on 10 T2-weighted MRL-acquired MRIs, from 10 patients, on the Monaco treatment planning system (Version: 5.59.02 Research, Elekta, Stockholm, Sweden). For each RTT and doctor, two clinical target volumes (CTV) were created following the PRISM (NCT03658525) and PACE (NCT01584258) protocol: Simultaneous truth and performance level estimation (STAPLE) structures were created using the five doctors’ contours to create “gold standard” CTVpsv and CTVsv volumes. Each RTT and doctor structure was then compared with the STAPLE structure using ADMIRE (Version: research 2.0 Elekta, Stockholm, Sweden) to generate a dice similarity coefficient (DSC). The DSC results were compared using a Mann Whitney U test. The inter-observer range of volumes was extracted. Results Fifty CTVpsv and fifty CTVsv structures were created for both doctors and RTTs. The median DSC for RTT and doctor structures compared to the STAPLE were not significantly different ( p= 0.18) (Table 1). Median (range) DSC Doctors RTTs CTVpsv 0.92 (0.88 – 0.97) 0.92 (0.86 – 0.96) CTVsv 0.92 (0.86 – 0.97) 0.91 (0.83 – 0.96) Table 1. Dice similarity coefficient for RTT and doctor contours compared to a STAPLE contour. CTVpsv; Of the 50 CTVpsv RTT structures, 30 volumes were within the doctors’ volume range (Figure 1). Six were smaller than the minimum doctor’s volume and 14 were larger than the maximum doctor’s volume. Of the six smaller, four were ≤ 1% smaller (0.1cm 3 to 0.3cm 3 ) and the remaining two were 7% (1.5cm 3 ) and 8% (1.8cm 3 ) smaller respectively. CTVpsv: prostate plus 1cm SVs CTVsv: prostate plus 2cm SVs

CTVsv; Of the 50 CTVsv RTT structures, 35 were within the doctors’ volume range. Three were smaller than the minimum doctor’s volume and 12 were larger than the maximum doctor’s volume. Of the three, one was < 1% smaller (0.3 cm 3 ), one 3.4% smaller (0.9 cm 3 ) and one 7.5% smaller (1.9 cm 3 ).

On visual inspection, the variation at the base and apex contributed to the largest difference in contour volume.

Conclusion