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contour propagation. For the automatic contouring
strategy the daily propagated contours were based on an
intra-patient atlas consisting of the manual contours of
the first day and propagated contours of other previous
days.The semi-automatic contouring strategy included
additional manual adjustments made by a technologist
after each daily automatic contour propagation serving as
input for the following days. All automatic and semi-
automatic contours were compared with the manual
contours of the corresponding day by calculating dice
coefficients, mean and Hausdorff distances. Timing
measurements were done for both strategies.
Results
Higher median dice coefficients with smaller ranges were
found for the semi-automatic strategy compared to the
automatic strategy (figure 1). However, large variations
after manual adjustments were still found for the GTV.
Outliers found in the mean and Hausdorff distances of the
automatic strategy were not seen in the semi-automatic
strategy (figure 2).
The contours were automatically propagated for day 2, 3,
4 and 5 in respectively 18, 38, 54 seconds and 1:13 minutes
on average. The propagated contours of the semi-
automatic strategy were manual adjusted with an average
time of 14:49 minutes (in comparison with approximately
45 minutes for full manual contouring). Manual
adjustments of the cranial and caudal slices of the
contours were most time consuming.
Conclusion
Automatic propagated contours for target and OARs need
manual adjustments for clinical acceptance. Mesorectum
and OARs adjustments can be made by an experienced
technologist and are not clinically relevant different from
the manual contours of an experienced radiation
oncologist. This semi-automatic contouring strategy can
be used in an online workflow for rectal boost treatment,
however further speed-optimisation is desirable.
PO-0906 Textural analysis of MR images to improve the
characterisation of recurrent prostate cancer
J. Stirling
1
, R. Alonzi
2
, P.J. Hoskin
2
, N.J. Taylor
1
, W.L.
Wong
1
, A.R. Padhani
1
, B. Sanghera
1
1
Paul Strickland Scanner Centre, Research, Northwood,
United Kingdom
2
Mount Vernon Hospital, Academic Oncology Unit,
Northwood, United Kingdom