Princess Margaret Hospital and Department of Radiation Oncology, University of Toronto, Canada.
Centre for Research in Complex Systems, Charles Sturt University, Australia.
To quantify the effect of delineation method on bladder DVH, observer variability (OV) and contouring time for prostate IMRT plans.
Planning CT scans and IMRT plans of 30 prostate cancer patients were anonymized. For 20 patients, 1 observer delineated the bladder using 9 methods. The effect of delineation method on the DVH curve, discrete dose levels and delineation time was quantified. For the 10 remaining CTs, 6 observers delineated bladder wall using 4 methods. Observer-based volume variation and intraclass correlation coefficient (ICC) were used to describe the dosimetric effects of OV.
Manual delineation of the bladder wall (BW_m) was significantly slower than any other method (mean: 20min vs. ⩽ 13min) and the dosimetric effect of OV was significantly larger (V70Gy ICC: 0.78 vs. 0.98). Only volumes created using a 2.5mm contraction from the outer surface, and a method providing a consistent wall volume, showed no notable dosimetric differences from BW_m in both absolute and relative volume.
Automatic contractions from the outer surface provide quicker, more reproducible and reasonably accurate substitutes for BW_m. The widespread use of automatic contractions to create a bladder wall volume would assist in the consistent application of IMRT dose constraints and the interpretation of reported dose.
Written by:
Rosewall T, Bayley AJ, Chung P, Le LW, Xie J, Baxi S, Catton CN, Currie G, Wheat J, Milosevic M. Are you the author?
Reference: Radiother Oncol. 2011 Aug 22. Epub ahead of print.
doi: 10.1016/j.radonc.2011.06.039
PubMed Abstract
PMID: 21864921
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