The effect of delineation method and observer variability on bladder dose-volume histograms for prostate intensity modulated radiotherapy

Tara Rosewall*, Andrew J. Bayley, Peter Chung, Lisa W. Le, Jason Xie, Siddhartha Baxi, Charles N. Catton, Geoffrey Currie, Janelle Wheat, Michael Milosevic

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    19 Citations (Scopus)

    Abstract

    Purpose: To quantify the effect of delineation method on bladder DVH, observer variability (OV) and contouring time for prostate IMRT plans. Materials and methods: 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. Results: Manual delineation of the bladder wall (BW-m) was significantly slower than any other method (mean: 20 min vs. ≤13 min) and the dosimetric effect of OV was significantly larger (V70 Gy ICC: 0.78 vs. 0.98). Only volumes created using a 2.5 mm 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. Conclusions: 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. Crown

    Original languageEnglish
    Pages (from-to)479-485
    Number of pages7
    JournalRadiotherapy and Oncology
    Volume101
    Issue number3
    DOIs
    Publication statusPublished - Dec 2011

    Keywords

    • organ at risk
    • external beam
    • IMRT
    • normal tissue
    • organ definition
    • observer error

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