Accumulation of rectum dose-volume metrics for prostate external beam radiotherapy combined with brachytherapy: evaluating deformably registered dose distribution addition using parameter-based addition

Calyn R. Moulton, Michael J. House, Victoria Lye, Colin I. Tang, Michele Krawiec, David J. Joseph, James W. Denham, Martin A. Ebert

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    6 Citations (Scopus)

    Abstract

    Introduction: To investigate the accuracy of deriving dose-volume histogram (DVH) parameters from deformably registered data by comparing values with the simple addition of DVHs from each phase of a combined external beam radiotherapy (EBRT)/high-dose-rate (HDR-BT) brachytherapy prostate treatment. Methods: Eighty-two patients received EBRT in 23 fractions of 2 Gy and HDR-BT TG43 in three fractions of 6.5 Gy. The HDR-BT CT was deformably registered to the EBRT CT. The rectum D0.1cc, D1cc, D2cc and D10cc were calculated in two ways. (i) Parameter-adding: the EBRT DVH parameters (or the EBRT prescription dose) were added to the unregistered HDR-BT DVH parameters. (ii) Distribution-adding: the parameters were extracted after the EBRT doses were 3D-summed with the registered HDR-BT doses. Resulting differences between the parameters were investigated. Results: The D0.1cc, D1cc and D2cc from parameter-adding were 21.3% (P < 0.001), 6.3% (P < 0.001) and 3.5% (P < 0.001) smaller than those from distribution-adding. The D10cc was 2.2% (P = 0.015) larger for distribution-adding. Conclusion: Distribution-adding was confounded by unsystematic inter/intra-observer rectum-contouring errors and registration accuracy near the anterior rectal wall. Consequently, clinical use of distribution-adding to assess rectal doses requires careful contour and registration evaluation. © 2017 The Royal Australian and New Zealand College of Radiologists

    Original languageEnglish
    Pages (from-to)534-542
    Number of pages9
    JournalJournal of Medical Imaging and Radiation Oncology
    Volume61
    Issue number4
    DOIs
    Publication statusPublished - 7 Aug 2017

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