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A dose based approach for evaluation of inter-observer variations in target delineation
Ingrid Kristensen1,2, Kristina Nilsson3, Måns Agrup4
1Department of Oncology, Clinical Sciences, Lund University, Lund, Sweden.
Technical Innovations & Patient Support in Radiation Oncology
|February 26, 2020
Summary
Inter-observer variations in pediatric radiation therapy target delineation were quantified using geometric and dosimetric methods. Incorporating dose-volume histograms (DVHs) with consensus volumes improves the evaluation of target delineation accuracy.
Area of Science:
- Radiation Oncology
- Medical Physics
- Pediatric Oncology
Background:
- Inter-observer variability in target delineation is a significant challenge in pediatric radiation therapy.
- Difficulties in pediatric target delineation stem from small patient numbers, target variability, and individual patient needs.
- Uncertainties in target delineation can lead to under- or over-dosage, impacting treatment efficacy and toxicity.
Purpose of the Study:
- To apply the concept of consensus volumes and quality treatment plans to visualize and quantify inter-observer target delineation variations.
- To evaluate inter-observer variations in dosimetric terms, complementing traditional geometric concordance indices.
- To demonstrate the utility of dose metrics in assessing target delineation diversity in pediatric cases.
Main Methods:
- Two pediatric cases (Hodgkin's disease and rhabdomyosarcoma) were analyzed.
- Variability in planning target volume (PTV) delineations from six centers was quantified using the generalized conformity index (CIgen).
- The STAPLE algorithm derived consensus volumes, and dose distributions were applied to these consensus volumes for dosimetric analysis.
Main Results:
- Considerable variation in target segmentation was observed, with average volume differences of 669 cm³ (case 1) and 109 cm³ (case 2).
- CIgen values were 0.53 and 0.70 for the two cases, respectively.
- Absolute volume dose-volume histograms (DVHs) provided insights into compliant and outlier target volumes, information obscured by concordance indices alone.
Conclusions:
- Absolute volume DVHs offer valuable and easily interpretable information for assessing target delineation uniformity.
- Integrating dosimetric evaluation with geometric indices enhances the understanding of inter-observer variability in pediatric radiation therapy.
- The proposed method aids in visualizing and quantifying target delineation uncertainties, potentially improving treatment planning accuracy.
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