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Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition
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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
PubMed

Insights

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.
Abstract

Keywords:
Inter-observer variationPediatric radiotherapyTarget delineationTreatment planning

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