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Method of computing direction-dependent margins for the development of consensus contouring guidelines
Liam S P Lawrence1, Lee C L Chin2,3, Rachel W Chan4
1Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
Radiation Oncology (London, England)
|April 14, 2021
Summary
This study introduces a new method for calculating clinical target volume (CTV) margins and interobserver variability in specific directions for radiation therapy. The findings provide recommended margins for intraosseous and extraosseous disease, aiding in guideline development.
Area of Science:
- Radiation Oncology
- Medical Physics
- Radiotherapy Planning
Background:
- Clinical target volume (CTV) contouring guidelines are essential for radiotherapy but often lack methods for directional margin recommendations.
- Existing interobserver variability metrics may not adequately capture directional disagreement in CTV margins.
- There is a need for standardized methods to compute directional margins reflecting tumor spread patterns.
Purpose of the Study:
- To present a novel algorithm for quantifying clinical target volume (CTV) margins and interobserver variability in clinician-specified directions.
- To aid in the development of consensus contouring guidelines for radiotherapy.
- To address the limitations of isotropic margins and direction-independent variability metrics.
Main Methods:
- The proposed algorithm was applied to 11 non-spine bone metastasis cases.
- Consensus CTV margins were computed for intraosseous and extraosseous disease spread.
- Interobserver variability was quantified using the median coefficient of variation for directional margins.
Main Results:
- Recommended intraosseous and extraosseous CTV margins were 7.0 mm and 8.0 mm, respectively.
- The median coefficient of variation for margin disagreement was 0.59 for intraosseous and 0.48 for extraosseous disease.
- The algorithm successfully quantified directional variability in expert CTV contouring.
Conclusions:
- The developed algorithm enables the generation of directional margin recommendations based on expert consensus.
- It quantifies interobserver variability in specified directions, improving contouring guideline development.
- This method is applicable to future studies aiming to refine radiotherapy planning and CTV delineation.
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