Development of a standardized method for contouring the larynx and its substructures

Objectives: Limiting radiation dose to the larynx can diminish effects of laryngeal dysfunction. However, no clear guidelines exist for defining the larynx and its substructures consistently on cross-sectional imaging. This study presents computed tomography (CT)-and magnetic resonance imaging (MRI)-based guidelines for contouring laryngeal organs-at-risk (OARs). Materials and Methods: Standardized guidelines for delineating laryngeal OARs were devised and used to delineate on CT and MRI for head-and-neck cancer patients. Volumetric comparisons were performed to evaluate consistency and reproducibility of guideline-based contours. Results: For the initial 5 patients the mean CT and MRI based larynx volume did not differ significantly between imaging modalities; 34.39 +/- 9.85 vs. 35.01 +/- 9.47 (p =.09). There was no statistical difference between the CT based mean laryngeal volume in the subsequent 44 patients compared to the initial 5 patients outlined on CT and the MRI scan (p = 0.53 and 0.62). The OAR volume for laryngeal substructures were not statistically different among patients or between imaging modalities. Once established, the guidelines were easy to follow. Conclusion: The guidelines developed provide a precise method for delineating laryngeal OARs. These guidelines need to be validated and clinical significance of outlining laryngeal substructures and dose-volume constraints should be investigated before routine implementation in clinic practice.