Development of a standardized method for contouring the larynx and its substructures
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RESEARCH
Open Access
Development of a standardized method for contouring the larynx and its substructures Mehee Choi1,4, Tamer Refaat1,5, Malisa S Lester2, Ian Bacchus1, Alfred W Rademaker3 and Bharat B Mittal1*
Abstract 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. Keywords: Head-and-neck cancer, Larynx anatomy, Swallowing dysfunction, Intensity-modulated radiotherapy, Organs at risk
Background The larynx plays an important role in speech and swallowing. Progressive laryngeal edema and fibrosis following radiotherapy for head and neck cancer can lead to long-term problems with phonation and swallowing and significantly compromise quality of life in cancer survivors [1,2]. The incidence of swallowing dysfunction significantly increases with intensified regimens, such as the addition of chemotherapy to radiotherapy [3-5]. Several studies have shown that reduced radiation dose to the larynx can diminish the effects of laryngeal dysfunction [6-9]. It remains unclear which substructures of the larynx, when irradiated, are most associated with swallowing dysfunction. With the advent of technologies such as intensity– modulated radiotherapy (IMRT), it is possible to selectively * Correspondence: [email protected] 1 Department of Radiation Oncology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, 251 E Huron, LC-178, Chicago, IL 60611, USA Full list of author information is available at the end of the article
spare dose to the larynx and its substructures as organs at risk (OARs), thereby reducing the risk of speech and swallowing dysfunction [1]. This has prompted the Radiation Therapy O
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