Functional Swallowing Units (FSUs) as organs-at-risk for radiotherapy. PART 2: Advanced delineation guidelines for FSUs

Radiother Oncol. 2019 Jan:130:68-74. doi: 10.1016/j.radonc.2018.09.022. Epub 2018 Dec 11.


Background and purpose: In a separate article (PART 1), a rationale and explanation of the physiology-and-anatomy-based concept of Functional Swallowing Units (FSUs) was presented. FSUs are swallowing muscles not included in the set of commonly defined swallowing organs at risk (SWOARs). They are involved in three crucial swallowing components: hyolaryngeal elevation (HLE), tongue base retraction (TBR) and tongue motion. This paper is a continuation of PART 1 and it provides detailed computed tomography (CT)-based delineation guidelines for FSUs, which presumably are also at risk of radiation-induced dysphagia.

Material and methods: Following analysis of swallowing physiology and human anatomy, presented in PART 1, CT-based delineation guidelines for defined FSUs were created. Delineation was performed by the first author and revised by a panel of experts.

Results and conclusions: Detailed delineation guidelines are presented for seven FSUs involved in HLE, TBR and tongue motion. The guidelines are supplemented by CT and MRI-based exemplary illustrations and complete CT/MRI-based delineation atlases (available online). This paper provides information essential to the implementation of the FSU concept in radiation practice, and supports uniform contouring, data collection and further improvement of swallowing sparing radiation-based strategies.

Keywords: (chemo)Radiation; Delineation; Head and neck cancer; Hyolaryngeal elevation; Swallowing organs at risk; Tongue base retraction.

Publication types

  • Guideline

MeSH terms

  • Deglutition / physiology
  • Deglutition / radiation effects
  • Deglutition Disorders / diagnostic imaging
  • Deglutition Disorders / etiology
  • Deglutition Disorders / physiopathology
  • Head and Neck Neoplasms / diagnostic imaging
  • Head and Neck Neoplasms / radiotherapy
  • Humans
  • Magnetic Resonance Imaging / methods
  • Organs at Risk / diagnostic imaging
  • Organs at Risk / physiology*
  • Organs at Risk / physiopathology
  • Organs at Risk / radiation effects
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Tomography, X-Ray Computed / methods