Tumor imaging of the head and neck in 18F-FDG PET/CT: Anatomy and patterns of disease spread

Learning Objectives 1. Understand the complex cross sectional anatomy of the head and neck (HN) region. 2. Diagnosing HN cancers by localizing it to its proper space of origin, and understanding the patterns of local disease spread. 3. Recognize the pitfalls of PET/CT in this region. 4. Know the manifestations and limitations of PET/CT in nodal staging. 5. Become aware of perineural spread of HN tumors. 6. Value of PET/CT in detection of distant metastasis and second primaries.

Positron Emission Tomography/Computed Tomography (PET/CT) with 2-[fluorine 18]fluoro-2-deoxy-d-glucose (18F-FDG) imaging is an integral part of the multidisciplinary approach to accurately diagnose and stage head and neck (HN) cancer. PET/CT imaging of HN cancers can be complicated and difficult to interpret due to the complex anatomy of this region. The aim of this presentation is to provide PET/CT readers with a simple road map to help analyze the multifaceted aspects of HN tumors. Localizing the HN tumor in the correct anatomical space is essential in reaching the accurate diagnosis of the tumor. Understanding the pattern of spread is critical in local staging. We will demonstrate the different anatomical spaces of the HN region, including the pharyngeal mucosal, parapharyngeal, masticator, parotid, carotid, retropharyngeal and pre/paravertebral, oral tongue, floor of mouth and laryngeal spaces. We will highlight the pattern of spread of tumors in these spaces, the hidden areas in the HN, and the PET/CT pitfalls in this area. We will demonstrate the PET/CT criteria of malignant lymph nodes, illustrating the cross section by level, nodal staging and highlight some PET/CT limitations in nodal staging. We will raise the awareness about the possibility of detecting spread of HN tumors along the cranial nerves (perineural spread), which could be incidentally seen on PET/CT. Finally we will discuss the unique role of PET/CT in M staging of HN patients.