Imaging of Head and Neck Cancer With CT, MRI, and US

Imaging of head and neck (HN) cancer is a challenge for many radiologists and largely due to the challenging anatomy in a small volume of the body. Additionally, multiple pathologies and the absence of an agreed-upon standard imaging protocol for staging and surveillance add complexity in choosing the most appropriate imaging study. Computed tomography (CT) is often the first-line imaging tool used as it is readily available, relatively cheaper than magnetic resonance (MR) and is rapidly acquired. In comparison, MR is hampered not just by its greater expense and time involved with an imaging study, but the optimization of MR techniques is difficult in this complex part of the body. Over the last decade, additional advanced techniques have been developed for both CT and MR such as dual-energy CT, and perfusion imaging with CT or MR, which may aid in making a more accurate diagnosis and predication of tumor behavior. Ultrasound (US) plays an important role in HN imaging, particularly in the pediatric age group for new neck masses, and in adult patients with known or suspected thyroid pathology. US is also useful for the evaluation of other superficial masses in the neck and for guiding fine needle aspiration. This article will focus on each imaging modality, reviewing the benefits and drawbacks of CT, MR, and US as well as additional or advanced techniques within each. It will highlight disease processes where a specific modality is strongly favored as the most appropriate imaging study, and specific HN tumor behaviors that require dedicated imaging protocols or techniques. This review will also discuss the entity of carcinoma of unknown primary, which is often imaged with PET/CT, but for which specific guidelines were introduced in the 8th edition of the American Joint Committee of Cancer/Union for International Cancer Control Staging Manuals.