Head and neck imaging evolves as subspecialty

Head and neck radiology is evolving and developing as a subspecialty area alongside neighboring disciplines of neuroradiology, general radiology, and interventional radiology. Clinical disciplines that cooperate with head and neck radiology include otorhinolaryngology, facial and dental surgery, skull bone surgery, radio-oncology, and pediatrics. Patients from the internal medicine and surgery departments are also evaluated with diagnostic head and neck radiology methods.

The emerging subspecialty covers cross-sectional imaging and conventional radiography of conditions involving the petrous bone, skull base and cranial nerves, the orbit, nasopharynx and sinuses, oral cavity, oro- and hypopharynx, larynx, neck, and salivary glands. It also covers the facial skeleton (including the teeth, mandible, and temporomandibular joints), deep spaces of the face, thoracic inlet, brachial plexus, and thyroid gland.

Any curriculum for subspecialty training in head and neck radiology should take into account recommendations from the European Association of Radiology (EAR). The existing curriculum for diagnostic radiology covers head and neck radiology during the four years of general radiological training. For those trainees who wish to specialize in the field, subspecialty training in head and neck radiology usually takes place in the fifth and sixth years. This training is covered by a separate EAR/European Society of Head and Neck Radiology (ESHNR) subspecialty curriculum, as indicated below. The aim of this curriculum is to prepare radiologists to dedicate a substantial amount of time to head and neck radiology. Successful trainees are expected to acquire the following:

ability to act as a consultant in regular multidisciplinary meetings;

knowledge of indications and contraindications for diagnostic procedures in the area of the head and neck;

ability to instruct clinical colleagues about major changes in diagnostic procedures, preventing unnecessary examinations;

thorough knowledge of the current literature and ability to transmit this specific knowledge to general radiologists; and

tools to pursue continuity and evolution of radiological diagnosis in the field of head and neck radiology.

The subspecialty curriculum describes the core of knowledge required and the necessary technical, communication, and decision-making skills. Trainees are assumed to have a thorough knowledge of the physical principles of different imaging methods and any possible contraindications and complications, including the effects and side effects of various contrast media. They should also be familiar with relevant imaging topics, particularly:

positioning/views of the face, temporal bone, mandible;

mean exposure doses at skin entrance, lens, and thyroid gland for conventional radiography, sialography, dacryocystography, and CT;

digital imaging and image processing pertinent to head and neck radiology;

multidetector CT (MDCT), 2D and 3D reconstructions, and virtual endoscopy techniques; and

specific MR sequences commonly used in head and neck imaging.

Technical developments in ultrasound, MDCT, and MRI are having an impact on all fields of head and neck radiology. New CT techniques, including CT angiography, provide comparative studies to MRI and MR angiography (Figures 1 and 2). MDCT is rapidly improving diagnostic evaluation in trauma, inflammation, and oncological indications, thanks to the acquisition of nearly isotropic data sets that can be viewed as multiplanar reconstructions. MRI techniques will improve further using rapid acquisition methods (e.g., SENSE), new spectroscopic imaging tools, and contrast agents. Multicenter studies will be initiated by the ESHNR to improve diagnostics and quality.

Image-guided head and neck procedures can be differentiated according to vascular and nonvascular procedures performed by image-guided biopsies using ultrasound, CT, or open and closed MRI. Advantages of ultrasound-guided procedures include the wide availability of equipment, low cost, and multiplanar capabilities. CT- and MR-guided procedures are reserved for complex processes, especially lesions in or near the skull base or parapharyngeal space and parapharyngeal lesions.

Thermoablative techniques, such as laser-induced thermotherapy, radio-frequency ablation, and the use of ablative drugs, have been incorporated within the field of interventional radiology. These techniques are currently used to treat recurrent benign tumors and cancer in the head and neck. They are minimally invasive and make it possible to monitor tumor destruction with real-time imaging.

Vascular procedures make up the second major area of interventional head and neck radiology. Highly advanced techniques allow procedures to be performed in the most delicate areas (Figure 3). Presurgical embolization is indicated mainly for juvenile angiofibroma, paragangliomas, hemangiomas, and lymphangiomas in different areas of the head and neck. Treatment of definite primary vascular occlusion is performed by interventional radiology under some circumstances. This is especially the case for arteriovenous fistulas (cavernous sinus fistulas) or as a palliative or symptomatic approach. Increasing demands for locoregional therapies in the head and neck region relate to local chemotherapy or gene therapy, in addition to percutaneous ablative techniques.

Head and neck radiology is still developing as a subspecialty. Diagnostic accuracy is continually improving, and detailed differential diagnoses are emerging. Many European groups are active in this field. The International Congress of Head and Neck Radiology, to be held in Frankfurt between 4 and 6 September 2003, will bring together members of ESHNR, the American Society of Head and Neck Radiology, and the Asian and Oceanian Society of Neuroradiology and Head and Neck Radiology. Everyone is invited to participate (http://www.ichnr2003.org/info.shtml).

PROF. DR. VOGL is head of the Institute of Diagnostic and Interventional Radiology, and DR. MACK is senior faculty radiologist, both at Johann Wolfgang Goethe-University in Frankfurt/Main, Germany.