New directions in head and neck imaging.

Computerized tomography (CT) and magnetic resonance imaging (MRI), positron emission tomography (PET) and the hybrid modality of PET/CT are sensitive and reliable tools for detection and staging of head and neck cancers. This article describes the role of PET/CT in initial staging of head and neck squamous cell carcinoma, the utility of CT/MR perfusion imaging in qualitative analysis of tumor tissue, and the usefulness of diffusion weighted MR and dynamic contrast-enhanced MR imaging in head and neck oncological imaging. J. Surg. Oncol. 2008;97:644–648. 2008 Wiley-Liss, Inc. Diagnostic imaging has come a long way from 1895 when Conrad Roentgen discovered X-rays. Conventional radiography and ancillary techniques like fluoroscopy and tomography had a relatively minor role in evaluation of neoplasms of the head and neck unless it encroached into the aero-digestive tract. Computerized tomography (CT) was introduced in the 1970s and revolutionized body imaging. It is inexpensive, fast, and ubiquitous in most medical centers. CT is quite good at delineating tumor extent and nodal disease. In squamous cell carcinoma, CT helped in tumor staging, which dictated patient management and related to prognosis [1]. Subsequently, helical multi-detector computerized tomography (MDCT) with 16 and now 64 detector rings has rapidly become the new industry standard in CT imaging. Magnetic resonance imaging (MRI) in the 1980s was a quantum jump in diagnostic imaging of the human body, including imaging of head and neck pathologies. Some of earliest investigations in head and neck imaging with MRI highlighted the ability of MRI to differentiate neoplastic from inflammatory lesions. MRI provides essential information about the deep extension of clinically detected masses and also delineates additional clinically unsuspected lesions [2]. It has added value for detection of soft tissue extent, marrow involvement, and perineural spread [3]. The excellent tissue characterization and multiplanar imaging capability of MR imaging results in more accurate diagnosis of neoplastic and benign processes [4,5]. However, early investigators credited MR imaging with greater precision in head and neck imaging than was warranted [6]. Conventional MR imaging did not have the last word in histological specificity, early detection of primary malignancy and differentiating neoplastic from inflammatory lymph nodes. In spite of early enthusiasm, MR imaging did not eliminate the need for biopsies or aspirations of lesions. Spin echo imaging is still the mainstay of MR imaging, but now various new techniques hold promise for the future of head and neck imaging. Positron emission tomography (PET) has been utilized since the 1970s for clinical imaging. PET scanning with 18 fluorodeoxyglucose (18FDG) can be used for staging and evaluation of recurrence for primary head and neck tumors. The principle for PET is based on the metabolism of the neoplasm, primary or recurrent, and is more sensitive than CT or MRI for T1-staged lesions [7]. The most recent innovation in PET systems is the hybrid PET/CT scanners. Integration of PET with CT scan in 2000 was a great leap forward and enhanced the clinical information from PET. Today all commercial PET scanners are sold as PET/CT. Various advanced techniques are utilized for answering some of the unresolved issues from conventional CT, MRI and PET.