Combined PET-CT in the head and neck: part 1. Physiologic, altered physiologic, and artifactual FDG uptake.

Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) has been effective for the diagnosis, staging, and restaging of malignancies of the head and neck region. However, lack of anatomic landmarks, variable physiologic uptake, and asymmetric FDG distribution in several altered physiologic states can confound image interpretation. In addition, many benign causes and several artifacts can simulate physiologic or pathologic FDG uptake in the head and neck. Combined PET-computed tomography (CT) is a unique imaging modality that permits anatomic and functional imaging on a single scanner with nearly perfect coregistration. Combined PET-CT provides information that cannot be obtained with PET or CT alone. In particular, PET-CT facilitates the interpretation of FDG uptake in the head and neck, an area that is characterized by dense and complex anatomic structures. An atlas of FDG uptake in this anatomic region was compiled on the basis of combined PET-CT findings in 11,000 patients. In general, patterns of FDG uptake were variable and often reflected patient activity during or immediately preceding the uptake phase. With the growing interest in PET-CT, interpreting radiologists and nuclear medicine physicians must be familiar with the patterns of FDG uptake in the head and neck to avoid misinterpretation or mis-diagnosis.

Combined PET-CT in the head and neck: part 2. Diagnostic uses and pitfalls of oncologic imaging.

Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) is effective for monitoring head and neck cancer. However, lack of anatomic landmarks, variable physiologic FDG uptake, and asymmetric FDG distribution in the neck can confound image interpretation. This is particularly true in the treated neck, where distortion of normal tissue planes makes detection of early disease recurrence difficult with conventional computed tomography (CT) and magnetic resonance imaging. Combined PET-CT helps prevent the misinterpretation of FDG PET findings in patients with head and neck cancer. Superior localization of FDG uptake with this technique can improve diagnostic accuracy and help avoid interpretative pitfalls. In the future, development of tumor-specific ligands will enhance the usefulness of PET-CT in the detection of initial tumors and tumor recurrence, in the evaluation of tumors with low FDG avidity, and in treatment targeting. Furthermore, improved scanner resolution will help address the limitations of PET-CT with respect to small lesions and may make this modality more valuable in initial tumor staging.