Читать книгу Salivary Gland Pathology - Группа авторов - Страница 79

Head and neck imaging has greatly benefited from the use FDG PET imaging for the staging, restaging, and follow‐up of neoplasms. The recent introduction of PET/CT has dramatically changed the imaging of diseases of the head and neck by directly combining anatomic and functional imaging.

The evaluation of the head and neck with FDG PET/CT has been significantly and positively affected with detection and demonstration of the extent of primary disease, lymphadenopathy, and scar versus recurrent or residual disease, pre‐surgical staging, pre‐radiosurgery planning and follow‐up post‐therapy.

The role of FDG PET or PET/CT and that of conventional CT and MRI on the diagnosis, staging, restaging, and follow‐up post‐therapy of salivary gland tumors has been studied (Keyes et al. 1994; Bui et al. 2003; Otsuka et al. 2005; Alexander de Ru et al. 2007; Roh et al. 2007). Although both CT and MRI are relatively equal in anatomic localization of disease and the effect of the tumors on local invasion and cervical nodal metastases, FDG PET/CT significantly improved sensitivity and specificity for salivary malignancies including nodal metastases (Otsuka et al. 2005; Uchida et al. 2005; Alexander de Ru et al. 2007; Jeong et al. 2007; Roh et al. 2007).

Early studies have demonstrated FDG PET's relative inability to distinguish benign from malignant salivary neoplasms (Keyes et al. 1994). The variable uptake of FDG by pleomorphic adenomas and the increased uptake and SUVs by Warthin tumors result in significant false positives (Jeong et al. 2007; Roh et al. 2007). In a similar manner, adenoid cystic carcinomas, which are relatively slower growing, may not accumulate significant concentrations of FDG and demonstrate low SUVs and therefore contribute to the false negatives (Jeong et al. 2007; Keyes et al. 1994). False negatives may also be caused by the relatively lower mean SUV of salivary tumors (SUV 3.8 ± 2.1) relative to squamous cell carcinoma (SUV 7.5 ± 3.4) (Roh et al. 2007). The low SUV of salivary neoplasms may also be obscured by the normal uptake of FDG by salivary glands (Roh et al. 2007). In general, FDG PET has demonstrated that lower grade malignancies tend to have lower SUV and vice versa for higher grade malignancies (Jeong et al. 2007; Roh et al. 2007). FDG PET has been shown to be more sensitive and specific compared to conventional CT or MRI (Otsuka et al. 2005; Cermik et al. 2007; Roh et al. 2007). Small tumor size can contribute to false negative results and inflammatory changes contribute to false positive results (Roh et al. 2007). The use of concurrent salivary scintigraphy with ⁹⁹mTc‐pertechnetate imaging can improve the false positive rate by identifying Warthin's tumors and oncocytomas, which tend to accumulate pertechnetate (and retain it after induced salivary gland washout) and have increased uptake of FDG (Uchida et al. 2005).