To compare primary tumor (18)F-fluorodeoxyglucose (FDG) maximum standardized uptake value (SUV(max)) and diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) obtained in the same patients with head and neck squamous cell carcinoma (HNSCC) to clarify the prognostic significance of both indexes. The study population comprised 26 patients with HNSCC visible on both pretreatment FDG PET/CT and DWI. Correlation between SUV(max) and ADC (b values; 0 and 800 seconds/mm(2)) was analyzed by the Spearman's rank test. Disease-free survival (DFS) was calculated by the Kaplan-Meier method. Prognostic significance was assessed by the long-rank test and Cox proportional hazards analysis. SUV(max) and ADC correlated significantly and negatively (ρ = -0.566, P = 0.005). High (>12.1) SUV(max) (P < 0.001), low (≤ 0.88) ADC (P = 0.009), high (T3-4) T stage (P = 0.030), and high (N2-3) N stage (P = 0.007) were significant in predicting poor 2-year DFS. The accuracy for predicting disease events was 81% (21/26) for SUV(max) (>12.1) and 73% (19/26) for ADC(≤ 0.88) without significant difference between them (P = 0.52). Disease event hazards ratios for significant unadjusted SUV(max) (P = 0.015) and ADC (P = 0.039) remained significant when adjusted for other dichotomized clinical covariates (SUV(max); P = 0.009-0.039, ADC; P = 0.017-0.037) except SUV(max) for ADC and ADC for SUV(max) and T stage. These results suggest that pretreatment primary tumor SUV(max) and ADC correlate significantly and negatively and both may have similar potential to predict DFS or disease events of HNSCC.

Objective: To evaluate the ¹⁸F-fluorodeoxyglucose (FDG) uptake features of idiopathic retroperitoneal fibrosis (IRF). Methods: ¹⁸F-Fluorodeoxyglucose positron emission tomographic (PET) or PET/computed tomographic findings were retrospectively reviewed in 6 patients with IRF. FDG PET or PET/computed tomography was performed 1 and 2 hours after FDG injection. The FDG level was scored using a 4-point scale, and the intensity of FDG uptake was quantified using the maximum standardized uptake value (SUVmax). Results: In the 1-hours images, intense FDG uptake by IRF was observed in 5 patients before steroid treatment, but no abnormal uptake was noted in 1 patient receiving steroid treatment. The SUVmax in IRF increased from a mean ± SD of 6.0 ± 1.2 (range, 4.9-7.6) to 7.6 ± 1.1 (range, 5.9-8.2) for all 4 patients who underwent 1 and 2 hours dual-time point imaging. Abnormal uptake was also noted in the mediastinum and the pancreas in 1 and 2 patients, and the diagnoses of mediastinal fibrosis and autoimmune pancreatitis were made, respectively. The SUVmax was stable or increased in the 3 lesions of mediastinal fibrosis and autoimmune pancreatitis. Conclusion: FDG PET may be a reliable means of evaluating disease activity and the extent of IRF, but dual-time point imaging may not be useful to differentiate malignancy from IRF.