Quantitative assessment of simultaneous F-18 FDG PET/MRI in patients with various types of hepatic tumors: Correlation between glucose metabolism and apparent diffusion coefficient.

PURPOSE: Metabolism and water diffusion may have a relationship or an effect on each other in the same tumor. Knowledge of their relationship could expand the understanding of tumor biology and serve the field of oncologic imaging. This study aimed to evaluate the relationship between metabolism and water diffusivity in hepatic tumors using a simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) system with F-18 fluorodeoxyglucose (FDG) and to reveal the metabolic and diffusional characteristics of each type of hepatic tumor. METHODS: Forty-one patients (mean age 63 ± 13 years, 31 male) with hepatic tumors (18 hepatocellular carcinoma [HCC], six cholangiocarcinoma [CCC], 10 metastatic tumors, one neuroendocrine malignancy, and six benign lesions) underwent FDG PET/MRI before treatment. Maximum standard uptake (SUVmax) values from FDG PET and the apparent diffusion coefficient (ADC) from the diffusion-weighted images were obtained for the tumor and their relationships were examined. We also investigated the difference in SUVmax and ADC for each type of tumor. RESULTS: SUVmax showed a negative correlation with ADC (r = -0.404, p = 0.009). The median of SUVmax was 3.22 in HCC, 6.99 in CCC, 6.30 in metastatic tumors, and 1.82 in benign lesions. The median of ADC was 1.039 × 10-3 mm/s2 in HCC, 1.148 × 10-3 mm/s2 in CCC, 0.876 × 10-3 mm/s2 in metastatic tumors, and 1.323 × 10-3 mm/s2 in benign lesions. SUVmax was higher in metastatic tumors than in benign lesions (p = 0.023). Metastatic tumors had a lower ADC than CCC (p = 0.039) and benign lesions (p = 0.004). HCC had a lower ADC than benign lesions, with a suggestive trend (p = 0.06). CONCLUSION: Our results indicate that SUVmax is negatively correlated with ADC in hepatic tumors, and each group of tumors has different metabolic and water diffusivity characteristics. Evaluation of hepatic tumors by PET/MRI could be helpful in understanding tumor characteristics.

Freiberg's disease: quantitative assessment of osteonecrosis on three-dimensional CT.

BACKGROUND: The extent of necrosis is the main determining factor in the outcome of osteonecrosis. There is no method for measuring the extent of osteonecrosis of the metatarsal head in Freiberg's disease. The purpose of this study was to determine the reliability and prognostic ability of a new method for measurement of the extent of osteonecrosis in Freiberg's disease on three-dimensional computed tomography. METHODS: A retrospective review of 11 cases with symptomatic Freiberg's disease in ten patients (5 males and 5 females; mean age, 27 years) undergoing computed tomography between July 2005 and September 2007 was performed. Two investigators (K.A.C. and H.K.O.) used a new method to measure the necrotic extent of the metatarsal head: the necrotic angle ratio of necrotic arc angle to normal arc angle of the articular surface on the sagittal reconstruction image of computed tomography. The interobserver reliability was determined for computed tomography measurement. Correlation between the Smillie staging using radiographs and the necrotic angle ratio on computed tomography was also evaluated. RESULTS: One patient presented with stage I disease (Smillie staging), one with stage II, two with stage III, five with stage IV, and two with stage V, respectively. The necrotic angle ratio of the metatarsal head was 14% in stage I, 21% in stage II, 34% in stage III, 43% in stage IV, and 53% in stage V. The interobserver reliability for computed tomography measurement was high (Cronbach α=0.96). We found the increase of the necrotic extent in proportion to the Smillie stage. The Smillie staging using radiographs and the necrotic angle ratio on computed tomography were significantly correlated. (P<0.05) CONCLUSIONS: Three-dimensional computed tomography measurement of the necrotic extent of the metatarsal head is a reliable and useful method in evaluating the staging of Freiberg's disease and may eventually help to optimize treatment.