Comparison of Monoexponential, Biexponential, Stretched-Exponential, and Kurtosis Models of Diffusion-Weighted Imaging in Differentiation of Renal Solid Masses

OBJECTIVE: To compare various models of diffusion-weighted imaging including monoexponential apparent diffusion coefficient (ADC), biexponential (fast diffusion coefficient [Df], slow diffusion coefficient [Ds], and fraction of fast diffusion), stretched-exponential (distributed diffusion coefficient and anomalous exponent term [α]), and kurtosis (mean diffusivity and mean kurtosis [MK]) models in the differentiation of renal solid masses. MATERIALS AND METHODS: A total of 81 patients (56 men and 25 women; mean age, 57 years; age range, 30–69 years) with 18 benign and 63 malignant lesions were imaged using 3T diffusion-weighted MRI. Diffusion model selection was investigated in each lesion using the Akaike information criteria. Mann-Whitney U test and receiver operating characteristic (ROC) analysis were used for statistical evaluations. RESULTS: Goodness-of-fit analysis showed that the stretched-exponential model had the highest voxel percentages in benign and malignant lesions (90.7% and 51.4%, respectively). ADC, Ds, and MK showed significant differences between benign and malignant lesions (p 0.05). CONCLUSION: Compared with conventional diffusion parameters, α may provide additional information for differentiating benign and malignant renal masses, while ADC remains the most valuable parameter for differentiation of RCC subtypes and for ccRCC grading.

The assessment of lymphatic system in lymphedema with magnetic resonance lymphangiography / 实用放射学杂志

Objective To evaluate the MR lymphangiography (MRL)in diagnosis of limb lymphedema.Methods A total of 582 patients with lymphedemtous limbs were enrolled in the study,MRL was performed at 3.0T MR.The morphology and enhancement of the lymph nodes,the number of lymphatic vessels and the lymph flow were evaluated.Results No matter in primary or secondary lymphedema,there were patients showed only lymph nodes affected,or only lymph vessels affected,and some patients showed both affected.Lymphatic aplasia,hypoplasia or hyperplasia were showed in primary lymphedema.Obstruction lymphatic vessels,and lym-phangiectasia were showed in secondary lymphedema.The velocity of lymph flow was (1.0±0.62)cm/min in affected limb of pa-tients with primary lymphedema,which was significantly slower than that of affected limb of patients with secondary lymphedema (2.22±1.64)cm/min(P<0.01)in dynamic contrast-enhanced MRL.In both type of lymphedema,the contrast enhanced lymph nodes showed less nodes with delayed enhancement and lower signal intensity,compared to that of lymph nodes in the contralateral normal side.Conclusion Dynamic contrast-enhanced MRL is helpful for assessing the anatomical and functional status of lymphatic system in lymphedematous limb.This new imaging techniques provides a powerful tool for the diagnosis of lymphedema.