Diagnostic Utility of Diffusion-weighted Magnetic Resonance Imaging in Differentiating Small Solid Renal Tumors （≤4 cm） at 3.0T Magnetic Resonance Imaging

Background： The aim of this study was to assess the performance of apparent diffusion coefficient （ADC） measurement obtained with diffusion-weighted magnetic resonance imaging （DW-MRI） to distinguish renal cell carcinomas （RCCs） from small benign solid renal tumors （〈4 cm）. Methods： In this cross-sectional study, 49 consecutive patients with histopathologically confirmed small solid renal tumors, and seven healthy volunteers were imaged using nonenhanced MRI and DW-MRI. The ADC map was calculated using the b values of 0, 50, 400, and 600 s/ mm2 and values compared via the Kruskal-Wallis and Mann-Whitney tests. The utility of ADC for differentiating RCCs and benign lesions was assessed using a receiver operating characteristic curve. Multiple nonenhanced MRI features were analyzed by Logistic regression. Results： The tumors consisted of 33 cases of clear-cell RCCs （ccRCCs） and 16 cases of benign tumors, including 14 cases of minimal fat angiomyolipomas and 2 cases ofoncocytomas. The ADCs showed significant differences among benign tumors （[0.90 ±0.52] x 10 x mm2/s）, ccRCCs （[1.53 ± 0.31 ] x 10 ^3 mm2/s） and the normal renal parenchyma （[2.22 ± 0.12]x 10^-3 mmVs） （P 〈 0.001）. Moreover, there was statistically significant difference between high and low-grade ccRCCs （P = 0.004）. Using a cut-offADC of 1.36± 10 3 mm2/s, DW-MRI resulted in an area under the curve （AUC）, sensitivity, and specificity equal to 0.839, 75.8%, and 87.5%, respectively. Nonenhanced MRI alone and the combination of imaging methods led to an AUC, sensitivity and specificity equal to 0.919, 93.9%, and 81.2%, 0.998, 97%, and 100%, respectively. The Logistic regression showed that the location of the center of the tumor （inside the contour of the kidney） and appearance of stiffblood vessel were significantly helpful for diagnosing ccRCCs. Conclusions： DW-MRI has potential in distinguishing ccRCCs from benign lesions in human small solid renal tumors （〈4 cm）, and in increasing the accuracy for diagnosing ccRCCs when combined with nonenhanced MRI.

Evaluation of the malignant potential of gliomas using diffusion-weighted and gadolinium-enhanced magnetic resonance imaging

Objective:This study aimed to determine whether the apparent diffusion coefficients(ADCs)determined by diffusion-weighted imaging(DWI)of magnetic resonance imaging(MRI)could facilitate the malignancy grading of various gliomas.Methods:Sixty patients with a primary cerebral glioma underwent diffusion-weighted and gadolinium-enhanced(Gd)T1-weighted MRI using a 1.5-T MRI scanner.Scoring was performed based on signal intensities on DWI and Gd images.The mean and minimum ADC values were calculated,and Ki-67 staining was performed for each histological sample to evaluate their tumor proliferative potential.Then,the DWI,Gd,and combined scores were analyzed and compared with the Ki-67 staining index and malignant grade.The relationships among the mean and minimum ADC values,Ki-67staining index,and malignant grade were also evaluated.Results:The minimum ADC was inversely correlated with the Ki-67staining index,with a low minimum ADC suggestive of tumor malignancy.The qualitative evaluation of the D score of water molecule diffusion on DWI accurately reflected the pathological grades of gliomas,with an effectiveness that was at least as good as the quantitative analysis using the minimum ADC.The diagnostic value of Gd images in determining glioma malignancy grades was inferior to that of DWI.Conclusion:Both DWI and gadolinium-enhanced images of MRI should be considered essential for the diagnosis of tumor malignancy.