Objective To evaluate the diagnostic value of dynamic contrast-enhanced MR angiography(DCE MRA)of the renal arteries.Methods 18 patients suspected with renal arterial diseases underwent DCE MR Angiography examinations.After 20 ml(0.15～0.20 mmol/kg)Gd-DTPA being injected quickly via cubital vein,a scaning and data acquisition with coronal three-demensional fast spoiled gradient(FSPGR)sequence was performed in a breath-hold time,the source images were introduced into work station for post processing,including maximum intensity projection(MIP)and multiplanner reconstruction(MPR),finally 3D DCE MRA images were obtained.Results A comparative study on renal artery stenosis and its degree between DCE MR angiography and DSA was done in 25 arteial segments of 12 cases.In 12 normal renal arteries shown by DSA,DCE MRA found 11 normal and one mild stenosis;Four moderate and one severe stenosis was shown by DCE MRA in five renal arteries with moderate stenosis identified by DSA;DCE MRA found five severe stenosis and three occlusion of renal anteries,which had accordance with DSA findings.Conclusion Dynamic contrast-enhanced MR angiography can accurately assess renal arterial diseases,the accuracy was especially higher in patients with severe arterial stenosis and occlusion.

Objective To investigate the imaging features of focal nodular hyperplasia and hepatocellular carcinoma on DWI. Methods The data of patients with histopathologically confirmed FNHs and HCCs between August 2008 and November 2010 were collected. A total of 24 patients with 26 FNH lesions and 36 patients with 39 HCC lesions were included in our study. All patients underwent breath-hold DWI with b = 500 s/mm2 and dynamic contrasted-enhanced (DCE) MRI. The imaging findings of FNHs and HCCs were retrospectively analyzed and compared. The signal intensity (SI) of the lesions on DWI were classified as iso-, slightly high, high SI and the distribution of SI between FNHs and HCCs was compared with Fisher exact test. ADC value and lesion-to-liver ADC ratio of FNHs and HCCs were measured and compared by using independent sample t test. ROC was performed to assess the diagnostic value of ADC value and lesion-liver ADC ratio in the characterization FNHs versus HCCs. Results Of 26 FNHs,23 manifested as isointensity or slightly high SI on DWI, but most 25 out of 39 HCCs showed high SI. The distribution of SI between FNHs and HCCs had significant difference ( P = 0. 000). The mean ADC value and lesion-liver ADC ratio for FNHs [ (1.76 ± 0. 62 ) × 10-3 mm2/s and 1.06 ± 0. 18, respectively ] were significantly higher ( P = 0. 001, P = 0. 000, respectively ) than those for HCCs [ ( 1.26 ± 0. 46 ) × 10-3mm2/s and 0. 79 ±0. 12, respectively]. The area (Az) under the ROC for the ADC value and lesionliver ADC ratio for the differentiation of FNHs versus HCCs were 0. 79 ± 0. 05 and 0. 85 ± 0. 05,respectively, with no significant difference (P =0. 270). The specificity of the two measures was 69. 23% and 97.44%, respectively, with significant difference (P = 0. 001 ). Conclusion FNH shows isointensity or slightly high SI with relatively higher ADC value and lesion-liver ADC ratio than those of HCCs on DWI,which is characteristic for its diagnosis and differentiation.