OBJECTIVE. The purpose of our study was to compare the utility of MR elastography (MRE) and diffusion-weighted imaging (DWI) in characterizing fibrosis and chronic hepatitis in patients with chroni...

Purpose: To evaluate apparent diffusion coefficient (ADC) values for characterization of a variety of focal liver lesions and specifically for differentiation of solid benign lesions (focal nodular hyperplasia [FNH] and adenomas) from solid malignant neoplasms (metastases and hepatocellular carcinoma [HCC]) in a large case series.Materials and Methods: A total of 542 lesions in 382 patients were evaluated. ADC values were measured in 166 hemangiomas, 112 hepatomas, 107 metastases, 95 cysts, 10 abscesses, 43 FNH, and nine adenomas. ADCs of 1.5 and 1.6 (×10⁻³ mm²/second) were selected as threshold values to separate benign and malignant lesions. Sensitivity, specificity, positive, and negative predictive values (PPV, NPV) were calculated. Comparisons were carried out with studentized range test.Results: There was high interobserver agreement in ADC measurements for all lesion types. The mean ADCs for cysts was 3.40 (×10 ⁻³ mm²/second), hemangiomas 2.26, FNH 1.79, adenomas 1.49, abscesses 1.97, HCC 1.53, and metastases 1.50. The mean ADC for benign lesions was 2.50 and for malignant lesions was 1.52. Cysts were easily distinguished from other lesions. There was, however, overlap between solid benign and malignant lesions.Conclusion: Benign lesions have higher mean ADC values than malignant lesions. However, ADC values of solid benign lesions (FNH and adenomas) are similar to malignant lesions (metastases, HCC) limiting the value of diffusion weighted imaging (DWI) for differentiating solid liver masses. J. Magn. Reson. Imaging 2010;32:138–147.

Normal urachal anatomy and embryology is reviewed, along with multimodality imaging findings of different types of urachal anomalies, potential complications, and mimics; management recommendations are provided on the basis of a review of the literature. Urachal anomalies are more common than previously thought, with more cases discovered incidentally, because of the increased use of cross-sectional imaging. Although an abnormal persistence of an embryologic communication between the bladder and the umbilicus is often recognized and managed in childhood, it may persist into adulthood, with a greater risk of morbidity. Congenital urachal anomalies that are detected early can benefit from an optimized management including surgical approach with a complete resection of the urachal remnant in cases when spontaneous resolution or medical management has failed. At imaging, the different types of urachal anomalies have a distinct appearance. A patent urachus is recognized as an elongated patent connection between the bladder and the umbilicus. An umbilical-urachal sinus is depicted as a blind focal dilatation at the umbilical end, whereas a vesicourachal diverticulum is a focal outpouching at the vesical end. Urachal cysts are visualized as midline fluid-filled ...

Purpose: To compare the diagnostic accuracy of magnetic resonance imaging elastography (MRE) and anatomic MRI features in the diagnosis of severe hepatic fibrosis and cirrhosis.Materials and Methods: Three readers independently assessed presence of morphological changes associated with hepatic fibrosis in 72 patients with liver biopsy including: caudate to right lobe ratios, nodularity, portal venous hypertension (PVH) stigmata, posterior hepatic notch, expanded gallbladder fossa, and right hepatic vein caliber. Three readers measured shear stiffness values using quantitative shear stiffness maps (elastograms). Sensitivity, specificity, and diagnostic accuracy of stiffness values and each morphological feature were calculated. Interreader agreement was summarized using weighted kappa statistics. Intraclass correlation coefficient was used to assess interreader reproducibility of stiffness measurements. Binary logistic regression was used to assess interreader variability for dichotomized stiffness values and each morphological feature.Results: Using 5.9 kPa as a cutoff for differentiating F3‐F4 from F0‐2 stages, overall sensitivity, specificity, and diagnostic accuracy for MRE were 85.4%, 88.4%, and 87%, respectively. Overall interreader agreement for stiffness values was substantial, with an insignificant difference (P = 0.74) in the frequency of differentiating F3‐4 from F0‐2 fibrosis. Only hepatic nodularity and PVH stigmata showed moderately high overall accuracy of 69.4% and 72.2%. Interreader agreement was substantial only for PVH stigmata, moderate for C/R m, deep notch, and expanded gallbladder fossa. Only posterior hepatic notch (P = 0.82) showed no significant difference in reader rating.Conclusion: MRE is a noninvasive, accurate, and reproducible technique compared with conventional features of detecting severe hepatic fibrosis. J. Magn. Reson. Imaging 2012;35:1356–1364.

Purpose: To retrospectively assess apparent diffusion coefficients (ADCs) of different subtypes of pancreatic endocrine tumors based on the World Health Organization (WHO) classification system and analyze the potentially responsible histopathologic characteristics.Materials and Methods: Following Institutional Review Board (IRB) approval, 18 patients with surgical pathology‐proven pancreatic endocrine tumors were evaluated. Tumors were subcategorized based on the WHO grading classification into well‐differentiated tumors with benign and uncertain behavior and endocrine carcinomas with well and poor differentiation. ADCs were measured on diffusion‐weighted (DW) images and compared using Student's t‐test and one‐way analysis of variance. The correlation between ADCs, tumor cellularity, Ki‐67 labeling index (an index of cell growth), and extracellular fibrosis were analyzed.Results: A difference was demonstrated in mean ADCs between well‐differentiated endocrine tumors (1.75 ± 0.53) and endocrine carcinomas (1.00 ± 0.19 × 10⁻³mm²/sec) (P < 0.01). After excluding the three well‐differentiated endocrine tumors with benign behavior and marked fibrosis, a significant inverse correlation between ADC values and cellularity of endocrine tumors was observed. An inverse correlation was seen between Ki‐67 labeling index and ADC values (r = −0.70; P < 0.01).Conclusion: Tumor cellularity and/or extracellular fibrosis may account for various ADCs in pancreatic endocrine tumors. ADC correlates well with the Ki‐67 labeling index and may help predict growth of endocrine tumors. J. Magn. Reson. Imaging 2011;33:1071–1079.