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BACKGROUND Endoscopic mucosal resection (EMR) for small (

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. © 2010 Wiley-Liss, Inc.

ssed in median and range and comparisons were performed using non-parametric tests. Results: Between January 2010 and November 2011, 26 patients (17 males, 65%) were included. Median age was 50 years. The underlying disease was acute (AP) (n=15, 58%) or chronic pancreatitis (n=11, 42%). Median time between onset of symptoms and drainage was 56 days (14-300) for AP patients. Antibiotics had been previously administered in 9 patients (35%). Indications for drainage included pain (n=13, 50%) and clinical suspicion of infection (n=9, 35%). The median delay between DW-MRI and EUS drainage was 0 days (0-14). Based on DW-MRI, median PFC size was 86mm (25-960) and the content was considered to contain high protein fluid (blood or pus) in 13 cases (50%). Restriction in diffusion in the PFC suggested infection in 6 patients (23%). Based on EUS, most of PFCs were hypoechogenic (n=22, 84.6%) and contained debris in 19 cases (73%). Aspirated fluid was described as pus in 7 cases (27%). Median CEA, protein and lipase levels were, respectively, 9ng/ml (0.3-350), 2.7 gr/dl (0.4-4.1) and 31915 IU/L (25-717270). Bacteriological cultures were positive in 9 patients (35%). Sensitivity, specificity, accuracy, negative and positive predictive values of DW-MRI for predicting PFC infection were respectively 55.5% (5/9), 94% (16/17), 80% (21/26), 80% (16/20) and 83% (5/6). These values increased if we considered only patients without previous antibiotics (n=17) (respectively 75%, 92%, 88%, 92% and 75%). Median ADC was significant lower in infected PFCs (2.8 vs 1.1, p= 0.045). Conclusions: DW-MRI is a promising diagnostic tool concerning PFC assessment before drainage. Preliminary results disclose high specificity and negative predictive values, which can help in excluding PFC infection and determining time of drainage.