Usefulness of diffusion-weighted imaging in the evaluation of renal masses.

OBJECTIVE: The objective of our study was to assess the value of diffusion-weighted imaging in differentiating among the various subgroups of renal masses. MATERIALS AND METHODS: This retrospective study measured the apparent diffusion coefficients (ADCs) of renal masses. Malignant lesions were confirmed with surgical pathology results. Benign cystic lesions were stable without treatment for a minimum follow-up of 24 months. RESULTS: There were 20 and 22 patients, respectively, with benign lesions (three abscess, 31 cysts) and malignant lesions (17 clear cell, five papillary, one chromophobe, and two transitional cell cancers). The malignant lesions were larger than the benign lesions (mean diameter, 4.2 vs 2.6 cm, respectively; p = 0.01, Student's t test). The ADC values of the benign lesions were significantly higher than those of the malignant lesions (mean, 2.72 vs 1.88 x 10(-3) mm(2)/s; p < 0.0001). The ADCs of the 31 benign cysts were significantly higher than those of the seven cystic renal cancers (2.77 vs 2.02 x 10(-3) mm(2)/s; p < 0.001). There was no significant difference between the ADCs of clear cell cancers and non-clear cell cancers (1.85 vs 1.97 x 10(-3) mm(2)/s; p = 0.18), but an ADC of less than 1.79 x 10(-3) mm(2)/s was seen only with clear cell cancer. The ADCs of high-grade clear cell cancers (Fuhrman grades III and IV) tended to be lower than those of low-grade clear cell cancers (1.77 vs 1.95 x 10(-3) mm(2)/s; p = 0.12). Among the clear cell cancers, an ADC value of greater than 2.12 x 10(-3) mm(2)/s was seen only with low-grade histology. For differentiating benign from malignant lesions, receiver operating characteristic (ROC) analysis showed an area under the ROC curve of 0.989 (95% CI, 0.919-0.996; p < 0.0001). CONCLUSION: ADC measurements may aid in differentiating among the various subgroups of renal masses, particularly benign cystic lesions from cystic renal cell cancers.

Diagnosis of chronic pancreatitis by using apparent diffusion coefficient measurements at 3.0-T MR following secretin stimulation.

PURPOSE: To prospectively measure pancreatic apparent diffusion coefficient (ADC) before and after secretin administration in subjects with and without chronic pancreatitis (CP) who underwent magnetic resonance (MR) cholangiopancreatography with diffusion-weighted (DW) imaging at 3.0 T. MATERIALS AND METHODS: Institutional review board approval of this HIPAA-compliant study was obtained. Healthy volunteers, and patients with suspected and/or known CP who were scheduled for MR cholangiopancreatography, were recruited and gave written informed consent. All subjects underwent 3.0-T MR cholangiopancreatography, including serial DW imaging sequences (b = 0, 200, and 400 sec/mm(2)) acquired for 15 minutes after secretin administration. The referring gastroenterologist then classified subjects as healthy or with mild or severe CP, given endoscopic retrograde cholangiopancreatographic and/or clinical findings. CP severity was analyzed for sex and age. Mean presecretin and maximum postsecretin ADCs were compared between groups. Pairwise mean ADCs for healthy versus mild CP patient groups, healthy versus severe CP patient groups, and mild versus severe CP patient groups were compared. Presecretin ADC threshold levels for CP discrimination were calculated (P < .05). RESULTS: Thirty-two subjects were imaged; four CP patients were excluded owing to severe artifact, and the remaining 28 (15 healthy patients, five with mild CP, and eight with severe CP) comprised the study population. All CP patients had endoscopic retrograde cholangiopancreatographic confirmation of CP. Mild or severe CP patients were older than healthy patients; sex distribution did not vary among groups. Mean presecretin and maximum postsecretin ADCs were higher in healthy patients than in either mild or severe CP groups (P < .01), but did not vary between mild and severe CP groups (P = .25-0.28). An ADC of less than 220 x 10(-5) mm(2)/sec was optimal for delineating between healthy and CP patients. CONCLUSION: Pancreatic ADC obtained with DW imaging at 3.0 T prior to secretin administration may help diagnose CP; postsecretin ADC response does not distinguish CP severity.