MR of Normal Pancreas: Comparison of Five Pulse Sequences and Enhancing Patterns on Dynamic Imaging

ABSTRACT

PURPOSE: To compare T1-weighted FLASH and turbo spin echo (SE) T2-weighted sequences with conventional T1-and T2-weighted sequences in imaging normal pancreas and to describe the enhancing patterns on dynamic MR imging. MATERIALS AND METHODS: Forty-four patients with presumed hepatic hemangiomas were studied at 1.0T or 1.5T by using conventional SE sequences (T1-weighted, T2-weighted, and heavily T2-weighted), turbo-SE T2-weighted sequences, and breath-hold T1-weighted FLASH sequences acquired before, immediately on, and at 1, 2, 3, and 5 or10 minutes after injection of a bolus of gadopentetate dimeglumine. No patients had either a history or its clinical features of pancreatic disease. Images were quantitatively analyzed for signal-difference-to noise ratios(SD/Ns) between the pancreas and peripancreatic fat. Percentage enhancement of the pancreas was measured on each dynamic MR image. Conspicuity of the pancreatic border was qualitatively evaluated according to a consensus, reached by three radiologists. RESULTS: Turbo-SE T2-weighted images had a significantly higher SD/N ratio(p<0.001) and better conspicuity of the pancreatic border (p<0.001 ) than SE T2- and heavily T2-weighted images ; T1-weighted SE images had a significantly higher SD/N ratio than T1-weighted FLASH images (p<0.001), but there was no significant difference between them in qualitative analysis (p=0.346). Percentage enhancement immediately on and at 1, 2, 3, 5, and 10 minutes after administration of contrast material was 39.9%, 44.5%, 42.9%, 40.8%, 36.3%, 29.9%, respectively, with peak enhancement at 1 minute. CONCLUSION: In MR imaging of normal pancreas, turbo-SE T2-weighted imaging is superior to SE T2- and heavily T2-weighted imaging, and SE T1-weighted imaging is superior to T1-weighted FLASH imaging. On serial gadolinium-enhanced FLASH imaging, normal pancreas shows peak enhancementat 1 minute.