Endocrine pancreatic tumours: which are the most useful MRI sequences?

Abstract

To determine magnetic resonance imaging (MRI) signal and enhancement characteristics of endocrine pancreatic tumours (ETPs) and which MR sequences show them most consistently. Fifty-five consecutive patients with 68 ETPs underwent 1.5-T abdominal MRI comprising T2-weighted, unenhanced T1-weighted and dynamic T1-weighted after injection of gadopentetate dimeglumine sequences. Twenty-one patients underwent diffusion-weighted imaging (DWI). Two radiologists identified the number, location, size, signal and enhancement patterns of ETPs, and determined a confidence scale indicating the presence of tumours on DWI. The results were compared with echo-endoscopy (endoscopic ultrasound) findings. The detection sensitivity was 95%, similar to that of echo-endoscopy. T2-weighted and T1-weighted sequences at the arterial phase had the highest contrast-to-noise ratio (CNR) median value. On DWI, the mean sensitivity was 65%. The mean apparent diffusion coefficient (ADC) value of ETP was significantly lower than in the normal parenchyma. In suspected ETP, MRI is a sensitive method, similar to echo-endoscopy and could be recommended as the first imaging technique. T2-weighted sequences and T1-weighted sequences in the arterial phase are the optimal pulse sequences. The quantitative assessment of ADC values is a promising tool for the characterisation of pancreatic lesions.