MRI at 0.55 T for Assessment of Pancreatic Intraductal Papillary Mucinous Neoplasms: An Intraindividual Comparison Versus 1.5-T and 3-T MRI.

Abstract

Background: Mid-field (0.55-T) MRI may offer an alternative to higher field strengths for pancreatic intraductal papillary mucinous neoplasms (IPMNs) surveillance given high-quality MRCP sequences enabled by longer T2 relaxation times and greater patient comfort resulting from a larger bore and reduced acoustic noise. However, SNR is lower at 0.55 T. Objective: To compare pancreatic IPMN assessment between MRI performed at 0.55 T versus at higher field strengths in terms of cyst feature characterization, image quality, and diagnostic confidence. Methods: This retrospective study included 35 patients (median age, 70 years; 25 female, 10 male) with a pancreatic IPMN who underwent abdominal MRI both at 0.55 T (performed between April 8, 2022 and November 15, 2023) and at 1.5 or 3 T (hereafter, 1.5/3 T) within a 13-month interval. Seven radiologists independently reviewed examinations for cyst characteristics as well as for image quality and diagnostic confidence (1-10 scales; 10=highest scores). Results: Across readers, agreement between 0.55 T and 1.5/3 T was excellent for IPMN type (Gwet's agreement coefficient 1 [Gwet's AC1], 0.87), presence of pancreatic duct dilation (Gwet's AC1, 0.94), cyst size (intraclass correlation coefficient, 0.96), diameter of diameter ducts (intraclass correlation coefficient, 0.99), and all five assessed suspicious cyst features (enhancing mural nodule <5 mm, enhancing mural nodule ≥5 mm, thickened enhancing walls/septae, abrupt pancreatic duct caliber change with upstream atrophy, enlarged peripancreatic lymph nodes, Gwet's AC1, 0.88-0.99); and was moderate for multifocality (Gwet's AC1, 0.62) and cyst location (Gwet's AC1, 0.55). Across readers, 0.55-T examinations, compared with 1.5/3-T examinations, showed lower mean image quality (7.5±1.7 vs 8.6±1.3, p<.001) and lower mean diagnostic confidence (8±1.7 vs 8.7±1.3; p<.001). However, all 0.55-T and 1.5/3-T examinations were considered diagnostic (diagnostic confidence ≥5) by all readers. One patient developed IPMN-related malignancy, which corresponded to a 5-mm enhancing mural nodule identified by one reader, who identified this finding at both field strengths. Conclusion: Agreement for suspicious cyst features was excellent at both field strengths. All 0.55-T examinations were considered diagnostic. Clinical Impact: The findings may help guide the application of 0.55-T MRI in longitudinal surveillance of pancreatic IPMNs and inform relevant technical improvement efforts.