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

BACKGROUND. Mid-field (0.55-T) MRI may offer an alternative to MRI performed at higher field strengths for surveillance of pancreatic intraductal papillary mucinous neoplasms (IPMNs), given the high-quality MRCP sequences enabled by longer T2 relaxation times and the greater patient comfort resulting from a larger bore and reduced acoustic noise. However, the SNR is lower at 0.55 T. OBJECTIVE. The objective of this study was to compare the assessment of pancreatic IPMNs by MRI performed at 0.55 T versus MRI conducted 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 women and 10 men) with a pancreatic IPMN who underwent abdominal MRI performed both at 0.55 T (conducted 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 the examinations to identify cyst characteristics as well as to determine image quality and diagnostic confidence (using scales of 1-10, with 10 denoting the highest score). RESULTS. Across readers, agreement between 0.55-T and 1.5/3-T MRI examinations was excellent for IPMN type (Gwet agreement coefficient 1 [Gwet AC1], 0.87), presence of pancreatic duct dilatation (Gwet AC1, 0.94), cyst size (intraclass correlation coefficient [ICC], 0.96), diameter of pancreatic duct (ICC, 0.99), and all five suspicious cyst features that were assessed (enhancing mural nodule < 5 mm, enhancing mural nodule ≥ 5 mm, thickened enhancing walls/septa, abrupt change in pancreatic duct caliber with upstream atrophy, and enlarged peripancreatic lymph nodes; Gwet AC1, 0.88-0.99), and it was substantial for multifocality (Gwet AC1, 0.62) and moderate for cyst location (Gwet 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 [SD] vs 8.6 ± 1.3, p < .001) and lower mean diagnostic confidence (8.0 ± 1.7 [SD] 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 the longitudinal surveillance of pancreatic IPMNs and inform relevant technical improvement efforts.