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

<b>BACKGROUND</b>. 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. <b>OBJECTIVE</b>. 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. <b>METHODS</b>. 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). <b>RESULTS</b>. 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, <i>p</i> < .001) and lower mean diagnostic confidence (8.0 ± 1.7 [SD] vs 8.7 ± 1.3; <i>p</i> < .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. <b>CONCLUSION</b>. Agreement for suspicious cyst features was excellent at both field strengths. All 0.55-T examinations were considered diagnostic. <b>CLINICAL IMPACT</b>. 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.