Purpose: To determine the usefulness of ultra-high-resolution magnetic resonance (MR) imaging at an ultra-high field strength (7.0. T), using a voxel volume of 9.5-14. nL, as means of evaluating the depth of mural invasion by esophageal carcinomas. Materials and Methods: Twenty esophageal specimens containing 20 carcinomas were studied using a 7.0-T MR imaging system with a four-channel surface coil. Ultra-high-resolution MR images were obtained with a field of view of 50-60mm×25-30mm, a matrix of 512×256, and a section thickness of 1.0mm, resulting in a voxel volume of 0.0095-0.014mm3 (9.5-14nL). Differences between tumor tissue and the esophageal wall layers and between tumor tissue and fibrosis were evaluated using visual signal intensity scoring measurements. MR images were then compared with histopathologic findings as the reference standard. Results: Ultra-high-resolution T2-weighted MR images at 7.0. T clearly depicted the normal esophageal wall in all 20 specimens (100%) as consisting of eight layers, which clearly corresponded to the tissue layers of the esophageal wall. Ultra-high-resolution T2-weighted MR images made it possible to differentiate between the tumor tissue and fibrosis clearly (P. <. 0.01). In all 20 esophageal carcinomas (100%), ultra-high-resolution T2-weighted MR images made it possible to determine the depth of tumor invasion in the esophageal wall as observed in the histopathologic sections. Regional lymph node involvement was also clearly depicted in four specimens. Conclusion: Ultra-high-resolution 7.0-T MR imaging, using a voxel volume of 9.5-14. nL, provides clear delineation of the esophageal wall layers, clear differentiation of tumor tissue from fibrosis, and excellent diagnostic accuracy for evaluating mural invasion by esophageal carcinomas.
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