Esophageal carcinoma: Ex vivo evaluation with diffusion-tensor MR imaging and tractography at 7 T

Purpose: To determine the feasibility of diffusion-tensor magnetic resonance (MR) imaging and tractography as a means of evaluating the depth of mural invasion by esophageal carcinomas. Materials and Methods: This study was approved by the institutional review board, and written informed consent was obtained from each patient. Twenty esophageal specimens, each containing a carcinoma, were studied with a 7.0-T MR imaging system equipped with a four-channel phased-array surface coil. Diffusion-tensor MR images were obtained with a field of view of 50-60 mm x 25-30 mm, matrix of 256 x 128, section thickness of 1 mm, b value of 1000 sec/mm², and motion-probing gradient in seven noncollinear directions. The MR images were compared with the histopathologic findings as the reference standard. The differences in diffusion-tensor MR imaging parameters between the carcinoma and the layers of the esophageal wall were statistically analyzed by using the Dunnett test. Results: In all 20 carcinomas (100%), the diffusion-weighted images, apparent diffusion coefficient (ADC) maps, fractional anisotropy (FA) maps, λ₁ maps, and direction-encoded color FA maps made it possible to determine the depth of tumor invasion of the esophageal wall that was observed during histopathologic examination. The λ₁ maps showed the best contrast between the carcinomas and the layers of the esophageal wall. The carcinomas had both lower ADC values and lower FA values than the normal esophageal wall; thus, the carcinomas were clearly demarcated from the normal esophageal wall. Diffusion-tensor tractography images were also useful for determining the depth of tumor invasion of the esophageal wall. Conclusion: Diffusion-tensor MR imaging and tractography are feasible in esophageal specimens and provide excellent morphologic data for the evaluation of mural invasion by esophageal carcinomas.