RESEARCH DESIGN AND METHODS

Patients and islet transplant protocol. Our center has now transplanted 10 patients with isolated islets using the Edmonton protocol for immunosuppression (7) under protocols approved by both the Food and Drug Administration and our institutional review board. Eight of the patients have completed the protocol, and each gained insulin independence. The four patients with the longest duration of graft function following intraportal islet transplantation were evaluated by MRI. Of note, for inclusion in the study all patients were required to have an ultrasound examination of the liver that documented absence of hepatic parenchyma or vascular abnormality including steatosis. Posttransplant ultrasound imaging was not routinely performed in our study. Cross-sectional imaging of the initial patient was prompted by attempt at second-dose islet transplant using ultrasound-guided portal vein cannulation at 13 months after the first dose. Ultrasound revealed an unusual pattern of multiple foci of increased hepatic echogenicity that obscured visualization of the portal vein. The study was interpreted as consistent with localized areas of steatosis versus multiple mass lesions or infection. This finding was followed-up with an MR study 1 week after uneventful infusion of the second islet dose. The subsequent three patients were imaged at 8, 11, and 12 months after islet transplantation to assess the universality of the findings in the index case.

MRI protocol. MRI is uniquely sensitive to microscopic lipid deposition in tissues by virtue of chemical shift imaging, whereby voxels of mixed water/lipid content display signal loss on opposed phase images (13). Chemical shift imaging via a modified two-point Dixon gradient echo sequence is routinely performed in clinical MRI of the liver (14) and was utilized to image patients who had received isolated allogeneic islets infused via the portal vein.