Magnetic resonance imaging of pancreatic islets transplanted into the right liver lobes of diabetic mice

Introduction. Pancreatic islets (PI) labeled with Feridex can be visualized using magnetic resonance imaging (MRI) after transplantation into the liver. However, there is still no accurate method of quantifying the signal loss caused by the iron contrast agent within transplanted tissue. The aim of this study was to test a new method for quantifying signal loss during the early posttransplantation period. Methods. Isolated mouse PI (C57BL/6 and BALB/c) were labeled in CMRL-1066 culture media supplemented with Feridex. Two hundred twenty PI were injected directly into the right liver lobes of BALB/c diabetic (streptozotocine 220 mg/kg) recipients (isografts, n = 3; allografts, n = 3). Animals were scanned at 3 T, on a whole body scanner equipped with a high-performance gradient insert and using the 3D FIESTA sequence, on days 1, 7, and 14. Signal loss was quantified by comparison of liver tissue with and without labeled PI. Signal loss detected on the first scan was rated as 100% and subsequent measurements were recalculated as relative numbers. Results. While the function of the isografts remained stable throughout the study, the allografts failed on days 5 and 10. A decrease in the amount of signal loss was observed in all animals and was comparable after the first week in both groups. However, there was a difference between groups after the second week (mean +/- SD; isografts, 100% double right arrow 61.8 +/- 6.74% double right arrow 47.18 +/- 7.14%; allografts, 100% double right arrow 59.39 +/- 8.54% double right arrow 38.16 +/- 6.81%). Conclusion. Disappearance of signal loss is comparable in all animals during the first week and seems to be independent of acute rejection.