This study developed a system to monitor intensity changes in the cardiac PET-MRI images of transplanted stem cells in vivo. A fusion system, consisting of 2 medical imaging modalities to monitor the changes in signal intensity in regions of interest (ROI) over time, was achieved.

Porcine ischemia reperfusion (IR) injury model was employed to assess the successful stem cell engraftment signal by manganese enhanced MRI (MEMRI). To validate the MEMRI signal, hAMSCs were transduced by PET reporter gene (RG) utilizing the herpes simplex virus-thymidine kinase transgene construct, which is expressed only in engrafted cells to trap 18F-FHBG radiotracer. One week after IR injury, the RG transduced hAMSCs were delivered via transendocardial injection into peri- and intra-infarct regions. PET-CT and MR locator-MEMRI-delayed enhanced MRI (DEMRI) images were acquired post hAMSC injection on days 0, 7, and 45. All pairs of CT and MR locator images were registered by gradient descent to optimize mutual information between the images generating transformation matrixes. These transformation matrixes were used to align PET with MEMRI and DEMRI and longitudinal images into common frames of reference. Additionally image pairs were fused into a single display. An ROI around the engrafted stem cells on MEMRI was copied to the same location on PET-CT longitudinally and average intensity was sampled at each time point.

AZE Technology, Inc. Stanford University.