Sci-Fri PM Imaging-11: Evaluation of SPECT/CT for Regenerative Medicine Applications: Tracking Transplanted Cells in a Large Animal Model

Introduction: The purpose of this study was to characterize the performance of dual‐radionuclide SPECT/CT in quantitative tasks associated with tracking transplanted cellsin vivo. Previous studies identified matters of hardware design, whereas we focus on biological variables impacting performance such as non‐specific uptake of radiolabels, and radiolabel dilution with cell colony growth.Methods: Using experimental SPECT/CT data, a canine digital phantom was developed of in vitro 111 In ‐radiolabeled stem cells, transfected with a reporter gene, transplanted into canine infarcted myocardium, and interrogated post‐transplantation using a peripherally‐injected 131 I ‐radiolabeled reporter probe. Single‐ and dual‐head SPECT/CT acquisitions were simulated. Simulations included physical effects of radionuclide‐specific attenuation, scatter, resolution, and dual‐radionuclide crosstalk. CT data was used to simulate photon attenuation. Performance was characterized using an estimation task, incorporating the statistical properties of SPECTimaging, where the precision of parameter estimates ( 111 In and 131 I radiolabel quantity, cell colony size and location, and background) was tracked as the phantom evolved to simulate 111 In ‐label efflux, cell colony growth, and improved reporter probe specificity. Results: In vitro pre‐labeling of transplanted cells with 111 In improved precision of parameter estimates via a priori size and location information. Precision of radiolabel quantity estimates improved with cell colony growth, despite 111 In radiolabel dilution; size and location parameters were influenced little. Precision of radiolabel quantity estimates improved with reduced 131 I reporter probe non‐specific uptake. Conclusion: The performance of SPECT/CT in cell tracking is influenced strongly by biological variables. These should be considered when planning experiments or developing SPECT/CT technology for cell tracking.