vivo detection of stem cells grafted in infarcted rat myocardium. J Nucl Med 46:816–822

The evaluation of stem cell–mediated cardiomyoplasty by non-invasive in vivo imaging is critical for its clinical application. We hypothesized that dual-tracer small-animal SPECT would allow simultaneous imaging of 99mTc-sestamibi to assess myocardial perfusion and of 111In-labeled stem cells to delineate stem cell engraftment. Methods: Three to 4 million rat embryonic car-diomyoblasts (H9c2 cells) were labeled with 11.1–14.8 MBq (0.3–0.4 mCi) of 111In-oxyquinoline and then injected into the border zones of infarcted myocardium of rats. 111In images were acquired with a SPECT scanner 2, 24, 48, 72, and 96 h after the stem cells were injected into the infarcted myocardium. To visualize the perfusion deficit in the infarcted myocardium, we injected 74 MBq (2 mCi) of 99mTc-sestamibi (Cardiolite) intrave-nously 48 h after grafting. Dual-isotope pinhole SPECT was used to image 99mTc-sestamibi uptake simultaneously with 111In to delineate retention of 111In-labeled stem cells. The presence of labeled stem cells was confirmed by autoradiography and histology. Results: SPECT of 99mTc-sestamibi was used to de-lineate perfusion deficits and infarcted myocardium. Bull’s-eye plots indicated that the 111In signal from the labeled stem cells overlapped the perfusion deficits identified from the 99mTc-ses-tamibi images. The 111In signal associated with the radiolabeled stem cells could be detected with SPECT of the heart for 96 h after engraftment. Conclusion: This study demonstrated the feasibility of using dual-isotope pinhole SPECT for high-resolu-tion detection of perfusion deficits with 99mTc-sestamibi and with 111In-labeled stem cells grafted into the region of the infarct. Key Words: myocardium; ischemia; stem cells; indium; sesta-mibi; SPEC