Sensitivity of Susceptibility-Weighted Imaging in Detecting Superparamagnetic Iron Oxide-Labeled Mesenchymal Stem Cells: A Comparative Study

Background: susceptibility-weighted imaging (swi) is extremely sensitive in the detection of superparamagnetic iron oxide (spio) nanoparticle-labeled cells. however, no study has compared molecular imaging for stem cell detection using swi and other mri pulse sequences. objectives: this study aims to assess the sensitivity of swi in detecting spio nanoparticle-labeled, human bone marrow-derived mesenchymal stem cells (spio-hmscs) compared with that of t2- and t2*-weighted imaging (t2wi and t2*wi, respectively) in a phantom and in vivo study in rats.materials and methods: a phantom was prepared with various cell concentrations. in one normal rat, spio-hmscs were implanted directly through burr holes into both caudate putamens, while in three rats without and six rats with photothrombotic infarction, 2.5 × 105/ml spio-hmscs were infused into the ipsilateral internal carotid artery (ica). t2wi, t2*wi, and swi findings were compared for dark regions representing spio-hmscs. results: swi and t2*wi detected 15 μl of 13 spio-hmscs/μl and 15 μl of 27 spio-hmscs/μl in the phantom, respectively and 3 μl of 333 spio-hmscs/μl and 3 μl of 167 spio-hmscs/μl in the normal rat brain (direct implantation). in the normal rat brain (ica infusion), one of the three cases showed numerous foci of dark regions dispersed throughout the brain on t2*wi and swi. dark regions surrounded the infarcts in all six infracted rat brains. the dark region was most prominent on swi, followed by t2*wi and t2wi in all six rats (p = 0.002). implanted spio-hmscs were confirmed using prussian blue staining. conclusions: swi is the most sensitive in the detection of spio-hmscs, with the dark regions representing spio-hmscs being more prominent on swi than on t2*wi and t2wi.