"MRI has been used to evaluate labeled cell migration and distribution. However, quantitative determination of labeled cell concentration using MRI has not been systematically investigated. In the current study, we investigated the relationships between labeled cell concentration and MRI parameters of transverse relaxation rate, R-2, and apparent diffusion coefficient (ADC), in vitro in phantoms and in vivo in rats after stroke....Our study suggests that MRI parameters have the potential to quantitatively determine labeled cell concentration in vivo."