Major obstacles in effective local drug delivery to a target site include non-invasive measurement of the concentration distribution after local administration. Herein, the development of a non-invasive in vitro magnetic resonance imaging (MRI) method is described to quantitatively study the distribution of drug surrogate and to measure fluid flow velocity in the region of interest (ROI). Dynamic contrast enhanced MRI was used to study diffusion–convection transport phenomena of a magnetic resonance contrast agent, Gd-DTPA, in 1% agarose gel. The relationship between the concentration of Gd-DTPA and T 1 relaxation time was determined using an inversion recovery MRI technique. The concentration distribution of Gd-DTPA images was estimated from a calibration curve relating T 1 relaxation time and the concentration of Gd-DTPA. Using the estimated concentration profiles, center-of-mass points were calculated in a series of time points in order to determine fluid flow velocity, which correlated well with the real volumetric flow velocity at early time points. In this study, we developed a method to analyze MR images quantitatively and to determine fluid flow velocity through a tissue in vivo. 
A novel center-of-mass method to measure fluid velocity with MRI