Rapid measurement of arterial input function in mouse tail from projection phases.

PURPOSE To measure the arterial input function (AIF) in a mouse tail at high temporal resolution with signal phase of MR projections. METHODS The technique involves the acquisition of one 2D image before injection, followed by a series of projections before, during, and after contrast injection. Differences in the signal phase, relative to the mean preinjection phase, were calculated and converted into a concentration of Gd. RESULTS An AIF with a temporal resolution of 100 ms was measured and verified with colorimetry (in a flow phantom) and mass spectrometry analysis (in vivo). The projection-based AIF is expected to better represent the rapid contrast kinetics in the blood following injection, thus improving the accuracy of quantitative dynamic contrast-enhanced-MRI analysis. Colorimetry experiments confirmed that signal phase is preferred over magnitude for a precise determination of an AIF. In-vivo experiments demonstrate the feasibility of our approach in mice. CONCLUSION AIFs can be measured quickly and precisely using phase from projections. Phase data are sensitive to the flow velocity; but this sensitivity is significantly reduced when flow compensation was used.