Described here are systems and methods for providing a non-invasive and continuous quantitative measurement of left ventricular stroke volume (“SV”) and flow volume during a magnetic resonance imaging (“MRI”) scan. In general, the method estimates quantitative measurements of SV from magnetohydrodynamic (“MHD”] voltages generated by blood flowing through the subjects vasculature while the subject is positioned in the magnetic field of an MRI system. A rapid calibration technique is provided to convert MHD voltages to estimates of blood flow, from which quantitative measurements of SV can be computed.