Localized real-time velocity spectra determination

The accurate measurement of flow velocity has long been a subject of NMR research. In the field of medical imaging, a variety of techniques primarily based on the principle of Fourier encoding have been described. Due to time constraints, necessary trade-offs exist between spatial versus velocity spectral resolution. In general, either the average velocity of individual pixels is displayed or velocity spectral determinations are made at the cost of spatial localization. The recent development of multidimensional excitation pulses makes spatial localization possible during the excitation phase of the pulse sequences. This approach, coupled with time varying gradient readout, can be used to obtain single-shot localized velocity spectra. Using these concepts, we have obtained in vivo real-time measurements of localized velocity spectra on our clinical imager.