1. A method for measuring a distribution of transit times of labeled spins in a sample via magnetic resonance imaging, comprising: providing a labeling plane and an imaging plane for a sample; modulating the magnetization of inflowing spins at the labeling plane using a complex sequence; and obtaining the distribution of transit times for the modulated spins from the labeling plane to each voxel of the imaging plane from a set of acquired image slices of the sample in a single unified acquisition, wherein the complex sequence has minimal autocorrelation over time and its frequency domain transform has no zeros, and wherein the frequency domain transform of the distribution of transit times is obtained by dividing the frequency domain transform of the acquired signal of each of the acquired image slices for each voxel by the frequency domain transform of the complex sequence on a voxel by voxel basis.