Volumetric measurement of perfusion and arterial transit delay using hadamard encoded continuous arterial spin labeling

Creating images of the transit delay from the labeling location to image tissue can aid the optimization and quantification of arterial spin labeling perfusion measurements and may provide diagnostic information independent of perfusion. Unfortunately, measuring transit delay requires acquiring a series of images with different labeling timing that adds to the time cost and increases the noise of the arterial spin labeling study. Here, we implement and evaluate a proposed Hadamard encoding of labeling that speeds the imaging and improves the signal-to-noise ratio efficiency. Volumetric images in human volunteers confirmed the theoretical advantages of Hadamard encoding over sequential acquisition of images with multiple labeling timing. Perfusion images calculated from Hadamard encoded acquisition had reduced signal-to-noise ratio relative to a dedicated perfusion acquisition with either assumed or separately measured transit delays, however.