Tissue perfusion in humans studied by fourier velocity distribution, line scan, and echo‐planar imaging

In tissue perfusion studies, FT velocity distribution imaging (VDI) intrinsically distinguishes signals from moving blood and volume-averaged tissue. Results in human thyroid gland, in vivo, using VDI line scan technique demonstrated separation of moving blood signal from glandular tissue, while VDI inner-volume echo-planar imaging of brain showed only CSF velocity above the image noise level. New alternating polarity gradient sequences which permit separation of diffusion and slow velocity are discussed. A novel method of 3D FT imaging (two spatial and one velocity dimension) combining inner-volume imaging and echo-planar imaging with velocity resolution of 0.15 mm/s per pixel is demonstrated. A novel graphical method of calculation and display of diffusion dependence in pulsed gradient sequences is presented.