Modeling cerebral blood flow and flow heterogeneity from magnetic resonance residue data

Existing model-free approaches to determine cerebral blood flow by external residue detection show a marked dependence of flow estimates on tracer arr ival delays and dispersion. In theory, this dependence can be circumvented by applying a specific model of vascular transport and tissue flow heteroge neity. The authors present a method to determine flow heterogeneity by magn etic resonance residue detection of a plasma marker. Probability density fu nctions of relative flows measured in six healthy volunteers were similar a mong tissue types and volunteers, and were in qualitative agreement with li terature measurements of capillary red blood cell and plasma velocities. Co mbining the measured flow distribution with a model of vascular transport y ielded excellent model fits to experimental residue data. Fitted gray-to-wh ite flow-rate ratios were in good agreement with PET literature values, as well as a model-free singular value decomposition (SVD) method in the same subjects, The vascular model was found somewhat sensitive to data noise, bu t showed far less dependence on vascular delay and dispersion than the mode l-free SVD approach.