MR imaging of cerebral perfusion by phase-angle reconstruction of bolus paramagnetic-induced frequency shifts.

Phase-angle images are acquired dynamically during bolus paramagnetic contrast injection and demonstrate a phase-enhancement effect in perfused cerebral tissues. Signal-to-noise is comparable to that of susceptibility-based signal loss (delta R*) images. Assuming that phase shift is proportional to the tissue paramagnetic agent concentration, as supported by experimental data, the integrated area of the phase time response curves estimated the relative gray to white matter blood volume as 1.8:1 and was sensitive to acute ischemia. The relation between tissue phase shift and concentration is considered.