SUSCEPTIBILITY EFFECTS IN POROUS-MEDIA IN THE PRESENCE OF FLOW

Magnetic resonance (MR) imaging of microvascular now is an important t opic in biomedicine because it permits access to the functional state of a biologic system. The internal heterogeneous magnetic field due to susceptibility differences within tissues is one of the factors that can affect signal intensity. A glass bead phantom simulating a porous medium was used to experimentally study the effect of the internal mag netic field on MR flow measurements. A physical model was developed to simulate the paths of the moving spins and the local magnetic field d istribution in the medium to estimate the signal intensity with spin-p hase analysis. The susceptibility variation inside the glass bead phan tom was estimated by comparing the simulation results with the experim ental data. Experiments were also performed with a tissue-simulating p hantom, and the results indicated that the effect of the internal fiel d inhomogeneity on in vivo microvascular flow measurements was negligi ble.