Direct FLASH MR imaging of magnetic susceptibility differences

A modified fast low-angle shot MR imaging sequence allows direct imaging of local field gradients introduced by susceptibility differences between neighboring tissues or surgical implants. Since image artifacts mainly occur as areas of signal losses due to inappropriate refocusing of the section selection gradient, the effects may be compensated for by proper gradient adjustments. The technique allows a rapid delineation of susceptibility effects in normal as well as pathologic situations (e.g., air-tissue artifacts in brain images, detection of hemorrhage, or after administration of paramagnetic contract media). On the other hand, metallic ligation and intracranial aneurysm clips may cause irreversible signal losses due to very small T2 relaxation times. Experiments have been carried out on phantoms and human volunteers