Comparison of diffusion anisotropy measurements in combination with the FLAIR-technique

Fluid-attenuated inversion recovery (FLAIR) technique offers an effective tool to diminish partial-volume averaging effects from cerebrospinal (CSF) signal with in vivo magnetic resonance imaging. CSF-suppressed and unsuppressed direction-dependent diffusion-weighted (DW) images are obtained with a DW spin-echo EPI sequence in a single acquisition scheme. Comparison of unsuppressed and CSF-suppressed apparent diffusion coefficient (ADC) maps yields consistent values for brain tissue in volunteers when no partial-volume effects are expected, but differs considerably at borders of parenchyma to ventricles and sulci. From theory and phantom studies, a corrected anisotropy index is introduced considering differences of statistical fit errors. Anisotropy of white matter is observed in normal brain of volunteers. Anisotropy index maps reveal destruction of fiber tracts in pathologic areas. Results of a preliminary study on 12 patients with intra-axial tumors indicate an improved delineation of tumor boundaries of FLAIR ADC maps against unsuppressed acquisition.