In vivo MR determination of water diffusion coefficients and diffusion anisotropy: correlation with structural alteration in gliomas of the cerebral hemispheres.

PURPOSE To determine whether a relationship exists between water diffusion coefficients or diffusion anisotropy and MR-defined regions of normal or abnormal brain parenchyma in patients with cerebral gliomas. METHODS In 40 patients with cerebral gliomas, diffusion was characterized in a single column of interest using a motion-insensitive spin-echo sequence that was applied sequentially at two gradient strength settings in three orthogonal directions. Apparent diffusion coefficients (ADCs) were derived for the three orthogonal axes at 128 points along the column. An average ADC and an index of diffusion anisotropy (IDA = diffusion coefficientmax-min/diffusionmean) was than calculated for any of nine MR-determined regions of interest within the tumor or adjacent parenchyma. RESULTS In cerebral edema, mean ADC (all ADCs as 10(-7) cm2/s) was 138 +/- 24 (versus 83 +/- 6 for normal white matter) with mean IDA of 0.26 +/- 0.14 (versus 0.45 +/- 0.17 for normal white matter). Solid enhancing central tumor mean ADC was 131 +/- 25 with mean IDA of 0.15 +/- 0.10. Solid enhancing tumor margin mean ADC was 131 +/- 25, with IDA of 0.25 +/- 0.20. Cyst or necrosis mean ADC was 235 +/- 35 with IDA of 0.07 +/- 0.04. CONCLUSION In cerebral gliomas ADC and IDA determinations provide information not available from routine MR imaging. ADC and IDA determinations allow distinction between normal white matter, areas of necrosis or cyst formation, regions of edema, and solid enhancing tumor. ADCs can be quickly and reliably characterized within a motion-insensitive column of interest with standard MR hardware.