In vivo brain edema classification: New insight offered by large b-value diffusion-weighted MR imaging

To assess the role of large b-value diffusion weighted imaging (DWI) in the characterization of the physicochemical properties of the water in brain edema under experimental and clinical conditions.

Vasogenic brain edema was induced in mice by means of cold injury. A total of 17 patients with extensive peritumoral brain edema were also investigated. The longitudinal relaxation time (T(1)) and apparent diffusion coefficient (D) were measured in the edematous area both in humans and in mice. D was calculated by using both mono- (D(mono)) and biexponential (D(fast) and D(slow)) approaches in the low and overall range of b-values, respectively. The D values were correlated with the T(1) values.

A strong linear correlation was found between T(1) and D(mono) in vasogenic brain edema, both in humans and in mice. After breakdown of D(mono) into fast and slow diffusing components, only D(fast) exhibited a strong correlation with T(1); D(slow) was unchanged in vasogenic brain edema.

Large b-value DWI can furnish a detailed characterization of vasogenic brain edema, and may provide a quantitative approach for the differentiation of edema types on the basis of the physicochemical properties of the water molecules. Application of the DWI method may permit prediction and follow-up of the effects of antiedematous therapy.