Study on the variations of the apparent diffusion coefficient in areas of solid tumor in high grade gliomas.

Present knowledge suggests that in glioblastoma multiforme the value of the apparent diffusion coefficient (ADC) is elevated in the solid part and hyperintense in T1, in spite of the elevated cellularity, and also in areas where peritumoral vasogenic edema is present. The purpose of our study has been to verify in vivo if the ADC increases in areas of solid tumor because of an increased presence of edema, like it happens in areas surrounding the tumor. Sixteen patients with histologically verified glioblastoma multiforme underwent a magnetic resonance (MR) examination with sequences: T1-weighted pre and post contrast, diffusion-weighted at b = 0 and b = 1000 s/mm(2), perfusion-weighted. One hundred sixty-five regions of interest (ROI) have been obtained for all set of patients. In each ROI we have estimated 4 parameters: ADC, intensity of T2-signal normalised to the white matter (SI(T2W)(n)), regional cerebral blood volume (rCBV), T1-signal enhancement (E%). With the SI(T2W)(n) the presence of edema was estimated. For each pair of measured parameters a statistical test of linear regression on the set of all ROI was made. A directed linear correlation between: ADC and SI(T2W)(n) (p <or= 0.001; r = 0.26), E% and SI(T2W)(n) (p <or= 0.001; r = 0.35), E% and ADC (p <or= 0.001; r = 0.33) is present. Also present is an inverse linear correlation between: ADC and rCBV (p <or= 0.05; r = 0.18). Any significant linear correlation between: E% and rCBV (r = 0.01), SI(T2W)(n) and rCBV (r = 0.13) was not found. In areas of solid tumor the increment of the ADC is correlated with the increment of edema: this result can be explained if we assume a three-dimensional diffusion. Furthermore, the increase of ADC is inversely correlated to the rCBV. The E% and the rCBV are statistically independent.