IN-VIVO ESTIMATION OF WATER-CONTENT IN CEREBRAL WHITE-MATTER OF BRAIN-TUMOR PATIENTS AND NORMAL INDIVIDUALS - TOWARDS A QUANTITATIVE BRAIN EDEMA DEFINITION

The ''building stones'' in MR imaging, namely the relaxation times (RT ) correlate in certain circumstances well with water content of cerebr al white matter (WM). It is, therefore, possible to estimate regional in vivo water content using RT imaging with an accuracy within +/- 2-4 %. The purpose of the present prospective investigation was to study t he RT's of cerebral WM and thereby estimate normal in vivo water conte nt. Furthermore, the method was used to study whether water content wa s different in the apparently normal cerebral hemisphere of brain tumo ur patients compared to normal individuals. RT data of the non-tumour bearing hemisphere in 42 brain tumour patients were compared to 35 nor mal individuals. Results: 1) Water content was significantly higher in the posterior WM as compared to frontal WM in both normal individuals and apparently normal WM in brain tumour patients and this appears to be a true physiological difference. 2) Water content of normal WM cor related positively with age. 3) There was no significant difference be tween RT data from the normal hemisphere in histologically different t ypes of brain tumours. 4) Water content was significantly higher in th e apparently normal WM of brain tumour patients compared to normal ind ividuals. 5) Based on the present results, a definite lower threshold of white matter oedema could be established as 75% water content, corr esponding to a Tl of 0.850 seconds.