MR DIFFUSION IMAGING OF HUMAN INTRACRANIAL TUMORS

We used MRI for in vivo measurement of brain water self-diffusion in p atients with intracranial tumours. The study included 25 patients (12 with high-grade and 3 with low-grade gliomas, 7 with metastases, 5 wit h meningiomas and 1 with a cerebral abscess). Apparent diffusion coeff icients (ADC) were calculated in a single axial slice through the tumo urs; the sequence was sensitive to diffusion along the cephalocaudal a xis. Our main finding was that ADC in contrast-enhancing areas within cerebral metastases was statistically significantly higher than ADC in contrast-enhancing areas in high-grade gliomas (P less than or equal to 0.05). Furthermore, the ADC in oedema surrounding metastases were s tatistically significantly higher the ADC in oedema around high-grade gliomas (P less than or equal to 0.02). The ADC in patients with menin giomas did not differ significantly from those seen with high-grade gl iomas or cerebral metastases. The highest ADC were found within cystic or necrotic tumour areas. In one patient with a cerebral abscess, sus pected of having a high-grade glioma, the ADC was similar to that in h igh-grade gliomas. The finding of higher ADC in cerebral metastases th an in high-grade gliomas may be helpful in trying to distinguish betwe en these tumours preoperatively; it suggests increased free extracellu lar and/or intracellular water fraction in cerebral metastases. The me thod seems to hold potential for further noninvasive characterisation of intracranial tumours.