A study of the apparent diffusion coefficient of grey and white matter in human ischaemic stroke.

We examined whether there was any difference in the value, and temporal evolution, of the apparent diffusion tensor trace (ADC) in acute and subacute grey and white matter lesions. Thirty-seven patients underwent diffusion imaging once (up to 3 days), 15 patients were scanned twice (up to 7 days), and seven patients were scanned three times (up to 14 days) after stroke. Values of the ratio of ischaemic to contralateral ADC (ADCr) were reduced on average by 30% (p<0.001) in the whole hyperintense region up to 7 days post-ictus. No difference was seen between ADCr values of grey and white matter in individual subjects within the patient groups scanned up to 7 days. However, in the subgroup of patients scanned beyond 7 days, ADCr for grey matter rose significantly (p=0.02) from ADCr approximately 0.7 (< 7 days) to 0.95 (> or = 10 days). This increase did not occur in white matter whose ADCr remained fairly constant (ADCr approximately 0.7) over the time course of the study.