Prediction of tissue survival after middle cerebral artery occlusion basedon changes in the apparent diffusion of water

Object. In this study the authors tested the hypothesis that the estimate o f the apparent diffusion coefficient (ADC) of water is a reliable pathophys iological index of the viability of ischemic brain tissue. Methods. Cerebral blood dow (( BF) and the cerebral metabolic rates of oxyg en and glucose CMRO2 and CMRglc respectively) were measured using positron emission tomography (PET) scanning before and after permanent middle cerebr al artery occlusion (MCAO) or reperfusion in pigs. The ADC value, which was measured using diffusion-weighted magnetic resonance DW MR) imaging was co mpared with physiological variables obtained by PET scanning and with histo logical findings. After both permanent MCAO and reperfusion, the decrease i n the ADC was significantly correlated with decrease in the CMRO2 and CMRgl c. The infarction coincided with a CMRO2 threshold of 50% of the value meas ured on the contralateral side. Thus, an ADC value of 80% or 75% of the con tralateral value reflected the CMRO2 threshold after permanent MCAO or repe rfusion, respectively. On DW MR images, lesions with ADC values above 80% o f the contralateral value are potentially reversible until 6 hours after MC AO, whereas lesions with ADC values below 75% of the contralateral value ar e irreversible as early as 2 hours after MCAO. Conclusions. The ADC of water provides a reliable pathophysiological index for tailoring therapy to the condition of individual stroke patients in cli nical practice.