Heterogeneity of Apparent Diffusion Coefficients Within Infarcts

To the Editor: Back et al1 recently reported apparent diffusion coefficient (ADC) measurements in acute stroke, finding no ADC fluctuations in peri-infarct regions over a 15-minute period. The reported data are convincing with regard to the temporal stability of infarct area within the 15-minute time window studied. We wish to address the issue of ADC spatial heterogeneity in stroke, specifically the authors’ contention that “there was a gradient of ADC reduction from the infarct periphery toward the infarct core.” They conclude that “this observation supports the view that the ischemia-induced early change in ADC is a blood flow-dependent event which reflects the severity (and duration) of the perfusion deficit.” As the authors have noted, this core-versus-periphery distinction in diffusion imaging has been previously advanced and is commonly accepted by the community of stroke researchers. However, it …