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(Stroke. 2001;32:1695.)
© 2001 American Heart Association, Inc.

Letters to the Editor

Heterogeneity of Apparent Diffusion Coefficients Within Infarcts

Pratik Mukherjee, MD, PhD; Robert C. McKinstry, MD, PhD; Joshua S. Shimony, MD, PhD; Erbil Akbudak, PhD; Abraham Z. Snyder, MD, PhD Thomas E. Conturo, MD, PhD

Mallinckrodt Institute of Radiology, Washington University Medical Center, St Louis, Missouri

Mark M. Bahn, MD, PhD

Department of Radiology, Mayo Clinic, Rochester, Minnesota

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 is possible that much of the ADC heterogeneity illustrated in Figures 2 through 4 of the article by Back et al¹ may reflect differences in ADC reduction between gray matter and white matter. Within the infarct, white matter structures appear to display lower ADC values than gray matter, a finding that is consistent with results from our investigation of acute and early subacute middle cerebral arterial stroke using diffusion tensor MR imaging.² Indeed, the "peel-like structure" of the region of greatest ADC reduction (Figure 4) noted by Back et al¹ closely resembles the morphology of white matter tracts. Our results from diffusion tensor imaging demonstrate that these areas of greatest ADC reduction within the . . . [Full Text of this Article]

T. Back, MD

Department of Neurology, Philipps University Marburg, Marburg, Germany

A. Gass, MD

NMR Research Neurology/Radiology, Department of Neurology, Universitaetsklinikum Mannheim, Mannheim, Germany

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