Dr. Bradley is Director of MRI at Long Beach Memorial Medical
Center in Long Beach, CA, and Professor of Radiology at the
University of California, Irvine, in Orange, CA. Dr. Dietrich is
Professor of Radiological Sciences and Director of MRI at the
University of California, Irvine, in Orange, CA. She is also a
member of the editorial advisory board of this journal.
A
s we enter the new millennium, it is apparent that one major
disease has benefited little by our improved ability to image it:
acute stroke. Recently, however, the increased availability of EPI
diffusion/perfusion imaging has given us a new and improved look at
the physiology underlying the extension of infarction following an
initial vascular occlusion. We are now able to distinguish
reversible cytotoxic edema from irreversible infarction, and to
identify the "ischemic penumbra" (i.e., the area of brain at risk
for extension of the initial infarction).
A recent phase III clinical trial of a new neuroprotective agent
used the volume of the lesion, as seen on EPI diffusion imaging, as
an entry condition. Efficacy was defined by the difference between
the volume of the abnormality on the initial diffusion image and
the volume of the abnormality on the final T2-weighted image. This
finding was significant because, for the first time, objective MR
measurements were used instead of subjective stroke rating
scales.
Undoubtedly, our success in improving the ability to visualize
subtle physiologic changes resulting from infarction will lead to
the introduction of new neuroprotective agents. We will soon be
able to actually save brain tissue, rather than the alternative of
merely teaching the stroke patient how to function as best he can
with the remaining brain tissue. Neuroprotective agents also will
play a similar role in salvaging the brain of infants who have
suffered anoxic-ischemic insults.
We look forward to the role MRI will play in the introduction
and implementation of these new neuroprotective agents. The
potential ability to save brain tissue represents the most
significant effect MRI has had on patient outcome since its
introduction almost two decades ago.