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Date: Fri, 26 Jan 2007 15:14:36 -0500
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Conversation: MRI MORE SENSITIVE THAN CT IN DIAGNOSING MOST COMMON FORM OF
ACUTE STROKE, FINDS NIH STUDY
Subject: MRI MORE SENSITIVE THAN CT IN DIAGNOSING MOST COMMON FORM OF ACUTE
STROKE, FINDS NIH STUDY
U.S. Department of Health and Human Services
NATIONAL INSTITUTES OF HEALTH
NIH News
National Institute of Neurological Disorders and Stroke (NINDS)
<http://www.ninds.nih.gov/>
FOR IMMEDIATE RELEASE: Friday, January 26, 2007
CONTACT: Marian Emr or Margo Warren, 301-496-5924,
<e-mail: [log in to unmask]>
MRI MORE SENSITIVE THAN CT IN DIAGNOSING MOST COMMON FORM OF ACUTE STROKE,
FINDS NIH STUDY
Results from the most comprehensive study to compare two imaging techniques
for the emergency diagnosis of suspected acute stroke show that magnetic
resonance imaging (MRI) can provide a more sensitive diagnosis than computed
tomography (CT) for acute ischemic stroke. The difference between MRI and
CT was attributable to MRI's superiority for detection of acute ischemic
stroke -- the most common form of stroke, caused by a blood clot. The study
was conducted by physicians at the National Institute of Neurological
Disorders and Stroke (NINDS), a part of the National Institutes of Health
(NIH). Findings appear in the January 27, 2007 edition of "The Lancet"[1].
"These NIH research findings on acute stroke imaging are directly applicable
to real-world clinical practice," said NIH Director Elias A. Zerhouni, M.D.
"The patients involved in this study were the typical cross-section of
suspected stroke patients that come into emergency rooms on a daily basis."
Furthermore, the study has good news for patients, according to Walter J.
Koroshetz, M.D., NINDS Deputy Director. "This study shows that
approximately 25 percent of stroke patients who come to the hospital within
three hours of onset, the time frame for approved clot-busting therapy, have
no detectable signs of damage. In other words, brain injury may be
completely avoided in some stroke victims by quick re-opening of the blocked
blood vessel," said Dr. Koroshetz.
The researchers conducted the study to determine whether MRI was superior to
CT for emergency diagnosis of acute ischemic and hemorrhagic stroke (caused
by bleeding into the brain). Standard CT uses x-rays which are passed
through the body at different angles and processed by a computer as
cross-sectional images, or slices of the internal structure of the body or
organ. Standard MRI uses computer-generated radio waves and a powerful
magnet to produce detailed slices or three-dimensional images of body
structures and nerves. A contrast dye may be used in both imaging
techniques to enhance visibility of certain areas or tissues.
Study results show immediate non-contrast MRI is about five times more
sensitive than and twice as accurate as immediate non-contrast CT for
diagnosing ischemic stroke. Non-contrast CT and MRI were equally effective
in the diagnosis of acute intracranial hemorrhage. Non-contrast CT has been
the standard in emergency stroke treatment, primarily to exclude hemorrhagic
stroke, which cannot be treated with clot-busting therapies.
"Many patients who come to hospitals with a suspected stroke ultimately have
a different diagnosis. Most possible stroke victims are first evaluated by
non-specialists, who may be reluctant to treat a patient for stroke without
greater confidence in the accuracy of the diagnosis. Our results show that
MRI is twice as accurate in distinguishing stroke from non-stroke," said
Steven Warach, M.D., Ph.D., director of the NINDS Stroke Diagnostics and
Therapeutic Section and senior investigator of the study. "Based on these
results, MRI should become the preferred imaging technique for diagnosing
patients with acute stroke."
Study leaders hope that because of its increased diagnostic accuracy, MRI
may lead to better patient outcomes and ultimately decrease the cost of
stroke care, through increased use of acute treatments and earlier
initiation of secondary prevention.
The study included 356 consecutive patients with suspected stroke arriving
at the NIH Stroke Center at Suburban Hospital in Bethesda, MD, a primary
stroke center that is designed to stabilize and treat acute stroke patients.
Stroke specialists conducted emergency clinical assessments with all
patients, including the NIH Stroke Scale which is used to measure stroke
severity. MRI was done prior to CT in 304 patients. Scans were initiated
within 2 hours of each other, with a median difference of 34 minutes.
Patients were excluded from the analysis if either CT or MRI was not done.
The images were sorted randomly and independently by two neuroradiologists
and two stroke neurologists.
Results of the study show standard MRI is superior to standard CT in
detecting acute stroke and particularly acute ischemic stroke. The four
readers were unanimous in their agreement on the presence or absence of
acute stroke in 80 percent of patients using MRI compared to 58 percent
using non-contrast CT. No significant difference using the two technologies
was seen in the diagnosis of acute intracranial hemorrhage, which is
consistent with previous findings.
"Although MRI is remarkably accurate in detecting early stroke damage, it
can't substitute for doctor's clinical judgment in making a stroke diagnosis
and deciding upon treatment," said Dr. Koroshetz. "Future studies are
needed to determine whether advanced contrast enhanced CT techniques can
afford the same level of clinical information more quickly and with less
expense," he added.
The National Institute of Neurological Disorders and Stroke is the nation's
primary funder of research on the brain and nervous system. More
information about stroke and other neurological disorders can be found on
the NINDS web site, <http://www.ninds.nih.gov>.
The National Institutes of Health (NIH) -- The Nation's Medical Research
Agency -- includes 27 Institutes and Centers and is a component of the U.S.
Department of Health and Human Services. It is the primary federal agency
for conducting and supporting basic, clinical and translational medical
research, and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and its programs,
visit <www.nih.gov>.
###
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[1] "Magnetic resonance imaging and computer tomography in emergency
assessment of patients with suspected acute stroke: a prospective
comparison." Chalela J, Kidwell CS, Nentwich LM, Luby M, Butman JA, Demchuk
AM, Hill MD, Patronas N, Latour L, Warach S. "The Lancet", Vol. 369,
January 27, 2007, pp. 293-298.
-------------------------------
This NIH News Release is available online at:
<http://www.nih.gov/news/pr/jan2007/ninds-26.htm>.
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