Published Online
on May 15, 2008

A more recent version of this article appeared on July 1, 2008

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Submitted on October 7, 2007
Revised on November 14, 2007
Accepted on November 22, 2007

Development and Validation of a Simple Conversion Model for Comparison of Intracerebral Hemorrhage Volumes Measured on CT and Gradient Recalled Echo MRI

Richard E. Burgess MD, PhD^*; Steven Warach MD, PhD; Timothy J. Schaewe DSc; Brittany R. Copenhaver BA; Jeffry R. Alger PhD; Paul Vespa MD; Neil Martin MD; Jeffrey L. Saver MD; and Chelsea S. Kidwell MD

From the Department of Neurology (R.E.B., B.R.C., C.S.K.), Georgetown University, Washington, DC; the National Institute of Neurological Disorders and Stroke (R.E.B., S.W.), National Institute of Health, Bethesda, Md; the Department of Neurology (T.J.S., J.R.A., J.L.S.), University of California, Los Angeles; the Department of Neurosurgery (P.V., N.M.), University of California, Los Angeles; and the Washington Hospital Center (C.S.K.), Washington, DC.

^* To whom correspondence should be addressed. E-mail: burgessri{at}ninds.nih.gov.

Background and Purpose—Gradient recalled echo MRI (GRE) has been shown to be as accurate as CT for the detection of acute intracerebral hemorrhage (ICH). However, because of the differences in the signal parameter being detected, apparent hemorrhage size is expected to vary by imaging modality, with GRE providing larger volumes attributable to susceptibility effects.

Methods—Image data from patients participating in 3 ICH studies were retrospectively reviewed. Patients with acute ICH were included if (1) concurrent MRI and CT were performed within 72 hours of symptom onset, and (2) each modality was performed within 240 minutes of each other. ICH volumes were calculated using a semiautomated image analysis program. The least squares method was used to develop a conversion equation based on a linear regression of GRE volume on CT volume.

Results—Thirty-six patients met inclusion criteria. MRI was performed first in 18, CT first in 18. Mean hemorrhage volume was 25.2cc (range 0.1 to 83.9cc) on CT and 32.7cc (range 0.1 to 98.7cc) measured on GRE. A linear relationship defined by CT Volume=GRE Volume*0.8 (Spearman's correlation coefficient=0.992, P<0.001) was derived.

Conclusions—Acute ICH volumes as measured on GRE pulse sequences are consistently larger than CT volumes. A simple mathematical conversion model has been developed: CT volume=0.8*GRE volume. This formula can be used in studies using both imaging modalities, across different studies, or to track ICH growth over time independent of imaging modality in an individual patient.

Key words: intracerebral hemorrhage • MRI • CT

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