Diffusion-weighted imaging with dual-echo echo-planar imaging for better sensitivity to acute stroke.
OBJECTIVE
Parallel imaging facilitates the acquisition of echo-planar images with a reduced TE, enabling the incorporation of an additional image at a later TE. Here we investigated the use of a parallel imaging-enhanced dual-echo EPI sequence to improve lesion conspicuity in diffusion-weighted imaging.


METHODS
Parallel imaging-enhanced dual-echo DWI data were acquired in 50 consecutive patients suspected of stroke at 1.5T. The dual-echo acquisition included 2 EPI for 1 diffusion-preparation period (echo 1 [TE = 48 ms] and echo 2 [TE = 105 ms]). Three neuroradiologists independently reviewed the 2 echoes by using the routine DWI of our institution as a reference. Images were graded on lesion conspicuity, diagnostic confidence, and image quality. The apparent diffusion coefficient map from echo 1 was used to validate the presence of acute infarction. Relaxivity maps calculated from the 2 echoes were evaluated for potential complementary information.


RESULTS
Echo 1 and 2 DWIs were rated as better than the reference DWI. While echo 1 had better image quality overall, echo 2 was unanimously favored over both echo 1 and the reference DWI for its high sensitivity in detecting acute infarcts.


CONCLUSIONS
Parallel imaging-enhanced dual-echo diffusion-weighted EPI is a useful method for evaluating lesions with reduced diffusivity. The long TE of echo 2 produced DWIs that exhibited superior lesion conspicuity compared with images acquired at a shorter TE. Echo 1 provided higher SNR ADC maps for specificity to acute infarction. The relaxivity maps may serve to complement information regarding blood products and mineralization.
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California sholdsworth@stanford.edu.
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SJ
Holdsworth
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Yeom
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Antonucci
Department of Radiology (J.B.A.), University of Washington, Seattle, Washington.
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Andre
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Rosenberg
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Aksoy
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Straka
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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NJ
Fischbein
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Bammer
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Moseley
From the Department of Radiology (S.J.H., K.W.Y., M.U.A., J.R., M.A., M.S., N.J.F., R.B., M.E.M., G.Z.), Stanford University, Stanford, California.
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Zaharchuk
Clinical Neuroscience (S.S.), Karolinska Institute, Stockholm, Sweden.
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Skare
D000208:Acute Disease; D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020521:Stroke / Q000473:pathology*