on October 25, 2007
Published online before print October 25, 2007, doi: 10.1161/STROKEAHA.107.483925
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Submitted on January 30, 2007
From the CHU de Bordeaux, Université Victor Segalen Bordeaux 2, Service de Neuroradiologie diagnostique et thérapeutique (T.T., V.D., E.P., P.M.), Service de Neurologie A (I.S., F.R., J.M.O.), Unité de soutien méthodologique à la recherche clinique et épidémiologique (J.A., G.C.), Departement de Pharmacologie (P.R.), Bordeaux, France; Société Theralys, Diagnostic and Therapeutic Image Analysis in Clinical Trials (C.P.), Bioparc, Lyon France. * To whom correspondence should be addressed. E-mail: vincent.dousset{at}chu-bordeaux.fr.
Background and Purpose—In the concept of ischemic penumbra, the volume of salvaged penumbra is considered as the volume of FLAIR normalization on follow-up MRI compared with early diffusion and perfusion abnormalities. Using magnetization transfer imaging, very sensitive to macromolecular disruption, we investigated whether FLAIR normalization was a good marker for tissue full recovery. Methods—We prospectively included 30 patients with acute middle cerebral artery stroke. Diffusion-weighted imaging (DWI) and perfusion-weighted imaging were performed within 12 hours after onset (MRI.1), and the final infarct was documented by MRI with FLAIR and magnetization transfer at 1-month follow-up (MRI.2). We compared magnetic transfer ratio of a normal region with values measured at 1 month (MRI.2) in 4 regions of interest: (1) the initial DWI hypersignal (CORE=DWI_MRI.1); (2) the infarct growth area (infarct growth=FLAIR_MRI.2-DWI_MRI.1); (3) the hypoperfused area that normalized (reversible perfusion abnormalities=perfusion-weighted imaging_MRI.1-FLAIR_ MRI.2); and (4) the early DWI abnormalities that normalized (reversible diffusion abnormalities=DWI_MRI.1- FLAIR_MRI.2). Results—In comparison with values obtained in normal tissue (magnetic transfer ratio=49.8%, SD=1.9), magnetic transfer ratio at 1 month was significantly decreased in reversible perfusion abnormalities (45.2%, SD=2.5; P<0.0001) and reversible diffusion abnormalities (43.2%, SD=2.8; P=0.0156). It was also markedly reduced, as expected, in the CORE (40.9%, SD=5.2) and infarct growth regions (43.1%, SD=2.0). Conclusions—Magnetic transfer ratio assessed presence of microstructural damages in the MRI-defined salvaged penumbra. This may imply cellular loss and partial infarction. Evaluation of the efficacy of therapies that promote reperfusion or neuroprotection may benefit from this additional information.
Revised on May 26, 2007
Accepted on May 29, 2007
Magnetization Transfer Imaging Shows Tissue Abnormalities in the Reversible Penumbra
Thomas Tourdias MD;
Key words: acute cerebral infarction • incomplete infarct • ischemic penumbra • magnetization transfer imaging