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Experimental Studies |
1 From the Department of Cardiovascular Pathology (B.S.P., F.D.K., A.F., R.K., E.K.M., A.P.B., R.V.) and Magnetic Resonance Microscopy Facility (K.P.), Armed Forces Institute of Pathology, Washington, DC; Department of Medicine, Cardiovascular Division, George Washington University Medical Center, Washington, DC (B.S.P.); and Biomedical Laboratory Research and Development Service, Veterans Health Administration, 810 Vermont Ave NW, Washington, DC (T.J.O.). Received December 30, 2004; revision requested March 14, 2005; revision received November 2; accepted December 1; final version accepted December 19. R.V. supported by a grant from the Center for Integration of Medicine and Innovative Technology and RO1 HL61799-02. Address correspondence to T.J.O. (e-mail: timothy.oleary{at}va.gov).
Purpose: To determine if magnetic resonance (MR) microscopy can yield images sufficient for discriminating early progressive atherosclerotic lesions from nonprogressive atherosclerotic lesions in human coronary arteries.
Materials and Methods: Institutional review board approval and informed consent were not required. Seventeen coronary artery segments (mean diameter, 2.8 mm ± 1.0 [standard deviation]) were collected within 36 hours after death from 11 cadavers (six men, five women; age range at death, 3365 years). Quantitative T1, T2, intensity-weighted (IW), and magnetization transfer (MT) maps were acquired with a 9.4-T vertical-bore magnet. Coronary artery lesions were classified as adaptive intimal thickening (AIT), pathologic intimal thickening (PIT), or intimal xanthoma (IXA). Internal anatomic fiducial landmarks and stains were applied to proximal and epicardial vessel surfaces and used to register histologic sections with MR images and thus enable comparison of MR images and Movat pentachromestained histologic specimens. Unique 0.00120.0287-cm2 regions of interest were visually identified on quantitative T1, T2, MT, and IW maps of AIT, IXA, and PIT lesions. Distributions of T1, T2, MT, and IW values were compared with Student t and Wilcoxon two-sample tests.
Results: MR microscopic images of nonprogressive AIT and IXA lesions revealed two intimal layers. The luminal intima had higher T1 and T2 values and lower MT values than did the medial intima; these findings were consistent with compositional differences observed in histologic sections. In the IXA lesion, T2 values of both intimal layers were markedly reduced when compared with T2 values of AIT lesions because of the accumulation of lipid-laden macrophages in both layers. Progressive PIT lesions had a typical multilayered appearance or foci with a short T2 relaxation time and low IW values; these features were not observed in AIT or IXA lesions.
Conclusion: MR microscopy enabled identification of morphologic arterial wall features that enable discrimination of progressive PIT lesions from nonprogressive AIT or IXA lesions.
© RSNA, 2006
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