This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Green, H. A.L. Articles by Gillard, J. H. Search for Related Content PubMed PubMed Citation Articles by Green, H. A.L. Articles by Gillard, J. H. Pubmed/NCBI databases Medline Plus Health Information MRI Scans Stroke Related Collections Acute Cerebral Infarction Imaging Computerized tomography and Magnetic Resonance Imaging

(Stroke. 2002;33:1517.)
© 2002 American Heart Association, Inc.

Original Contributions

Increased Anisotropy in Acute Stroke

A Possible Explanation

Hadrian A.L. Green, MB ChB; Alonso Peña, PhD; Christopher J. Price, BSc, MRCP; Elizabeth A. Warburton, MRCP, DM; John D. Pickard, MS, FRCS, FMedSci; T. Adrian Carpenter, PhD Jonathan H. Gillard, BSc, MD, FRCR

From the Departments of Neurosurgery (H.A.L.G., A.P., J.D.P., T.A.C.), Engineering (A.P.), Neurology (CJ.P., E.A.W.), and Radiology (J.H.G.) and the Wolfson Brain Imaging Centre (H.A.L.G., A.P., J.D.P., T.A.C., J.H.G.), Addenbrooke’s Hospital and the University of Cambridge, Cambridge, UK.

Correspondence to Dr H.A.L. Green, The Wolfson Brain Imaging Centre, Box 65, Addenbrooke’s Hospital, Cambridge CB2 2QQ, UK. E-mail halg2{at}wbic.cam.ac.uk

Background and Purpose— The increase in fractional anisotropy (FA) in acute stroke has yet to be explained. Using an engineering methodology known as pq diagrams, we sought to explain the increase in FA by describing changes in the total magnitude of the diffusion tensor (L) as well as the isotropic (p) and anisotropic (q) components.

Methods— Diffusion tensor imaging was performed in 10 patients with stroke <27 hours old. The diffusion tensor was decomposed into the p and q components and plotted to describe the diffusion trajectories. FA was also calculated and compared.

Results— There was significant and consistent reduction in p, q, and L (p: mean, -50.0%; range, -36.6% to -64.5%; q: mean, -50.8%; range, -30.8% to -72.8%; L: mean, -50.3%; range, -37.0% to -65.1%). There were inconsistent changes in FA (mean, -0.5%; range, -44.9% to +45.0%). Five patients had elevated FA due to proportionately higher loss of L than q.

Conclusions— Changes in FA only occur when there is a change in the ratio of q/L. Acute elevation of FA occurred in the context of a larger reduction in L than q. The elevation in FA occurs in the context of a reduction in the anisotropic tensor and therefore is a consequence of ratio-metric measurement. This appears to clarify the reported increase in FA in terms of alterations in the shape of the apparent diffusion tensor. pq diagrams appear to offer improved resolution of acute diffusion changes in ischemia.

Key Words: diffusion • magnetic resonance imaging • stroke

This article has been cited by other articles:

				E. A. Wilde, S. R. McCauley, J. V. Hunter, E. D. Bigler, Z. Chu, Z. J. Wang, G. R. Hanten, M. Troyanskaya, R. Yallampalli, X. Li, et al. Diffusion tensor imaging of acute mild traumatic brain injury in adolescents Neurology, March 18, 2008; 70(12): 948 - 955. [Abstract] [Full Text] [PDF]

				S.J. Price, R. Jena, N.G. Burnet, P.J. Hutchinson, A.F. Dean, A. Pena, J.D. Pickard, T.A. Carpenter, and J.H. Gillard Improved Delineation of Glioma Margins and Regions of Infiltration with the Use of Diffusion Tensor Imaging: An Image-Guided Biopsy Study. AJNR Am. J. Neuroradiol., October 1, 2006; 27(9): 1969 - 1974. [Abstract] [Full Text] [PDF]

				J. V. Guadagno, E. A. Warburton, P. S. Jones, D. J. Day, F. I. Aigbirhio, T. D. Fryer, S. Harding, C. J. Price, H. A. Green, O. Barret, et al. How affected is oxygen metabolism in DWI lesions?: A combined acute stroke PET-MR study. Neurology, September 12, 2006; 67(5): 824 - 829. [Abstract] [Full Text] [PDF]

				J. V. Guadagno, P. S. Jones, T. D. Fryer, O. Barret, F. I. Aigbirhio, T. A. Carpenter, C. J. Price, J. H. Gillard, E. A. Warburton, and J.-C. Baron Local Relationships Between Restricted Water Diffusion and Oxygen Consumption in the Ischemic Human Brain Stroke, July 1, 2006; 37(7): 1741 - 1748. [Abstract] [Full Text] [PDF]

				A Pena, H A L Green, T A Carpenter, S J Price, J D Pickard, and J H Gillard Enhanced visualization and quantification of magnetic resonance diffusion tensor imaging using the p:q tensor decomposition Br. J. Radiol., February 1, 2006; 79(938): 101 - 109. [Abstract] [Full Text] [PDF]

				R. K. Gupta, K. M. Hasan, A. M. Mishra, D. Jha, M. Husain, K. N. Prasad, and P. A. Narayana High Fractional Anisotropy in Brain Abscesses versus Other Cystic Intracranial Lesions AJNR Am. J. Neuroradiol., May 1, 2005; 26(5): 1107 - 1114. [Abstract] [Full Text] [PDF]

				C. van Pul, J. Buijs, M. J. A. Janssen, G. F. Roos, M. T. Vlaardingerbroek, and P. F. F. Wijn Selecting the Best Index for Following the Temporal Evolution of Apparent Diffusion Coefficient and Diffusion Anisotropy After Hypoxic-Ischemic White Matter Injury in Neonates AJNR Am. J. Neuroradiol., March 1, 2005; 26(3): 469 - 481. [Abstract] [Full Text] [PDF]

				J. Konishi, K. Yamada, O. Kizu, H. Ito, K. Sugimura, K. Yoshikawa, M. Nakagawa, and T. Nishimura MR tractography for the evaluation of functional recovery from lenticulostriate infarcts Neurology, January 11, 2005; 64(1): 108 - 113. [Abstract] [Full Text] [PDF]

				A. S. Field, K. Hasan, B. J. Jellison, K. Arfanakis, and A. L. Alexander Diffusion Tensor Imaging in an Infant with Traumatic Brain Swelling AJNR Am. J. Neuroradiol., August 1, 2003; 24(7): 1461 - 1464. [Abstract] [Full Text] [PDF]