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(Stroke. 2008;39:2348.)
© 2008 American Heart Association, Inc.

Original Contributions

Characterization of White Matter Injury in a Hypoxic-Ischemic Neonatal Rat Model by Diffusion Tensor MRI

Silun Wang, MPhil; Ed X. Wu, PhD; Chung Nga Tam, MPhil; Ho-Fai Lau, MPhil; Pik-To Cheung, FRCR Pek-Lan Khong, FRCR, MD

From the Department of Diagnostic Radiology (S.W., C.N.T., P.-L.K.), The University of Hong Kong; the Laboratory of Biomedical Imaging and Signal Processing, Department of Electrical and Electronic Engineering (E.X.W., H.-F.L.), The University of Hong Kong; and the Department of Pediatric and Adolescent Medicine (P.-T.C.), The University of Hong Kong, Hong Kong.

Correspondence to Pek-Lan Khong, Department of Diagnostic Radiology, The University of Hong Kong, Blk. K, Room 406, Queen Mary Hospital, The University of Hong Kong, 102 Pokfulam Rd, Hong Kong. E-mail plkhong{at}hkucc.hku.hk

Background and Purpose— We evaluate white matter (WM) injury after hypoxic-ischemic (HI) insult in a neonatal rat model using diffusion tensor imaging (DTI) to determine whether _|| and are able to characterize type and severity of brain damage.

Methods— Eighteen 7-day-old Sprague-Dawley rats underwent unilateral ligation of left common carotid artery followed by 50 minutes (n=9) or 90 minutes (n=9) of hypoxia at 37°C. Rats were divided into 2 groups, according to absence (group A, n=11) or presence (group B, n=7) of cystic lesions on D7 post-HI T2-weighted imaging. DTI was performed for all rats at D1 and for group A rats at D7 post-HI. Signal intensity of ipsilateral and contralateral external capsule (EC) on D1 was compared by paired t test, with histological correlation.

Results— Group A rats had significantly reduced FA, elevated trace, elevated _, and similar _|| on D1 in the ipsilateral compared to contralateral EC, whereas group B rats had significant reduction in all parameters in the ipsilateral EC. Elevated trace normalized on D7 in group A rats. Histopathologic results demonstrated reduced myelination in group A noncystic HI and severe necrosis in group B cystic HI.

Conclusions— Increased with no significant change in _|| appears to characterize noncystic WM injury with reduced myelination, whereas reduction in both _|| and characterize severe damage with loss of structural integrity and necrosis. Combining with FA and trace, _|| and provide additional information which reflects type and severity of HI injury.

Key Words: MRI • diffusion tensor imaging • white matter • neonatal rat • hypoxic-ischemic

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