Anisotropic water diffusion in white and gray matter of the neonatal piglet brain before and after transient hypoxia-ischaemia.
Measurements of tissue water apparent diffusion coefficient (ADC) performed with diffusion sensitization applied separately along the x, y, and z axes revealed significant diffusion anisotropy in both cerebral white and gray matter in six newborn (< 24 h old) piglets. Mean baseline white matter ADC for a particular region of interest was 125.8% (SD 32.0%; p < .001) greater when the diffusion gradients were applied along the y axis as compared to along the x. For the cortical gray matter region considered, the situation was reversed, the mean ADC value measured along x exceeding that along y by 15.2% (SD 6.1%; p < .01). Forty-three hours subsequent to a transient cerebral hypoxic-ischaemic insult, phosphorous MRS measurements indicated that the animals had suffered severe secondary cerebral energy failure. This was accompanied by a significant (p < .01) decrease in the white matter anisotropy, such that the mean y direction ADC now exceeded that along the x by only 70.9% (SD 29.4%; p < .03). There was no change in the gray matter anisotropy. The average of the ADC values measured in the x, y, and z directions had decreased by 35.3% (SD 18.5%; p < .01) in white matter and 31.4% (SD 21.9%; p < .05) in cortical gray matter. Diffusion anisotropy measurements may provide additional information useful in the characterisation of hypoxic-ischaemic injury in the neonatal brain, and must be considered if tissue water ADC values are to be unambiguously interpreted in this context.
Thornton
J S
JS
Department of Medical Physics and Bioengineering, University College London, UK.
Ordidge
R J
RJ
Penrice
J
J
Cady
E B
EB
Amess
P N
PN
Punwani
S
S
Clemence
M
M
Wyatt
J S
JS
D000818:Animals; D000831:Animals, Newborn; D016880:Anisotropy; D001238:Asphyxia Neonatorum / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D002534:Hypoxia, Brain / Q000378:metabolism* / Q000473:pathology; D007231:Infant, Newborn; D002546:Ischemic Attack, Transient / Q000378:metabolism* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D013552:Swine