Purpose:To investigate the utility of functional and morphological magnetic resonance imaging (MRI) to assess the extent of brain injury in a hypoxia-ischemia (HI) piglet model and further to validate that the desired ischemic injury was successfully induced. Materials and Methods:MRI was performed at 1.5 T in anesthetized piglets (N ϭ 10, age ϭ 12-36 hours). Relative cerebral blood flow (rCBF), time-to-peak (TTP) contrast, and apparent diffusion coefficient (ADC) were estimated at different time points pre-, during, and post-HI. The effect following bilateral clamping of the carotid arteries was assessed by contrast-enhanced MR angiography (MRA) and phase contrast MR angiography (PCA) (N ϭ 4). Results:A linear correlation was observed between relative cerebral perfusion reduction and cerebral ADC during HI (r 2 ϭ 0.85, P Ͻ 0.05). There was no correlation between rCBF reduction during 30 minutes of HI and cerebral ADC after 30 or 150 minutes of reperfusion/reoxygenation (RR). Conclusion:The combination of morphological and functional (perfusion and diffusion) MRI enabled consistent assessment of both the presence and absence of complete occlusion as well as the functional significance of the occlusion. WITH THE ADVANCES IN REPRODUCTIVE and neonatal intensive care, clinicians are now confronted with an increasing number of surviving high-risk newborns that suffer from considerable neurologic morbidity that is often associated with lifelong handicaps (1). New diagnostic tools are therefore needed to detect early brain injury and monitor interventions aimed at minimizing or preventing irreversible brain injury. Magnetic resonance imaging (MRI) is an attractive diagnostic modality in the developing brain because of the high contrast resolution of this technique combined with its relative noninvasiveness (2). MR perfusion and diffusion imaging have proved to be sensitive tools for early detection of brain injury (3-5).The piglet model is commonly used in medical research, due to its similarities to the human brain (6). Studies have shown that the gray/white matter distribution, changes in brain morphology during development, and sequence of nervous system maturational changes are comparable for pigs and humans. Also, the overall shape and gyral pattern of the piglet brain are similar to those of the human's (7,8).The availability of a well-controlled piglet model is of great importance for many types of studies aimed at investigating neonatal injury due to hypoxia-ischemia (HI). Such a model requires a sensitive method to assess the degree of functional changes caused by the induction of HI. Another important aspect is to have a sensitive imaging method to validate that total carotid occlusion has indeed been achieved. This was performed by MR angiography (MRA). Such a combined functional (perfusion and diffusion) and morphological (tissue and vessel anatomy) assessment can now be provided by MRI using novel imaging methods combined with new MR contrast agents. In the current study, we have utilized an intravascular ...
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