[Results of magnetic resonance imaging in the acute phase of cerebral infarction]. / Résultats de l'imagerie par résonance magnétique a la phase aiguë de l'infarctus cérébral.

ABSTRACT

Brain ischemia is now possible to trace through the multiple facets of MRI, morphological as well as functional. Experimental studies have been conducted for many years and clinical feasibility is reached. Although the initial decrease in blood flow does not influence morphological imaging, this early phase is shown with functional MRI, either with diffusion imaging or with cerebral blood volume imaging. The later is achieved either with the calculation of the integral of the first passage of a bolus of a diffusible paramagnetic agent or with the circulation of positive or negative blood pool contrast agents. This may serve to confirm an early diagnosis before inclusion in therapeutic trials. Immediate metabolic changes are reflected on phosphorus and proton spectroscopy achievable during the same session as imaging. This type of information may at this stage serve as a reference. It allows observation of the turnover of lactate over time in the lesion and the neuronal loss shown by decreased N-acetyl-aspartate. Edema, as a reaction to ischemia, builds up over time and has already been described for long as it modifies T1- and T2- weighted sequences. Similarly the breakdown of the blood-brain barrier is well known on conventional sequences because it produces contrast enhancement.