MRI Perfusion Findings in Acute Cerebral Infarction and Perfusion Parameters Used in the Evaluation Penumbra

Abstract

Objective: In this trial, our objective is to emphasize the importance of the magnetic resonance perfusion in the early diagnosis and therapy of cerebral ischemia and to discuss the reliable perfusion maps for identifying peunumbra.

Material and Methods: Participants of this trial have been selected among patients who applied to the Ege University Radiology Department with cerebrovascular event and had an acute infarct which was diagnosed by MR. Among 20 of these patients, dynamic suceptibilite contrast (DSC) imaging with 1.5 T MR Magnetom Vision, Siemens, Erlangen, Germany) was performed with standart head bandage. At contrast perfusion imaging a bolus of 0.1 mmol/kg Gadolinium was injected by a speed of 3ml/sec. Multishot echoplanar imaging (EPI) imaging was performed for determining the changes at T2* relaxation time. The DSC perfusion parametres and function maps were obtained and eveluated at the postprocessing stage. The precence of penumbra was diagnosed by comparing the perfusion maps with difusion images.

Results: Seventy nine percent of the patients had a lesser degree of cerebral blood volume (CBV) and cerebral blood flow (CBF) at the infarcted area then contrary hemisphere but at 11% of the patients there was no difference with contrary hemisphere. Five percent of the patients had remarkable blood flow increase. This was thought to be cause of the important role of the brain's autoregulation function. There was an expected delay at 90% of the patients in contrast passing time and peak time. By comparing the diffusion with perfusion maps, the penumbra was diagnosed at 4 patients by mean transit time (MTT) and time to pic (TTP) maps, at 3 patients by CBF map and at 1 patient by CBV map.

Conclusion: The early diagnosis and evaluation of acute ischemic stroke, improves the patients' quality of life. The perfusion MR has a pathfinder role in the diagnosis and therapy of acute infarct. Penumbra is a dynamic tissue and the treatment after the early identifying of the penumbra, defines the patients prognosis. The most reliable perfusion map for determining the penumbra is controversial and much more trials are need to be done about this subject. According to recent trials and our investigation, the penumbra area seems to be larger which is determined by using the TTP and MTT maps. This condition is due to the exaggerated appearance of the ischemic penumbra secondary to the benign oligemia with severe arterial occlusive changes. In the literature the most reliable maps are relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) maps for demonstrating the last infarct area and our findings are also in the same way.