ABSTRACT
The purpose of the study to evaluate the role of diffusion and perfusion functional MRI in evaluation of the hyperacute and acute stroke patients and the benefit of each examination and what can add. One hundred thirty patients with clinical suspicion of ischemic brain lesions selected to this study. DWI was performed, Fluid Attenuation Inversion Recovery [FLAIR] WI and T2WI sequences also done for comparison with the DWI; three-dimensional time of flight [3D-TOF] magnetic resonance angiography [done in 86 patients] and perfusion-weighted images were obtained following administration of a bolus of gadolinium [done in 31 patients]. PWI images and color maps [rCBV, TTP, MTT] were generated. Patients were classified according to the onset of the ischemic lesions into: Hyperacute ischemic infarction Time period: Group I [< 6 hours from the onset], group II [patients presented at 6- 24 hours]. and group III [presented from 1[st] to the 7[th] days from the onset] DWI b1000 showed the ischemic lesions as a bright signal in all cases [of the group I], with sensitivity of 100% for detection of the ischemic lesions, while FLAIR sequence showed faint hyperintense signal in 13 cases and no lesions detected in 16 patients with a sensitivity of 44.8% for detection of the ischemic lesions. MRA detect no abnormalities in 13 cases while diffuse atherosclerotic changes were found in 39.2% of patients [51 patients]. Perfusion study was done only in 17 cases of the 1[st], in 7 cases of the 2[nd] group and in 7 cases of the 3[rd] group. We have only one patient with mild affection of the penumbra [TTP delay from the normal state of perfusion was less than 4 seconds while rCBV was normal], this patient received thrombolytic therapy with good response. Six patients with moderate affection of the penumbra [The TTP delay was between 4-6 seconds; one with decreased rCBV and 5 cases with average rCBV] Five of them showed good response after thrombolytic therapy. Comparison of the size of the lesions of the group [I] patients by perfusion and diffusion study revealed: Seven cases with PI and DWI of the same size; two of them were with increased regional cerebral blood volume, one with mild TTP delay, and the other with marked TTP delay. The remaining five cases presented with no change of cerebral blood volume; two of them with mild TTP delay and the remaining three cases with no TTP delay. Two patients presented with small lesion in DWI with no associated PWI defect and patients received only supportive measures and complete recovery occurred within 24 hours and diagnosed as TIA. Information obtained by MRI about an ischemic lesion is so extensive and a single early MRI study is all that most patients presenting with stroke syndrome will need. The ability of DWI to identify areas of cerebral ischemia and infarction within hours of their presentation, with sensitivity reaching 100%. Perfusion-weighted imaging [PWI] provided an answer to a fundamental question prior to initiation of treatment: is the ischemic brain parenchyma already reperfused, insufficiently perfused, or completely avascular. PWI measures the seventy of ischemia and accurately differentiates irreversibly injured core from penumbral, salvageable tissue. Earlier and more accurate diagnosis by MRI methods will reduce costs arising from diagnostic error and treatment delay