| ObjectiveIschemic cerebral stroke (cerebral infarction) is very common in China, which has high occurrence rate, reoccurence rate and disability rate. It has been one of the main causes of death in our country. Imaging examination plays an important role in the diagnosis and prognostic evaluation in patients with ischemic stroke. Though conventional MRI is very helpful for the diagnosis of cerebral infarction, but it can not provide the hemodynamic information of ischemic tissue. Cerebral ischemic reperfusion (CIR) often occurs after the revascularization under the ischemia condition. Though early thrombolytic therapy could save the ischemic penumbra and reduce the degree and area of infarction, it may lead to hemorrhage which is recognized to be of great importance to clinical treatment. Therefore, to explore a technique that can simply and accurately assess the perfusion status and reperfusion injury in patients with ischemic stroke is very important for the diagnosis and therapy in patients with ischemia. As dynamic susceptibility contrast (DSC) MRI could detect the early perfusion abnormality of ischemic cerebral tissue, it has been widely used in stroke. But DSC has some technical limitations such as high-pressure injector and contrast agents are needed in DSC, which increase the technical difficulty and cost. Furthermore, DSC can not display the intracerebral hemorrhage accompanied with the cerebral stroke and the arterial thrombosis. Susceptibility-weighted imaging (SWI) is a new MR technique which is based on the high sensitivity to paramagnetic substances and blood oxygen level dependent (BOLD) effect. It can noninvasively display cerebral vein and detect microbleeds. Thus SWI has the potential in the diagnosis and therapy of cerebral ischemia. Our aim was to compare SWI and DSC in acute ischemia and investigate the value of SWI in assessing hemodynamic status of ischemic tissue and reperfusion injury.Methods46 patients (27 males,19 females, mean age 64 year) with acute ischemic stroke within 3 days of symptom onset were enrolled in this study. The conventional brain MRI (T1WI, T2WI, FLAIR and DWI), high-resolution SWI and DSC were performed on all subjects by using SIEMENS Trio Tim 3.0T MR scanner. The MR findings of the SWI and DSC were observed and compared. For qualitative analysis, MR findings of DSC were grouped into four categories (hypoperfusion, normal perfusion, delayed perfusion or hyperperfusion), while SWI findings were categorized into three types according to the changes of vein numbers (increased veins, decreased veins, normal veins) and signal intensity of the ischemic lesion. Mann-Whitney test was used for qualitative analysis. Three regions of interest (ROI) were defined in the diffusion-weighted imaging abnormalities and mirror regions in the contralateral normal brain tissues, respectively. Signal intensity ratios of infracted region to the normal contralateral region were calculated and compared by using a paired t test.ResultsIn 38 out of 46 patients, all DSC showed hypoperfusion, while SWI demonstrated veins reduction or disappearance in infarcted area and veins dilatation in peri-infarcted region in 32 patients, and vein reduction or disappearance in both infracted and peri-infarcted area in 6 patients; in the other 8 patients, DSC showed perfusion deficitin 3 cases, delayed perfusion in 2 and hyperfusion in 3 cases, while SWI showed normal in all the 8 cases. Qualitative analysis demonstrated there was no significant difference between the two techniques (Z=2.361, P>0.05). The mean signal intensity ratio infracted region to the normal contralateral region on DSC was 0.83±0.26, while SWI was 0.91±0.24, and no significant difference was revealed between the two techniques (t=0.729, P> 0.05). In addition, SWI detected hemorrhage in infracted region in 12 patients, and in peri-infarcted area in 6 patients, while conventional MRI and DSC didn't demonstrate the hemorrhage in all these patients.Conclusion1. Compared to DSC, SWI can noninvasively demonstrate the hemodynamic status of ischemic tissue and provide a new simple technique for evaluating brain perfusion status.2. The high-resolution SWI is sensitive in detecting hemorrhage in cerebral ischemic lesions, which is helpful for evaluating the degree of CIR and provides imaging evidence for reasonable treatment.3. SWI can be combined with routine MRI and provide more valuable information in the diagnosis, therapy and progronostic evaluation of acute cerebral ischemic stroke. |
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