| Background and objective:With the development of MRI equipment, MRI examination has been improved from simple conventional morphology examination to functional examination. Functional MRI is the focus of the current imaging research, which plays an important role for the evaluation in the procedure of diagnosis and treatment of cerebrovascular diseases. Although DSA is the most accurate tool for evaluating cerebral blood vessel,, it only demonstrate structural changes of cerebral blood vessels and can't evaluate brain morphology and function which are vitally important to make treatment plan and to evaluate treatment effect. MRI examination, especially functional MRI, including MR diffusion weighted images (MR DWI) and perfusion weighted images(MR PWI), DWI could compensate the shortage of DSA imaging, which not only could demonstrate the morphological and pathological of brain tissue but also could evaluate cerebral water molecules diffusion and cerebral blood microcirculation state for patients with cerebrovascular diseases in the micro leve. DWI could detect early brain infarction and display its dynamic changes, which have important clinical significance in qualitative and quantitative diagnose of the acute cerebral infarction. PWI examination scan can finish in a very short time, which could show the whole cerebral perfusion during the first pass through the whole brain. At present, it is the best imaging way for evaluating cerebral hemodynamics of patients. DWI combining PWI should have important clinical significance for evaluation in pre-and post-Interven-tional treatment of cerebrovascular diseases.But now there is few studies to be reported about this issue. In our study, DWI, PWI techniques in high tesla MRI unit are used before and after intracranial endovascular stenting, to prospectively analyze the value of fMRI in selecting the operation indication before treatment and assessing the improment and recovery of cerebral blood perfusion after the operation.Material and method:1. Patients selection:28 patients who were not only diagnosed as unilateral MCA stenosis by DSA but also had MCA supply area infarction were selected. All the patients underwent MRI scan. Six of them were excluded from the study because they were suspected as arteritis and received conservative treatment with drugs. The other 22 patients with atherosclerosis finally conducted MCA stenting were chosed as study population.2. examination and therapeutic method:2.1 Preoperative examination:the time intervals from the last recurrence time to MRI examination are as follows:the shortest time were seven hours, the longest time 48 hours, the median time 20 hours. The routine MRI,DWI,MRA and PWI examinations were taken using Siemens 3.0 T Trio Tim MR scanner. Before the operation all the patients had whole brain DSA under local anesthesia. Adopting Seldinger technique, put duct through femoral artery to bilateral internal carotid arteries super-selectively to acquire whole brain angiography.2.2.Therapeutic method:the time intervals from stenting treatment to MRI examination are as follows:48 hours to 96 hours reexamination in th 22 patients and the median time got 65 hours. All the patients acquired intracranial endovascular stenting under general anesthesia promulgation and Wingspan stents were layed aside in the narrow section, after confirming the position right the stents were released.2.3.Postoperative examination:Routine MRI,DWI,MRA and PWI examinations were taken using the same protocols as preoperative examinations.2.4.Image post-processing:The original PWI images were processed by perfusion software provided by Siemens super post-processing working station. Based on the routine MRI images,regions of interest(ROIs) in the parts of the frontal lobe, temporal lobe, basel gangalia and the parietal lobe were selected respectively, then the same size ROIs were chosed using mirror method in the contralateral normal-appearing brain hemisphere. The ROIs did not include the regions of old cerebral infarction. The area of ROI was 0.16cm2 and perfusion parameters of each ROI were compared with the corresponding parameter in cerebellum to acquire relative cerebral blood volume(rCBV),relative cerebral blood flow(rCBF),relative meantransit time (rMTT) and time to peak (TTP).The parameters change before and after the operation were compared quantitatively. The averages of parameters in ROIs of each person before and after interventional operation were calculated respectively, then averages of these parameters of all the 22 patients were calaculated which would be used as analysis parameters to precisely compare the changes between before and after the operation.3.Statistical methods:All the data was analyzed by SPSS 16.0 software package. Data was showed as average±SD, and the perfusion change before and after operation was analyzed by match t test analysis. P<0.05 has statistically significant difference.Results:1. MRI results of preoperation:1.1 Results of conventional MRI:28 patients with middle cerebral artery stenosis who were confirmed by DSA were all displayed on MRA images,22 atherosclerosis patients of them have cerebral infarction of ipsilateral blood-supply territory of middle cerebral artery, including 10 patients located in temporal lobe,5 in temporal occipital lobe and 7 in occipital lobe.1.2 Results of fMRI:15 patients showed acute cerebral infarction on DWI imagesand 7 showed subacute or chronic infarctions. All of 22 patients had abnormal perfusion findings on PWI images, mainly including rMTT and TTP prolonged. Quantitative analysis displayed:blood supply of narrow vessel PWI rCBV average was 1.20±0.18,rCBF was 1.47±0.51, rMTT wasl.26±0.49,TTP was 1.15±1.03.2. MRI results of postoperation:2.1.Results of conventional MRI:22 patients who were performed by stenting, the acute cerebral infartion had became to subacute phase on plain MRI images.2.2.Results of fMRI:2 new cerebral infarction were displayed on DWI images, the PWI images show changes:the extension of MTT, TTP induced. Quantitative analysis displayed:blood supply of narrow vessel:PWI rCBV average was 1.20±0.24, rCBF was 1.48±0.06, rMTT was 1.09±0.05, TTP was 1.06±0.54.3. Compared MRI results between preoperation and postoperation:3.1.Results of conventional MRI:the acute cerebral infartion had became to subacute phase on plain MRI images.3.2.Results of fMRI:Compared with preoperation on DWI images,2 patients diplayed acute cerebral infartion. The perfusion improved on PWI images:the extension of MTT, TTP induced. Quantitative analysis displayed:in the blood supply area of narrow vessel the average rCBV values were 1.13±0.32 and 1.21±0.24,respectively, before and after the operation, and there was no significance difference (p=0.560>0.05) between the average rCBV values between pre-and post-operration; the average rCBF values were 1.47±0.51 and 1.48±0.06, respectively, before and after the operation, and there was no significance difference (p=0.085>0.05) between the average rCBF values between pre-and post-operration; the average rMTT values were 1.26±0.49 and 1.09±0.05, espectively, before and after the operationaverage, and there was significant difference (p=0.000<0.05) between the average rMTT values between pre-and post-operration; the average TTP values were 1.15±1.03 and 1.06±0.54, respectively before and after the operation, and there was significant difference(p=0.001<0.05) between the average TTP values between pre-and post-operration.Conclusion:1. The conventional and functional MRI examinations before treatments could make sense in selecting interventional treatment indications for those patients with symptomatic intracranial artery stenosis.2. DWI combining conventional MRI before operation could confim the extents, sizes and phases of cerebral infartion for patients undergoing interventional treatment for cerebral arterial stenosis and whether new infarction lesions occur after the operation. PWI could showed the blood microcirculation perfusion ischemic conditions at the stenosed vessel supply brain regions before operation, and evaluate the perfusion improvement conditions at the stented artery blood supply areas after postoperatively3. Intracranial endovascular stenting could remarkably improve rMTT and TTP in the ischemic brain area. However, rCBV and rCBF could not get obvious improvement during a short time after treatment. |
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