The Investigation Of DWI Evolution Of Brain Ischemia Penumbrain Hyperacute And Acute Stages

[Objective] The incidence of cerebral infarction (CI) accounted for 75 percent of ischemic vascular diseases, which has severely threatened personal health and life quality for its high mortality and disability incidence. Early diagnosis and treatment were important to prognosis. In this study, CI with different time of attack were collected. MR DWI was performed in all the cases, and DTI were performed in some cases. Our purpose is to study the role of different sequences in hyperacute cerebral infarction and their values of diagnosis of CI with different time of attack, and to identify the present time window and range and ischemic penumbra (IP).[Materials and Methods] From January in 2005 to March in 2006, 35 cases of hyperacute and acute CI proved by MRI were collected. CT examination was performed to exclude hemorrhage. The diameters of maximum lesion acreage on DWI were all higher than 1.5 cm. The follow-up examinations were performed until 3 day. So the total examination times were 67.According to the time of attack, 67 cases with acute cerebral infarct were divided into six groups:â‘ <3h, n=7;②≥3h^<6h, n=6;(3)≥6h <12h, n=12;④≥ 12h^<24h, n=21;(⑤≥24h^<48h, n=7;⑥≥48h⁷2h, n=14. Conventional MR scan, including axial and saggital T₁WI and axial and coronal T₂WI, and axial DWI were performed in all the cases. Follow-up MRI examinations were performed until 48h after the time of attack in all the patients with hyperacute CI. Four region of interest (ROI) were measured on DWI. Parameters measured included apparent diffusioncoefficient (ADC) and exponential apparent diffusion coefficient (EADC). Point a, b and c were located within the high signal intensity region. Point a was infarct core, i.e. the highest diffusion-limited region, Point c was infarct margin, and Point b was the midpoint between Point a and c. Point d demonstrated normal signal intensity just adjacent to high signal intensity. The relative ratios between infarct lesions and collateral normal brain were calculated to avoid location error. So relative ADC (rADC) and relative EADC (rEADC). Statistical analysis was performed by SPSS 11.0 software package, t test and ANOVA were used within each group and among different groups. Differences were considered statistically significant at P less than 0.05.[Results]1. General evolution on DWIThe ischemic lesion showed high signal intensity on DWI in each group. With the duration of time, the range of lesion became larger and larger, and the margin of lesion became clearer and clearer. The ADC values of lesions were lower than that of normal brain tissue. The degree of decreasing in infarct margin was lower than that in infarct core. The ADC value in infarct periphery was slightly lower than that of normal brain tissue. The color and range of infarct lesion on ADC map changed correspondingly.2. rADC changes of different time within each groupThe rADC of Point d statistically differed from those of Point a, b and c within each group (P<0.05). There were significant differences of rADC among Point a, b and c from 3h to 24h (P<0.05), but there were no significant difference of rADC among them after 24h (P>0.05). This results suggested infarct margin evoluted just the same as infarct core progressively. The results of rEADC were similar to those of rADC.3. Compare between DTI and DWIAll the cases showed abnormal signal intensity on DCavg map, and the range of lesion on it was equal to that on DWI. The lesion also showed abnormal signal intensity on FA, RA and 1-VR map, but the margin was unclear. [Conclusion]1. In hyperacute and acute CI, the diffusion of water molecule was remarkably lower than that in normal brain tissue, but it was different between infarct core and infarct margin. In acute CI, there were significant differences of the diffusion-limited degree between infarct core and infarct margin, suggesting infarct margin may be IP. And the time window may be until 24h.2. The area adjacent to infarct lesion showed normal signal intensity on DWI but with slightly limited diffusion, and would be present from acute stage to 3 days after the time of attack. When the range of infarct lesion enlarged, this region also had IP. But when the range of infarct lesion was relative stable, this region may be benign oligemia.3. The Creative points: For the first time to trace hyperacute and acute CI by DWI in order to observe the range and evolution of IP.