ABSTRACT
Objective To investigate the usefulness of different-b-value diffusion weighted imaging (DWI) in patients with early cerebral infarction and obtain the optimal b value of early cerebral infarction.Methods DWI at b-value of 1,000,2,000,and 3,000 s/mm2 was performed for 40 patients within 72 h after the onset of stroke using a GE Signa HDx 3.0T MRI scanner.Post-processing was done by the DWI specific software Function Tool to gain signal intensity and mean apparent diffusion coefficient in the lesions center and the contralateral normal brain tissue,respectively.The sensitivity of conventional MRI and different-b-value DWI was calculated in the diagnosis of early cerebral infarction.Results In 40 patients with early cerebral infarction,the sensitivity of b-values of 1,000,2,000,and 3,000 s/mm2 (DWIb=1 000,DWIb=2 000,DWIb=3 000) and conventional MRI in the diagnosis of early cerebral infarction were 100％,97.5％,97.5％,72.5％,respectively.With b value increased,signal intensity and ADC value declined.Under the condition of different b values,signal intensity and ADC value were statistically significant in region of interest (P＜0.05).Conclusion DWI is superior to conventional MRI scan in monitoring early cerebral infarction.With the increase of b value,the sensitivity is the higher to hyperacute cerebral infarction,the signal contrast is obvious,while signal to noise ratio of the image reduces.It is suggested that brain tissue contrast and the sensitivity to the new cerebral infarction is more predictable on b value =1,000 DWI than on the other DWIs.
ABSTRACT
Objective To assess the value of CT perfusion imaging in differentiation of mild from moderate liver fibrosis .Methods 18 patients with mild liver fibrosis (F1 phase) and 21 ones with moderate fibrosis (F2 and F3 phase) confirmed by liver biopsy were analyzed ,and all patients underwent the liver 256‐slice CT perfusion imaging .The differences in the CT parameters including hepatic arterial perfusion (HAP) ,portal venous perfusion (PVP) ,total liver perfusion (TLP) and time to peak (TTP) between dif‐ferent fibrosis were analyzed .ROC curve was used to evaluate the ability of perfusion indexes to distinguish mild from moderate liver fibrosis ,then the maximum Youden index was selected as a cutoff point to calculate the sensitivity and specificity .Results Compared with the mild fibrosis ,the TTP [(43 .86 ± 13 .41)s vs (37 .84 ± 9 .97)s ,P=0 .034)] in liver with moderate fibrosis was significantly increased .However ,no differences in the HAP ,PVP and TLP were found .The ROC curve analysis showed that a TTP threshold of 41 .7 s allowed discrimination of mild from moderate fibrosis with a sensitivity of 72 .7% and a specificity of 75% .Conclusion 256‐slice CT perfusion imaging can reflect the hemodynamic changes of liver fibrosis ,and the TTP may help to discriminate mild from moderate fibrosis .