Experimental Study Of The Brain Parenchymal Lesions In Acute Cerebral Venous Occlusion With Functional MRI And CT

Part â…  Modeling of acute experimental cerebral venous occlusion and evaluation with MR diffusion and perfusion weighted imagingObjective To improve the model of acute cerebral venous occlusion and establish a stable animal model to be similar to clinical disease; To evaluate the model with MR diffusion and perfusion weighted imaging (DWI and PWI) in observing the changing regularity of the brain parenchymal lesions. Methods Twenty-eight cats were randomly divided into 3 groups, including embolism group (n=18), ligation group (n=6) and sham operation group (n=4). Embolism group and ligation group were performed respectively by injection of the cellulose acetate polymer (CAP) solution into the superior sagittal sinus (SSS) and by ligation of the posterior part of the SSS. DWI and PWI were performed at an interval of 1, 3, 6, 12, 24 and 48h after operation. Brain parenchymal lesions were observed dynamically and compared with pathological changes. Results Sixteen cats in embolism group were operated successfully. In embolism group, nineteen lesions were detected on DWI mainly with hypointensity on exponential Apparent Diffusion Coefficient (eADC) maps in 10 cats. Lesions with hyperintensity or mixed with both hyperintensity and hypointensity were observed in 1 to 3 hours. The signal intensity was complicated in 12 hours; twenty-three abnormal perfusion regions were detected on PWI in 13 cats. Mean time to enhance (MTE) is prolonged, while regional cerebral blood volume (rCBV) could be increased, normal or decreased. Relative MTE (rMTE) of the central and marginal region prolonged slightly in 1,3,6h and prolonged obviously in 12h. Relative rCBV (rrCBV) of the central region in lesions decreased obviously in 6h, while rrCBV of marginal region decreased gradually in 12h and obviously in 24h. Relative rCBV of the central and marginal region in 6, 12, 24h showed significant difference (t₆=-5.73, t₁₂=-3.22, t₂₄=-4.22 respectively, P<0. 05). There were cast-like materials formed by CAP within SSS, bridging veins and cortical veins in 16 cats. The microscopic changes were mainly vasogenic edema and followed by venous hemorrhagic infarction in 12h. No abnormal findings were observed in ligation group and sham operation group. Conclusion Modeling of acute cerebral venous occlusion by injection of CAP solution into SSS is feasible. The model is suitable for pathophysiological and radiological studies of acute cerebral venous occlusion. DWI combined PWI has great value in judging the dynamic changes and the etiopathogenesis of brain parenchymal lesions in acute cerebral venous occlusion. Part â…¡ CT perfusion imaging in acute experimental cerebral venous occlusion: Comparison with diffusion and perfusion MR imagingObjective To evaluate a model of acute cerebral venous occlusion with CT perfusion imaging (CTPI) and to compare the value of CTPI with MR diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) in evaluating the brain parenchymal lesions. Methods Twenty-two cats were randomly divided into 2 groups, including operation group (n=18) and sham operation group (n=4). Acute cerebral venous occlusion was induced by injection of the cellulose acetate polymer (CAP) solution into the superior sagittal sinus (SSS). CTPI were performed at an interval of 1, 3, 6, 12, 24 and 48h after operation. The hemodynamic changes were observed in each group. Detection ratios of lesions, lesion volumes and the degree of brain parenchymal injury were compared with DWI and PWI. Results Abnormal cerebral blood flow perfusion regions were detected in 12 cats in operation group by CTPI. Regional cerebral blood volume (rCBV) increased, regional cerebral blood flow(rCBF) decreased and mean transit time (MTT) prolonged slightly in the lesions in 1h. Both rCBV and rCBF decreased in the center of the lesions, while rCBV increased, normal or decreased, rCBF decreased in the marginal region in 3-6h. rCBV and rCBF decreased obviously both in the central and marginal regions in 12²4h. No abnormal changes were observed in sham operation group. CTPI detected 20 lesions in 12 cats, while DWI detected 19 lesions in 10 cats, PWI detected 23 abnormal perfusion regions in 13 cats. The lesion volumes on PWI mean time to enhance (MTE) maps showed no significant difference with that on CTPI-rCBF (t=1.54, P>0.05). The evaluation of the degree of brain parenchymal injury on PWI and CTPI-rCBV showed good consistency (Kappa=0.69, P<0.01). Conclusion CT perfusion imaging is accurate and sensitive in evaluating hemodynamics of acute cerebral venous occlusion and is useful in the early evaluation of the consequences for brain parenchymal lesions. DWI and PWI have good consistency with CTPI in judging the brain parenchymal lesions in acute cerebral venous occlusion.Part â…¢ Experimental study of the brain parenchymal lesions in acute cerebral venous occlusion with magnetic resonance spectroscopyObjective To evaluate the value of magnetic resonance spectroscopy (MRS) in observing the dynamic metabolic changes of the brain parenchymal lesions in acute experimental cerebral venous occlusion. Methods Thirty cats were randomly divided into 2 groups, including operation group (n=24) and sham operation group (n=6). The modeling of acute cerebral venous occlusion in operation group was performed by injection of the cellulose acetate polymer (CAP) solution into the superior sagittal sinus (SSS). MRS was continually performed at an interval of 1, 3, 6, 12, 24 and 48h after operation for each group to observe the brain parenchymal lesions. The metabolic concentrations of N-acetylaspartate (NAA), Choline (Cho), Creatine (Cr), Lactate and Lipid (LL) and their ratios of NAA/Cr, Cho/Cr, LL/Cr were analyzed. The metabolite in the central, marginal regions of the lesions, peripheral regions adjacent to the lesions and the contralateral normal side were measured and the statistical results were analyzed. Results In operation group, abnormal signal regions were detected on conventional MRI and DWI in 15 cats, NAA, Cho, Cr in the center of the lesions were decreased in 3h, while NAA, Cho in the marginal regions were decreased in 6h, Cr decreased in 12h, LL in the center and marginal regions increased obviously in 1h and decreased gradually later. NAA/Cr, Cho/Cr, LL/Cr in the center and marginal regions showed statistical difference over the time period of measurement (F=5.14 and 3.09, 9.90 and 5.62, 9.16 and 3.35, P<0.05). LL/Cr in the peripheral regions adjacent to the lesions increased obviously in 1h and 3h. NAA/Cr between the center and marginal regions showed statistical difference in 3, 6, 12h (t=-3.15, -3.66, -2.75 respectively, P<0.05). LL/Cr between the center and marginal regions showed statistical difference in 1, 3, 6h (t=5.37, 4.47, 2.40 respectively, P<0.05). No abnormal findings were detected on conventional MRI and DWI in 9 cats in operation group. MRS curve showed symmetry both sides and no obvious LL peak observed in all time point. Pathologic examination showed the lesions were mainly vasogenic edema, followed by necrosis with venous hemorrhagic infarction in 12h. No abnormal changes were observed in sham operation group. Conclusion A reduction of NAA, Cho, Cr and significant increase of LL are the main characteristic of the brain parenchymal lesions and MRS has great value in investigating the changes of the metabolites and the pathogenesis of the brain parenchymal lesions in cerebral venous occlusion.Part â…£ The preliminary application of MR diffusion tensor imaging and fiber tractography in acute experimental cerebral venous occlusionObjective To evaluate a model of acute cerebral venous occlusion with MR diffusion tensor imaging (DTI), and to evaluate the value of DTI in observing diffusion regularity of the brain parenchymal lesions and the integrity of white matter fiber tracts. Methods Thirty cats were randomly divided into 2 groups, including operation group (n=24) and sham operation group (n=6). Operation group were performed by injection of the cellulose acetate polymer (CAP) solution into the superior sagittal sinus (SSS). Conventional MRI and DTI were continually performed at an interval of 1, 3, 6, 12, 24 and 48h after operation for each group to observe the brain parenchymal lesions, parametric maps were reconstructed, average diffusion coefficient (AvgDC) and fractional anisotropy (FA) were measured in the lesions and calculated the ratio to the contralateral corresponding regions, the integrity and connectivity of white matter tracts were showed by fiber tractography (FT). Pathology examination were compared with MR data. Results In operation group, the brain parenchymal lesions were detected in 15 cats. Compared with contralateral corresponding regions, AvgDC values decreased in 1h, increased in 3h and increased obviously in 12h. FA values were decreased in all time point after operationon. AvgDC and FA of the lesions and the contralateral corresponding regions showed significant difference (P<0.005). The AvgDC ratio and FA ratio showed significant difference (F=62.07 and 9.37 respectively, P<0. 05). FT showed displayment of white matter fiber tracts and running through the lesions in 1h, damage or disruption in 6h and breaking in the edge of the lesions in 12h. Pathologic examination showed the lesions were cytotoxic edema in 1h, mainly vasogenic edema in 3h, followed by necrosis with venous hemorrhagic infarction in 12h. No abnormal changes were observed in sham operation group. Conclusion DTI can clearly depict and assess quantitatively the dynamic changes of brain parenchymal lesions in acute cerebral venous occlusion, FT is better in displaying damage or displacement of white matter fiber tracts than conventional MRI.