| Background and PurposeHydrocephalus is a common neurological condition characterized by dilation of the cerebral ventricles and (or) subarachnoid, usually caused by obstruction of cerebrospinal fluid (CSF) flow. The purpose of this study is to visualize the enlargements of ventricular system of hydrocephalus and seek an optimized method to evaluate the severity of ventricular enlargement by using high-resolution MRI and voxel-based computional image analyses.Materials and methodsEighteen adult mongrel dogs(12-15kg, nine male and nine female) were used for this study. To induce hydrocephalus,0.5ml/kg of 25% sterile kaolin suspension was injected into the cisterna magna. The high resolution thin images of the canine brain were acquired at 3.0 Tesla MRI scanner, which were transferred for postprocessing analyses.A set of templete of animal's cerebral tissues were established, based on it the whole brain and ventricular system were segmented by SPM software, and the volumes of.the canine whole brain (gray matter, white matter, CSF) and ventricular system were meaured; the ventricular-brain ratio and Evan's ratio were employed to evaluate the severity of hydrocephalus, the correlation between the two ratios were also compared through a simple theory model of hydrocepalous. Finally, the volume rendering of the whole brain and ventricular system were displayed.ResultsThere were 8 dogs of kaolin-induced hydrocephalus,which were divided into two groups, namely, the acute phase group(n=4) and chronic phase group(n=4), and 3 control dogs. The different structures of the canine brain were segmented successfully by the tissue probability-liked maps which was created by ourselves. There were no correlations among the volume of whole brain and the time duration of hydrocephalus, the Ventricular-brain Ratio(VBR) and the Evan's Ratio (ER)(R<0, R2=0.3853;R<0, R2=0.0937;R< 0,R2=0.0582,respectively).Whereas, the correlation among the volume of ventricular system and VBR and ER were very high(R>0, R2=0.9803,R2=0.8703,respectively); the correlation(R>0, R2=0.2564)between VBR and the time duration of hydrocephalus was higher than that of the volume of ventricular system and the time duration of hydrocephalus(R>0,R2=0.1894);The correlation(R>0, R2=0.2987)between ER and the time duration of hydrocephalus was higher than that of the bifrontal span of lateral ventricles and the time duration of hydrocephalus(R>0, R2=0.2743);the correlation between the ER and VBR was also high(R>0,R2=0.8268). In addition, from 4 day to 60 day after the injection of kaolin, the change degree of ventricular-brain ratio (0.212/0.021)was higher than that of ER(0.29/0.19),which was approximately 6.6 times higher than the the latter's.For the theory model of hydrocephalous, the correlation between the VBR and the volume of whole brain(R2=1)was higher than that of the ER and the volume of whole brain (R2=0.9577);furthermore, with the increase of ventricular dilation, the correlation between the Evan's ratio and the enlargement of ventricular volume would be drop gradually. The three-dimensional images of the whole brain displayed that the gyri and sulci of brain surface became flat and shallow as the ventricles expanded.ConclusionThe conclusions were as follows:It showed that the method of establishing experimental hydrocephalous model was feasible by injecting kaolin suspension into the canine brain cisterna magna.The different structures of brain (gray mater, white mater and ventricular system) were successfully segmented by using SPM software and the templete of animal's cerebral tissue which was established by ourselves, and the volume of the different structures were successfully measured.Compared to the Evans ratio(ER), the ventricular-brain ratio(VBR) was more sensitive to detect the change of ventricular volume.To evaluate minor hydrocephalus, the ER may be the same effective as the VBR; however, to evaluate serious hydrocephalous, the ER may be not as accurate as the VBR to map the severity of hydrocephalus.The high resolution imaging of magnetic resonance and the techniques of image postprocessing could support to in vivo 3D display the shape and structural changes of canine brain caused by hydrocephalus. Background and PurposeHydrocephalus is a common neurological condition characterized by dilation of the cerebral ventricles and (or) subarachnoid, usually caused by obstruction of cerebrospinal fluid (CSF) flow. The purpose of this study is to investigate the values of diffusion tensor imaging and diffusion tensor-derived tractorgraphy in demonstrating periventricular white matter injury of hydrocephalous.Materials and methodsEighteen adult mongrel dogs(12-15kg, nine male and nine female) were used for this study. To induce hydrocephalus,0.5ml/kg of 25% sterile kaolin suspension was injected into the cisterna magna. The diffusion tensor imaging was performed on the canine brain at a 3.0 Tesla MRI scanner. The ADC value and FA value were measured in three regions:the superior area of lateral ventricles, the corpus callosum and the white mater bundles around the bilateral ventricles. The vital white matter tracts (include corpus callosum, pyramidal tract, the white mater bundles around the bilateral ventricles) were reconstructed by using diffusion tensor-derived tractorgraphy. These MRI findings were correlated with their pathological results (stained with hematoxylin and eosin) which were made after the canines were euthanized.ResultsThere were 8 dogs of kaolin-induced hydrocephalus, which were divided into two groups, namely, the acute phase group (n=4) and chronic phase group (n=4), and 3 control dogs.In the superior area of lateral ventricles of the acute group, the mean value of ADC (1212.67±35.06)was significantly higher(P=0.000,P<0.05)than that of the control group (900.13±30.24),and the mean value of FA (353.41±1.34) was lower (P=0.049, P<0.05) than that of the controls(391.46±0.62); for the chronic group, the mean value of ADC (1036.43±51.75) remained higher(P=0.068,P>0.05) than that of the controls, the mean value of FA(370.65±6.67) remained lower (P=0.332,P>0.05) than that of the controls. In the corpus callosum of the acute group, the mean value of ADC(1199.31±221.89)was slightly higher than that of the control group(1180.87±193.10), and the mean ADC value of the chronic group increased further, but there were no significant difference compared with the controls (P=0.332, P>0.05);on the contrary, the mean FA value of the acute group (412.21±55.03)was slightly lower than that of the control group (438.09±61.38), and the mean FA value of the chronic group (385.74±24.26) decreased further, but there were no significant difference compared with the controls (P=0.304, P>0.05).The mean ADC value in the white mater bundles around the bilateral ventricles slightly decreased in the acute group (738.29±4.26) and the chronic group (711.1±44.36), compared with the controls (749.78±13.56);but the mean FA value of the acute group(647.42±11.65) was slightly higher than the controls (637.46±0.84), and the mean FA value of the chronic group (628.98±7.73)slightly deceased, but there were no significant differences compared with the controls (P>0.05). Diffusion tensor-derived tractorgraphy displayed that the corpus callosum distorted greatly, with some areas even disrupted in the acute group; and the integrity of the corpus callosum was almost destructed and even disappeared in the chronic group; the pyramidal tract and other white mater bundles around the bilateral ventricles stretched along the dilated ventricles. The pathological findings showed that there were obvious inflammation and edema in the acute phase of hydrocephalous; and in the chronic phase of hydrocephalous, the severity of inflammation and edema reduced, but with some gliosis, white matter bundles distortion and destruction, and cortical neurons degeneration.ConclusionDiffusion tensor imaging with the measurements of ADC and FA values is able to show periventricular injury caused by hydrocephalous beyond those seen with conventional MR imaging. Especially, Diffusion tensor-derived tractorgraphy can further characterize the white matter bundles structural changes in the damaged periventricular regions of hydrocephalous. These results may be helpful to find pathophysiological mechanism of hydrocephalous if further studing with the manifestations and neurobehavioral cognitive exams. |
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