| As the primary reason of vision decline, visual pathway diseases including glaucoma, anterior optic pathway lesion, brain infarction and brain tumor, would lead to irreversible damage of visual function if not treated properly. DTI (diffusion tensor imaging) provided information about the identification and characterization of white matter fibers in neuroimaging as well as the visual system, which was made by whole visual pathways of normal volunteers and common diseases including brain infarction and brain tumor of optic radiation. Treatment strategy differs from patients due to different reflections of optic radiation caused by diseases. The main treatment of cerebral infarction is neurology, while tumor mainly depends on surgery. Most of the meningiomas can be surgical resection. Surgery is the main method in the treatment of brain glioma, but show morphological irregularity, postoperative radio-chemotherapy is usually conducted. Solitary brain metastasis has some different characteristic features in MRI imaging. DTT offer methods to study the relationship between lesion and optic radiation.Objects:DTI is widely used in reflecting the microstructure of brain and investigating the integrity white matter fibers. To assess whether measurement of diffusion tensor imaging parameters within occipital and temporal lobe of optic radiation could show the way of fiber or not, FA was used to identify the tumor. This study demonstrates the utility of diffusion tensor tractography (DTT) in delineating the course of the whole visual pathway including the optic nerve, optic chiasm, optic tract, optic radiation and lateral geniculate nucleus. On one hand, DTT evaluates prognosis of patients suffering from cerebral infraction by identifying the change of optic radiation fibre, based on which to cure with thrombolysis. On the other hand, DTT rebuilds optic radiation fibre of patients with brain tumors and analyzes the relationship between optic radiation fibre and brain tumors to schedule operation plan and estimate prognosis. Methods:DTI was obtained from twenty healthy volunteers without vision impairment and MRI abnormal, forty-five patients with cerebral infarction and forty patients suffering from brain tumors who underwent conventional MRI, DWI, DTI and enhancement scan in brain tumors patients. Subjects were instructed to perform a simple eye fixation task during DTI acquisition. DTI was acquired on each people with a single-shot echo planner imaging sequence:slice thickness=2.5mm, intersection gap=0, b=1000s/mm2,25directions, NEX=1, TR/TE=8000/86.7ms, FOV=24, during the scanning range though the AC-PC,31slices were selected. Upload the images to GE-AW4.5workstation and manage the data of DTI by FUNCTOOL:1The regions of interest (ROI) were as follows:optic nerve, optic chiasm, optic tract, optic radiation and lateral geniculate nucleus."AND" or "OR" was selected to depict the integrity visual pathways.2Regions of interest (ROIs) were placed in infarction and normal contralateral tissue, fractional anisotropy (FA), apparent diffusion coefficient (ADC), volume ratio anisotropy(VRA), exponential attenuation(EA) were obtained in and analyzed by the SPSS17.0statistical software.3Placed the regions of interest (ROIs) in brain tumor that was enhanced, The fractional anisotropy (FA) were obtained to evaluate the brain tumors of the optic radiation, DTT rebuilds optic radiation fibre of patients with brain tumors and analyzes the relationship between optic radiation fibre.Results:1Visual pathway fibers including optic nerve, optic chiasm, optic tract, optic radiation and lateral geniculate nucleus were analyzed by DTI and DTT images, optic chiasm were not well demonstrated because of the bone and air.2Regions of interest (ROIs) were placed in infarction and normal contralateral tissue for tracking the visual pathways. Different parameters were measured. FA, ADC, VRA and EA were calculated in different parts of infarctions of optic radiation: FA is useful to differentiate hyper-acute stroke from acute and sub-acute stroke. FA values increased slightly in hyper-acute(t=0.56, p>0.05)and decreased in acute, values of ADC in infarction regions in hyper-acute and acute phases were lower than that of the contralateral tissue(t=7.15, p<0.05; t=12.56, p<0.05). In sub-acute phase, ADC was of no significant difference(t=2.60,p>0.05), In chronic phase, ADC was higher(t=10.61, p<0.05). From the Pearson correlation analytic results:There was positive correction between FA and VRA(r=0.789) and negative correction between ADC and EA(r=-0.743). DTT was used to show the way and change of visual pathway.3FA of meningioma was obviously higher than that of glioma and metastatic tumor. FA of glioma was higher than that of metastatic tumor. FA of low grade glioma was higher than that of high grade glioma. The relationship between tracts and tumors was mainly classified into two types:type I is displacement, type Ⅱ is disruption. Meningiomas and low grade gliomas were mainly displacement while metastatic tumors and high grade gliomas were mainly disruption.9Meningiomas,2metastatic tumors,5low grade gliomas and1high grade glioma were mainly displacement while1meningioma,7metastatic tumors,3low grade gliomas and12high grade gliomas were mainly disruption.Conclusions:DTI is sensitive to the visual pathway and the relevant DTI parameters of the optic radiation are obviously different in this study, which indicates that the infarction of different stages is different in visual of patients. According to this, we can improve the visual outcomes. The kinds of tumors were identified by FA and exists differences among different tumors. Fiber tractography of the optic radiation with DTT in regions of infarction could be traced. DTT can also show the reconstructed fiber of optic radiation, the exact location of the lesion related to these tumor was observed to design a reasonable surgical plan for preserving vital tracts while maximizing tumor resection. |
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