| ObjectivesTo detect the range of normal values of the anterior visual pathway DTI index in normal adults and analysis the distribution characteristics and influencing factors.To investigate the change characteristics of the anterior visual pathway DTI index and DTT graph structure in sellar region tumors and analysis the relationship between the changes of visual function and prognosis.Methods38 healthy adult volunteers were selected.There were 20 female patients,18 male patients with a mean age of(38.2± 15.9)years(range,18 to 80 years).They have no history of ophthalmology,diabetes and so on.They now have no positive symptoms and signs of the visual transmission system.They are also able to cooperate with vision,visual field examination and MRI scan.Using 3.0T MR Skyra scanner(Siemens,Berlin,Germany),not only routine sequence scans,but also readout segmented echo planar imaging sequence(RS-EPI)are scanning on the anterior visual pathway axial DTI(TLC scanning to find suitable positioning piece with tilt angle,with the anterior visual pathway structure form clearly).with 9 segments,30 diffusion gradient directions.Image scanning was carried out by the same image kegaonian endowment technicians,using 3.0T MR Skyra scanner with postprocessing workstation software,DTI index collection and DTT image reconstruction were completed by two senior radiologists.The FA and ADC values were detected in the middle of the optic nerve,optic chiasm,and bilateral optic tract points on behalf of its anterior visual pathway of each part of FA and ADC values.After treatment,the anterior optic tract bundles were reconstructed on DTT images,and the morphology and structure were observed.To further study on sellar tumor group and healthy control group,patients with sellar region tumors were selected from the General Hospital of Fuzhou and were treated with surgery.Exclusion criteria:with the sellar region outside of intracranial tumor,radiotherapy or tumor recurrence received preoperative or postoperative residual reoperation,immunohistochemical results for non neoplastic diseases,MRI scanning taboo,or poor compliance patients can not complete follow-up of the patients after the operation.A total of 21 patients with sellar tumors were selected.At the same time,21 healthy adults were selected as control group.Sellar tumor group and the healthy adult control group tumors underwent axial DTI scan at the same time within 1 weeks before surgery.Patients with sellar tumors were reexamined on the anterior visual pathway DTI at 4 months after surgery.The visual function was assessed by the VIS scale.The anterior visual pathway was divided into 3 parts,the anterior tumor optic nerve,the tumor area optic chiasm and the posterior tumor optic nerve.The measurement method was the same as that of healthy adult controls.The FA value and ADC value of each site of anterior visual pathway in the two groups were measured,and the values of the above 3 parts were calculated.The differences of these values and their relationship with VIS classification were analyzed.Statistical analysis was carried out using SPSS20.0 version software,P<0.05 considered statistically significant.ResultsThe anterior visual pathway DTI color coded FA image performance:normal anterior visual pathway is more uniform green signal.ADC image performance:normal anterior visual pathway is gray,which can be distinguished with normal gray level of brain tissue,and cerebrospinal fluid is white signal.DTT can display three-dimensional normal fiber bundle morphology of anterior visual pathway,and postprocessing software interface can observe the anterior visual pathway DTT fiber bundles at arbitrary rotation angle.There was a significant negative correlation between the quantitative FA and ADC value of anterior visual pathway DTI(r =-O.693,P<0.001).The FA and ADC values of the entireanterior visual pathway were not related to sex and age(P>0.05).There were significant differences in FA value and ADC value on different parts of anterior visual pathway(P<0.05).There was a significant difference between optic chiasma and optic nerve and optic tract(P>0.05).There was no significant difference between optic nerve and optic nerve(P<0.05).The FA value was the lowest and the ADC value was the highest at the intersection.In the sellar tumor group,the morphology and structure of the fiber bundles in the anterior visual pathway were observed in DTT(continuous,interrupted,full or sparse).It can also be used to observe the spatial location relationship between the anterior optic fiber bundle and the tumor:the anterior optic nerve fiber bundle is extruded and deformed by the tumor or is surrounded by tumor tissue.The morphology of the anterior optic fiber bundle in the sellar tumor group was not related to the VIS score of visual function(P>0.05).However,it was significantly correlated with prognosis(P<0.05).According to the prognostic value of VIS score of visual function,the patients with anterior optic nerve fiber morphological structure of the continuous type before operation,4 months after surgery,their visual function recovery was better than the interruption type(P<0.05).The value of FA in the 3 regions of the optic nerve,the anterior optic nerve and the posterior optic nerve of the tumor was significantly lower than that of the control group(P<0.05).But the ADC value was significantly higher than that of healthy adult control group(P<0.05).There was significant difference in FA and ADC values in each part of anterior visual pathway(P<0.001).However there was no significant difference between optic nerve and optic nerve(P>0.05).The value of FA was significantly lower than that of optic nerve and optic tract(P<0.001).The value of ADC was significantly higher than that of optic nerve and optic nerve(P<0.001).There was significant difference in FA value between the 3 groups in the control group(P<0.001).But there was no significant difference between optic nerve and optic nerve(P=0.998).The optic chiasm was significantly lower than that of optic nerve and optic nerve(P<0.001).There was significant difference in ADC value between the 3 groups in the control group(P<0.001).But there was no significant difference between optic nerve and optic nerve(P=0.122).The optic chiasm was significantly higher than that of optic nerve and optic nerve(P<0.001).The FA value of the anterior visual pathway in 4 months in Sellar tumor group after operation was significantly higher than that before operation(P<0.05),and ADC value decreased significantly(P<0.05).Among them,the FA value of the optic nerve,the anterior optic nerve and the posterior optic nerve of the tumor 4 months after the operation of the tumor were significantly increased(P<0.05)and the degree of recovery of the optic chiasm was greater than that of optic nerve and optic nerve(P<0.05).The ADC value of 4 months after the operation also occurred similar to the recovery of FA value.The preoperative FA and ADC values were not related to VIS score and grade Sellar in tumor group(P>0.05).The improvement rate of FA value in the patients with sellar region tumors was 92.9%,which was significantly higher than that in the FA group(P=0.006).Thus,the change of sellar tumors after operation the cross site FA value is a good predictor of the prognosis of visual function,the sensitivity,specificity,positive predictive value and negative predictive value were 86.7%,83.3%,92.9%,71.4%.ConclusionsFA and ADC are sensitive and reliable indicators of DTI,which can be used for quantitative analysis of anterior visual pathway.DTT can display three-dimensional structure of anterior visual pathway nerve fibers,which can be used to judge the prognosis of patients with tumor of the sellar region.The prognosis of the patients with continuous morphology of the superior anterior visual pathway of DTT was better than that of the interrupted type.The anterior visual pathway DTI index of patients with sellar tumors would vary in the whole anterior approach,especially at the intersection.These changes occurred in different parts of the anterior visual pathway after operation,and related to the improvement of visual function In particular,the change of FA value in the anterior and posterior part of the sellar region tumors is a predictor of high sensitivity to visual function.FA value was positively correlated with visual function prognosis. |
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