Tractography Of Optic Radiation In Healthy Adults Based On Diffusion Tensor Magnetic Resonance Imaging And The Preliminary Application Of Fiber Tracking In Neuronavigation

PartⅠ:Preliminary assessment of fiber tractography method of optic radiation based on diffusion tensor imagingObjective:To investigate optimal scan plan for optic radiation tractography and image postprocessing method which is acceptable for clinic diagnosis and treatment. Methods:DT images were obtained in 10 healthy volunteers(6 men,4 woman) with an average age of 28 years,by using a 1.5T MR imaging scanner with single-shot echo-planar imaging with SENSE technique.MPG was applied in 6,14,and 32 independent directions. To tract optic radiation fibers,Software DTI Studio was used for image postprocessing with a multi-ROIs measure accompanied by 'or','and'and 'not'operation.To value image effect by comparing its SNR,the demonstration of Meyer's loop,analysing the difference average length of fibers and mean fibers/voxel between the three groups,the software SPSS 11.5 was used.Results:there are no significance difference for SNR in the three groups;32MPG group obviously better than 6MPG group in the demonstration of Meyer's loop;there are statistical difference in average fiber length and mean fibers/voxel between the three groups.Conclusion:A acceptable fiber tract image can be obtained in moderate scan time(about 5 minutes ) under 32MPG with a method of Multi-ROIs image postprocessing in 1.5T MRI scaner.PartⅡ:Preliminary assessment of the Meyer'loop of the optic radiation in healthy adults by DTI tractographyObjective:Visual defect due to optic radiation injury is a common complication of temporolobectomy.To decrease incidence of this complication,the track and localization of optic radiation fibers and the individual variation of Meyer'loop were valuated in healthy adult volunteers by MR fiber tracking.Methods Diffusion magnetic resonance images were obtained from 25 healthy volunteers(12 men,13 women),an average age of 31.5 years(18-50 years),performed by 1.5T MR imaging scanner.Multiple ROIs were used for fiber reconstruction by the software DTI Studio.The distance between the anterior limit of Meyer'loop and the temporal tip(MT) and the fraction of anisotropy(FA) from one side were compared with those from contraside by paired t test and the tendency of the dispersion of MT was described using SPSS11.5.Results 49 optic radiation fibers were successfully reconstructed in 25 volunteers.The localization and track of optic radiation fibers can be clearly demonstrated by tractography.The value of MT is 43.24(30.62---59.74) mm,standard deviation:7.71,coefficient of variation:18%. The values of MT,and FA of optic radiation in the left side were(43.49±8.12) mm, (0.53±0.10) and those counterpart in the right side were(43.21±7.54)mm and(0.53±0.07) respectively.The t values of paired MT and FA of both optic radiation were 0.12,0.00 and P values were 0.91,1.00 respectively.There is no significant difference between values about MT,FA on both sides in health human groups.Conclusion The intersubject variability of MT is considerable in healthy volunteers.And preoperative measurement of the MT will be helpful to predict the risk of the incidence of visual defect and to decrease the rate of the complication.PartⅢ:The Preliminary Application of Diffusion Tensor Magnetic Resonance image in the NeuronavigationObjetive:To evaluate the application of diffusion tensor image in intracranial neoplasm,To encourage the application of fiber tracking in neuronavigation in the surgery and improve the curative effect.Methods:14 patients(male 8 cases,female 6 cases,Mean age 44.5 years) who had been underwent fiber tract navigation surgery for the the intracranial lesions.To postprocess the DTI image,the software DTI Studio was used.To transform BMP image to DCM,the software POWER DICM 3.50 was used.The tractography image was integrated into navigation antomic images.To analyse the DTI image,we reviewed the relative literature.Results:All images of major white matter fibers were respectively integrated into navigation antomic images preoperatively.From DTI image,we can find the relationship between the lesions and major fiber bundles:fiber bundles abnormal localization in 7 cases(7/14);fiber bundles interrupted in 3cases(3/14);the close relationship between fibers and lesions,but no abnormal localiztion(4/14).The follow-up results showed:the main function which the lesions involved in had some recovery in four patients(4/14),no any change in nine cases(9/14), and went bad in one case(1/14).Conclusion:DTI can contribute to the diagnosis and differential of intracranial losions,and provide important imformation for the surgical plan; fiber tract navigation can improve the rate of total resection of lesions and the protection of an important fiber bundles.