The Advantages And Clinical Application Of Two-tensor Unscented Kalman Filter Tractography In The Reconstruction Of The Arcuate Fasciculus

Background and Objective: The integration of diffusion tensor tractography of the arcuate fasciculus(AF)and neuronavigation has been widely used in glioma surgery,in order to maximize the extent of resection of glioma and minimize the extent of damage to the neurologic function.However,given the drawbacks of fibers-crossing effects,partial volume effects and abnormal diffusivity of white matter in the intra-and peri-tumoral areas,the result of fiber tractography using the conventional single-tensor model is still unsatisfactory.To address these problems,we presented and applied a novel technique using a two-tensor unscented Kalman filter(UKF)algorithm,named as two-tensor UKF tractography.In this thesis,we would like to perform the following three researches: Firstly,to investigate the advantages of two-tensor UKF tractography in the reconstruction of AF in healthy volunteers.Secondly,to investigate the advantages of two-tensor UKF tractography in the reconstruction of AF in patients with gliomas involving eloquent language areas,aiming to achieve better fiber reconstruction and thus help the neurosurgeons to obtain a maximal safe resection.Finally,to employ this technique in the longitudinal research for patients with gliomas involving eloquent language areas before and after surgery.Specifically,we quantified the restorative condition of AF by comparing the pre-and postoperative volume of AF,and correlated the alteration of AF with the alteration of language function,in order to provide some reference for the recovery of language function of giloma patients from the perspective of language-related white matter change.Methods and Results: Part one,The Advantages of Two-tensor UKF Tractography in the Reconstruction of the Arcuate Fasciculus in Healthy Volunteers.Twenty right-handed healthy volunteers were enrolled,and all of them received 3D T1-structure imaging and diffusion tensor imaging(DTI)scanning.Both the traditional single-tensor streamline tractography and two-tensor UKF tractography were applied to reconstruct the direct long segment,anterior fronto-parietal segment and posterior temporal-parietal segment of the left AF.Results from the two different tractography algorithm were compared visually and quantitatively.The results showed as follows:(1)When single-tensor streamline tractography was applied to reconstruct the left AF,it failed to reconstruct the long segment of AF in 3 cases,the anterior segment in 2 cases and the posterior segment in one case.While two-tensor UKF tractography was able to trace the three segments of AF in all of 20 cases successfully.(2)After we compared the anatomical morphology of AF by the two methods,we found the phenomenons as below: Both the rostral and caudal terminations of the long segment in single gyrus in 64.7% cases by single-tensor streamline tractography,and in detail the former mainly in premotor cortex and the latter mainly in posterior middle temporal gyrus;The rostral terminations of the anterior segment in single gyrus in all cases and the caudal terminations in 88.9% cases by single-tensor streamline tractography,and in detail the former mainly in premotor cortex and the latter mainly in supramarginal gyrus;The rostral terminations of the posterior segment in single gyrus in 68.4% cases and the caudal terminations in 84.2% cases by single-tensor streamline tractography,and in detail the former mainly in posterior middle temporal gyrus and the latter mainly in angular gyrus.While the terminations of AF distributed more widely and the branching fibers seemed more intact by two-tensor UKF tractography than that by single-tensor streamline tractography.The rostral terminations of the long segment in 75% cases mainly both in the inferior frontal gyrus and premotor cortex,and the caudal terminations of the long segment in 90% cases mainly in the superior,middle and inferior temporal gyrus;The rostral terminations of the anterior segment in 70% cases mainly both in the inferior frontal gyrus and premotor cortex,and the caudal terminations of the anterior segment in 80% cases mainly both in the supramarginal gyrus and angular gyrus;The rostral terminations of the posterior segment in 75% cases mainly both in the superior,middle and inferior temporal gyrus,and the caudal terminations of the posterior segment in 80% cases mainly both in the supramarginal gyrus and angular gyrus.(3)After we compared the volumes of AF by the two methods,we found that the volume of long segment(t=14.812,P<0.001),anterior segment(t=9.372,P<0.001)and posterior segment(t=16.406,P < 0.001)of the left AF by two-tensor UKF tractography was significantly larger than that by single-tensor streamline tractography.Part two,The Advantages of Two-tensor UKF Tractography in the Reconstruction of the Arcuate Fasciculus in Patients with Gliomas Involving Eloquent Language Areas.Forty-three right-handed patients with gliomas involving eloquent language areas were enrolled,and all of them received 3D T1-structure imaging and DTI scanning on the day before operation.According to the method of first part,both the traditional single-tensor streamline tractography and two-tensor UKF tractography were applied to reconstruct the direct long segment,anterior fronto-parietal segment and posterior temporal-parietal segment of the left AF.Results from the two different tractography algorithm were compared visually and quantitatively.The results showed as follows:(1)When single-tensor streamline tractography was applied to reconstruct the left AF,it failed to reconstruct the long segment of AF in 16 cases,the anterior segment in 12 cases and the posterior segment in 8 cases.While two-tensor UKF tractography was applied to reconstruct the left AF,it failed to reconstruct the long segment of AF in only one case,the anterior segment in 4 cases and the posterior segment in 2 cases.(2)In the 18 cases with tumor volume lager than 50 cm3,single-tensor streamline tractography failed to reconstruct the long segment of AF in 6 cases,the anterior segment in 6 cases and the posterior segment in 3 cases,while two-tensor UKF tractography was able to trace the long segments of AF in all of 18 cases successfully,but failed to reconstruct the anterior segment in 2 cases and the posterior segment in one case.(3)In the 10 cases with obvious peritumoral edema,single-tensor streamline tractography failed to reconstruct the long segment of AF in 4 cases,the anterior segment in 4 cases and the posterior segment in 6 cases,while two-tensor UKF tractography was able to trace the long segments of AF in all of 10 cases successfully,but failed to reconstruct the anterior segment of AF in 3 cases and the posterior segment in 2 cases,and the reconstructive fibers seemed more denser.(4)Some fibers of AF were able to be traced inside the marginal parts of tumor in 2 cases with low grade gliomas by single-tensor streamline tractography,while more denser fibers were able to be traced inside the marginal parts of tumor in 6 cases by two-tensor UKF tractography.Both of the two methods failed to trace the fibers inside the high grade gliomas.(5)The volume of long segment(t=17.208,P<0.001),anterior segment(Z=5.442,P<0.001)and posterior segment(Z=5.579,P<0.001)of the left AF by two-tensor UKF tractography was significantly larger than that by single-tensor streamline tractography,and the branching fibers of AF delineated by two-tensor UKF tractography seemed significantly more than that by single-tensor streamline tractography.Part three,Predictive Value of Two-tensor UKF Tractography in the Reconstruction of the Arcuate Fasciculus in Patients with Gliomas Involving Eloquent Language Areas.Nine right-handed patients with gliomas involving eloquent language areas successfully postoperative follow-up were enrolled,and all of them received 3D T1-structure imaging and DTI scanning before operation and one to six months after operation.Two-tensor UKF tractography was applied to reconstruct the direct long segment,anterior fronto-parietal segment and posterior temporal-parietal segment of the bilateral AF.To account for the different pre-and postoperative conditions of the long,anterior and posterior segment of left AF,the postoperative relative ratio of AF(RRAF)was calculated in each patient according to the following formula: RRAF =(volume of the postoperative left AF/volume of the postoperative right AF)/(volume of the preoperative left AF/volume of the preoperative right AF).An RRAF greater than 1.0 indicated increased visualization of the postoperative left AF.Language assessment was conducted in almost the same period of time as MRI scanning using the aphasia battery of Chinese,including spontaneous speech,comprehension,repetition,naming,reading and writing.Aphasia quotient(AQ)was calculated from the score of the first four language functions and adopted to evaluate the severity of aphasia.To account for the different pre-and postoperative conditions,changes in language functions was calculated in each patient according to the following formula: substraction score in language function =(postoperative score in language function)-(preoperative score in language function).The results showed as follows: Postoperative RRAF of long segment of the left AF was positively correlated with substraction score in AQ(r=0.777,P=0.014),substraction score in comprehension(r=0.711,P=0.032)and substraction score in repetition(rs=0.74,P=0.023);Postoperative RRAF of posterior segment of the left AF was positively correlated with substraction score in comprehension(rs=0.850,P=0.007)and substraction score in repetition(rs=0.747,P=0.033).Conclusions: 1 Two-tensor UKF tractography outperform single-tensor streamline tractography in estimating the extent and degree of connectivity of the AF language pathway in complex regions in healthy volunteers.Two-tensor UKF tractography provide the ability to trace a larger volume,more widely distributing terminations and more intact branching fibers of long,anterior and posterior segment of the left AF than single-tensor streamline tractography.2 Two-tensor UKF tractography outperform single-tensor streamline tractography in estimating the extent and degree of connectivity of the AF language pathway affected by gliomas and/or peritumoral abnormalities.Two-tensor UKF tractography provide the ability to trace a larger volume and more intact branching fibers of long,anterior and posterior segment of the left AF than single-tensor streamline tractography.Two-tensor UKF tractography is also worth its effort in cases with large volume,obvious peritumoral edema and can better visualize the tracts inside the marginal parts of low grade gliomas.3 Two-tensor UKF tractography can relatively completely visulize and quantitate AF in patients with gliomas involving eloquent language areas,thereby display the restorative condition of the postoperative AF.This study preliminarily shows that increasing the volume of long segment of the left AF may be a predictor of a well restoration of postoperative language function.The restoration of postoperative long and posterior segment of the left AF may be helpful for the improvement of patients' language comprehending and repeating ability.However,due to the small number of cases in this study,it is necessary to increase the sample size to further confirm the reliability of predictive value of AF restoration in the reversion of language function.