From Neurosurgical Planning to Histopathological Brain Tumor Characterization: Potentialities of Arcuate Fasciculus Along-Tract Diffusion Tensor Imaging Tractography Measures

Abstract

Background: Tractography has been widely adopted to improve brain gliomas' surgical planning and guide their resection. This study aimed to evaluate state-of-the-art of arcuate fasciculus (AF) tractography for surgical planning and explore the role of along-tract analyses in vivo for characterizing tumor histopathology.Methods: High angular resolution diffusion imaging (HARDI) images were acquired for nine patients with tumors located in or near language areas (age: 41 ± 14 years, mean ± standard deviation; five males) and 32 healthy volunteers (age: 39 ± 16 years; 16 males). Phonemic fluency task fMRI was acquired preoperatively for patients. AF tractography was performed using constrained spherical deconvolution diffusivity modeling and probabilistic fiber tracking. Along-tract analyses were performed, dividing the AF into 15 segments along the length of the tract defined using the Laplacian operator. For each AF segment, diffusion tensor imaging (DTI) measures were compared with those obtained in healthy controls (HCs). The hemispheric laterality index (LI) was calculated from language task fMRI activations in the frontal, parietal, and temporal lobe parcellations. Tumors were grouped into low/high grade (LG/HG).Results: Four tumors were LG gliomas (one dysembryoplastic neuroepithelial tumor and three glioma grade II) and five HG gliomas (two grade III and three grade IV). For LG tumors, gross total removal was achieved in all but one case, for HG in two patients. Tractography identified the AF trajectory in all cases. Four along-tract DTI measures potentially discriminated LG and HG tumor patients (false discovery rate < 0.1): the number of abnormal MD and RD segments, median AD, and MD measures. Both a higher number of abnormal AF segments and a higher AD and MD measures were associated with HG tumor patients. Moreover, correlations (unadjusted p < 0.05) were found between the parietal lobe LI and the DTI measures, which discriminated between LG and HG tumor patients. In particular, a more rightward parietal lobe activation (LI < 0) correlated with a higher number of abnormal MD segments (R = −0.732) and RD segments (R = −0.724).Conclusions: AF tractography allows to detect the course of the tract, favoring the safer-as-possible tumor resection. Our preliminary study shows that along-tract DTI metrics can provide useful information for differentiating LG and HG tumors during pre-surgical tumor characterization.

Qualitative and Visual Along-Tract Analysis of Diffusion-Based Parameters in Patients with Diffuse Gliomas

“…The visual assessment of WM tracts is made easy with the graphical presentation showing qualitative information and concomitant tumor presence. Similar graphs have also been demonstrated by others [ 37 , 55 , 60 ] with minor differences. Although the graphical presentation of along-tract analysis may be a potential tool in a clinical workflow, it is highly flawed by the fact that the WM tracts have been reconstructed in MNI space and have been altered length wise, hence they cannot be directly translated to patient-specific cases.…”

“…This method provides a more detailed picture of variations along the tract, allowing for a graphical presentation which can visualize alterations and specific functions associated with different segments of the WM tract. Along-tract analysis has previously been used in a variety of applications; however, the results that have been published warrant further exploration into accuracy and limitations [ 37 , 43 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ].…”

Atypical brain structural connectivity and social cognition in childhood maltreatment and peer victimisation

“…A 10% threshold to the maximum of connectivity was applied for all tracts to filter false-positive connections due to the probabilistic tractography algorithm. This tractography protocol, which has been previously compared to other tractography methods for the arcuate fasciculus [ 68 ] and tested in the presence of brain tumours [ 69 – 71 ], is used for other WM tracts in the current study.…”

Assessing robustness of quantitative susceptibility-based MRI radiomic features in patients with multiple sclerosis

“…To reconstruct the WM tracts, diffusivity was modelled along the spatial eigenvector using the tensor model and high-order fibre modelling and probabilistic streamline approach used for crossing fibres evaluation 50 . The WM tracts analysed were: Arcuate fasciculus (AF), cortico-spinal tract (CST), frontal aslant tract (FAT), Inferior fronto-occipital fasciculus (IFOF), optic radiation (OR), Uncinate fasciculus (UF).…”