AUTHOR=Zoli Matteo , Talozzi Lia , Martinoni Matteo , Manners David N. , Badaloni Filippo , Testa Claudia , Asioli Sofia , Mitolo Micaela , Bartiromo Fiorina , Rochat Magali Jane , Fabbri Viscardo Paolo , Sturiale Carmelo , Conti Alfredo , Lodi Raffaele , Mazzatenta Diego , Tonon Caterina 

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

JOURNAL=Frontiers in Neurology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2021.633209

DOI=10.3389/fneur.2021.633209

ISSN=1664-2295

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 fascicle (AF) tractography for surgical planning and explore the role of along-tract analyses in vivo for characterizing tumor histopathology.  
Methods: HARDI diffusion-weighted images were acquired for nine patients with tumors located in or near language areas (age: 41±14 years, mean±standard deviation; 5 males) and thirty-two 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 modelling and probabilistic fiber tracking. Along-tract analyses were performed, dividing the AF into fifteen segments along the length of the tract defined using the Laplacian operator. For each AF segment, diffusion tensor imaging (DTI) measures were compared to those obtained in healthy controls (HCs). The hemispheric Laterality Index (LI) was calculated from language task fMRI activations in frontal, parietal, and temporal lobe parcellations. Tumors were grouped into low/high grade (LG/HG). 
Results. Four tumors were low-grade (LG) (one dysembryoplastic neuroepithelial tumor, three glioma grade II) and five high-grade gliomas (HG) (two grade III, 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 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=-.732), and RD segments (R=-.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.