Fiber-tract localized diffusion coefficients highlight patterns of white matter disruption induced by proximity to glioma

Abstract

Gliomas account for 26.5% of all primary central nervous system tumors. Recent studies have used diffusion tensor imaging (DTI) to extract white matter fibers and the diffusion coefficients derived from MR processing to provide useful, non-invasive insights into the extent of tumor invasion, axonal integrity, and gross differentiation of glioma from metastasis. Here, we extend this work by examining whether a tract-based analysis can improve non-invasive localization of tumor impact on white matter integrity. This study retrospectively analyzed preoperative magnetic resonance sequences highlighting contrast enhancement and DTI scans of 13 subjects that were biopsy-confirmed to have either high or low-grade glioma. We reconstructed the corticospinal tract and superior longitudinal fasciculus by applying atlas-based regions of interest to fibers derived from whole-brain deterministic streamline tractography. Within-subject comparison of hemispheric diffusion coefficients (e.g., fractional anisotropy and mean diffusivity) indicated higher levels of white matter degradation in the ipsilesional hemisphere. Novel application of along-tract analyses revealed that tracts traversing the tumor region showed significant white matter degradation compared to the contralesional hemisphere and ipsilesional tracts displaced by the tumor.

Retrospective analysis of hemispheric structural network change as a function of location and size of glioma

“…Most connections also showed an increase in fibre count while also exhibiting a decrease in structural integrity. This is consistent with previous works stating tumour impact on microstructural integrity is directly correlated to lesion proximity ( Mair et al , 2018 ; D’Souza et al , 2019 ). An increase in connections between several nodes, though consistent with previous findings of increased ipsilesional fibre count, warrants further exploration ( Kong et al , 2016 ; Ormond et al , 2017 ).…”

“…Previous studies have shown the localized effect of gliomas on surrounding microstructural integrity of white matter fibres, noting an increase in degradation with increasing proximity ( D’Souza et al , 2019 ). However, the widespread, non-microstrucutral changes have yet to be defined ( Fig.…”

“…Data were collected retrospectively from patient chart review through the application of a consent exempt institutional review board (IRB) protocol wherein only clinical data were reviewed after deidentification by a member of the study team. The initial subject population ( n = 37) considered for the following novel analyses contained a subset of cases ( n = 13) from two prior publications ( Ormond et al , 2017 ; D’Souza et al , 2019 ). The initial patient population ( n = 37) was then screened before analysis.…”

Acute changes in diffusion tensor-derived metrics and its correlation with the motor outcome in gliomas adjacent to the corticospinal tract

“…We emphasize the importance of standardizing MRI acquisition and postprocessing imaging, especially the time at which the postoperative control study is performed. Other studies that correlated MRI data with the motor outcome are based on preoperative studies[ 9 , 14 , 19 , 40 ] that provide limited prognostic information. In our series, we also distinguished patients with transient postoperative motor deficits from those with permanent deficits.…”

In vivo Restricted-Diffusion Imaging (RDI) is sensitive to differences in axonal density in typical children and adults

“…Unlike most other diffusion metrics, RDI does does not depend on an underlying diffusion model or numerical optimization to estimate model parameters, making it easily applicable to a wider range of databases and clinical scanner protocols. RDI’s sensitivity to cell density has been useful in differentiating tissue in patients with tumors 44, 45 , as well as measuring therapeutic benefits of deep brain stimulation 46 . In a phantom study by Yeh et al, the optimized restricted diffusion showed an almost perfect correlation of 0.998 with cell density 1 .…”