Abstract
While the diagnosis of high-grade glioma (HGG) is still associated with a considerably poor prognosis, neurosurgical tumor resection provides an opportunity for prolonged survival and improved quality of life for affected patients. However, successful tumor resection is dependent on a proper surgical planning to avoid surgery-induced functional deficits whilst achieving a maximum extent of resection (EOR). With diffusion magnetic resonance imaging (MRI) providing insight into individual white matter neuroanatomy, the challenge remains to disentangle that information as correctly and as completely as possible. In particular, due to the lack of sensitivity and accuracy, the clinical value of widely used diffusion tensor imaging (DTI)-based tractography is increasingly questioned. We evaluated whether the recently developed multi-level fiber tracking (MLFT) technique can improve tractography of the corticospinal tract (CST) in patients with motor-eloquent HGGs. Forty patients with therapy-naïve HGGs (mean age: 62.6 ± 13.4 years, 57.5% males) and preoperative diffusion MRI [repetition time (TR)/echo time (TE): 5000/78 ms, voxel size: 2x2x2 mm3, one volume at b=0 s/mm2, 32 volumes at b=1000 s/mm2] underwent reconstruction of the CST of the tumor-affected and unaffected hemispheres using MLFT in addition to deterministic DTI-based and deterministic constrained spherical deconvolution (CSD)-based fiber tractography. The brain stem was used as a seeding region, with a motor cortex mask serving as a target region for MLFT and a region of interest (ROI) for the other two algorithms. Application of the MLFT method substantially improved bundle reconstruction, leading to CST bundles with higher radial extent compared to the two other algorithms (delineation of CST fanning with a wider range; median radial extent for tumor-affected vs. unaffected hemisphere – DTI: 19.46° vs. 18.99°, p=0.8931; CSD: 30.54° vs. 27.63°, p=0.0546; MLFT: 81.17° vs. 74.59°, p=0.0134). In addition, reconstructions by MLFT and CSD-based tractography nearly completely included respective bundles derived from DTI-based tractography, which was however favorable for MLFT compared to CSD-based tractography (median coverage of the DTI-based CST for affected vs. unaffected hemispheres – CSD: 68.16% vs. 77.59%, p=0.0075; MLFT: 93.09% vs. 95.49%; p=0.0046). Thus, a more complete picture of the CST in patients with motor-eloquent HGGs might be achieved based on routinely acquired diffusion MRI data using MLFT.
Highlights
Gliomas represent the most common malignant brain tumors in adults, with an average annual age-adjusted incidence rate of ~4.67 to 5.73 per 100,000 population [1, 2]
We evaluate a novel method for improved fiber tractography of the corticospinal tract (CST) in patients suffering from motor-eloquent high-grade glioma (HGG), which aims to tackle the issue of missing fiber branching of currently existing tractography procedures
Representative exemplary cases for CST reconstruction by DTIbased tractography, constrained spherical deconvolution (CSD)-based tractography, and multi-level fiber tracking (MLFT) are shown in Figures 2, 3
Summary
Gliomas represent the most common malignant brain tumors in adults, with an average annual age-adjusted incidence rate of ~4.67 to 5.73 per 100,000 population [1, 2]. HGGs can be regarded as chronic progressive diseases and typically show infiltrative growth behavior, which renders curative treatment almost impossible for the majority of affected patients [3, 5]. Multiple factors including histopathological characteristics, molecular tumor biology, as well as functional eloquence of the affected brain region contribute to individual therapy decision-making in clinical practice [9, 10]. A maximum extent of resection (EOR) has been associated with prolonged survival rates and better quality of life [11,12,13,14,15,16,17]. Mostly depending on individual tumor location, achieving a maximum EOR can be in conflict with preserving specific functions, such as the ability to move or speak without constraints.
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