Abstract
ObjectiveUp to now, fiber tractography in the clinical routine is mostly based on diffusion tensor imaging (DTI). However, there are known drawbacks in the resolution of crossing or kissing fibers and in the vicinity of a tumor or edema. These restrictions can be overcome by tractography based on High Angular Resolution Diffusion Imaging (HARDI) which in turn requires larger numbers of gradients resulting in longer acquisition times. Using compressed sensing (CS) techniques, HARDI signals can be obtained by using less non-collinear diffusion gradients, thus enabling the use of HARDI-based fiber tractography in the clinical routine.MethodsEight patients with gliomas in the temporal lobe, in proximity to the optic radiation (OR), underwent 3T MRI including a diffusion-weighted dataset with 30 gradient directions. Fiber tractography of the OR using a deterministic streamline algorithm based on DTI was compared to tractography based on reconstructed diffusion signals using HARDI+CS.ResultsHARDI+CS based tractography displayed the OR more conclusively compared to the DTI-based results in all eight cases. In particular, the potential of HARDI+CS-based tractography was observed for cases of high grade gliomas with significant peritumoral edema, larger tumor size or closer proximity of tumor and reconstructed fiber tract.ConclusionsOvercoming the problem of long acquisition times, HARDI+CS seems to be a promising basis for fiber tractography of the OR in regions of disturbed diffusion, areas of high interest in glioma surgery.
Highlights
Due to their rapid growth and infiltrative nature, gliomas remain one of the challenges in neurological surgery, those tumors located in direct vicinity of eloquent cortical areas or fiber bundles
The potential of High Angular Resolution Diffusion Imaging (HARDI)+compressed sensing (CS)-based tractography was observed for cases of high grade gliomas with significant peritumoral edema, larger tumor size or closer proximity of tumor and reconstructed fiber tract
Overcoming the problem of long acquisition times, HARDI+CS seems to be a promising basis for fiber tractography of the optic radiation (OR) in regions of disturbed diffusion, areas of high interest in glioma surgery
Summary
Due to their rapid growth and infiltrative nature, gliomas remain one of the challenges in neurological surgery, those tumors located in direct vicinity of eloquent cortical areas or fiber bundles. Besides long-time used electrostimulation methods, particular magnetic resonance imaging (MRI)-modalities were established to display functional cortical sites or fiber bundles non-invasively. These data can be integrated into the navigation system and displayed intraoperatively, which has been shown to contribute to low postoperative morbidity [4,5]. DTI is based on a set of diffusion images acquired for at least six different gradient directions and one reference image [6] With these data, the diffusion properties within each voxel can be calculated by the Stejskal Tanner equation, resulting in a 2nd order tensor. Another problem appearing with DTI-based fiber tractography is the resolution of fibers in areas of disturbed diffusion, for example due to tumor or peritumoral edema [10,11,12]
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