Probabilistic vs. deterministic fiber tracking and the influence of different seed regions to delineate cerebellar‐thalamic fibers in deep brain stimulation

Abstract

This study compared tractography approaches for identifying cerebellar-thalamic fiber bundles relevant to planning target sites for deep brain stimulation (DBS). In particular, probabilistic and deterministic tracking of the dentate-rubro-thalamic tract (DRTT) and differences between the spatial courses of the DRTT and the cerebello-thalamo-cortical (CTC) tract were compared. Six patients with movement disorders were examined by magnetic resonance imaging (MRI), including two sets of diffusion-weighted images (12 and 64 directions). Probabilistic and deterministic tractography was applied on each diffusion-weighted dataset to delineate the DRTT. Results were compared with regard to their sensitivity in revealing the DRTT and additional fiber tracts and processing time. Two sets of regions-of-interests (ROIs) guided deterministic tractography of the DRTT or the CTC, respectively. Tract distances to an atlas-based reference target were compared. Probabilistic fiber tracking with 64 orientations detected the DRTT in all twelve hemispheres. Deterministic tracking detected the DRTT in nine (12 directions) and in only two (64 directions) hemispheres. Probabilistic tracking was more sensitive in detecting additional fibers (e.g. ansa lenticularis and medial forebrain bundle) than deterministic tracking. Probabilistic tracking lasted substantially longer than deterministic. Deterministic tracking was more sensitive in detecting the CTC than the DRTT. CTC tracts were located adjacent but consistently more posterior to DRTT tracts. These results suggest that probabilistic tracking is more sensitive and robust in detecting the DRTT but harder to implement than deterministic approaches. Although sensitivity of deterministic tracking is higher for the CTC than the DRTT, targets for DBS based on these tracts likely differ.

PSA and VIM DBS efficiency in essential tremor depends on distance to the dentatorubrothalamic tract

“…Additionally, the diffusion data used from the human connectome project is superior in quality to most images acquired during clinical routine and while a population-based average tract might neglect individual neuroanatomic aberrations, it might also be less prone to tracking errors which have been shown to occur when identifying individual DRTTs. 15 Most importantly, the average deviation of individual patient DRTTs from our population-based DRTT was within the range of image accuracy (see supplementary material). We employed probabilistic fiber tracking, as it might be better in detecting the DRTT than the deterministic algorithms embedded in commercially-available stereotactic planning software.…”

Deep brain stimulation: Connectivity profile for bradykinesia alleviation

“…Note, however, that our data sample for tremor symptoms was limited and that tractography is less sensitive in detecting decussating than ipsilateral fibers. 28 Similarly, our data showed no contingency between effectiveness for rigidity alleviation and DRTT targets. Instead, rigidity alleviation was associated with ascending brainstem (ML, FAL, BIC) and intralaminar thalamic fibers (f-H1, IML).…”

“…Tractography based on 64 orientations may be superior to fewer orientations in detecting the DRTT and adjacent fiber tracts 28 and may result in more reliable and less noisy estimates of diffusion parameters. Instead of examining tractographies on a standardized template brain, we examined the individual tractograms on patient-specific images.…”

“…We used probabilistic tractography, which tends to be more accurate in visualizing white matter pathways than deterministic approaches, especially in situations with crossing or kissing fibers. 28 may better reflect the stimulated brain tissue, we refrained from this to avoid overlapping seed regions. Our data were collected by different scanners (1.5T, 3T) and gradient orientation schemes (30, 64) as we applied the latest MRI technique as soon as available.…”

A combined diffusion‐weighted and electroencephalography study on age‐related differences in connectivity in the motor network during bimanual performance

“…Approaches can be deterministic, like the one used here, or probabilistic. Recently, however, Kupper et al (), Khalsa, Mayhew, Chechlacz, Bagary, and Bagshaw (), Schlaier et al () and Sarwar, Ramamohanarao, and Zalesky () showed that deterministic tractography often agrees with probabilistic tractography. While this may be considered convincing evidence, studies like (Jeurissen, Leemans, Jones, Tournier, & Sijbers, ) render the need for future studies to address this comparison in more detail.…”