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Feasibility of Diffusion Tractography for the Reconstruction of Intra-Thalamic and Cerebello-Thalamic Targets for Functional Neurosurgery: A Multi-Vendor Pilot Study in Four Subjects.

Jakab A, Werner B, Piccirelli M, Kovács K, Martin E, Thornton JS, Yousry T, Szekely G, O'Gorman Tuura R - Front Neuroanat (2016)

Bottom Line: While CTT resolved the anatomically correct trajectory of the tract individually, high volumetric variability was found across subjects and between scanners.DTI can be applied in the clinical, preoperative setting to reconstruct the CTT and to localize subdivisions within the lateral thalamus.In our pilot study, such subdivisions moderately matched the borders of the ventrolateral-posteroventral (VLpv) nucleus and the ventral-posterolateral (VPL) nucleus.

View Article: PubMed Central - PubMed

Affiliation: Center for Magnetic Resonance Imaging Research, University Children's HospitalZürich, Switzerland; Computational Imaging Research Lab, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of ViennaVienna, Austria.

ABSTRACT
Functional stereotactic neurosurgery by means of deep brain stimulation or ablation provides an effective treatment for movement disorders, but the outcome of surgical interventions depends on the accuracy by which the target structures are reached. The purpose of this pilot study was to evaluate the feasibility of diffusion tensor imaging (DTI) based probabilistic tractography of deep brain structures that are commonly used for pre- and perioperative targeting for functional neurosurgery. Three targets were reconstructed based on their significance as intervention sites or as a no-go area to avoid adverse side effects: the connections propagating from the thalamus to (1) primary and supplementary motor areas, (2) to somatosensory areas and the cerebello-thalamic tract (CTT). We evaluated the overlap of the reconstructed connectivity based targets with corresponding atlas based data, and tested the inter-subject and inter-scanner variability by acquiring repeated DTI from four volunteers, and on three MRI scanners with similar sequence parameters. Compared to a 3D histological atlas of the human thalamus, moderate overlaps of 35-50% were measured between connectivity- and atlas based volumes, while the minimal distance between the centerpoints of atlas and connectivity targets was 2.5 mm. The variability caused by the MRI scanner was similar to the inter-subject variability, except for connections with the postcentral gyrus where it was higher. While CTT resolved the anatomically correct trajectory of the tract individually, high volumetric variability was found across subjects and between scanners. DTI can be applied in the clinical, preoperative setting to reconstruct the CTT and to localize subdivisions within the lateral thalamus. In our pilot study, such subdivisions moderately matched the borders of the ventrolateral-posteroventral (VLpv) nucleus and the ventral-posterolateral (VPL) nucleus. Limitations of the currently used standard DTI protocols were exacerbated by large scanner-to-scanner variability of the connectivity-based targets.

No MeSH data available.


Related in: MedlinePlus

Reconstruction of the CTT with diffusion tractography.(A) population-averaged connectivity map (yellow-red color) overlaid onto a cross-sectional image (T1-weighted MRI). Slice levels are relative to the AC-PC plane, and three major anatomical landmarks have been annotated, ac, anterior commissure, mcl, mid-commissural line, pc, posterior commissure. (B) 3D visualization of the population-averaged CTT. Different opacities correspond to the population probability from 50th percentile to 90th percentile.
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Figure 5: Reconstruction of the CTT with diffusion tractography.(A) population-averaged connectivity map (yellow-red color) overlaid onto a cross-sectional image (T1-weighted MRI). Slice levels are relative to the AC-PC plane, and three major anatomical landmarks have been annotated, ac, anterior commissure, mcl, mid-commissural line, pc, posterior commissure. (B) 3D visualization of the population-averaged CTT. Different opacities correspond to the population probability from 50th percentile to 90th percentile.

Mentions: The CTT was reconstructed for each of the 10 datasets of the four participants. The typical trajectory of the DTI based reconstruction was the following. The tract emerged from the ipsilateral dentate nucleus, crossed to the opposite hemisphere at the level of superior cerebellar peduncle, and then passes medially and across the red nucleus. Cross-sectional images with annotations of the thalamic nuclei and major anatomical landmarks are shown in Figure 5A. The intra-thalamic terminations of the CTT overlapped with the VLpv nucleus, but due to the technical limitations of DTI tractography, the CTT fibers appeared outside the thalamus and subthalamus, and continued to a diverse set of supratentorial areas. In order to provide plausible visualizations of the tract, we limited the field of view to the subthalamus and thalamus. A notable left–right asymmetry was detected on the population level, in which the right CTT (originating from left cerebellum) was found to be more strongly connected to its pathway targets. Compared to the intra-thalamic targets, the CTT reconstruction showed significantly larger variability across the population. In some cases, the pathway was split and alternative routes were taken, possibly due to errors in the estimation of crossing fibers. In some cases, zero or a very low inter-subject overlap was reported using the 95th percentile of connectivity values, possibly due to splitting of the pathway into alternative routes, or due to the diminished sensitivity of locating the fibers at a single connectivity threshold. As observed for the intra-thalamic CBTs, the inter-scanner variability was similar to the inter-subject variability (Table 2).


Feasibility of Diffusion Tractography for the Reconstruction of Intra-Thalamic and Cerebello-Thalamic Targets for Functional Neurosurgery: A Multi-Vendor Pilot Study in Four Subjects.

Jakab A, Werner B, Piccirelli M, Kovács K, Martin E, Thornton JS, Yousry T, Szekely G, O'Gorman Tuura R - Front Neuroanat (2016)

Reconstruction of the CTT with diffusion tractography.(A) population-averaged connectivity map (yellow-red color) overlaid onto a cross-sectional image (T1-weighted MRI). Slice levels are relative to the AC-PC plane, and three major anatomical landmarks have been annotated, ac, anterior commissure, mcl, mid-commissural line, pc, posterior commissure. (B) 3D visualization of the population-averaged CTT. Different opacities correspond to the population probability from 50th percentile to 90th percentile.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940380&req=5

Figure 5: Reconstruction of the CTT with diffusion tractography.(A) population-averaged connectivity map (yellow-red color) overlaid onto a cross-sectional image (T1-weighted MRI). Slice levels are relative to the AC-PC plane, and three major anatomical landmarks have been annotated, ac, anterior commissure, mcl, mid-commissural line, pc, posterior commissure. (B) 3D visualization of the population-averaged CTT. Different opacities correspond to the population probability from 50th percentile to 90th percentile.
Mentions: The CTT was reconstructed for each of the 10 datasets of the four participants. The typical trajectory of the DTI based reconstruction was the following. The tract emerged from the ipsilateral dentate nucleus, crossed to the opposite hemisphere at the level of superior cerebellar peduncle, and then passes medially and across the red nucleus. Cross-sectional images with annotations of the thalamic nuclei and major anatomical landmarks are shown in Figure 5A. The intra-thalamic terminations of the CTT overlapped with the VLpv nucleus, but due to the technical limitations of DTI tractography, the CTT fibers appeared outside the thalamus and subthalamus, and continued to a diverse set of supratentorial areas. In order to provide plausible visualizations of the tract, we limited the field of view to the subthalamus and thalamus. A notable left–right asymmetry was detected on the population level, in which the right CTT (originating from left cerebellum) was found to be more strongly connected to its pathway targets. Compared to the intra-thalamic targets, the CTT reconstruction showed significantly larger variability across the population. In some cases, the pathway was split and alternative routes were taken, possibly due to errors in the estimation of crossing fibers. In some cases, zero or a very low inter-subject overlap was reported using the 95th percentile of connectivity values, possibly due to splitting of the pathway into alternative routes, or due to the diminished sensitivity of locating the fibers at a single connectivity threshold. As observed for the intra-thalamic CBTs, the inter-scanner variability was similar to the inter-subject variability (Table 2).

Bottom Line: While CTT resolved the anatomically correct trajectory of the tract individually, high volumetric variability was found across subjects and between scanners.DTI can be applied in the clinical, preoperative setting to reconstruct the CTT and to localize subdivisions within the lateral thalamus.In our pilot study, such subdivisions moderately matched the borders of the ventrolateral-posteroventral (VLpv) nucleus and the ventral-posterolateral (VPL) nucleus.

View Article: PubMed Central - PubMed

Affiliation: Center for Magnetic Resonance Imaging Research, University Children's HospitalZürich, Switzerland; Computational Imaging Research Lab, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of ViennaVienna, Austria.

ABSTRACT
Functional stereotactic neurosurgery by means of deep brain stimulation or ablation provides an effective treatment for movement disorders, but the outcome of surgical interventions depends on the accuracy by which the target structures are reached. The purpose of this pilot study was to evaluate the feasibility of diffusion tensor imaging (DTI) based probabilistic tractography of deep brain structures that are commonly used for pre- and perioperative targeting for functional neurosurgery. Three targets were reconstructed based on their significance as intervention sites or as a no-go area to avoid adverse side effects: the connections propagating from the thalamus to (1) primary and supplementary motor areas, (2) to somatosensory areas and the cerebello-thalamic tract (CTT). We evaluated the overlap of the reconstructed connectivity based targets with corresponding atlas based data, and tested the inter-subject and inter-scanner variability by acquiring repeated DTI from four volunteers, and on three MRI scanners with similar sequence parameters. Compared to a 3D histological atlas of the human thalamus, moderate overlaps of 35-50% were measured between connectivity- and atlas based volumes, while the minimal distance between the centerpoints of atlas and connectivity targets was 2.5 mm. The variability caused by the MRI scanner was similar to the inter-subject variability, except for connections with the postcentral gyrus where it was higher. While CTT resolved the anatomically correct trajectory of the tract individually, high volumetric variability was found across subjects and between scanners. DTI can be applied in the clinical, preoperative setting to reconstruct the CTT and to localize subdivisions within the lateral thalamus. In our pilot study, such subdivisions moderately matched the borders of the ventrolateral-posteroventral (VLpv) nucleus and the ventral-posterolateral (VPL) nucleus. Limitations of the currently used standard DTI protocols were exacerbated by large scanner-to-scanner variability of the connectivity-based targets.

No MeSH data available.


Related in: MedlinePlus