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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

Inter-scanner reproducibility of connectivity based intrathalamic targets.(A) 3D visualization of the inter-scanner variability of precentral CBT over the study population; (C) 3D visualization of the inter-scanner variability of VLpv CBT over the study population; (E) 3D visualization of the inter-scanner variability of VPLp CBT over the study population; (B) dependency of the inter-scanner variability of the precentral CBT volume on the applied connectivity threshold; (D) dependency of the inter-scanner variability of the VLpv CBT volume on the applied connectivity threshold; (F) dependency of the inter-scanner variability of the VPLp CBT volume on the applied connectivity threshold.
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Figure 6: Inter-scanner reproducibility of connectivity based intrathalamic targets.(A) 3D visualization of the inter-scanner variability of precentral CBT over the study population; (C) 3D visualization of the inter-scanner variability of VLpv CBT over the study population; (E) 3D visualization of the inter-scanner variability of VPLp CBT over the study population; (B) dependency of the inter-scanner variability of the precentral CBT volume on the applied connectivity threshold; (D) dependency of the inter-scanner variability of the VLpv CBT volume on the applied connectivity threshold; (F) dependency of the inter-scanner variability of the VPLp CBT volume on the applied connectivity threshold.

Mentions: While the pre- and postcentral gyrus CBT were largely reproducible across different scanners (Figures 6A,B,E,F), the VLpv CBT showed considerable variability (Figures 6C,D), as well as a larger volume and a modest interhemispheric asymmetry. We investigated the inter-scanner reproducibility of the CBT structures by comparing both the volumetric overlaps and the center-point distances. The maximum of the volumetric overlap was observed at similar connectivity percentiles as in the previous experiments; however, the center-point distances measured showed considerable differences between scanners of different vendors. The results obtained from Scanner 1 were found to match better the center-points of the ABTs, and the minimum Euclidean distances were below 2 mm when the CBT was thresholded at the 75th percentile. A similar effect was not observed using the data from the other two scanners. The volumetric overlaps for each of the 3 CBTs showed similar curves with maximum peaks at 90–95th percentiles. As summarized in Table 2, the overlap between CBTs across all subjects and scans was between 58 and 69% for the thalamic targets. When decoupling the variability into inter-subject within-scanner and intra-subject inter-scanner variability, we observed that for most of the structures, the inter-subject overlap was similar to the inter-scanner variability. Only in the case of the postcentral gyrus connections were the inter-scanner variability significantly higher (Table 2), meaning that the vendor type (Scanners 1–3) caused more variability than the anatomical differences between individuals after non-linear standardization.


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)

Inter-scanner reproducibility of connectivity based intrathalamic targets.(A) 3D visualization of the inter-scanner variability of precentral CBT over the study population; (C) 3D visualization of the inter-scanner variability of VLpv CBT over the study population; (E) 3D visualization of the inter-scanner variability of VPLp CBT over the study population; (B) dependency of the inter-scanner variability of the precentral CBT volume on the applied connectivity threshold; (D) dependency of the inter-scanner variability of the VLpv CBT volume on the applied connectivity threshold; (F) dependency of the inter-scanner variability of the VPLp CBT volume on the applied connectivity threshold.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Inter-scanner reproducibility of connectivity based intrathalamic targets.(A) 3D visualization of the inter-scanner variability of precentral CBT over the study population; (C) 3D visualization of the inter-scanner variability of VLpv CBT over the study population; (E) 3D visualization of the inter-scanner variability of VPLp CBT over the study population; (B) dependency of the inter-scanner variability of the precentral CBT volume on the applied connectivity threshold; (D) dependency of the inter-scanner variability of the VLpv CBT volume on the applied connectivity threshold; (F) dependency of the inter-scanner variability of the VPLp CBT volume on the applied connectivity threshold.
Mentions: While the pre- and postcentral gyrus CBT were largely reproducible across different scanners (Figures 6A,B,E,F), the VLpv CBT showed considerable variability (Figures 6C,D), as well as a larger volume and a modest interhemispheric asymmetry. We investigated the inter-scanner reproducibility of the CBT structures by comparing both the volumetric overlaps and the center-point distances. The maximum of the volumetric overlap was observed at similar connectivity percentiles as in the previous experiments; however, the center-point distances measured showed considerable differences between scanners of different vendors. The results obtained from Scanner 1 were found to match better the center-points of the ABTs, and the minimum Euclidean distances were below 2 mm when the CBT was thresholded at the 75th percentile. A similar effect was not observed using the data from the other two scanners. The volumetric overlaps for each of the 3 CBTs showed similar curves with maximum peaks at 90–95th percentiles. As summarized in Table 2, the overlap between CBTs across all subjects and scans was between 58 and 69% for the thalamic targets. When decoupling the variability into inter-subject within-scanner and intra-subject inter-scanner variability, we observed that for most of the structures, the inter-subject overlap was similar to the inter-scanner variability. Only in the case of the postcentral gyrus connections were the inter-scanner variability significantly higher (Table 2), meaning that the vendor type (Scanners 1–3) caused more variability than the anatomical differences between individuals after non-linear standardization.

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