reliability of connectivity-based thalamic segmentation ... of connectivity... · reliability of...
TRANSCRIPT
Reliability of connectivity-based thalamic segmentation for targeting in
noninvasive neuromodulation using MR-guided Focused Ultrasound
Angela E. Downes M.D.1, Jeffrey Elias M.D.2, Nader Pouratian M.D., Ph.D.3
1 Department of Neurosurgery, Morsani, College of Medicine, University of South Florida, Tampa, Florida
2 Department of Neurosurgery, University of Virginia Health Sciences Center, University of Virginia, Charlottesville, VA
3Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
MR-guided Focused Ultrasound
MR-guided Focused Ultrasound
Martin E, Jeanmonod D: High-intensity focused ultrasound for noninvasive functional neurosurgery. Ann Neurol.2009.
Essential Tremor
• Excellent study model • Most common movement disorder
• Surgical therapies
• Deep brain stimulation • RF thalamotomy • SRS
• VIM
Surgical treatments
• Lesioning is not extinct…
• DBS has complications
How can we make it better?
• Traditional Targeting Methods – Indirect targeting
– Direct targeting
– Intraoperative microelectrode recordings
Indirect Targeting
Limited due to intersubject anatomic variability
STN (relative to midcommisural point): X: 10-12 mm lateral Y: 2-4 mm posterior Z: 4-6 mm inferior
GPi (relative to midcommisural point): X: 19-22 mm lateral Y: 2-4 mm anterior Z: 4-5 mm inferior
VIM (relative to midcommisural point): X: Upper extremity: 12-14 mm lateral of midline Lower extremity: 14-16 mm lateral of midline Y: 5-6 mm anterior to PC OR 25% of the length of AC-PC behind MCP Z: 0 mm inferior
Sing
le
Subj
ect
452
Subj
ects
Improved Structural Imaging: Direct Targeting
Limited because (1) not all targets are visible (e.g., within the thalamus) (2) Even if visualized, connectivity and function of visualized
structure not known for the individual patient VIM Thalamus
Deus
chl G
: Tre
atmen
t of p
atien
ts wi
th es
sent
ial tre
mor.
The
Lanc
et N
euro
logy:2
011
Intraoperative Microelectrode Recordings
Identify electrophysiological activity consistent with target
2013… What tools do we have now? Brain mapping
Advances in neuroimaging
Structural
Diffusion weighted
Probabilistic diffusion
tractography
Fractional anisotropy
7T MRI
Functional
fMRI, PET
Connectivity-based thalamic segmentation
Pouratian et al. Journal of N
eurosurgery. 2011.
Validation of connectivity-based thalamic segmentation for DBS targeting for tremor
DBS Electrode
Region of Maximal Thalamic Connectivity With Premotor Cortex
Validation of connectivity-based thalamic targeting for FUS
• Hypothesis: Optimal location for FUS lesion colocalizes with thalamic voxels with the highest probability of connectivity with primary motor cortex
• Retrospective image analysis • 15 patients 12 connectivity maps
Primary motor connectivity
Primary somatosensory connectivity
FUS Lesion
Probabilistic connectivity based thalamic targeting
Excellent outcome High concordance
Poorer outcome Low concordance
Concordance of Automated M1-Thalamus with Final DBS FUS Lesion Position
A
B
C
Poorer outcome High concordance
Concordance of Automated M1-Thalamus with Final DBS FUS Lesion Position
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
ROC Curve 2 mm Sphere
Future directions
• Try different cortical connectivity – Premotor cortex, supplementary motor cortex
• Unknowns with FUS – Where is efficacious point in lesion? – Variaiblity across patients with size, shape,
intensity of lesion
• Incorporate side effects into analysis
Conclusions
• Tailored therapies
• Probabilistic tractography correlates both structure and function
• FUS has a real future as a noninvasive neurosurgical tool