cami days december 2015 presentation nguyen-duc
TRANSCRIPT
This work was partly supported by the French ANR within the Investissements d'Avenir program (Labex CAMI)
under reference ANR-11-LABX-0004.
Tracking of structures for the endovascular
treatment of aortic pathologies
08/12/2015 1
Long Hung Nguyen-Duc
INSERM, U1099, Laboratoire de Traitement du Signal et de l’Image (LTSI)
Université de Rennes 1, Rennes
Thesis supervisor: Prof. Pascal Haigron
Clinical partners: vascular surgery (Rennes, Grenoble), interventional cardiology (Rennes)
08/12/2015 2
I. Context and objectives
Anatomy of the aorta
I. Context and objectives
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Aortic valve stenosis (AVS)
• Narrowing of the aortic valve opening
• Calcified aortic valve leaflets
Pathologies
stenosis/aneurysm
Abdominal aortic aneurysm (AAA)
• Localized rupture of the parallelism
of the aortic walls
For example:
I. Context and objectives
08/12/2015 4
Endovascular repair
Transcatheter aortic valve
implantation (TAVI)
Endovascular aneurysm repair
(EVAR)
- Catheterization under 2D X-ray guidance.- Vasculatures are visible only instantly with contrast product injection.- Intra-operative positioning and deployment have to be performed at the site planned from the pre-operative CT.
X-ray angiographic and
fluoroscopic guidance
Aortic valve stenosis
(AVS)
TranscatheterHeart Valve
(THV)
Aortic abdominal aneurysm
(AAA)
Catheterization
Device positioning and deployment
I. Context and objectives
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Electromagnetic tracking of endovascular devices (motionless structures)
- Navigation by using electromagnetic tracking system (EMTS)
- Track endovascular devices with respect to the vasculature
3D-3D registration between the EMT 3D space and the patient anatomy 3D
space.
Image-based tracking of vasculatures (moving structures)
- Navigation by using fluoroscopic X-rays imaging
- Track the vasculature with respect to endovascular devices
Real-time 2D object tracking in low-contrasted fluoroscopic sequences
Motivation: to limit the use of X-rays and contrast agent in the course of endovascular
interventions.
• Augmented perception: to reconsider/improve the tracking of endovascular devices and /
or vasculatures
II. Electromagnetic tracking of endovascular devices
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Electromagnetic tracking (EMT)
Could be used to locate devices through tissues.
The first issue: matching of the 3D EMT coordinate system and the 3D patient coordinate system.
Field generator Magnetic field Vascular structure Catheter tip
position and direction
II. Electromagnetic tracking of endovascular devices
matching
II. Electromagnetic tracking of endovascular devices
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Registration between the EMT 3D space and the patient 3D space
Current limitations:
- Low accuracy (distortion, velocity errors, registration errors) : 3-5mm
- Compatibility with the clinical workflow : fiducial-free approach?
Main objective: to propose a robust and precise 3D-3D registration approach that does not
require fiducial landmarks placed into the patient.
General idea: using of the tracked trajectories of the magnetic sensor inside the vasculature.
3D-3D Transformation
Rotation, Translation ?
Intra-operative
3D electromagnetic trajectory
Pre-operative CT
3D description of the patient vasculature
[de Lambert A et al., EJVES 2012]
[Manstad-Hulaas F et al., 2007]
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Proposed registration approach
Entire lumen Centerlines Minimum Bending
Energy Path (minBEP)Reduced lumen
Potential location of the EM trajectory within the lumen
The EM outliers compared to the 3D vasculature description are managed by a robust framework.
due to dissimilarity between the 3D EM trajectory and the 3D vasculature description
distortion of the magnetic field, velocity errors [Alfred M. Franz et al., TMI 2014]
II. Electromagnetic tracking of endovascular devices
Intra-operative
3D electromagnetic
Trajectory (ET)
Pre-operative CT
3D description
of the patient vasculature (VL)
Analysis of different distance criteria between the electromagnetic trajectory and the 3D description of the
patient vasculature.
non constrained constrained
outliers
outliers
Pre-operative CT
3D description
of the vasculature
electromagnetic points
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Proposed registration approach
Based on a RANSAC strategy, with two hypotheses :
“Inliers” inside the 3D vasculature description.
The optimal transformation must brings most of the points into the arterial lumen.
RANSAC Principle
(RANdom SAmple Consensus [Fischler, Bolles 1981])
II. Electromagnetic tracking of endovascular devices
In set of data points
Out
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Experimental results
Phantom study of RANSAC-based 3D-3D registration between EM trajectories and the vasculature
P1
P2 P3
P4
Positions/
3D description
P1 P2 P3 P4 Mean Stdev
Entire lumen 1.825 1.801 1.576 2.627 1.957 0.433
Reduced lumen 1.720 0.887 0.897 2.205 1.427 0.211
Centerlines 1.596 1.313 0.677 2.080 1.416 0.285
minBEP 2.646 1.849 2.212 3.816 2.631 0.854
Registration and navigation interfaces implemented in
C++ with CamiTK [C. Fouard et al., 2012]
- For each 3D vasculature description, the registration
procedure was repeated 9 times.
- Errors are reported from 4 different positions.
- Error measurement by exploiting the CBCT.
Target Registration Errors
Constrained EM trajectory
Positions/
3D description
P1 P2 P3 P4 Mean Stdev
Entire lumen 3.456 3.134 2.205 3.389 3.046 0.578
Reduced lumen 3.147 2.979 2.125 3.019 2.817 0.467
Centerlines 2.984 2.761 1.924 2.777 2.612 0.470
minBEP 2.653 2.796 1.695 2.527 2.417 0.494
Non constrained EM trajectory
II. Electromagnetic tracking of endovascular devices
III. Image-based tracking of vasculatures
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III. Image-based tracking of vasculatures
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Objective: to provide additional references for endovascular devices positioning and deployment.General idea: tracking of aortic valve calcifications in intra-operative fluoroscopic images in order totrack the aortic valve plane.
Several approaches for object tracking :
• Recursive tracking [Lucas, B.D., Kanade T, 1981]
• Tracking-by-detection [Ozuysal, M., 2007]
• Adaptive methods [Kalal, Z., 2011]
Difficulties: size and density of calcifications, low-contrasted fluoroscopic images.
III. Image-based tracking of vasculatures
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Based on an adaptive detection scheme, the tracking process consists in:• Finding new patches that correspond to the initial calcification patch.• Learning of appearance changes of the target calcification.
Proposed method : Tracking of calcifications using online learning
• Variance filter
• Pixel pair comparisons
III. Image-based tracking of vasculatures
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Experimental Results
Qualitative results
Tracking errors reported from 10 sequences
Tested on 10 patients• Average detection rate greater than 88%.• Tracking error less than 1.0mm for 93.3% ofthe tracked frames.• Average processing time less than 30ms foreach frame.
Change of image quality Presence of guidewireLow-contrasted fluoroscopic images
III. Image-based tracking of vasculatures
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Application to computer-assisted navigation in the context of TAVI
Example of augmented fluoroscopic sequence
!
Trackingofaorticvalvecalcifications
Pre-operative
3DModels+3D/2DStaticRegistration
Intra-operative
2DLandmarks
Dynamicoverlayof2DlandmarksLiveFluoroscopicImages Dynamicoverlayof3Dmodels
III. Conclusions and Perspectives
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Conclusions
Solutions to contribute to the endovascular navigation.
Electromagnetic tracking of endovascular devices (motionless structures)
RANSAC-based fiducially-free 3D-3D registration for electro-magnetic navigation.
Without Intra-operative X-ray Imaging, without fiducial landmark. [SURGETICA 2014]
Phantom study: precision of 1.4mm.
Perspectives: in vivo experiment to assist catheter navigation and reach specific targets (renal artery
catheterization).
Image-based tracking of vasculatures (moving structures)
Novel approach to track the aortic valve calcifications in fluoroscopy imaging (mean error less than 1.0mm).
[GRETSI 2015]
Minimal user-interaction is required to initialize the algorithm.
Could be used to track the aortic valve plane that represents the moving target for endoprosthesis deployment,
in order to limit the use of contrast agent. [IEEE EMBC 2013]
Could be applied also for the tracking of other structures of interest. [SURGETICA 2014]
Perspectives: combination with electromagnetic tracking of devices for navigation inside the moving structure.
Thank you!