advanced 3d guidance for evar procedures - … · advanced 3d guidance for evar procedures gilles...
TRANSCRIPT
Advanced 3D Guidance for EVAR Procedures
Gilles Soulez, MD, MSc
University of Montreal
Disclosure & Acknowledgments
• Research Grants• Canadian Health Research Institute
• Canadian Fundation of Innovation
• Natural Sciences and Engineering Research Council
• Fonds Recherche Québec-Santé
• Siemens Medical
• Cook Medical
• CAE
• Patent licensing (Cook Medical)
Current limitation of CT planning and 2D DSA guidance for EVAR
• Procedure planning performed on CTA
• DSA guidance• Radiation exposure and CIN
• Need to recreate ideal projection for each procedural step
• No visualization of thrombus to delineate landing zones
• Increasing incidence of complex EVAR
• Hostile neck
• Branched/Fenestrated
• Chimney
Renal function & EVAR
• GFR ml/min• Stage 1 >90
• Stage 2 60-89
• Stage 3 30-59
• Stage 4 15-29
• Stage 5 < 15
Brown LC. An Surg 2010;251-966-975
Irradiation
• EVAR & irradiation1
• Planning CT
• EVAR + CT FU at 1, 3, 6 and 12 months and annually
• 145-205 mSv on 5 years• 70-year-old = attributable cancer risk = 0.60% (1 in 170).
• 50-year-old = 1.03% (1 in 100)
• 30% of CT scan unnecessary 2
• Stochastic injuries due to staff exposition3
1.White HA. J Cardiovasc Surg 2010 51:95-104 2. Zhou W. J Vasc Surg 2010 3. Stecker MS-JVIR-2009
• Alignment 3D and 2D projection
• Real time fluoroscopy with2D/3D overlay
• Synchronization of 3D rendering with C-arm angulation
Improve guidance 3Droadmap
Per-operative 2D/3D Workflow
Limitation of overlaying CT volume rendering and fluoro
• Thrombus outline is not seen
• Superposition of VR will mask guidewires, delivery device and stent markers
• Only a rigid registration can be performed since you do not have a mathematical geometric model (Mesh)
How to improve volume overlay
• Fading in and out
• Stent boost
• Use vessel transparent dysplay
• Complete segmentation of AAA lumen and thrombus outlines
• Create a lumen and thrombus mesh
• Dysplay only the mesh
Dijkstra-ML-J-Vasc-Surg-2011Tacher-V-JVIR-2013
AAA segmentation and modeling• Longitudinal view of the
AAA
• Outerwall segmentation from the celiac trunk to one selected iliac artery
• Segmentation plans defined on transverse section of the AAA
• 3D rendering of the AAA lumen and thrombus
• Automated D-Max and volume measurements
Kauffmann C et al. EJR 2011;77:502-8
Automatic CT segmentation for lumen and thrombus
Planning
• Define centerlines• Aorta, iliac, renal arteries• CT, SMA• Internal iliac arteries
• Propose and define the best working view for each procedural steps
• Orthogonal projection to target vessel centerline
• Adjust if needed for C-arm mechanical range
3D/3D Registration
• Perform a CBCT• Before draping
• Automatic bone registration• Spine/spine
• Fine tuning of registration based on vascular
• Calcification alignement• Vessel ostia
• Projection of 3D CT mesh in the fluoroscopic spac
• Synchronization of C-arm, table, magnification with the new 3D/3D space
Registration with Biplanar Fluoroscopy
• Separate VR of spine and aortic lumen from CT
• Spine fusion /biplanar fluoroscopy
• Replacement of spine by aortic lumen
• Advantage• Dose• Easy
• Drawback• Absence of precise vascular
alignement
Rigid registration
Live DSA correction
Live DSA correction
Registration accuracy
Registration renal arteries Error X axis
Error z axis
Before correction mm 10.6±11 7.4±5.3
Bone based correction mm 3.5±2.5 4.6±3.7
DSA correction mm 0.6±0.7 0.3±0.4
•3D/3D registration is generated at the onset of the procedure (before patient draping)
•Need to minimize patient motion
•Influenced by anesthesia
•Arm position
Kaufmann et al. JVIR 2015
Optimization of overlay for bone correction
• Substraction of bone marrow to outline bone contours
• Manual bone based correction of the 3D/3D alignement during fluoroscopy
• Manual alignement optimization based on DSA
• Mean error on renal• 1.95 ±2.46 mm (0-7 mm)
Fukuda-T et al. Europ-J Vascular-Endovasc-Surg-2013
Iliac artery
• Iliac centerline deviation• 38.3±15.6mm
• Ostia internal iliac artery• Ipsi lateral
• 5.6±2mm (x axis)
• 4.3±3mm (z axis)
• Contralateral• 6.1±3mm (x axis)
• 5.5±4.2 (z axis)
Kaufmann et al. JVIR 2015
Vascular displacement is a concern
Deformation induced by endovascular devices
Elastic registration with automated detection of endovascular devices
Lessard S et al. Med Eng Phys 2015
Device segmentation
• Errors at the internal iliac ostia estimation after a mesh deformation, measured offline
• 28 patients (21 EVAR and 7 FEVAR)
• 43 measures
• Before correction mean error 11.3±7mm
• After correction 1.99±2.03 mm
• 19 no error
• Principal suspected causes of error
• External iliac high curvature
• High calcification score
Preliminary results
Lessard S et al. Manuscript in preparation
Deformation influenced by calcification and curvature
Ideal Workflow for minimizing misregistration
• AAA mesh creation > MIP or VR overlay
• CBCT > biplanar ?• Better alignment of vascular structure on CBCT (calcification)
• Continuous and automated process of bone correction to correct bone displacement
• Apply correction on CBCT/CT fusion model
• Update of vascular structure• Guidewire (geometric centerline alignement)• After each DSA
• Mechanical modeling (FEA)
Clinical utility for standard EVAR
• 72 pts database /matching based on BMI
• 16 vessel navigator
• 16 conventional DSA
Stangenberg-L-J-Vasc-Surg-2015
2D/3D interesting for complex EVAR
• Increasing proportion of EVAR in hostile neck anatomies
• Fenestrated/branched SG/chimney procedures
• Helpful to align fenestration and catheterize side vessels
Fenestrated/branched EVAR
Tacher-V et al JVIR 2013
Clinical utility
Clinical utility: fenestrated, branched SG
• 72 patients FEVAR• 41 no CT fusion
• 31 after CT fusion
• Less• Fluoro, procedure time
• Radiation, Contrast dose
• Less blood loss (p<0.0001)
• Trend for lower hospital stay (p=0.07)
Mc Nally et al. J Vasc Surg 2015
102 pts intra-operative fusionStandard (44)/Fenestrated (18)/Branched (26)/Thoracic (14)
Hartault-A-Eur-J-Vasc-Endovasc-Surg-2015
Comprehensive biomechanical modeling of EVAR
• Developing a comprehensive patient-specific biomechanical model of the aorto-iliac vascular structure and surrounding organs
• Intra-luminal thrombus
• Abdominal fat
• Spine
• Simulating EVAR to perform advanced procedural planning
• Assessing arterial deformations during EVAR
• Improving 2D/3D roadmap guidance (elastic registration using the simulation outputs
• Performing procedural rehearsal for physicians training
EVAR simulation
• Use the mesh to create a biomechanical model
• Aorta• Stent-graft
• Use Finite element analysis to estimate the interaction between SG and aorta
• Simulate SG deploiement to optimize SG planning
• Simulate vessel deformation to optimize image guidance
• Procedure reharsal for training
Roy D et al. IMA Journal of Applied Mathematics 2014;79:1011-1026
Displacement = 80mm
Lumen only
Finite element mesh
Points defining the spine curve
Done in 10 min. from segmentation files.
Simulation: aorta
Roy D et al. Numerical analysis 2014
Overall Workflow
StartPatients AAA, Thrombus, Spine, Pelvic
Bone and Fat Reconstruction
Deformation and configuration
Plug in for translating patient data to LSDYNA
Select stent-graft
Deployment Simulation
Zero Pressure GeometrySimu
lation
Translating simulation result to prioperative softwareR
oad
map
Tools identification
Proper simulation selection
Tools detection
3D roadmap
Patient geometry reconstruction
Thrombus
Patient from LCTI database
Spine
Lumen
ORS software
Numerical Model
Device Characterization (Cook Medical)
1
23
Equivalent mean properties for typical sections of body and leg catheters.
123
Eaxial = 402 MPaEcirc. = 165 MPa
Stent(Steel/nitinol)
Graft(Dacron)
Abdominal fat characterization
• The hyper-Viscoelastic material is considered for the surrounding organ
• The experimental data on human adipose
tissue is taken from Gerhard Sommer et al.
Stress strain data
Vessel Wall characterization
• AAA exhibits significant anisotropic behavior
Stress strain data
39
•Hyperelastic Matrix •Collagen fibers reinforcement•Layered structure of AAA
Matrix Fibers
I=IntimaM=MediaA=Adventitia
Results: Arterial deformation by guidewires
Dugas A et al. CVIR 2012;35:779-87
Results: Stent-Graft Deployment
(1) (2) (3)
(4) (5)
(6)
41
Results: Stent-Graft Deployment
Multimodal image fusion and simulation for EVAR
• 3D roadmap will minimize procedure time, contrast, irradiation and complication in complex EVAR procedures
• Improved visualization and correction if overlay done after AAA segmentation and mesh creation
• Automated device detection useful to perform geometric correction during the procedure
• Biomechanical simulation of AAA, SG and their mutual interaction will play a major role in the future