X ray Based Imaging in Neurovascular Intervention Requirements and Challenges

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1 University of Massachusetts X ray Based Imaging in Neurovascular Intervention Requirements and Challenges Division Neuroimaging and Intervention & The New England Center for Stroke Research Departments of Radiology, Neurology and Neurosurgery

2 Disclosure BSC (Educational Grant, Clinical Research) Ev3 (Consultant, Research Grant, Clinical Research) Codman J&J (Consultant, Educational Grant, Clinical Research) Micrus (Consultant, Educational Grant, Clinical Research) Microvention (Educational Grant, Consultant) Surpass Med Ltd (Stockholder, Clinical Research) Medtronic (Consultant) Penumbra (Consultant, Clinical Research) Covidien (Consultant) Soteira (Consultant) Philips (Research Grant, Equipment support) NIH (NIBIB 1R21EB ; NINDS 5R01NS ; NINDS 1R21NS A1)

3 Ischemic and Hemorrhagic Stroke in USA Stroke is the third cause of death and leading cause of disability in the United States 700,000 new or recurrent stroke per year Approximately 87% ischemic 40% due to large vessel occlusions Every 45 seconds someone in the U.S. has a stroke 160,000 fatal per year Stroke cost estimated at $62.7 billion in year recurrence rate for stroke 24 42% ~ 50,000 aneurysms treated (~30,000 ruptured)

4 Medical Devices for Recanalization MERCI Retriever Multi MERCI trial: 17 center, noncontrolled, technical efficacy study (n=177) Recanalization in 55% of pts Procedural complications in 9.8% mrs 2 at 90 days: 36% 49% in pts with recanalization 9.6% in pts without recanalization Smith WS, Sung G, Saver J, et al., for the MERCI Trial Investigators. Stroke 2008, 39: 1205

5 Medical Devices for Recanalization Penumbra System Penumbra trial: 24 center, noncontrolled, technical efficacy study (n=125) Recanalization in 82% of pts ICA occlusion 18% VB occlusion 9% Procedural but not device related complications in 3.2% mrs 2 at 90 days: 25% 29% in pts with recanalization 9% in pts without recanalization Presented at the 2008 ASA International Stroke Conference in New Orleans by Cameron McDougall, M.D. on behalf of the Penumbra Stroke Trial investigators.

6 Acute Ischemia: Left ICA Dissection and Thromboembolic MCA Occlusion CT, CT Angiography and CT Perfusion 60 y o m w NIHSS 21 (global aphasic and R UE/LE hemiplegia

7 Left ICA dissection and MCA Occlusion Digital Subtraction Angiography

8 Acute Stenting in left ICA dissection and MCA Occlusion Enterprise VRD* *Stenting procedure approved on case by case base by local IRB and FDA

9 Acute Stenting in left ICA dissection and MCA Occlusion Enterprise VRD stent* *Approved on case by case base by local IRB and FDA

10 Acute Stenting in left ICA dissection and MCA Occlusion Enterprise VRD*

11 Acute Stenting in left ICA dissection and MCA Occlusion CT Post Revasc CT D 2 MR FLAIR D 4 NIHSS 5 on D5 post revascularization

12 What are the Challenges Extravascular/Medical Management (minimally invasive) Endovascular Vessel Wall Biomechanics Physiology/ Flow Dynamics Vessel Wall Biological Response Coagulation System Anatomy/Morphology

13 Biplane 3D Neuroendovascular Surgical Suite The Endovascular Microscope Flat Panel Detector

14 Major Challenges Delayed care due to lack of integration of multimodality imaging within the proximity Improvement of spatial and temporal resolution of present imaging angiography system needed including faster sampling by FD Soft tissue characterization

15 Morphology/Anatomy

16 Normal 3 D vascular anatomy

17 Imaging Illustrative case: Dysplastic PICA Aneurysm CT Angiography

18 DSA Image and 3 D Angiogram

19 Intraoperative view

20 Anatomy/Morphology Current Features High resolution angiography 3D angiography Roadmap 3D Roadmap Integration of arterial, capillary and venous structures within the same display Requirements/Challenges Integration of information on soft tissue and vascular structures (e.g., calcification) Higher tissue contrast resolution Image segmentation of various sources within sub mm accuracy (MR, CT, DSA) Motion artifacts (breathing, head motion, vasculature pulsatility, brain motion)

21 Development of Soft Tissue Imaging Cone Beam CT Case: Small brain arteriovenous malformation in a 6 y o boy with parenchymal hemorrhage

22 DSA

23 Soft tissue Imaging Cone Beam CT

24 Small bavm subependymal anterior thalamus at the level of foramen of Monro

25 Real High resolution Roadmap Dural arteriovenous fistula with subdural hematoma

26 Acrylate Infusion Roadmap

27 Implants/Devices

28 Brain Aneurysm Implants Coils Stents Flow Diverter Pre Post 6 mo FU

29 Stent Wall Apposition and Kink

30 Stent covering an underlying plaque/clot

31 Scatter Radiation

32 Flow Diverter Insufficient spatial resolution Flow Diverter

33 Device and Vasculature Loss of Details due to Similarity in X ray Attenuation

34 Device and Soft Tissue Current Features Improved spatial resolution with integration of tissue imaging (cone beam CT) Improved devicevasculature information Some soft tissue information Requirements/Challenges Higher spatial resolution Higher tissue contrast Scatter radiation with high amount of metal mass (coils) Motion artifacts (arterial pulsation, brain pulsation, breathing, head motion) Introduction of new nonmetallic implants/materials

35 Physiology

36 Physiology Ischemic Stroke: CBF, CBV, MTT and integration of imaging and intervention using the same FD unit Pre and Post Revascularization: Assessment of Brain Perfusion in Vasospasm, Intracranial Disease (ICD) and Extracranial Disease (ECD) Flow quantification and Flow pattern characterization for brain aneurysm Characterization of Tumor vascularity

37 Acute Ischemia: Left ICA Dissection and Thromboembolic MCA Occlusion CT, CT Angiography and CT Perfusion

38 Tissue Perfusion Current Features Some soft tissue information (hematoma, CSF, vasculature) Good spatial resolution and contrast sensitivity CBV Some information on flow Requirements/Challenges Higher temporal resolution Higher FD sampling rate CBF, CBV, MTT Characterization of flow patterns and quantification of flow (contrast attenuation) Motion artifacts (arterial pulsation, brain pulsation, breathing, head motion)

39 High Speed Rotation for Cone Beam CT

40 Ahmed, Zellerhoff, Strother, et al. AJNR 2009

41 Comparison CTP and C arm CT Regions of white matter, gray matter and basal ganglia were studied iv contrast injection Ahmed, Zellerhoff, Strother, et al. AJNR 2009

42 Ahmed, Zellerhoff, Strother, et al. AJNR 2009

43 Flow Diversion in Brain Aneurysm

44 Key Questions Brain Aneurysms and Flow Is there an interaction between flow and aneurysm growth and rupture? Can the interaction between flow and vascular wall biology be modeled? Flow diveters: virtual implantation Limitations of mathematical modeling

45 Aneurysmal Disease: Multi-Factorial Problem low WSS high WSS endothelial dysfunction excess NO apoptosis HEMODYNAMICS remodeling degenerative remodeling intimal thickening wall weakness CLINICAL genetics gender, age smoking history of SAH hypertension ANEURYSM initiation growth stabilization rupture BIOMECHANCICS PERI ANEURYSMAL ENVIRONMENT wall stress growth & remodeling sharp contacts increased stress wall injury Courtesy of Dr. C Putman smooth contacts extra structural support stabilization

46 Large Impingement Small Impingement Inflow Jet Concentration and Impingement Size Various Aneurysm Types CFD Studies Courtesy of Dr. C Putman Diffuse Concentrated

47 Virtual vs Conventional Angiography Conventional Angiogram Virtual Angiogram CFD Analysis Cebral,J.R.,R.Pergolizzi,andC.M.Putman, Computational fluid dynamcis modeling of intracranial aneurysms: qualitatively comparison with cerebral angiography. Academic Radiology, 14(7): , 2007.

48 Virtual Angiograms: Flow Effect and Residence Time Pre coiling Post coiling Courtesy of Dr. C Putman

49 Flow Blockage by Coils Flow Pattern Iso Velocity Courtesy of Dr. C Putman

50 Virtual Angiograms Pre-Stenting Post-Stenting

51 Optimization of Flow Diverter

52 Particle Image Velocimetry Average hydrodynamic circulation T 1 r r Γ m = Γ ( t ) d t w h e r e : Γ = ( V ) n d A T 0 A Lieber, Nikolaidis, Wakhloo Ann Biomed Eng 1998

53 Flow Diverter in Rabbit Elastase Aneurysm Contrast washout and X ray attenuation Pre FD Post FD 3 wks FU

54 MATHEMATICAL MODEL Use of Functional Angiography Convection Diffusion t 1 e 2σ 1 f(t)=ρ 2 e 1 dη + σπ 2 τ 1 0 t η (η μ) 2 τ 1 ρ 2 2 t (η μ) t 1 e 2σ 2 τ dη 1 e 2 0 σ 2π σ,μ = Contrast injection related parameters. ρ 1 τ 1 ρ 2 τ 2 = Relative magnitude of contrast convected out of aneurysm. = Convection time constant. = Relative magnitude of contrast diffused out of aneurysm. = Diffusion time constant. Lieber, Gounis, Chander, Wakhloo Crit. Rev Biomed Eng 2004

55 Rabbit Elastase Aneurysm Flow diverters

56 Arterial Phase High speed DSA immediately after Flowdivertor Flow stagnation and delayed contrast washout Arterial Capillary Phase Flowdivertor Ophthalmic Artery

57 Surpass Flowdivertor Flow stagnation and delayed contrast wash out Capillary Phase Venous Phase Late Venous Phase Retinal Blush Retinal Blush Retinal Blush

58 MRI (Axial source images TOF with contrast) Before Surpass Flowdivertor 24 hours after Surpass Flowdivertor

59 Virtual Stenting Second Generation Integration of Morphology and Flow Information

60 Vessel Wall Biomechanics

61 Wall Compliance Effects Some Observations: 30+ patients imaged with dynamic DSA & 4DCTA 2/3 of aneurysm exhibit motion, 1/3 no motion 2/3 of blebs deformed with larger amplitude than sac BA tip aneurysms had a bending motion of the BA Wall motion characteristics varied from patient to patient Wall Tracking Sforza D, Putman C, Oubel E, DeCraene M, Frangi A, Cebral JR, Characterization of wall motion in cerebral aneurysms from dynamic angiography, Proc. ASNR, New Orleans, Zones Rigid Deforming Dempere Marco, L., E. Oubel, M.A. Castro, C.M. Putman, A.F. Frangi, and J.R. Cebral, Estimation of wall motion in intracranial aneurysms and its effects on hemodynamic patterns. Lecture Notes in Computer Science, 4191:

62 Thank you We are what we repeatedly do. Excellence, then, is not an act, but a habit. Aristotle 384 BC 322 BC