2012 Proceedings - International Tissue Elasticity Conference

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059 EFFECTS OF THE WALL INCLUSION SIZE AND MODULUS CONTRAST ON THE REGIONAL PULSE WAVE PROPAGATION ALONG THE ARTERIAL WALL IN SILICO. Danial Shahmirzadi 1 and Elisa E. Konofagou 1 – Presented by RX Li 1 . 1 Columbia University, VC 12–232, 622 West 168th Street, New York, NY, 10032, USA. Background: Arterial stiffness has previously been reported as an independent indicator of cardiovascular diseases such as aortic aneurysm. Existing stiffness measurements methods in vivo are either invasive (e.g., catheterization) or provide only an average global estimate (e.g., tonometry). Previous studies of pulse wave propagation along inhomogeneous arterial walls have shown that a global PWV estimate might not effectively detect the presence of local stiffness changes [1]. Pulse wave imaging (PWI) is a noninvasive and local estimation method [2–4] for regional pulse wave velocity (PWV) measurement and visualization. Aims: Examining the effects of inclusion size and modulus contrast on the regional pulse wave propagation and velocity along the simulated arterial wall. Methods: A 3D fluid structure interaction (FSI) simulation of pulse wave propagation was performed in Coupled Eulerian–Lagrangian (CEL) explicit solver of Abaqus 6.10–1 (Simulia, RI, USA). The Lagrangian domain, mimicking the canine aorta, composed of a straight geometry tube (L=250mm; ri=12 mm, t=2.2mm) with a linearly elastic wall (Ewall=5.12MPa, ρwall=1050kg/m3 and Poisson's ratio ν=0.48). The Eulerian domain encompassed the Lagrangian tube, simulating the presence of a Newtonian fluid medium (ρfluid=1000kg/m3 , speed of sound C0=1483m/s and viscosity η=0.0001Pa.s). The FSI was defined as a frictionless two–way coupling between the tube and the fluid medium. The tube inlet and outlet were fully constrained in x–y–z directions, and a rectangular initial velocity (V0=5m/s) was applied on the inlet as the driving force for the dynamic wall motion. The first simulation was performed on the homogenous wall (no inclusion) as the reference model. The effects of the inclusion size were examined based on a set of simulations of the wall containing a 2 and 10mm long inclusion with a Young's modulus of 1.50 times the Ewall=5.12MPa. To examine the effects of the inclusion modulus contrast, a set of simulations were performed on the wall containing a 2mm long inclusion with a Young's modulus of 1.50 and 2.00 times the Ewall=5.12MPa. The wall radial displacement along the entire tube length (longitudinal spatial resolution of 5mm) was measured at multiple time–points (temporal resolution of 0.375ms), and the information was mapped onto a 2D spatio–temporal plane which allowed the visualization of the entire wave propagation. Figure 1: Spatio–temporal plot: (A) Homogenous wall: Ewall=5.12MPa; (B) Inclusion wall: Einc=1.5×Ewall, Linc=2mm; (C) Inclusion wall: Einc=1.5×Ewall, Linc=10mm; (D) Inclusion wall: Einc=2.0×Ewall, Linc=2mm. Results: Figure 1 provides the spatio–temporal plots of the wall displacement for the homogenous wall (Figure 1A), and the inhomogeneous walls (Figures 1B–1D). It is seen that a small portion of the main forward wave gets reflected at the site of the inclusion while the rest continues to travel forward beyond the inclusion site under a PWV which remains almost unaffected (not shown)[1]. Quantitative and qualitative reflection patterns depend on the inclusion properties, e.g. increase in both the inclusion size (Figures 1B–1C) and modulus contrast (Figures 1B–1D) was found to increase the reflection wave magnitude. Also, the low wall displacement at the inclusion site forms a standing wave whose width is correlated to the inclusion size (Figures 1B–1C). Conclusions: This study of pulse wave propagation along the inhomogeneous arterial walls in silico highlighted the need for regional PWV measurements, such as those obtained by PWI, in order to detect the changes in regional wall stiffness. In particular, it was found that spatio–temporal plots of the wall displacement contain qualitative and quantitative information that can collectively be used to obtain the size and modulus contrast of the zone entailing the regional changes. Future studies will focus on examining the pathological conditions, such as the inhomogeneity in modulus and geometry seen in aortic aneurysm, in order to determine the implications in PWI in vivo. References: [1] Shahmirzadi et al.: Artery Res, in press, 2012. [2] Fujikura et al.: Ult Imag, 29(3), pp. 137–54, 2007. [3] Luo et al.: IEEE Ultras Symp, pp. 859–62, 2008. [4] Vappou et al.: Am J Hyp, 23(4), pp. 393–398, 2010. 64 Axial Location (mm) 0 50 100 150 200 (A) Forward 0 50 Inclusion site 100 150 200 (B) Forward Reflected Standing 250 250 250 250 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 Time (ms) Time (ms) Time (ms) Time (ms) 0 50 Inclusion site 100 150 200 (C) Forward 0 Reflection 50 Standing Inclusion site 100 150 200 (D) Forward Reflection Standing indicates Presenter
Session MPT–1: Mechanical Properties of Tissues – I Wednesday, October 3 4:30P – 5:45P 005 ACUTE EFFECTS OF CANNABINOÏD RECEPTORS ACTIVATION ON BRAIN MECHANICAL PROPERTIES AND CEREBRAL BLOOD FLOW IN THE JUVENILE RAT HIPPOCAMPUS. Simon Chatelin 1 , Marie Humbert–Claude 2 , Philippe Garteiser 1 , Valérie Vilgrain 1 , Bernard E. Van Beers 1 , Zsolt Lenkei 2 , Ralph Sinkus 1 . 1 Paris Diderot University, Sorbonne Paris Cité, INSERM, CRB3, UMR773, Paris, FRANCE; 2 Laboratoire de Neurobiologie, ESPCI–CNRS, UMR7637, Paris, FRANCE. Background: Recent studies suggest a significant influence of type-1 cannabinoïd receptors (CB1R) on the puberty maturation processes [1] including neuronal remodeling and modifications of cortical mechanical properties in the postnatal brain. A preliminary study showed a decrease of the hippocampus elasticity within 15 minutes after CB1R agonist injection [2]. Aims: To assess the significance and causes of this effect, MR–Elastography (MRE) and Arterial Spin Labeling (ASL) perfusion imaging were performed, as illustrated in Figures 1 and 2 respectively. Methods: The experimental protocol (carried out in a 7T MRI scanner) consisted of an anatomical T2–weighted MR scan, a baseline MRE acquisition, intra–peritoneal drug injection, a delay of 15 minutes and a second MRE acquisition. The tests were conducted on 10 day old rats (n=11) injected with the cannabinoïd receptor (CB1R) agonist CP55940 (0.7mg/kg). MRE was acquired using a spin–echo sequence with EPI (Echo Planar Imaging) readout and synchronous motion–encoding gradients to encode 3 orthogonal displacement maps in phase images (10 axial slices of 300μm isotropic resolution). Mechanical waves were generated using a uni–axial modal exciter (1000Hz). Results: Elasticity values were expressed as percent of baseline Gd values (4.35±0.23 and 2.62±0.25kPa for h. and th. respectively). CP55940 injection induced a significant decrease of the elastic modulus in the hippocampus (-16.5±4.9%, p=0.0013) (Figure 3). No significant modification was observed in the thalamus (p>0.1). This effect was significantly reversible (p
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PROCEEDINGS of the Eleventh Interna
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Dear Conference Delegate: 2 Welcome
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4 CONFERENCE-AT-A-GLANCE Eleventh I
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(Session SAS continued from previou
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Wednesday 7:45A - 8:00A OPENING REM
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(Session FIP continued from previou
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7:00P - 8:00P Buses to the Hôtel N
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Page 22 and 23: Session EEX: Equipment Exhibit 20 V
Page 24 and 25: 22 AUTHOR INDEX AUTHOR PAGE AUTHOR
Page 26 and 27: 24 ABSTRACTS Eleventh International
Page 28 and 29: 26 Session SAS: Oral Presentations
Page 30 and 31: 036 3D RECONSTRUCTION OF IN VIVO AR
Page 32 and 33: 057 THE ACCUMULATION OF DISPLACEMEN
Page 34 and 35: 080 SHEAR MODULUS RECONSTRUCTION WI
Page 36 and 37: 34 Session POS: Posters Tuesday, Oc
Page 38 and 39: 033 TOWARDS QUANTITATIVE ELASTICITY
Page 40 and 41: 044 IMAGE GUIDED PROSTATE RADIOTHER
Page 42 and 43: 068 APPLICATIONS OF COHERENCE OF UL
Page 44 and 45: 42 Session CAA-1: Clinical and Anim
Page 46 and 47: 064 ELASTOGRAPHIC FINDINGS COMPARIS
Page 48 and 49: 088 TISSUE ELASTICITY AS A MARKER O
Page 50 and 51: 079 REAL-TIME STRAIN IMAGING OF THE
Page 52 and 53: 015 ON THE ADVANTAGES OF IMAGING TH
Page 54 and 55: 019 FULLY AUTOMATED BREAST ULTRASOU
Page 56 and 57: 048 COMPRESSION SENSITIVE MAGNETIC
Page 58 and 59: 027 ELASTIC MODULUS RECONSTRUCTION
Page 60 and 61: 056 RECONSTRUCTING THE MECHANICAL P
Page 62 and 63: 60 Session CVE-1: Cardiovascular El
Page 64 and 65: 039 IMAGING VULNERABLE PLAQUES WITH
Page 68 and 69: 023 IN VIVO HEEL PAD ELASTICITY INV
Page 70 and 71: 038 DYNAMIC SHEAR ELASTICITY PROPER
Page 72 and 73: 70 Session IND: Industrial Presenta
Page 74 and 75: Invited Presentation: 099 THE MODER
Page 76 and 77: 74 Session MIP-2: Methods for Imagi
Page 78 and 79: 065 NON-INVASIVE MECHANICAL STRENGT
Page 80 and 81: 072 INFERRING TISSUE MICROSTUCTURE
Page 82 and 83: 80 Session CAA-2: Clinical and Anim
Page 84 and 85: 009 IN VITRO COMPARISON OF ULTRASOU
Page 86 and 87: 040 MONITORING CRYOABLATION LESIONS
Page 88 and 89: 032 ANALYSIS OF THE INFLUENCE OF IN
Page 90 and 91: 002 ANALYSIS OF THYROID NODULES VIS
Page 92 and 93: 043 ROLE AND OPTIMISATION OF THE IN
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Page 96 and 97: 028 PLANE WAVE IMAGING FOR FAST VAS
Page 98 and 99: 042 REPRODUCIBILITY STUDIES IN SHEA
Page 100 and 101: 054 EXPERIMENTAL EVALUATION OF SIMU
Page 102 and 103: 089 DIRECT ELASTIC MODULUS RECONSTR
Page 104 and 105: 081 MR ELASTOGRAPHY OF IN-VIVO AND
Page 106 and 107: 090 IDENTIFICATION OF NONLINEAR TIS
Page 108 and 109: 075 SHEAR WAVE GENERATION FOR ELAST
Page 110 and 111: 061 SINGLE-HEARTBEAT 2-D MYOCARDIAL
Page 112 and 113: 069 SHEAR WAVE VELOCITY ACQUIRED BY
Page 114 and 115: 074 PERFORMANCE ASSESSMENT AND OPTI
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030 SENSITIVITY OF MAGNETIC RESONAN
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116 Session MMT: Mechanical Measure
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029 IN VIVO TIME HARMONIC MULTIPLE
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053 COMBINED ULTRASOUND AND BIOIMPE
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122 Amirauté Conference Center Flo
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124 Please Fill Out Both Sides Conf
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2012 Proceedings - International Tissue Elasticity Conference

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