Nouveaux marqueurs de la pathologie de l aorte thoracique 1- I2MR, Inserm, CHU de Rangueil, Toulouse, 2- I3M, Université de Montpellier 2, Montpellier, 3- ALARA OCFIA (ANR 2007) optimised computational functional imaging for arteries
Iterative reconstructions Detector size number Reconstruction algorithms
Wider (Zaxis direction) Finer (spatial resolution) Faster (scan speed) Spatial resolution Minimal slice thickness Focal spot size Matrix size
TAVI / TEVAR Planning : Radiation dose Aorta CAP CTA: -34% Iodine load: -44%
SCANNER DE PERFUSION Injection de 40 cc d iode Débit ~ 5-7 cc/s Acquisitions itératives Recalage élastique AF (ml/min/100 ml)
VELOCITY (m/sec) VORTICITY (m.s -2 ) WALL SHEAR STRESS (WSS) (Pa) AORTIC WALL STRESS COMPLIANCE
3D CTA Definition of inlet and outlet boundary condition
At the aortic inlet, boundary conditions were set according to typical physiological conditions with pulsatile pressure of 120/ 80 mmhg, a heart rate of 75 BPM, and an average cardiac output. Flow distribution conditions of 12% to the IA, 8% to the LCCA and 7% to the LSA were imposed. At the descending aorta outlet, the time-dependent flow rate at the descending aorta was dictated by mass conservation, leaving about 75% of blood to flow towards lower body.
Evaluation 3D de la fonction globale et segmentaire du ventricule gauche
rousseau.h@chu-toulouse.fr
rousseau.h@chu-toulouse.fr Applications cliniques Anévrysmes Dissections Suivi post therapeutique
rousseau.h@chu-toulouse.fr
rousseau.h@chu-toulouse.fr Conclusions: dimensional differences in thoracic aorta between systolic and diastolic phase are significant. Annals of Vascular Surgery 2016
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Displacement force vector are helicoidal & force magnitude changes over the cardiac cycle.
Rates of growth of aortic aneurysms are highly variable among different individuals. The simplified Law of Laplace cannot explain why different patients initially presenting with equivalent maximum diameters, have different rates of diameter progression afterwards. Increas in diam. in mm 5,29 ± 0,59 R. Limat et al. 6,88 ± 0,91 30-39 40-49 > 50 mm 7,45 ± 1,71 Initial Transversal Diameter
WSS quantification could be an important biomarker of disease progression
The aortic media regulates tissue biology and biomechanics Tissue histopathology. Aortic wall regions are exposed to elevated WSS (middle, red region), due to eccentric transvalvular BAV flow (left). This manifests in the expression of abnormal tissue metrics of aortopathy (right). Front. Physiol., 10 July 2017
rousseau.h@chu-toulouse.fr Applications cliniques Anévrysmes : risque evolutifs Dissections Suivi post therapeutique
Applications 1. Sélection des bons candidats pour l'aorte ascendante et les Type B non compliquées 1. Travaux expérimentaux 2. Essais cliniques 2. Stratégie thérapeutique 3. Étude de suivi
Entry tears Re entry True and false lumen Collaterals Satoshi Numata et al. Eur J Cardiothorac Surg 2016;49:1578-1585
D Dillon-Murphy Biomech Model Mechanobiol. 2016; 15:
Streamlines Entry Tear 1 WSS vectors OSI oscillatory shear index Entry Tear 2 peak systole mid diastole Medical Engineering & Physics, Volume 36, Issue 3, 2014, 275 284
Recommendations Class Level In all patients with AD, medical therapy including pain relief and blood pressure control is recommended. In patients with type A AD, urgent surgery is recommended. I B I C In patients with acute type A AD and organ malperfusion, a hybrid approach (i.e. ascending aorta and/or arch replacement associated with any percutaneous aortic or branch artery procedure) should be considered. IIa B In uncomplicated type-b AD, medical therapy should always be recommended. In uncomplicated type-b AD, TEVAR should be considered. In complicated type-b AD, TEVAR is recommended. I C In complicated type-b AD, surgery may be considered. IIa C I IIa IIa C B
Do you routinely stent uncomplicated type B aortic dissection? 7,8% routinely stent 130 centers in US & worlwide 37,4% routinely stent based on various imaging criteria 54,8% do not routinely stent uncomplicated TBAD
Pros: Long term benefit (mortality) Remodelling Adverse events : Stroke Death Paraplegia Retrograde dissection Reintervention COSTS A patient-specific approach designed to intervene only in patients that are at high risk of developing complications should improve the long-term outcome of these patients.
G Van Bogerijen, J Tolenaar & al. J Vasc Surg 2014;59:1134-43 Radiologic Predictors Aortic geometry Level Aortic diameter > 40 mm Rapid enlargement > 10 mm/y A A Entry tears characteristics Primary entry tear > 10 mm False lumen characteristics FL diameter of >22 mm A A A
Applications 1. Sélection des bons candidats pour l'aorte ascendante et les Type B non compliquées 1. Travaux expérimentaux 2. Essais cliniques 2. Stratégie thérapeutique 3. Étude de suivi
Relationship between tear height and flow rate in false lumen. Relationship between tear position and flow rate in the false lumen. Ratio of tear maximum width to aortic diameter. Zhuo Cheng, & al. Journal of Vascular Surgery, 2013,
CONCLUSION Elevated WSS immediately distal to the origin of LSA accompanies the development of a RTAD and may therefore constitute a new risk factor for this condition. CFD simulations may therefore potentially be of predictive value in risk stratification of RTAD in patients with type B dissection. Those patients should be monitored more frequently by means of clinical examination ;and imaging and more rigid control of hypertension should be applied.
International Journal of Cardiology2016, Authors Year No. of cases Alimo hammadi 2015 1 Study focus of CFD modelling and simulations 3D flow domain combined with 3 element Windkessel models of patient-specific FSI simulations Chen et al. 2013 1 Flow communication/exchange between TL and FL Cheng et al. 2010 1 Patient-specific model for detailed analysis of hemodynamics Cheng et al. 2014 1 In vivo velocity comparison between PC-MRI and CFD simulations Cheng et al. 2015 8 Effects of morphological features of dissected aorta on hemodynamic changes. Karmonik et al. 2011 1 Simulated 4 scenarios with entrance or exit tear present or occluded, simulating EVAR and surgical treatment. Karmonik et al. 2011 1 Quantitative assessment of hemodynamic changes of WSS in the FL after EVAR. Karmonik et al. 2012 1 Association between aortic geometries changes and hemodynamic changes Karmonik et al. 2013 1 Comparison of type B dissection with healthy aorta Shang et al. 2015 14 Correlation of CFD simulations with long-term clinical outcomes in medically managed and surgically treated patients. Tse et al. 2011 1 Quantitative analysis of hemodynamics in pre-and post aneurysmal dissecting aorta. Wan Ab Naim 2014 1 Wan Ab Naim et 2015 1 Impact of number of re-entry tears on hemodynamic changes (with simulation of re-entry tear of 10 and 16mm diameter, respectively). Vortical structure and its interaction with WSS to predict FL formation, with simulation of increased and decreased diameters of the FL. Zhang et al. 2014 3 Wall pressure changes and effects on longitudinal propagation of aortic dissection.
Applications 1. Sélection des bons candidats pour l'aorte ascendante et les Type B non compliquées 1. Travaux expérimentaux 2. Essais cliniques 2. Stratégie thérapeutique 3. Étude de suivi
Can we predict the results of Rx Stent Graft Short S.G. to exclude entry tear? Long thoracic S. G.? Additional bare stent / distal aorta? Fenestration? Bare stents in aorta or branches? False lumen occlusions?
Anton
Applications 1. Sélection des bons candidats pour l'aorte ascendante et les Type B non compliquées 1. Travaux expérimentaux 2. Essais cliniques 2. Stratégie thérapeutique 3. Étude de suivi
The Windkessel effect.
TEVAR stiffened the thoracic aorta by 2-fold diminish the Windkessel function considerably and might be associated with TEVAR-related complications, including stent-graft-induced dissection and aneurysmal dilatation.
rousseau.h@chu-toulouse.fr Computational fluid dynamics may assist in the prediction of aortic thrombus formation in hemodynamically complex cases and help guide repair strategies.
VORTICITE
Functional vascular imaging of virtual dual branches, Chimney or Periscope stent grafts configurations
rousseau.h@chu-toulouse.fr Mais pas d information «patient spécifique»
4D PC-MRI Combining Anatomy and Function
Comparison of CFD data and acquired 4D PC-MRI flow data at peak systole and mid-diastole. Also shown are the CT image data at two locations showing suspected secondary tears which were not apparent on the 4D PC-MRI data Biomech Model Mechanobiol. 2016; 15: 857 876.
Acquisition Time 20s 40s / 40 slices 40s (8 cm with 2mm thickness = 30 min) 51
4D Flow 4D Flow High scanning time Time of x-, y-, or z-dir sample selection Motion artifact Respiration Low signal Velocity of ENCoding (VENC) CFD (MFN) Boundary conditions (pressure) Physical models (static, viscosity..) Wall definition Fidelity MRI and CFD integrated method PIV Accuracy 52 CFD
Validation YALES2 BIO (0,7mm) 4 D Flow MRI (2mm) Inlet
Scanners Rapidité Résolution spatiale Dynamique Perfusion Accessibilité Les études fonctionnelles nécessitent une vérification et une validation. Irradiation Conditions limites Post traitement Importance des conditions limites? Importance de la résolution spatiale?