3D dynamic model of healthy and pathologic arteries for ultrasound technique evaluation Simone Balocco a CREATIS, Université de Lyon, INSA de Lyon, Université Lyon 1, CNRS UMR 5220, INSERM U630, Lyon, France and Microelectronic Systems Design Laboratory, Università di Firenze, Firenze, Italy Olivier Basset and Jacques Azencot CREATIS, Université de Lyon, INSA de Lyon, Université Lyon 1, CNRS UMR 5220, INSERM U630, Lyon, France Piero Tortoli Microelectronic Systems Design, Université de Firenze, Firenze, Italy Christian Cachard CREATIS, Université de Lyon, INSA de Lyon, Université Lyon 1, CNRS UMR 5220, INSERM U630, Lyon, France Received 15 February 2008; revised 6 October 2008; accepted for publication 6 October 2008; published 11 November 2008 A 3D model reproducing the biomechanical behavior of human blood vessels is presented. The model, based on a multilayer geometry composed of right generalized cylinders, enables the rep- resentation of different vessel morphologies, including bifurcations, either healthy or affected by stenoses. Using a finite element approach, blood flow is simulated by considering a dynamic displacement of the scatterers erythrocytes, while arterial pulsation due to the hydraulic pressure is taken into account through a fluid-structure interaction based on a wall model. Each region is acoustically characterized using FIELD II software, which produces the radio frequency echo signals corresponding to echographic scans. Three acoustic physiological phantoms of carotid ar- teries surrounded by elastic tissue are presented to illustrate the model’s capability. The first corre- sponds to a healthy blood vessel, the second includes a 50% stenosis, and the third represents a carotid bifurcation. Examples of M mode, B mode and color Doppler images derived from these phantoms are shown. Two examples of M-mode image segmentation and the identification of the atherosclerotic plaque boundaries on Doppler color images are reported. The model could be used as a tool for the preliminary evaluation of ultrasound signal processing and visualization techniques. © 2008 American Association of Physicists in Medicine. DOI: 10.1118/1.3006948 Key words: 3D model, acoustic, fluid dynamics, arterial mechanics, ultrasound measurements I. INTRODUCTION Modern ultrasound US equipment enables the accurate vi- sualization of human arteries and the measurement of param- eters such as blood velocity and wall thickness and disten- sion. However, some limitations remain when complex arterial geometries or difficult flow conditions need to be imaged. 1,2 Novel measurement, signal processing, and visualization techniques designed to overcome current imaging limitations require preliminary tests. Hence, there is a need for an in- silico validation based on a mathematical model. Such a model should produce realistic radio frequency rf echo sig- nals and US images of clinically relevant blood vessels and tissues. A first 3D model of arteries coupling biomechanical and acoustic analysis was proposed by Jensen 3,4 for simulation of US RF signals. The kinetic laws used for the displacement of the erythrocytes were based on Wormersley’s 5 and Evans’s 6 fluid-dynamics equations, while wall pulsation was deduced from in vivo measurement statistics. 7 This dynamic flow model was based on the hypotheses of an infinitely long cylindrical tube and laminar approximation of the blood ve- locity profile. Fang 8 has proposed simulations of Doppler US signals from vessels with various degrees of stenosis. The power spectral density of Doppler signals is estimated using the approach proposed by Bian. 9 Fang considered only steady flow conditions with different inlet velocity amplitudes, and the geometry included a two-dimensional straight tube with a stenosis. The fluid-dynamic assumptions made by Jensen and Fang prevent the simulation of curved vessels, bifurcations, and complex geometries, which characterize most human arter- ies. In the vicinity of bifurcations, flow separates and forms recirculation regions and inversion flows 10 and therefore can- not be modeled with a simple laminar profile. In addition, given the pulsatile character of cardiac beating, during sys- tolic acceleration-deceleration, the flow becomes unstable and transition to turbulence may occur. 11,12 A more complex nonlinear model of the fluid dynamics of blood displacement is needed to better reproduce human blood flow behavior. Oung and Forsberg 13 introduced a 3D model of arteries coupling acoustic analysis with advanced biomechanical 5440 5440 Med. Phys. 35 „12…, December 2008 0094-2405/2008/35„12…/5440/11/$23.00 © 2008 Am. Assoc. Phys. Med.