Characterization of a multi-element clinical HIFU system using acoustic holography and nonlinear modeling

Abstract

High-intensity focused ultrasound (HIFU) is a treatment modality that relies on the delivery of acoustic energy to remote tissue sites to induce thermal and/or mechanical tissue ablation. To ensure the safety and efficacy of this medical technology, standard approaches are needed for accurately characterizing the acoustic pressures generated by clinical ultrasound sources under operating conditions. Characterization of HIFU fields is complicated by nonlinear wave propagation and the complexity of phased-array transducers. Previous work has described aspects of an approach that combines measurements and modeling, and here we demonstrate this approach for a clinical phased array transducer. First, low-amplitude hydrophone measurements were performed in water over a scan plane between the array and the focus. Second, these measurements were used to holographically reconstruct the surface vibrations of the transducer and to set a boundary condition for a 3-D acoustic propagation model. Finally, nonlinear simulations of the acoustic field were carried out over a range of source power levels. Simulation results were compared to pressure waveforms measured directly by hydrophone at both low and high power levels, demonstrating that details of the acoustic field including shock formation are quantitatively predicted.

High-intensity ultrasonic waves in fluids

“…This is the so-called one-way approximation (Dagrau et al, 2011). Then the numerical solution of the Westervelt equation becomes doable for many practical situations (Jing et al, 2011;Kreider et al, 2013;Yuldashev and Khokhlova, 2011). When computer resources are limited, solution of the Westervelt equation becomes impossible even in the one-way approximation.…”

“…In a given application, it may be important to know more details about the pressure field. Nowadays, this task can be successfully solved numerically using the KZK or Westervelt equations, at least in a homogeneous medium (Bessonova and Wilkens, 2013;Kreider et al, 2013).…”

Stochastic ray tracing for simulation of high intensity focal ultrasound therapy

“…If a phonon passes through a region, the value of the observable is updated according to Eqs. (21)- (25). Specifically, if the observable is pressure over a pixel,…”

“…These parameters correspond to the Philips Sonalleve HIFU platform (Philips Healthcare, Vantaa, Finland). A transducer unit of this same type was recently analyzed by Kreider et al 25 The layers above the tank model the gel pad and biological tissues (skin, subcutaneous fat, muscle, and uterus, respectively). When feasible, tissue parameters have been aligned with the literature.…”

Anatomical-based model for simulation of HIFU-induced lesions in atherosclerotic plaques

“…Several numerical models already exist for simulation of the treatment process [18,19] and predicting the outcomes of some other procedures. In addition, some groups have studied the non-linear thermal effect of the wave propagation [20][21][22] and the vascular damage induced by ultrasound [23,24].…”