Safety and feasibility study of non-invasive robot-assisted high-intensity focused ultrasound therapy for the treatment of atherosclerotic plaques in the femoral artery: protocol for a pilot study

Introduction Peripheral arterial disease (PAD) is an atherosclerotic disease leading to stenosis and/or occlusion of the arterial circulation of the lower extremities. The currently available revascularisation methods have an acceptable initial success rate, but the long-term patency is limited, while surgical revascularisation is associated with a relatively high perioperative risk. This urges the need for development of less invasive and more effective treatment modalities. This protocol article describes a study investigating a new non-invasive technique that uses robot assisted high-intensity focused ultrasound (HIFU) to treat atherosclerosis in the femoral artery. Methods and analysis A pilot study is currently performed in 15 symptomatic patients with PAD with a significant stenosis in the common femoral and/or proximal superficial femoral artery. All patients will be treated with the dual-mode ultrasound array system to deliver imaging-guided HIFU to the atherosclerotic plaque. Safety and feasibility are the primary objectives assessed by the technical feasibility of this therapy and the 30-day major complication rate as primary endpoints. Secondary endpoints are angiographic and clinical success and quality of life. Ethics and dissemination Ethical approval for this study was obtained in 2019 from the Medical Ethics Committee of the University Medical Center Utrecht, the Netherlands. Data will be presented at national and international conferences and published in a peer-reviewed journal. Trial registration number NL7564

Deep localized hyperthermia with ultrasound-phased arrays using the pseudoinverse pattern synthesis method

One of the major limitations of hyperthermia as a cancer treatment modality is the lack of heating equipment and techniques capable of consistent therapeutic heating of deep-seated tumors. This thesis introduces a new pattern synthesis method capable of precisely controlling the power deposition level at a set of control points in the treatment volume using ultrasound phased arrays. This method, called the pseudoinverse pattern synthesis method, reduces the pattern synthesis problem to one of estimating the minimum-norm least-square solution to a matrix equation of the form, Hu = p, where u is the array excitation vector, p is the desired complex pressure at the control points, and H is a matrix propagation operator from the surface of the array to the control points. A useful solution to this problem is obtained when the number of control points is less than the number of elements of the array and the matrix H is full rank. This solution, called the minimum-norm solution, allows the array to be focused at several points simultaneously. This multiple-focus approach is important when ultrasound is used as a heating agent as it reduces the spatial-peak temporal-peak intensity required to generate a specified heating pattern. Furthermore, the minimum-norm solution allows the optimization of the array excitation efficiency and the intensity gain at the control points. These quantities are very significant for achieving deep localized heating with phased arrays. In fact, optimization of the intensity gain at the control points generally results in removal of high intensity interference patterns from the synthesized field. The removal of high intensity interference patterns eliminates one of the major disadvantages of multiple focusing. The pseudoinverse pattern synthesis method is introduced and discussed in detail. Simulation results are used to demonstrate its powerful capabilities as a pattern synthesis method. Its generality is demonstrated by the use of several different array structures to synthesize different multiple-focus patterns. Simulation results indicate that direct synthesis of multiple-focus patterns can provide an alternative to single-focus scanning. Finally, measured intensity profiles using a prototype cylindrical-section array agree well with theoretically predicted profiles.U of I OnlyETDs are only available to UIUC Users without author permissio

On The Design Of A Transversal Filter Bank For Parallel Processing Multiple Image Lines In Real-Time Acoustic Imaging

We present a new method for designing a transversal filter bank for parallel processing echo data in real-time active acoustic imaging. The method is based on a discretized linear spatio-temporal formulation of an imaging system which uses transmitter arrays with coded-excitation. The filter coefficients are derived from a pseudo-inverse operator which not only decouples echoes from different image lines, but also provides pulse compression along the range direction. The new method, together with the proposed coded-excitation imaging modality, may find many applications in SONAR, NDE and biomedical imaging areas. 1. INTRODUCTION Simultaneous acquisition and processing of a large number of image lines in real-time acoustic imaging can be achieved by using transmitter arrays with coded-excitation (or coded-aperture transducers) [1, 2, 3, 4, 5]. Ideally, this approach requires generating orthogonal coded wavefronts along different image lines. Thus the echo data can be processed in para..

Motion Compensation Algorithm for Non-Invasive Two-Dimensional Temperature Estimation Using Diagnostic Pulse-Echo Ultrasound

The feasibility of real-time non-invasive spatio-temporal temperature estimation from pulse-echo diagnostic ultrasound data has been previously demonstrated in stationary phantoms. The method is based on first estimating the axial shifts of the RF-echo data due to local changes in the speed of sound and thermal expansion in the propagating medium, and then differentiating these estimates along axial direction to obtain the temperature rise map. In a clinical setup, however, translation, rotation and deformation affect the estimates. In this paper we introduce an algorithm to compensate for tissue translation and uniform deformation along the axial and lateral directions of the ultrasonic imaging plane. This is achieved by separating the components of the time-shift map due to temperature rise (a local effect, occurring within the vicinity of the heated region) from the component due to translation and deformation (effect observed over a larger region). A rubber phantom experiment was d..

NON-INVASIVE DETECTION OF THERMAL EFFECTS DUE TO HIGHLY FOCUSED ULTRASONIC FIELDS

A non-invasive technique for the localization and evaluation of thermal effects in tissue due to focused high intensity ultrasound beams is described in this paper. A combined therapy/imaging transducer assembly is used to deliver a specific dose (ultrasound time-intensity product) to a tissue sample and to gather A-mode data as a function of time. In-vitro experiments performed on calf liver and in-vivo experiments performed on rat brains and liver have shown the following: 1. Reflection coefficients calculated based on a low-order autoregressive (AR) tissue model assumption and signal entropy follow the temperature rise at the heating point; 2. Heated region size and position can be monitored with high accuracy. Such information could be used effectively for feedback purposes during a rapid heating hyperthermia or ultrasound surgery procedure. 1 Introduction Highly focused, high intensity ultrasonic fields have been successfully used to form lesions in different locations and types..

Solution To The Inverse Scattering Problem Using A Modified Distorted Born Iterative Algorithm

We present a new distorted Born iterative algorithm for diffraction tomography which introduces kernel distortions only at carefully selected pixel locations. This algorithm attains the performance levels achieved by existing distorted Born iterative techniques, while maintaining the robustness of the Born iterative technique, especially in noisy situations. In addition, the algorithm has lower computational complexity and faster convergence rate when compared with existing distorted Born iterative algorithms. We present numerical simulations of the algorithm in noisy and noise-free environments. We also discuss an elementary experimental setup which is being used to validate our tomographic imaging algorithms. 1 Introduction In diffraction tomography, the goal is to solve for a function which represents the region being imaged using measurements of the acoustic field at points outside that region. Such a problem, which is termed the inverse scattering problem, is nonlinear and no exa..

NON-INVASIVE SPATIO-TEMPORAL TEMPERATURE ESTIMATION USING DIAGNOSTIC ULTRASOUND

A method for non-invasively estimating tissue temperatures using 2D diagnostic ultrasound imaging arrays is presented in this paper. It is based on a linear relationship between the apparent speckle pattern displacements and temperature, as seen on acquired A-lines when the sample is heated by external heating fields. The proportionality constant between speckle displacement and temperature is determined by the differential change in the speed of sound due to temperature and the linear coefficient of thermal expansion of the material. Accurate estimation of the displacements and proportionality constant translates into accurate, calibrated, high-resolution (2 mm spatial, sub- ffi C) noninvasive 2D spatio-temporal sample temperature estimates. The mathematical background of this method and experimental results are shown. 1 Introduction One of the advantages of ultrasound treatments for therapy is the non-invasive manner in which ultrasound energy can be delivered to the treatment vo..