Sound bullets for enhanced biomedical ultrasound systems

Lead Research Organisation: University of Leeds
Department Name: Electronic and Electrical Engineering

Abstract

Ultrasound is used in many applications, including medical imaging, non-destructive evaluation, therapeutic ultrasound etc. In all these cases, there is usually a need for the formation of images or the creation of a focal region. Current methods for the generation of optimal acoustic fields generally rely on a linear process within the transducer. This linear transduction process influences the resultant properties in terms of spatial resolution and maximum intensity, noting that there are fundamental limits on the spatial resolution and power densities that can be achieved in such focal regions. In recent work in the area of acoustics, it has been demonstrated that a new type of acoustic signal can be generated via non-linear effects in chains of particles, which act as a kind of waveguide. These are based on the propagation of solitary waves. These have been studies at low frequencies, but this study will look at the posibility of using these new structures for use in biomedical ultrasound. Materials that support solitary waves are not used in standard ultrasonic work; little has been published on their use, despite the fact that a step change in performance may be possible. In this proposal, such waves will be generated within ultrasonic sources containing multiple solitary wave chains, at frequencies in the 500 kHz - 5 MHz range. To our knowledge, this has not been investigated before. Arrays are also possible, where each chain forms a single element. Because the chains would be primarily coupled along their length, but not laterally between each chains, issues arising from mechanical cross-coupling might be avoided. Pre-compression of each chain would alter the propagation velocity within it, so that beam-steering/focussing to be created. The propagation charaistics also change with signal amplitude, leading to the possibility of an acoustic diode. These new innovations would have applications in such areas as ultrasound-enhanced drug delivery, High Intensity Focussed Ultrasound (HIFU) for the treatment of tumours, and harmonic imaging.

Publications

10 25 50
 
Description The research developed new methods to convert simple excitation signals into broadband signals suitable for imaging. The technology is based on solitary waves progressing in closely grouped spheres, similar to newtons cradle but on the micro-scale.

In this study, an analytical model is created to predict the motion of a finite material attached to a granular chain as a matching layer. An experimental setup is created to verify the estimated motion of the matching material with the new model. The setup consists of a one-dimensional chain of six aluminum spheres, a vitreous carbon matching layer, and an ultrasonic horn. The ultrasonic horn generates a narrow-band input of a 25-cycle sinusoidal tone burst with a center frequency of 73 kHz and a-6-dB bandwidth of 3.5 kHz.The output is measured in water as a train of wideband ultrasonic pulses with a-6-dB bandwidth of 280 kHz,which is predicted with the model as 252 kHz. The results derived in this research work indicate that such chain like systems may be of interest to the biomedical ultrasound community,where a train of high-frequency impulses might have applications in imaging, microbubble dynamics, and high-intensity therapy
Exploitation Route The technology could eventually lead to new types of transducers that can be used for both diagnostic imaging and therapeutic purposes.
Sectors Electronics,Healthcare

 
Description The research findings are early stages but have been extensively published. The collaboration have led on to two successful grants "Therapy Ultrasound Network for Drug Delivery & Ablation Research (ThUNDDAR) Grant Reference: EP/N026942/1 with UCL, Imperial, ICR and Oxford and proposal EP/N034813/1 High Resolution Biomedical Imaging Using Ultrasonic Metamaterials with Warwick and Nottingham. Progressing the findings in both application led healthcare domain (therapeutic ultrasound) and physical metamaterials research.
First Year Of Impact 2015
Sector Education,Electronics,Healthcare,Manufacturing, including Industrial Biotechology
 
Description Responsive Mode
Amount £830,216 (GBP)
Funding ID EP/N034813/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2016 
End 11/2019
 
Description Sound bullets for enhanced biomedical ultrasound systems 
Organisation University College London
Department Mechanical Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Physical acoustics and advanced simulation of nonlinear systems.
Collaborator Contribution Experimental facilities including rapid prototyping of a new solitary wave transducer array.
Impact Yes this collaboration is multidisciplinary. 1. There has been a submitted grant on Metamaterials with Warwick 2. The formation of a successful grant for Healthcare Network Plus with UCL (Therapy Ultrasound Network for Drug Delivery & Ablation Research (ThUNDDAR) Grant Reference: EP/N026942/1)
Start Year 2014
 
Description Sound bullets for enhanced biomedical ultrasound systems 
Organisation University College London
Department Mechanical Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Contribution of acoustic experimental facilities to Warwick as part of the grant. Contribution of robotics fabrication facilities as part of the grant
Collaborator Contribution Contribution of simulation facilities by UCL Contribution of micro-fabrication facilities from Warwick
Impact Warwick, School of Engineering (EP/K030159/1) UCL Mechanical Engineering (EP/K032070/1
Start Year 2014
 
Description Sound bullets for enhanced biomedical ultrasound systems 
Organisation University of Warwick
Department School of Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Contribution of acoustic experimental facilities to Warwick as part of the grant. Contribution of robotics fabrication facilities as part of the grant
Collaborator Contribution Contribution of simulation facilities by UCL Contribution of micro-fabrication facilities from Warwick
Impact Warwick, School of Engineering (EP/K030159/1) UCL Mechanical Engineering (EP/K032070/1
Start Year 2014