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Sandy Cochran

University of Dundee, School of Medicine, Faculty Member

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Johns Hopkins University

Johannes Preiser-Kapeller

Austrian Academy of Sciences

Thomás A S Haddad

Universidade de São Paulo

Pakistan Institute of engineering and applied science (PIEAS)

Petros Bouras-Vallianatos

National & Kapodistrian University of Athens

University of Ljubljana

Duke University

National Yang Ming Chiao Tung University

Marvin Thepsoparn

Chulalongkorn University

André van Zundert

The University of Queensland, Australia

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Papers by Sandy Cochran

Net-shape ceramic processing as a route to ultrafine scale 1-3 connectivity piezoelectric ceramic-polymer composite transducers

by Katherine Kirk and Sandy Cochran

Ultrasonics …, 2004

Potential applications of high frequency ultrasound exist because of the high spatial resolution ... more Potential applications of high frequency ultrasound exist because of the high spatial resolution consequent upon short wavelength. The frequencies of interest, typically from 25 MHz upwards, are easily supported by modern instrumentation but the capabilities of ultrasonic transducers have not kept pace and the transducers in high frequency commercial ultrasonic systems are still made with single-phase crystal, ceramic or piezopolymer materials. Despite potential performance advantages, the 1-3 connectivity piezoelectric ceramic-polymer composite materials now widely used at lower ultrasonic frequencies have not been adopted because of manufacturing difficulties. These difficulties are centred on fabrication of the 1-3 piezoceramic bristle-block comprising tall, thin pillars upstanding from a supporting stock. Fabrication techniques which have been explored already include injection moulding, mechanical dicing, and laser machining. Here, we describe an alternative technique based on viscous polymer processing (VPP) to produce net shape ceramic bristle-blocks. VPP produces green-state ceramic with rheological properties suitable for embossing. We outline how this can be created then report on our work to fabricate PZT bristle-blocks with lateral pillar dimensions of the order of 50 lm and height-to-width ratios of the order of 10. These have been backfilled with low pre-cure viscosity polymer and made into complete 1-3 piezocomposite transducer elements. We outline the performance of the transducers in terms of electrical impedance and pulse-echo behaviour and show that it corresponds well with computer modelling. We conclude that VPP is a promising technique to allow the established advantages of piezocomposite material to be exploited at higher frequencies than have been possible so far.

Piezoelectric 1–3 Composites for High Frequency Ultrasonic Transducer Applications

by Katherine Kirk and Sandy Cochran

Ferroelectrics, 2004

A new net shape process has been developed to fabricate 1–3 piezocomposites. Solid polymer moulds... more A new net shape process has been developed to fabricate 1–3 piezocomposites. Solid polymer moulds and high solid loading lead zirconate titanate (PZT) paste, made by the viscous polymer processing (VPP), have been utilised in an embossing/lost mould method. 1–3 structures with PZT pillar feature sizes of 50–100 μm and aspect ratios of 5–10 have been fabricated successfully, and the composites have been characterized by electrical impedance and pulse-echo measurements. The results show that the viscous polymer processing is a very promising technique for the fabrication of 1–3 composites for high frequency ultrasonic transducer applications.

Screen-printed ultrasonic 2-D matrix array transducers for microparticle manipulation

Ultrasonics, 2015

This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ... more This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ultrasonic transducer array, operating at frequency approximately 7.5 MHz, to demonstrate the potential of this fabrication technique for microparticle manipulation. All layers of the array are screen-printed then sintered on an alumina substrate without any subsequent patterning processes. The thickness of the thick film PZT is 139 ± 2 µm, the element pitch of the array is 2.3 mm, and the dimension of each individual PZT element is 2 × 2 mm 2 with top electrode 1.7 × 1.7 mm 2 . The measured relative dielectric constant of the PZT is 2250 ± 100 and the dielectric loss is 0.09 ± 0.005 at 10 kHz. Finite element analysis was used to predict the behaviour of the array and to optimise its configuration. Electrical impedance spectroscopy and laser vibrometry were used to characterise the array experimentally. The measured surface motion of a single element is on the order of tens of nanometres with a 10 Vpeak continuous sinusoidal excitation. Particle manipulation experiments have been demonstrated with the array by manipulating Ø10 µm polystyrene microspheres in degassed water. The simplified array fabrication process and the bulk production capability of screenprinting suggest potential for the commercialisation of multilayer planar resonant devices for ultrasonic particle manipulation.

Images in anesthesiology: shear wave elastography: novel technology for ultrasound-guided regional anesthesia

by Shilpa Munirama, Roos Eisma, Joyce Joy, Sandy Cochran, and Graeme Mcleod

Anesthesiology, 2013

Simultaneous Measurement of Thermophysical Properties of Tissue-Mimicking Phantoms for High Intensity Focused Ultrasound (HIFU) Exposures

by Sandy Cochran and Zhihong Huang

Abstract Tissue-mimicking phantoms, including bovine serum albumin phantoms and egg white phantom... more

Periodic shock-emission from acoustically driven cavitation clouds: A source of the subharmonic signal

Ultrasonics, 2014

Single clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes ... more Single clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22 MPa, have been observed via high-speed shadowgraphic imaging at 1 Â 10 6 frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48 MPa generated shock-waves with an average period of 7.9 ± 0.5 ls, corresponding to a frequency of f 0 /2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8 ± 0.3, 15.8 ± 0.3, 19.8 ± 0.2 ls, at pressure amplitudes of 0.64, 0.92 and 1.22 MPa, corresponding to the higher-order subharmonics of f 0 /3, f 0 /4 and f 0 /5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) < 0.01 (r = 0.996, taken over all data). Subtracting the isolated acoustic shock profiles from the raw signal collected from the detector, demonstrated the removal of subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200 lm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0 MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.

Innovative manufacturing and 3-dimensional packaging methods of micro ultrasonic transducers for medical applications

This article presents the innovative manufacturing and 3-dimensional packaging of a miniaturized ... more This article presents the innovative manufacturing and 3-dimensional packaging of a miniaturized ultrasonic transducer for medical applications. A spirally rolled-up flexible circuit was employed for the interconnection of a linear transducer array to be used in a needle size footprint. Photolithography, precision dicing and low temperature conductive bonding are amongst the technologies under investigation for the realization of this high

Physics and Medicine 3 The importance of physics to progress in medical treatment

Lancet, 2012

Physics in therapy is as diverse as it is substantial. In this review, we highlight the role of p... more Physics in therapy is as diverse as it is substantial. In this review, we highlight the role of physics-occasionally transitioning into engineering-through discussion of several established and emerging treatments. We specifi cally address minimal access surgery, ultrasound, photonics, and interventional MRI, identifying areas in which complementarity is being exploited. We also discuss some of the fundamental physical principles involved in the application of each treatment to medical practice.

Echogenic Regional Anaesthesia Needles: A Comparison Study in Thiel Cadavers

by Roos Eisma, Sandy Cochran, and Graeme Mcleod

Ultrasound in Medicine and Biology, 2012

Ultrasound guidance is now the standard procedure for regional nerve block in anaesthesiology. Ho... more Ultrasound guidance is now the standard procedure for regional nerve block in anaesthesiology. However, ultrasonic visualisation of needle manipulation and guidance within tissues n remains a problem. Two new echogenic needles (Pajunk and Braun) have been introduced to anaesthesiology clinical practice, but evaluation has been restricted to preserved animal tissue. In this study the visibility of both echogenic needles was compared to a standard non echogenic needle in a Thiel cadaver model. A total of 144 intramuscular injections were made in the upper arm in-plane and out-of-plane to the ultrasound beam at 4 angles (30o, 45o, 60o and 75o). The visibility of the needle was assessed by two independent, blinded observers using a 5-point Likert ordinal scale. Weighted Kappa for interobserver agreement was 0.77 (95% CI: 0.68 -0.86). The Pajunk Echogenic needle was more visible than the Braun Standard needle in-plane (P=0.04), and the Braun Standard and Braun Echogenic needles out of plane (P=0.02). Independent predictors of visibility using logistic regression were needle (p<0.001) and plane of insertion (p=0.08), Receiver Operator Characteristic (ROC) area under the curve 0.90. In conclusion, the Pajunk echogenic needle offers the best visibility for ultrasound guided regional anaesthesia.

Ultrasound Activated Nano-Encapsulated Targeted Drug Delivery and Tumour Cell Poration

Advances in Experimental Medicine and Biology, 2011

Introduction : Recently, ultrasonic drug release has been a focus of many research groups for sti... more Introduction : Recently, ultrasonic drug release has been a focus of many research groups for stimuli responsive drug release. It has been demonstrated that a focused ultrasound (FUS) beam rapidly increases the temperature at the focused tissue area. One potential mechanism of drug targeting is to utilize the induced heat to release or increase penetration of chemotherapy to cancer cells. The efficiency of targeted drug delivery may increase by using FUS beam in conjugation with nanoencapsulated drug carriers.

Progress towards ultrasound applications of new single crystal materials

by Sandy Cochran and Katherine Kirk

Journal of Materials Science-materials in Electronics, 2005

In recent years, single crystal materials with better piezoelectric properties than the existing ... more In recent years, single crystal materials with better piezoelectric properties than the existing ceramics have become available. These new materials will potentially provide improved performance in ultrasonic applications such as NDT, sonar and biomedical diagnosis. In order to select the best material and optimize transducer design, comparison must be carried out. However, due to material and transducer fabrication costs, initial

Loss effects on adhesively-bonded multilayer ultrasonic transducers by self-heating

Ultrasonics, 2010

Multilayer ultrasonic transducers are widely being used for high power applications. In these app... more Multilayer ultrasonic transducers are widely being used for high power applications. In these applications, typical Langevin/Tonpilz structures without any adhesive bondings however have the disadvantage of limited bandwidth. Therefore adhesively-bonded structures are still a potential solution for this issue. In this paper, two-layer piezoelectric ceramic ultrasonic transducers with two different adhesive bondlines were investigated comparing to a single-layer transducer in terms of loss effects during operation with excitation signals sufficient to cause self-heating. The theoretical functions fitted to the measured time-temperature dependency data are compared with experimental results of different piezoelectric transducers. Theoretical analysis of loss characteristics at various surface displacements and the relationship with increasing temperature are reported. The effects of self-heating on the practical performance of multilayer ultrasonic transducers with adhesive bondlines are discussed.

Focused ultrasound ablation using real time ultrasound image guidance

by Sandy Cochran, X. Xiao, and Zhihong Huang

Focused ultrasound surgery (FUS) is showing significant potential as a non-invasive medical inter... more Focused ultrasound surgery (FUS) is showing significant potential as a non-invasive medical intervention without percutaneous access for ablation (cell destruction by heating) of tumours. MRI is frequently used to guide FUS surgery (MRgFUS). Although the MRI can acquire multiple slices per second, organ motion is not accounted for in the repositioning of the sonication using MRI. Ultrasound, with realtime imaging, and which is less costly and easier to use than MRI, may become an alternative. In this paper we present a real-time ultrasound image guidance method suitable for tracking the motion of organs and ablating tissue. To demonstrate the potential of ultrasound imaging for real-time guidance of FUS, a 6-degree-of-freedom (DOF) robot has been used to control a FUS transducer and position the focus at a target that has been segmented from a real-time ultrasound video. A moving phantom is designed to test the feasibility of the tracking and the control method.

Acoustic Tractor Beam

by Sandy Cochran and Zhengyi Yang

Physical Review Letters, 2014

Negative radiation forces act opposite to the direction of propagation, or net momentum, of a bea... more Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system.

Progress towards transducers and arrays for real-time high frequency biomedical ultrasound imaging

by Carl Meggs, Sandy Cochran, and Nigel Bush

The Journal of the Acoustical Society of America, 2008

ABSTRACT As research into transducers and arrays for real-time high frequency biomedical ultrasou... more ABSTRACT As research into transducers and arrays for real-time high frequency biomedical ultrasound imaging continues, it is becoming increasingly clear that major applications exist for systems with significantly higher spatial resolution than those already available for human clinical imaging. A key area of research remains the design and fabrication of the transducer or array. It is now accepted that piezocomposite is the material of choice and composite design and conventional dice-and-fill fabrication techniques have been optimised to allow 40 MHz operation, corresponding to wavelengths around 40 um. This expands the range of applications of piezocomposites but is still limited in terms of resolution of fine structures, for example at cellular level and to explore harmonic imaging. In this paper, we report continuing progress in work on new design techniques and fabrication processes with the potential for fabricating arrays that operate up to 100 MHz. The net-shape micromoulding fabrication technique for the ceramic within our composites is outlined, new single element transducer designs and array fabrication based on advanced surface finishing and photolithographic processes are described, and results are presented illustrating key performance data such as the point spread function, insertion loss and imaging of post mortem human tissue.

Directed jetting from collapsing cavities exposed to focused ultrasound

Applied Physics Letters, 2012

ABSTRACT We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst ... more ABSTRACT We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst of focused ultrasound. Alignment of the ultrasound focus and the pressure amplitudes in the vicinity of the cavity dictate the direction and length of the resulting jet, respectively. We interpret our observations in terms of radiation forces exerted on the cavity, due to the pressure gradient introduced to the ultrasound focus by its presence. We support our hypothesis with a linear analysis of the force distribution across the cavity surface, at the moment of maximum inflation, which shows reasonable predictive agreement with the observed jet characteristics.

Shear Wave Elastography

by Shilpa Munirama, Joyce Joy, Sandy Cochran, and Graeme Mcleod

Anesthesiology, 2013

An evaluation of Thiel-embalmed cadavers for ultrasound-based regional anaesthesia training and research

by Roos Eisma, Sandy Cochran, and Graeme Mcleod

Ultrasound, 2010

Working hours of UK trainee doctors have recently been reduced to 48 hours per week, reducing exp... more Working hours of UK trainee doctors have recently been reduced to 48 hours per week, reducing exposure to clinical cases. As such, there is widespread acceptance that trainees need to train in environments other than the ward or operating theatre in order to gain practical skills. Formalin-fixed cadavers demonstrate gross muscle and nerve anatomy but needle insertion under ultrasound guidance is poor. In contrast, a new development in medical simulation is the use of Thiel-embalmed cadavers, developed by Professor Thiel of the University of Graz, Austria, using a novel preservation technique that retains full flexibility of the limbs. Thiel cadavers have been used to successfully simulate laparoscopic surgery, neurosurgery and oral surgery. This paper investigates, for the first time, the application of ultrasound-based regional anaesthesia to the Thiel cadaver by tracing the course of peripheral nerves, injecting local anaesthetic around nerves, and reproducing inadvertent intraneural injection by injecting preservative directly into the nerve. The Thiel cadaver provides good conditions for anaesthetists to simulate regional anaesthetic block techniques using ultrasound.

Net-shape ceramic processing as a route to ultrafine scale 1-3 connectivity piezoelectric ceramic-polymer composite transducers

by Katherine Kirk and Sandy Cochran

Ultrasonics …, 2004

Potential applications of high frequency ultrasound exist because of the high spatial resolution ... more Potential applications of high frequency ultrasound exist because of the high spatial resolution consequent upon short wavelength. The frequencies of interest, typically from 25 MHz upwards, are easily supported by modern instrumentation but the capabilities of ultrasonic transducers have not kept pace and the transducers in high frequency commercial ultrasonic systems are still made with single-phase crystal, ceramic or piezopolymer materials. Despite potential performance advantages, the 1-3 connectivity piezoelectric ceramic-polymer composite materials now widely used at lower ultrasonic frequencies have not been adopted because of manufacturing difficulties. These difficulties are centred on fabrication of the 1-3 piezoceramic bristle-block comprising tall, thin pillars upstanding from a supporting stock. Fabrication techniques which have been explored already include injection moulding, mechanical dicing, and laser machining. Here, we describe an alternative technique based on viscous polymer processing (VPP) to produce net shape ceramic bristle-blocks. VPP produces green-state ceramic with rheological properties suitable for embossing. We outline how this can be created then report on our work to fabricate PZT bristle-blocks with lateral pillar dimensions of the order of 50 lm and height-to-width ratios of the order of 10. These have been backfilled with low pre-cure viscosity polymer and made into complete 1-3 piezocomposite transducer elements. We outline the performance of the transducers in terms of electrical impedance and pulse-echo behaviour and show that it corresponds well with computer modelling. We conclude that VPP is a promising technique to allow the established advantages of piezocomposite material to be exploited at higher frequencies than have been possible so far.

Piezoelectric 1–3 Composites for High Frequency Ultrasonic Transducer Applications

by Katherine Kirk and Sandy Cochran

Ferroelectrics, 2004

A new net shape process has been developed to fabricate 1–3 piezocomposites. Solid polymer moulds... more A new net shape process has been developed to fabricate 1–3 piezocomposites. Solid polymer moulds and high solid loading lead zirconate titanate (PZT) paste, made by the viscous polymer processing (VPP), have been utilised in an embossing/lost mould method. 1–3 structures with PZT pillar feature sizes of 50–100 μm and aspect ratios of 5–10 have been fabricated successfully, and the composites have been characterized by electrical impedance and pulse-echo measurements. The results show that the viscous polymer processing is a very promising technique for the fabrication of 1–3 composites for high frequency ultrasonic transducer applications.

Screen-printed ultrasonic 2-D matrix array transducers for microparticle manipulation

Ultrasonics, 2015

This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ... more This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ultrasonic transducer array, operating at frequency approximately 7.5 MHz, to demonstrate the potential of this fabrication technique for microparticle manipulation. All layers of the array are screen-printed then sintered on an alumina substrate without any subsequent patterning processes. The thickness of the thick film PZT is 139 ± 2 µm, the element pitch of the array is 2.3 mm, and the dimension of each individual PZT element is 2 × 2 mm 2 with top electrode 1.7 × 1.7 mm 2 . The measured relative dielectric constant of the PZT is 2250 ± 100 and the dielectric loss is 0.09 ± 0.005 at 10 kHz. Finite element analysis was used to predict the behaviour of the array and to optimise its configuration. Electrical impedance spectroscopy and laser vibrometry were used to characterise the array experimentally. The measured surface motion of a single element is on the order of tens of nanometres with a 10 Vpeak continuous sinusoidal excitation. Particle manipulation experiments have been demonstrated with the array by manipulating Ø10 µm polystyrene microspheres in degassed water. The simplified array fabrication process and the bulk production capability of screenprinting suggest potential for the commercialisation of multilayer planar resonant devices for ultrasonic particle manipulation.

Images in anesthesiology: shear wave elastography: novel technology for ultrasound-guided regional anesthesia

by Shilpa Munirama, Roos Eisma, Joyce Joy, Sandy Cochran, and Graeme Mcleod

Anesthesiology, 2013

Simultaneous Measurement of Thermophysical Properties of Tissue-Mimicking Phantoms for High Intensity Focused Ultrasound (HIFU) Exposures

by Sandy Cochran and Zhihong Huang

Abstract Tissue-mimicking phantoms, including bovine serum albumin phantoms and egg white phantom... more

Periodic shock-emission from acoustically driven cavitation clouds: A source of the subharmonic signal

Ultrasonics, 2014

Single clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes ... more Single clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22 MPa, have been observed via high-speed shadowgraphic imaging at 1 Â 10 6 frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48 MPa generated shock-waves with an average period of 7.9 ± 0.5 ls, corresponding to a frequency of f 0 /2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8 ± 0.3, 15.8 ± 0.3, 19.8 ± 0.2 ls, at pressure amplitudes of 0.64, 0.92 and 1.22 MPa, corresponding to the higher-order subharmonics of f 0 /3, f 0 /4 and f 0 /5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) < 0.01 (r = 0.996, taken over all data). Subtracting the isolated acoustic shock profiles from the raw signal collected from the detector, demonstrated the removal of subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200 lm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0 MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.

Innovative manufacturing and 3-dimensional packaging methods of micro ultrasonic transducers for medical applications

This article presents the innovative manufacturing and 3-dimensional packaging of a miniaturized ... more This article presents the innovative manufacturing and 3-dimensional packaging of a miniaturized ultrasonic transducer for medical applications. A spirally rolled-up flexible circuit was employed for the interconnection of a linear transducer array to be used in a needle size footprint. Photolithography, precision dicing and low temperature conductive bonding are amongst the technologies under investigation for the realization of this high

Physics and Medicine 3 The importance of physics to progress in medical treatment

Lancet, 2012

Physics in therapy is as diverse as it is substantial. In this review, we highlight the role of p... more Physics in therapy is as diverse as it is substantial. In this review, we highlight the role of physics-occasionally transitioning into engineering-through discussion of several established and emerging treatments. We specifi cally address minimal access surgery, ultrasound, photonics, and interventional MRI, identifying areas in which complementarity is being exploited. We also discuss some of the fundamental physical principles involved in the application of each treatment to medical practice.

Echogenic Regional Anaesthesia Needles: A Comparison Study in Thiel Cadavers

by Roos Eisma, Sandy Cochran, and Graeme Mcleod

Ultrasound in Medicine and Biology, 2012

Ultrasound guidance is now the standard procedure for regional nerve block in anaesthesiology. Ho... more Ultrasound guidance is now the standard procedure for regional nerve block in anaesthesiology. However, ultrasonic visualisation of needle manipulation and guidance within tissues n remains a problem. Two new echogenic needles (Pajunk and Braun) have been introduced to anaesthesiology clinical practice, but evaluation has been restricted to preserved animal tissue. In this study the visibility of both echogenic needles was compared to a standard non echogenic needle in a Thiel cadaver model. A total of 144 intramuscular injections were made in the upper arm in-plane and out-of-plane to the ultrasound beam at 4 angles (30o, 45o, 60o and 75o). The visibility of the needle was assessed by two independent, blinded observers using a 5-point Likert ordinal scale. Weighted Kappa for interobserver agreement was 0.77 (95% CI: 0.68 -0.86). The Pajunk Echogenic needle was more visible than the Braun Standard needle in-plane (P=0.04), and the Braun Standard and Braun Echogenic needles out of plane (P=0.02). Independent predictors of visibility using logistic regression were needle (p<0.001) and plane of insertion (p=0.08), Receiver Operator Characteristic (ROC) area under the curve 0.90. In conclusion, the Pajunk echogenic needle offers the best visibility for ultrasound guided regional anaesthesia.

Ultrasound Activated Nano-Encapsulated Targeted Drug Delivery and Tumour Cell Poration

Advances in Experimental Medicine and Biology, 2011

Introduction : Recently, ultrasonic drug release has been a focus of many research groups for sti... more Introduction : Recently, ultrasonic drug release has been a focus of many research groups for stimuli responsive drug release. It has been demonstrated that a focused ultrasound (FUS) beam rapidly increases the temperature at the focused tissue area. One potential mechanism of drug targeting is to utilize the induced heat to release or increase penetration of chemotherapy to cancer cells. The efficiency of targeted drug delivery may increase by using FUS beam in conjugation with nanoencapsulated drug carriers.

Progress towards ultrasound applications of new single crystal materials

by Sandy Cochran and Katherine Kirk

Journal of Materials Science-materials in Electronics, 2005

In recent years, single crystal materials with better piezoelectric properties than the existing ... more In recent years, single crystal materials with better piezoelectric properties than the existing ceramics have become available. These new materials will potentially provide improved performance in ultrasonic applications such as NDT, sonar and biomedical diagnosis. In order to select the best material and optimize transducer design, comparison must be carried out. However, due to material and transducer fabrication costs, initial

Loss effects on adhesively-bonded multilayer ultrasonic transducers by self-heating

Ultrasonics, 2010

Multilayer ultrasonic transducers are widely being used for high power applications. In these app... more Multilayer ultrasonic transducers are widely being used for high power applications. In these applications, typical Langevin/Tonpilz structures without any adhesive bondings however have the disadvantage of limited bandwidth. Therefore adhesively-bonded structures are still a potential solution for this issue. In this paper, two-layer piezoelectric ceramic ultrasonic transducers with two different adhesive bondlines were investigated comparing to a single-layer transducer in terms of loss effects during operation with excitation signals sufficient to cause self-heating. The theoretical functions fitted to the measured time-temperature dependency data are compared with experimental results of different piezoelectric transducers. Theoretical analysis of loss characteristics at various surface displacements and the relationship with increasing temperature are reported. The effects of self-heating on the practical performance of multilayer ultrasonic transducers with adhesive bondlines are discussed.

Focused ultrasound ablation using real time ultrasound image guidance

by Sandy Cochran, X. Xiao, and Zhihong Huang

Focused ultrasound surgery (FUS) is showing significant potential as a non-invasive medical inter... more Focused ultrasound surgery (FUS) is showing significant potential as a non-invasive medical intervention without percutaneous access for ablation (cell destruction by heating) of tumours. MRI is frequently used to guide FUS surgery (MRgFUS). Although the MRI can acquire multiple slices per second, organ motion is not accounted for in the repositioning of the sonication using MRI. Ultrasound, with realtime imaging, and which is less costly and easier to use than MRI, may become an alternative. In this paper we present a real-time ultrasound image guidance method suitable for tracking the motion of organs and ablating tissue. To demonstrate the potential of ultrasound imaging for real-time guidance of FUS, a 6-degree-of-freedom (DOF) robot has been used to control a FUS transducer and position the focus at a target that has been segmented from a real-time ultrasound video. A moving phantom is designed to test the feasibility of the tracking and the control method.

Acoustic Tractor Beam

by Sandy Cochran and Zhengyi Yang

Physical Review Letters, 2014

Negative radiation forces act opposite to the direction of propagation, or net momentum, of a bea... more Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system.

Progress towards transducers and arrays for real-time high frequency biomedical ultrasound imaging

by Carl Meggs, Sandy Cochran, and Nigel Bush

The Journal of the Acoustical Society of America, 2008

ABSTRACT As research into transducers and arrays for real-time high frequency biomedical ultrasou... more ABSTRACT As research into transducers and arrays for real-time high frequency biomedical ultrasound imaging continues, it is becoming increasingly clear that major applications exist for systems with significantly higher spatial resolution than those already available for human clinical imaging. A key area of research remains the design and fabrication of the transducer or array. It is now accepted that piezocomposite is the material of choice and composite design and conventional dice-and-fill fabrication techniques have been optimised to allow 40 MHz operation, corresponding to wavelengths around 40 um. This expands the range of applications of piezocomposites but is still limited in terms of resolution of fine structures, for example at cellular level and to explore harmonic imaging. In this paper, we report continuing progress in work on new design techniques and fabrication processes with the potential for fabricating arrays that operate up to 100 MHz. The net-shape micromoulding fabrication technique for the ceramic within our composites is outlined, new single element transducer designs and array fabrication based on advanced surface finishing and photolithographic processes are described, and results are presented illustrating key performance data such as the point spread function, insertion loss and imaging of post mortem human tissue.

Directed jetting from collapsing cavities exposed to focused ultrasound

Applied Physics Letters, 2012

ABSTRACT We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst ... more ABSTRACT We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst of focused ultrasound. Alignment of the ultrasound focus and the pressure amplitudes in the vicinity of the cavity dictate the direction and length of the resulting jet, respectively. We interpret our observations in terms of radiation forces exerted on the cavity, due to the pressure gradient introduced to the ultrasound focus by its presence. We support our hypothesis with a linear analysis of the force distribution across the cavity surface, at the moment of maximum inflation, which shows reasonable predictive agreement with the observed jet characteristics.

Shear Wave Elastography

by Shilpa Munirama, Joyce Joy, Sandy Cochran, and Graeme Mcleod

Anesthesiology, 2013

An evaluation of Thiel-embalmed cadavers for ultrasound-based regional anaesthesia training and research

by Roos Eisma, Sandy Cochran, and Graeme Mcleod

Ultrasound, 2010

Working hours of UK trainee doctors have recently been reduced to 48 hours per week, reducing exp... more Working hours of UK trainee doctors have recently been reduced to 48 hours per week, reducing exposure to clinical cases. As such, there is widespread acceptance that trainees need to train in environments other than the ward or operating theatre in order to gain practical skills. Formalin-fixed cadavers demonstrate gross muscle and nerve anatomy but needle insertion under ultrasound guidance is poor. In contrast, a new development in medical simulation is the use of Thiel-embalmed cadavers, developed by Professor Thiel of the University of Graz, Austria, using a novel preservation technique that retains full flexibility of the limbs. Thiel cadavers have been used to successfully simulate laparoscopic surgery, neurosurgery and oral surgery. This paper investigates, for the first time, the application of ultrasound-based regional anaesthesia to the Thiel cadaver by tracing the course of peripheral nerves, injecting local anaesthetic around nerves, and reproducing inadvertent intraneural injection by injecting preservative directly into the nerve. The Thiel cadaver provides good conditions for anaesthetists to simulate regional anaesthetic block techniques using ultrasound.