BME Header
        HALIFAX, NOVA SCOTIA | CANADA
 BME Home
 Research - Ultrasound
 Research - Ear Lab
 Research - SENSE Lab
 Collaborators
 BMNG 5260 News
 ECED 4760 News
 ECED 3202 News
 Publications
 Fabrication (FABLAB)
 Contact Us













 
 Transducer Design, Fabrication, and Characterization for Medical Devices



 Jeremy Brown, Ph.D.
 Associate Professor
profile pic



Ultrasound Research:

Development of a High-Resolution High-Frequency Ultrasound Imaging System


Most ultrasound imaging systems operate in the frequency range from 3 to 5 MHz. This frequency range provides an image resolution of approximately 1 mm. By increasing the frequency, the ultrasound wavelength is decreased and finer resolution can be obtained. Recently, several high-frequency (30 – 100 MHz) ultrasound systems have been developed for imaging the eye, skin, vascular system, and even small animals for biological studies. These high-frequency systems can resolve tissue structures ranging from 20 to 100 microns in size. In spite of improved resolution, high-frequency ultrasound systems are not routinely used in clinical practice because they are currently based on single-element geometrically shaped transducers. The fixed geometry of these devices introduces a trade-off between resolution and depth of field. In low-frequency ultrasound systems, a great improvement in image quality is achieved by replacing the single-element transducer with a transducer array and electronic beamformer. This combination allows the ultrasound energy to be focused at a wide range of depths within the tissue. Unfortunately, developing a suitable array and beamformer is complicated by the increased ultrasound frequency. Generally, as the frequency is increased, the components of an ultrasound system become miniaturized and more sophisticated.


annular array
Figure 1: Photograph of an annular array through a microscope.

Transducer arrays are usually fabricated by cutting kerfs into and through the transducer substrate to create a series of individual elements. On lower frequency devices, these grooves can be machined using a diamond cutter or a laser. The small dimensions of a high-frequency array make conventional machining methods extremely difficult. As an alternative to machining, fabricating the array by simply depositing an appropriate electrode pattern on the surface of the substrate is being investigated. These arrays are fabricated using various micro-fabrication techniques, which include photolithography to define the electrode pattern, and ultrasonic wire bonding to make the electrical contacts. Figure 1 shows a photograph of an annular transducer array taken through a microscope. It shows the electrode pattern and the ultrasonic wire-bonds. The outer diameter of the array is 2 mm and the space separating the array elements is 10 microns. The fundamental operating frequency of this transducer is 50 MHz.


beamformer
Figure 2: Photograph of an electronic beamformer
In order to synthetically focus a transducer array, an accompanying electronic device called a “beamformer” is required. It is not feasible, however, to implement conventional beamforming techniques at high frequencies due to the high sampling resolution that is required. Currently we are working on developing a novel beamformer specifically designed for high-frequency ultrasound arrays. To date, the design has been based on a variable sampling technique, which samples the ultrasonic signals from the individual array elements in a rapidly changing delay pattern. The sampling is controlled using high-speed field programmable gate arrays (FPGAs) to obtain the high resolution that is required.


Figure 3: Image of a guinea pig cochlea with comparison to a histology slide.

The performance of our imaging system  (array + beamformer) is currently being tested by imaging in-vitro tissue phantoms, as well as in-vivo guinea pigs. My research program is focused on developing a miniaturized phased array endoscope for imaging the inner ear cochlea.  Although hearing  loss is  one of the most  common  chronic conditions worldwide,  there are currently no truly diagnostically effective imaging modalities for imaging the auditory system. High Frequency Ultrasound on the other hand holds the promise of high-resolution, high frame rates, excellent patient safety and less-invasiveness than any technique currently being used for ear imaging. Figure 3 shows an image generated in our lab of a guinea pig cochlea using a 50MHz ultrasound  array  scanner. it is compared to a histology  slide of a  guinea pig  cochlea (different  guinea pig)

 
linear array
Figure 4: Photograph of a linear phased array transducer through a microscope.

Presently, we are working on developing an imaging system based on a high-frequency linear phased array transducer (figure 4). There are major advantages to linear phased array transducers. They can generate images with extremely high frame rates, they can generate a large field of view from a small aperture, and they can be packaged into a small miniaturized endoscope. High frame-rate imaging is vitally important in auditory imaging as it is a dynamic system and measuring the response to acoustic stimulus may provide important diagnostic information.  Recently, we have developed a prototype linear phased array and its performance currently being characterized.


       PUBLICATIONS:

· J.A. Brown, S. Subdaresh J. Leadbetter, S. Cochran, R. Adamson, “Mass-Spring Matching Layers for High Frequency Ultrasound Transducers: A New Technique Using Vacuum Deposition,"IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 61, pp. 1911-1921, 2014

· Y. Zhang, P.Garland, R. Adamson, J.A. Brown, “The Quenched State with Dominant Shear Vibration Mode Originated from Domain Reconfiguration in [001] Oriented PMN-PT Single Crystals,” Journal of Applied Physics, Vol. 115, no. 21, pp. 214101-214101-10, 2014 (Featured Cover Article)

· A. Bezanson, R. Adamson, J.A. Brown, “Fabrication and Performance of a High Frequency Forward Looking Phased Array Endoscope,” IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 61, pp. 33-43, 2014

· H. Hanafi, L. Posada, S. Bhatawadekar, J.A. Brown and G. Maksym, “A Resonance Mode Piezoelectric Device for Measurement of Respitory Mechanics,” Journal of Biomedical Science and Engineering, Vol. 6, pp. 1062-1071, 2013

· J.A. Brown, K. Dunphy, J. Leadbetter, R. Adamson, O. Beslin, “Fabrication and Performance of Single-Crystal Lead Magnesium Niobate-Lead Titanate (PMN-PT) Hydrophone for Increased Sensitivity ,” Journal of the Acoustical Society of America, 134:2, pp.  1031-1038, 2013.

· Z. Torbatian, R. Adamson,  J.A. Brown, “Experimental Verification of Pulse probing Technique for Phase Coherence Grating Lobe Suppression,” IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 60, pp. 1324-1332, 2013 ( Front cover article)

· C. McKnight, M. Bance, J.A. Brown, D. Doman, R. Adamson, “Direct Measurements of the Dispersion Relation in the Human Skull,” JASA, Vol. 133:1, pp. 136-145, 2013

· J.A. Brown, J. Leadbetter, M. Leung, A. Bezanson, R. Adamson, “A Low-Cost Open-Source High Frame-Rate High-Frequency Imaging System,” Proc. IEEE Ultrasonics Symposium, pp. 549-552, 2013

· A. Bezanson, A. Adamson, J.A. Brown, “Fabrication and Performance of a Miniaturized 64 Element High Frequency Phased Array,” Proc. IEEE Ultrasonics Symposium, pp. 765-768, 2013

· J.A. Brown, K. Dunphy, J. Leadbetter, R. Adamson, O. Beslin, “A Single Crystal Acoustic Hydrophone for Increased Sensitivity,” Proc. Acoustical Society of America Symposium, Vol. 19, pp. 070056, 2013

· H. Vihvelin, J. Leadbetter, J.A. Brown, R. Adamson “A Modulator and Driver for a High Efficiency Ultrasonic Link Providing Power and Signal to an Implanted Hearing Aid,” Proc. Acoustical Society of America Symposium, Vol. 19, pp. 030028, 2013

· J. Leadbetter, J.A. Brown, R. Adamson, “The Design of Ultrasonic Lead Magnesium Niobate-Lead Titanate (PMN-PT) Composite Transducers for Power and Signal Delivery to an Implanted Hearing Aid,” Proc. Acoustical Society of America Symposium, Vol. 19, pp. 030029, 2013

· Z. Torbatian, P.Garland, R. Adamson, M. Bance, J.A. Brown, “Listening to the Cochlea with High Frequency Ultrasound,” Ultrasound in Medicine and Biology, Vol 38:12, pp. 2208-2217, 2012

· P. Garland, A. Bezanson, R. Adamson, J.A. Brown, “Discovery of Microscopic Tegragonal Structure of <001> Oriented PMN-PT after quenching,” Proc. IEEE Ultrasonics Symposium, pp. 2521-2524, 2012

· A. Bezanson, R. Adamson, J.A. Brown, “Fabrication of a Miniaturized 64-Element Phased Array," Proc. IEEE Ultrasonics Symposium, pp. 2114-2117, 2012

· Z. Torbatian, P.Garland, R. Adamson, M. Bance, J.A. Brown, “A Virtual Point Source Pulse Probing Technique for Supressing Grating Lobes in Large Pitch Phased Arrays,” Proc. IEEE Ultrasonics Symposium, pp. 1291-1294, 2012

· P. Garland, A. Bezanson, R. Adamson, J.A. Brown, “Experimental and Finite Element Model Directivity Comparison between PZT and PMN-PT Kerfless Arrays,” Proc. IEEE Ultrasonics Symposium, pp. 458-461, 2011

· Z. Torbatian, P.Garland, R. Adamson, M. Bance, J.A. Brown, “Direct Measurements of Basilar Membrane Motion Using Pulsed-Wave Doppler High-Frequency Ultrasound,” Proc. of Mechanics of Hearing Workshop, 2011

· P. Garland, A. Bezanson, R. Adamson, J.A. Brown, “Experimental and Finite Element Model Directivity Comparison between PZT and PMN-PT Kerfless Arrays,” Proc. IEEE Ultrasonics Symposium, pp. 458-461, 2011

· A. Bezanson, R. Adamson, J.A. Brown, “A Low Cost High Frame Rate Piezoelectric Scanning Mechanism for High Frequency Ultrasound Systems," Proc. IEEE Ultrasonics Symposium, pp. 365-368, 2011

· Z. Torbatian, R. Adamson, M. Bance, J.A. Brown, “Experimental Verification of a Split Aperture Transmit Beamforming Technique for Suppressing Grating Lobes in Large Pitch Phased Arrays," Proc. IEEE Ultrasonics Symposium, pp. 1139-1142, 2011

· R.W. Deas, R. Adamson, L.L. Curran, F.M. Makki, M.L. Bance, J.A. Brown, “Audiometric thresholds measured with single and dual BAHA motors: the effect of phase,” International Journal of Audiology, Vol. 49(12), pp. 993-999, 2010

· J. Yin, M. Lee, J.A. Brown, E. Cherin, F.S. Foster, "Effect of Pillar Geometry On High Frequency Piezo-Composite Transducers," IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 57, pp. 957-967, 2010.

· R.J. Pennings, A. Ho, J.A. Brown, R.G. Van Wijhe, M. Bance, “Analysis of Vibrant Soundbridge Placement Against the Round Window Membrane in a Human Cadaveric Temporal Bone Model,” Otology and Neurotology, Vol. 31(6),  pp. 998-1003, 2010

· Z. Torbatian, R. Adamson, M. Bance, J.A. Brown, “A Split Aperture Transmit Beamforming Technique with Phase Coherence Grating Lobe Supression,” IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 57(11),  pp. 2588-2595, 2010

· R. Adamson, M. Bance, J.A. Brown, “A Piezoelectric Bone-Conduction Bending Hearing Actuator,” Journal of the Acoustical Society of America, Vol. 128(4), pp. 2003-2008,  2010

· J.A. Brown, Z. Torbatian, R. Adamson, R. Van Wijhe, R.J.E. Pennings, G.R. Lockwood, M.L. Bance, High-Frequency Ex-Vivo Ultrasound imaging of the Auditory System, Ultrasound in Medicine and Biology, Vol. 35, pp. 1899-1907, 2009

· J.A. Brown, E. Cherin, J. Yin, F.S. Foster, Fabrication and Performance of High-Frequency Composite Transducers with Triangular Pillar Geometry, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 56, pp. 827-836, 2009.

· E. Cherin, J.A. Brown, S. Masoy, H. Shariff, R. Karshafian, R. Williams, P. Burns, F.S. Foster, Radial Modulation Imaging of Microbubble Contrast Agents at High Frequency, Ultrasound in Medicine and Biology, Ultrasound in Medicine and Biology, Vol. 34(6), pp. 949-962, 2008.

 

·  J.A. Brown, F.S. Foster, A. Needles, E. Cherin, G.R. Lockwood, Fabrication and Performance of a 40 MHz Linear Array based on a 1-3 Composite with Geometric Elevation Focussing, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 54, pp. 1888-1894, 2007.

 

·  C.E.M. Demore, J.A. Brown, G.R. Lockwood, Investigation of Cross-Talk in Kerfless Annular Arrays for High Frequency Imaging, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 53, pp.1046-1056, 2006.

 

·  J.A. Brown, G.R. Lockwood, A Digital Beamformer for High-Frequency Annular Arrays, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 52, pp.1262-1269, 2005.

 

·  J.A. Brown, C.E.M. Demore, G.R. Lockwood, Design and Fabrication of Annular Arrays for High-Frequency Ultrasound, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 51, pp.1010-1017, 2004.

 

·  J.A. Brown, G.R. Lockwood, A Low-Cost, High-Performance Pulse Generator for Ultrasound Imaging. IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, Vol. 49 pp.848-851, 2002.


· R.W. Deas, R. Adamson, P. Garland, M. Bance, J.A. Brown, Combining Auditory and Tactile Inputs to Create a Sense of Auditory Space, Proc. Acoustical Society of America Symposium, Vol. 11, pp. 015003, 2011


· C.Mcknight, R. Adamson, M. Bance, D. Doman, J.A. Brown, Three Dimensional Laser Doppler Vibrometry of the Dry Human Skull, Proc. Acoustical Society of America Symposium, Vol. 11, pp. 020004, 2011


·  Z. Torbatian, R.Adamson, M. Bance, J.A. Brown, Transmit Beamforming Techniques for Supressing Grating Lobes in Large Pitch Phased Arrays, Proc. SPIE Medical Imaging Symposium, 2011


·  R. Adamson, Z. Torbatian, M. Bance, J.A. Brown, A High-Frequency Beamformer Design Based on variable PMN-PT SAW delays, Proc. IEEE Ultrasonics Symposium, 2009.

 

·  Z. Torbatian, R. Adamson, R. Pennings, R. Van Wijhe, M.Bance, J.A. Brown, Imaging the Auditory System: A New Application of High-Frequency Ultrasound, Proc. IEEE Ultrasonics Symposium, 2009

 

·  J. Yin, M. Lee,  J.A. Brown, F.S. Foster, Geometry Effect on Piezo-Composite Transducers with Triangular Pillars, Proc. IEEE Ultrasonics Symposium, pp. 1421-1424, 2008.


·  J.A. Brown, E. Cherin, J. Yin, F.S. Foster, Fabrication and Performance of a High-Frequency Geometrically Focussed Composite Transducer with Triangular Pillar Geometry, Proceedings IEEE Ultrasonics Symposium. pp. 80-83, 2007.

 

·  E. Chérin, J.A. Brown, H. Shariff, R. Karshafian, R. Williams, P.N. Burns, F.S. Foster, S.E. Måsøy, Radial Modulation Imaging of Microbubbles at High Frequency, Proceedings IEEE Ultrasonics Symposium.pp. 888-891, 2007.

 

·  J.A. Brown, F.S. Foster, A. Needles, G.R. Lockwood, Photograph Through a Microscope of a 40 MHz Linear Array, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control (Front Cover Image), Vol. 54, 2007.

 

·  J.A. Brown, F.S. Foster, A. Needles, G.R. Lockwood, A 40 MHz Linear Array based on a 1-3 Composite with Geometric Elevation Focussing, Proceedings IEEE Ultrasonics Symposium. pp. 256-259, 2006.

 

·  J.A. Brown, Design, Fabrication, and Performance of a High-Frequency, Annular-Array-Based Ultrasound Imaging System, Ph.D. Thesis, Queen’s University, 2005.

 

·  J.A. Brown, G.R. Lockwood, Design of Sparse Annular Arrays for High Frequency Imaging. Proceedings IEEE Ultrasonics Symposium, pp.125-128, 2005.

 

·  J.A. Brown, C.E. Morton-Demore, F.S. Foster, G.R. Lockwood, Performance of a 50 MHz AnnularArray Based Imaging System. Proceedings IEEE Ultrasonics Symposium, pp.760-763, 2004.

 

·  J.A. Brown, C.E.M. Demore, G.R. Lockwood, Photograph Through a Microscope of a 50 MHz Annular Array, IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control (Front Cover Image), Vol. 51, 2004.

 

·  J.A. Brown, C.E. Morton, G.R. Lockwood, Fabrication and Performance of 40-60 MHz Annular Arrays, Proceedings IEEE Ultrasonics Symposium, pp.869-872, 2003.


· J.A. Brown, G.R. Lockwood, Gate Array Beamformer for High Frequency Annular Arrays. Proceedings IEEE Ultrasonics Symposium, pp.1658-1661, 2002



Course Announcements

ECED 3202 Analog Electronics
ECED 4760 Introduction to Biomedical Engineering and Biosignal Analysis
BMNG 5260 Principles of Medical Imaging


Collaborators:
 
Dr. Manohar Bance
Associate Professor

Departments of Surgery, Division of Otolaryngology

Dr. Rob Adamson
Assistant Professor
Biomedical engineering


Dr. Geoff Maksym
Professor
Biomedical engineering


Dr. Darrel Doman
Assistant Professor
Mechanical Engineering

 

Dr. Steve Aiken
Assistant Professor
School of Human Communication Disorders
 
Dr. Aaron Newman
Assistant Professor
Psychology
 
Contacts:

Info on Biomedical Engineering at Dalhousie, please contact:
Sandra Pereira
School of Biomedical Engineering
Dalhousie University
Halifax, N.S. B3H 1W2 Canada
Tel: 902.494.3427
Fax: 902.494.6621
Email: bme@dal.ca
www.dal.ca/bme


Info on my lab and the research we do, please contact:
Jeremy A. Brown, Ph.D.
Centre for Clinical Research

5790 University Ave., rm. 247
Halifax, Nova Scotia, Canada
B3H 1V7

Tel: 902.473.1515
Email:
J.Brown@Dal.ca