Associate Professor, Department of Electrical and Computer Engineering, School of Biomedical Engineering
Our lab designs and fabricates high-frequency ultrasound transducers, with applications ranging from small animal imaging to auditory imaging. We operate a clean room fabrication facility at Caital Health where ultrasound probes are designed, built and tested.
Research in our laboratory is focused on the design, fabrication, and testing of both ultrasonic and sonic frequency piezoelectric transducers and associated electronic hardware for medical applications. Our research in ultrasonic transducers is concentrated on the development of high-frequency (>30MHz) array transducers and piezo-composite materials for high-resolution medical imaging. Our research in sonic frequency transducers is concentrated on the development of novel, surgically implanted hearing aids.
|64+ Channel high frequency phased array beamformer: Currently, Dr. Brown is working on developing a high frame rate 64 channel beamformer for the high frequency phased array endoscope. Developing a beamformer for ultrasound frequencies that approach 50 MHz, is very challenging because the delay resolution required for adequate beamforming is sub nano-second. Further to the very high delay resolution required, a high frequency beamformer for phased arrays also requires very large delay ranges (> 1us), and extremely high data rates (~100 GB/s). The current prototype under development is based on multiple high performance synchronized FPGA in order to achieve the extremely high data rates, fine delay resolution, and large delay ranges. The image processing and display is subsequently accomplished using a Python-based application that is capable of extremely high frame rates.|
|Novel Grating lobe suppression beamforming methods: In a conventional phased array, an element pitch of approximately ½ l is required in order to suppress grating lobes. This would create two major problems in developing a 40-50 MHz endoscope of similar dimensions. First, in order to obtain the same lateral resolution as my current array twice the number of elements are required. This necessitates twice as much area for the interconnect and prevents the total outer packaging of the endoscope to match our current device. Second, manufacturing such fine pitch (15-20 microns) is extremely difficult using either a micro dicing saw or a laser ablation. This is because the minimum kerf width achievable with these technologies is approximately 10 microns, which in turn leaves very little active piezoelectric material. To overcome these major limitations, Dr. Brown is developing novel transmit beamforming strategy that allow the grating lobes to be suppressed in a phased array with large pitch. This beamforming strategy in combination with the novel microfabrication techniques are what have allowed the successful packaging of the forward looking phased array into the world’s first combination of miniature endoscopic form factor with 40+ MHz operating frequency.|
|New imaging tools for the human Auditory system: The performance of Dr. Brown’s imaging system (array + beamformer) is currently being tested by imaging in-vitro tissue phantoms, as well as in-vivo guinea pigs. This project is focused on quantifying the efficacy of the phased array endoscope for different auditory pathologies. 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 holds the promise of high-resolution, high frame rates, excellent patient safety and less-invasiveness than any technique currently being used for ear imaging. Dr. Brown would like to begin pre-clinical human imaging trials in 2015.|
|C.A. Samson, A. Bezanson, J.A. Brown, “A Sub Nyquist, Variable Sampling, High Frequnecy Phased Array Beamformer,” IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control, (In Press, manuscript no. TUFFC-07930-2016, published online with IEEE early access Dec. 2016).|
|T. Landry, J. Rainsbury, R. Adamson, M. Bance, J.A. Brown, “Real-Time Imaging of the Human Middle Ear,” Hearing Research, Vol. 326, pp. 1-7, 2015.|
|J.A. Brown, S. Sundaresh, J. Leadbetter, A. Bezanson, 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  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.|
|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).|
|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.|
|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.|
|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.|