A Scalable Beamforming Architecture for Portable/Wearable Ultrasound Imaging
- Category: Circuits & Systems, Medical Electronics
- Tags: anantha chandrakasan, bonnie lam, healthcare
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Download as PDFAn ultrasound image is formed from a collection of ultrasonic beams transmitted and received by an array of transducer elements. As the resolution of an image and the range over which an image is to be formed increase, so do the number of these transducer elements and the corresponding digital processing units. The intensive signal processing power required for ultrasound imaging [1] means that conventional ultrasound systems are often large and expensive, and this demand for processing power can only worsen as more transducers and signal channels are implemented. In applications such as point-of-care diagnostics in rural areas, the movement to a portable and low-power ultrasound imaging system is warranted.
Beamforming, which in its simplest form involves delaying, scaling, and summing to produce a coherent signal from the collection of received beams, has been identified as an area for algorithmic research and development [2] . In this work, an 8-channel wide, scalable digital beamformer is implemented with feedback for power reduction. Two modes of operation are available: coarse and fine beamforming. In the coarse beamforming mode, digitized data from an evenly spaced subset of transducer elements are processed, providing a low-quality image of the full region of interest, which yields power savings by turning off the analog front end electronics and analog-to-digital converters corresponding to the unused 50% or 75% of array channels (schematically shown in Figure 1). Figures 2a and b show the coarse images for quarter and half resolution coarse beamforming modes. Next, the user can specify a smaller region in which a higher quality image is desired, which is then beamformed by the same 8-channel wide processing unit using all available channels (an example of the full region full resolution image is shown in Figure 2c).
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- Figure 1: Ultrasound imaging system block diagram with feedback control for power reduction.
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- Figure 2: Comparison of beamformed images generated in the two coarse and one fine beamforming mode.
- M. Ali, D. Magee, and U. Dasgupta, “Signal processing overview of ultrasound systems for medical imaging,” Texas Instruments, Dallas, TX, SPRAB12, 2008. [↩]
- S. Stergiopoulos, Advanced Signal Processing Handbook: Theory and Implementation for Radar, Sonar, and Medical Imaging Real-Time Systems. Boca Raton: CRC Press, Inc., 2000. [↩]