Time reversal beamforming for powering ultrasonic implants

Benedict, Braeden; Ghanbari, Mohammad Meraj; Alarnouti, Sina Faraji; Ersumo, Nathan Tessema; Muller, Rikky

doi:10.1109/ner49283.2021.9441162

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…It has been demonstrated that a phased array could be partitioned in half, with each sub-array used to target one implant [14], [16]. This technique was compared to one using the principle of superposition which allows the entire array aperture to be used to simultaneously power multiple implants [18].…”

Section: Introductionmentioning

confidence: 99%

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Phased array beamforming methods for powering biomedical ultrasonic implants

Benedict¹,

Ghanbari²,

Muller³

2022

Preprint

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Millimeter-scale implants using ultrasound for power and communication have been proposed for a range of deep-tissue applications, including neural recording and stimulation. However, published implementations have shown high sensitivity to misalignment with the external ultrasound transducer. Ultrasonic beamforming using a phased array to these implants can improve tolerance to misalignment, reduce implant volume, and allow multiple implants to be operated simultaneously in different locations. This paper details the design of a custom planar phased array ultrasound system, which is capable of steering and focusing ultrasound power within a 3D volume. Analysis and simulation is performed to determine the choice of array element pitch, with special attention given to maximizing the power available at the implant while meeting FDA limits for diagnostic ultrasound. Time reversal is proposed as a computationally simple approach to beamforming that is robust despite scattering and inhomogeneity of the acoustic medium. This technique is demonstrated both in active drive and pulse-echo modes, and it is experimentally compared with other beamforming techniques by measuring energy transfer efficiency at varying depths and angles. Simultaneous power delivery to multiple implants is also demonstrated.

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Section: Introductionmentioning

confidence: 99%

“…To initially power the implant, the array would start in an unfocused high-power mode (Fig. 2(b)) and/or sweep its focus using standard delay-and-sum beamforming [18].…”

Section: Introductionmentioning

confidence: 99%

Phased array beamforming methods for powering biomedical ultrasonic implants

Benedict¹,

Ghanbari²,

Muller³

2022

Preprint

Self Cite

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“…An alternative is to use time-reversal beamforming [4]. This is a simple and computationally efficient method that can accurately focus acoustic energy regardless of tissue scattering or tissue inhomogeneity.…”

Section: Introductionmentioning

confidence: 99%

A microwatt telemetry protocol for targeting deep implants

Kawasaki

Subramaniam

Saccher

et al. 2021

2021 IEEE International Ultrasonics Symposium (IUS)

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Implantable medical devices are becoming smaller and more deeply implanted in the human body for various applications (i.e., neurostimulation, drug delivery, bone fracture monitoring). Therefore, an efficient ultrasound power transfer link is needed to charge these devices. However, this is challenging because each ultrasound transducer has limited angular sensitivity. This work proposes a low-power telemetry protocol that can reliably feedback the power sent to the implant with backscattered ultrasound. The protocol works by sending two consecutive interrogation signals and connecting a circuit on the receiver that modulates only one of the two signals. The modulated signal can be decoded with an external ultrasound probe. In this work, the circuit was built, verified, and compared with simulation results. It was shown that the telemetry protocol could accurately localize the receiving ultrasound element at sub-mm precision at a 10 cm depth.

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Augmented ultrasonography with implanted CMOS electronic motes

et al. 2022

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Modern clinical practice benefits significantly from imaging technologies and much effort is directed toward making this imaging more informative through the addition of contrast agents or reporters. Here, we report the design of a battery-less integrated circuit mote acting as an electronic reporter during medical ultrasound imaging. When implanted within the field-of-view of a brightness-mode (B-mode) ultrasound imager, this mote transmits information from its location through backscattered acoustic energy which is captured within the ultrasound image itself. We prototype and characterize the operation of such motes in vitro and in vivo. Performing with a static power consumption of less than 57 pW, the motes operate at duty cycles for receiving acoustic energy as low as 50 ppm. Motes within the same field-of-view during imaging have demonstrated signal-to-noise ratios of more than 19.1 dB at depths of up to 40 mm in lossy phantom. Physiological information acquired through such motes, which is beyond what is measurable with endogenous ultrasound backscatter and which is biogeographically located within an image, has the potential to provide an augmented ultrasonography.

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Time reversal beamforming for powering ultrasonic implants

Cited by 8 publications

References 12 publications

Phased array beamforming methods for powering biomedical ultrasonic implants

Phased array beamforming methods for powering biomedical ultrasonic implants

A microwatt telemetry protocol for targeting deep implants

Augmented ultrasonography with implanted CMOS electronic motes

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