Mr. John A. Merrill Profile

John A. Merrill

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Publications (3)

Proceedings Article | 3 March 2020 Paper

Photoacoustic microscopy for bone microstructure analysis

John Merrill, Siqi Wang, Yue Zhao, Jesus Arellano, Liangzhong Xiang

Proceedings Volume 11241, 112410H (2020) https://doi.org/10.1117/12.2550372

KEYWORDS: Bone, Tissue optics, Photoacoustic microscopy, Spatial resolution, Transducers, Tissues, Analytical research, Absorption, Photoacoustic imaging, Biopsy

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Proceedings Article | 15 March 2019 Presentation + Paper

Electroacoustic tomography (EAT): linear scanning with a single element transducer

Ali Zarafshani, John Merrill, Siqi Wang, Mengxiao Wang, Bin Zheng, Liangzhong Xiang

Proceedings Volume 10955, 1095513 (2019) https://doi.org/10.1117/12.2512812

KEYWORDS: Transducers, Acoustics, Tomography, Tissues, Signal detection, Real time imaging, Ultrasonics, Ultrasonography, Electrodes, Signal processing, Acoustic emission

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Proceedings Article | 15 March 2019 Paper

Electroacoustic tomography system with nanosecond electric pulse excitation source

Ali Zarafshani, John Merrill, Siqi Wang, Bin Zheng, Liangzhong Xiang

Proceedings Volume 10955, 109551B (2019) https://doi.org/10.1117/12.2513051

KEYWORDS: Transducers, Acoustics, Tomography, Tissues, Ultrasonics, Electrodes, Imaging systems, Real time imaging, Signal detection, Signal processing, Acoustic emission

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The new technique for the imaging guidance to real-time monitoring of electroporation-based medical interventions could be based on the electroacoustic tomography (EAT), where the electric field applied for the electroporation process leads to induced acoustic signals based on the flow of electrical current inside the target conductive tissue. A microsecond to nanosecond electric-pulse (𝜇𝑠 − 𝑛𝑠𝐸𝑃) excitation source is an essential part of this new imaging guided to real-time monitoring electroporation process. This paper presents the design, configuration, and measurement of a compact, low-cost high voltage MOSFET-based pulsed excitation source and the simple structure of the EAT system with the single channel ultrasonic transducer to acquire acoustic signals and complemented by experimentation of its function based on agar-conductive phantom studies. The high-voltage pulsed excitation source has variable pulse widths ranging from 100 𝑛𝑠 𝑡𝑜 10 𝜇𝑠 electric pulse with a variable pulse potential magnitude of up to 1200 Volts (V). The high-voltage 𝜇𝑠 − 𝑛𝑠𝐸𝑃 is powered from a variable input source of 11.3 to 16 V in direct current (DC) and a power controller using a 0 V to 5 V in DC power line so that it is able to provide 0 to full output in potential magnitude. The high-intensity, ultra-short pulsed electric field is then connected to two electrodes separated by a distance (d) where 𝑑 = 1500𝜇𝑚 𝑡𝑜 3400 𝜇 mounted into the conductive media. An unfocused ultrasound transducer with central frequency of 500 kHz is used to acquire real-time acoustic signals. Various conductive media, including two agar-based phantoms with conductivity of 1 𝜇𝑆/𝑐𝑚 , 34 𝑚𝑆/𝑐𝑚 were studied using this pulsed excitation source to induce corresponding acoustic signals. Results indicate feasibility of the enhancing the EAT system that used up to 8 kV/cm, 𝜇𝑠 𝑡𝑜 𝑛𝑠 pulsed excitation source used in the electroporation-based clinical processes enhancing the EAT system as an imaging guidance to real-time, in-situ monitoring for the electroporation-based techniques.

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