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PhD Dissertation_Fatemeh Marefat.pdf (9.69 MB)

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Toward Cuffless Blood Pressure Monitoring: Integrated Microsystems for Implantable Recording of Photoplethysmogram

Marefat, Fatemeh
http://orcid.org/0000-0001-6073-7416
http://rave.ohiolink.edu/etdc/view?acc_num=case1595441087168539

Abstract Details

2020, Doctor of Philosophy, Case Western Reserve University, EECS - Electrical Engineering.
In this work, design and development of photoplethysmogram (PPG) readout systems are presented for implantable blood pressure (BP) monitoring as a foundational block of the next-generation networked neuroprosthesis (NNP) systems. A miniaturized Gen-I PPG readout system is developed for recording of PPG signal subcutaneously from muscle groups in minimally invasive fashion as a step toward chronic implantation. The Parylene–C-coated sensor boards were implanted subcutaneously on the quadriceps muscle group of an anesthetized laboratory rat, yielding PPG recordings. These devices are also adopted in a human trial test for studying indirect, cuff-less BP estimation based on pulse arrival time algorithms showing motivating results. Following that, to improve performance of the PPG readout system, two PPG readout integrated circuits (ROICs) are developed as Gen-II and Gen-III systems. A 10-bit light-to-digital converter (LDC) is proposed that uniquely employs a 1st-order, continuous-time, incremental delta-sigma modulator (I–ΔΣM) as an ultralow-power PPG recording front-end along with an on-chip 2-channel light-emitting diode (LED) driver. The LDC digitizes photodiode (PD) light-induced current in a single-stage manner that in addition to supported duty-cycled operation allows for huge power saving. Moreover, the I–ΔΣM uniquely allows for operation in intermittent conversion phases that enables a priori direct measurement of dc and ambient light-induced components of the PD current for signal-aware on-the-fly dc subtraction and ambient light removal before digitization facilitating high-quality measurement of small PPG signal. Fabricated in 0.18μm 1P/6M CMOS, the PPG ROIC features a high dynamic range (DR) of 92.7dB, dissipates 8.1μW and 1.95mW in the recording front-end and the LED (with its driver), respectively, with ~10% duty cycling at pulse repetition frequency (PRF) of 100Hz. Following that, the Gen-III system is developed as a complete PPG ROIC using 13-bit LDC based on a 2nd-order continuous-time I–ΔΣM that greatly reduces LDC conversion time and hence total ROIC power consumption while at the same time achieves higher resolution in the LDC. Fabricated in 0.18µm 1P/6M CMOS, the PPG ROIC shows a high-fidelity PPG recording and features a high DR of 108dB dissipating 280µW with LDC consuming 15.7µW from 1.5V and one LED (and its driver) dissipating 264µW from 2.5V with 3.2% duty cycling at PRF of 250Hz. Finally, the entire PPG ROIC is wirelessly powered through 3-mm tissue using a capacitive link while high-fidelity PPG signal is recorded from a human fingertip paving the path toward enabling a wirelessly-powered implantable PPG recording system as a foundational block of the next-generation NNP systems.
Pedram Mohseni (Advisor)
Kevin Kilgore (Committee Member)
Hossein Miri Lavasani (Committee Member)
Francis Merat (Committee Member)
Biomedical Engineering; Biomedical Research; Electrical Engineering; Health Care
Biomedical Implants; Implantable Microsystems; Implantable Photoplethysmography; CMOS Integrated Circuits; PPG readout IC; Cuffless blood pressure monitoring; Light-to-digital converter; Continuous-time incremental delta sigma modulator; Current sensing

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Citations

  • Marefat, F. (2020). Toward Cuffless Blood Pressure Monitoring: Integrated Microsystems for Implantable Recording of Photoplethysmogram [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1595441087168539

    APA Style (7th edition)

  • Marefat, Fatemeh. Toward Cuffless Blood Pressure Monitoring: Integrated Microsystems for Implantable Recording of Photoplethysmogram . 2020. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1595441087168539.

    MLA Style (8th edition)

  • Marefat, Fatemeh. "Toward Cuffless Blood Pressure Monitoring: Integrated Microsystems for Implantable Recording of Photoplethysmogram ." Doctoral dissertation, Case Western Reserve University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1595441087168539

    Chicago Manual of Style (17th edition)

case1595441087168539
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.