A Silicon Integrated fdNIRS System for Absolute Oximetry and Multimodal Applications.
Miao, Yun.
2019
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This work presents the
design and validation of a silicon integrated frequency domain near infrared
spectroscopy (fdNIRS) system. fdNIRS can noninvasively measure the absolute
concentration of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) in tissue. The tissue
hemodynamics is a useful biomarker in functional brain studies, sports medicine, and the
diagnosis of a variety of diseases. Most ... read moreexisting fdNIRS system are benchtop instruments
based on discrete electronics and sensors. A silicon integrated solution will not only
reduce the size and cost of fdNIRS system but also enable more compact multi-modal
platforms. An optimal system architecture based on avalanche photodiode (APD) and
application-specified integrated circuit (ASIC) is proposed. APD has a much smaller
footprint and requires lower biasing voltage compared with photomultiplier tubes (PMT).
As a solid-state sensor, APD also has a superior resistance to mechanic shock, humidity,
and magnetic fields, which make it ideal for portable fdNIRS system. A dual channel
fdNIRS ASIC is implemented on a standard 130nm CMOS process. Each fdNIRS channel
provides 120dBΩ transimpedance gain at 80MHz with a power consumption of 30mW,
while tolerating up to 8pF input capacitance. A photocurrent between 10nA to 450nA can
be detected with a phase resolution down to 0.2°. A transcranial direct-current
stimulation (tDCS) is also integrated on the ASIC, which makes it suitable for
closed-loop brain stimulation applications. The on-chip programmable voltage-controlled
resistor (VCR) stimulator can support a stimulation current from 0.6mA to 2.2mA with
less than 1% variation, which covers the required current range of tDCS. A low-cost
fdNIRS prototype is developed based on the ASIC. The APD, fdNIRS ASIC, power management
circuits, and time-multiplexed laser arrays are integrated on printed circuit boards
(PCBs). Labview based data acquisition and control system is implemented. Signal
processing and calibration algorithms are realized in Matlab environment. The prototype
successfully measured the optical parameters of solid tissue phantoms. The maximum error
is less than 10% after calibration. The absolute concentration of HbO and HbR is also
successfully extracted in human test.
Thesis (Ph.D.)--Tufts University, 2019.
Submitted to the Dept. of Electrical Engineering.
Advisor: Valencia Koomson.
Committee: Valencia Koomson, Sergio Fantini, Robert Jacob, and Kemal Kulovic.
Keyword: Electrical engineering.read less - ID:
- f4752w146
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