Implementing Effective Noise Reduction Techniques in Implantable NIRS Sensors.

Area of Science:

• Biomedical Engineering
• Optical Sensing
• Signal Processing

Background:

• Near-Infrared Spectroscopy (NIRS) is a noninvasive technique for tissue hemodynamics and physiological monitoring.
• Implantable NIRS sensors offer advantages but are susceptible to Common-Mode Voltage (CMV) interference, degrading signal quality.
• Existing NIRS methods struggle with limited sampling depth and spatial resolution, necessitating advanced sensor designs.

Purpose of the Study:

• To develop and validate a novel active Common-Mode Voltage (CMV) cancellation technique for implantable NIRS sensors.
• To enhance the signal-to-noise ratio (SNR) and accuracy of NIRS measurements in the presence of CMV interference.
• To improve the clinical reliability and applicability of NIRS technology for internal organ monitoring.

Main Methods:

• An electrical model of the patient's body and NIRS sensor was developed to characterize CMV interference.
• A novel active CMV cancellation (ACC) electronic circuit was designed, employing a common-mode amplifier to invert and reintroduce the CMV signal.
• The ACC circuit was validated using analytical simulations and experimental measurements on fingertip and palm data.

Main Results:

• The ACC technique effectively attenuated CMV (50 and 60 Hz) by 80 to 90 dB.
• CMV suppression was demonstrated within a bandwidth of 0.1 to 100 Hz without system instability.
• Experimental data confirmed significant suppression of CMV, validating the method's efficacy.

Conclusions:

• The proposed active CMV reduction technique substantially improves the SNR and accuracy of NIRS signals.
• This method enhances the reliability of implantable NIRS sensors, enabling more precise physiological monitoring.
• The technique holds significant clinical relevance for advanced patient care and internal organ assessment.