A Nonuniform Sampling Lifetime Estimation Technique for Luminescent Oxygen Measurements for Biomedical Applications.

Area of Science:

• Biomedical Engineering
• Optical Sensing
• Materials Science

Background:

• Intensity-based luminescence measurements are susceptible to confounding factors, limiting their accuracy.
• Accurate measurement of transcutaneous oxygen is vital for assessing arterial oxygen levels.
• Existing techniques for luminescence lifetime determination can be complex and prone to offset errors.

Purpose of the Study:

• To present a novel, offset-immune technique for precise luminescence lifetime determination.
• To apply this technique for accurate measurement of transcutaneous oxygen.
• To develop a robust analog subsystem for efficient and accurate luminescence lifetime measurement.

Main Methods:

• Utilized a novel switched-capacitor circuit for long integration times and to prevent amplifier saturation.
• Implemented an analog subsystem in 180-nm CMOS technology, including a transimpedance amplifier and comparator.
• Employed a time-difference measurement between fixed-voltage steps to extract the luminescence time constant.

Main Results:

• Achieved a measured mean error of 1.9% without postprocessing.
• Demonstrated a readout circuit energy consumption of 16 μJ per calculation with a FoM_W of 177 nJ/conv.
• Successfully detected changes in transcutaneous oxygen levels in preliminary human subject tests.

Conclusions:

• The novel technique provides precise and offset-immune luminescence lifetime measurements.
• The developed sensor effectively measures transcutaneous oxygen, offering a superior alternative to intensity-based methods.
• The system shows promise for non-invasive monitoring of oxygen levels in clinical applications.