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Characterization of a Pixel-Level Binarized Autocorrelator for Large Array Multispeckle Diffuse Correlation
Summary
We developed a resource-efficient 1-bit autocorrelator for multispeckle diffuse correlation spectroscopy (mDCS) to enable wearable blood flow monitoring. This innovation significantly reduces hardware needs for real-time microvascular measurements.
Area of Science:
- Biomedical Optics
- Optical Instrumentation
- Signal Processing
Background:
- Multispeckle Diffuse Correlation Spectroscopy (mDCS) offers real-time microvascular blood flow monitoring in deep tissues.
- Current mDCS adoption in wearables is hindered by high computational resource demands for autocorrelation.
- Efficient hardware solutions are crucial for advancing mDCS in portable healthcare applications.
Purpose of the Study:
- To propose and validate a resource-efficient 1-bit autocorrelator for in-pixel computation in mDCS systems.
- To reduce the hardware complexity and resource utilization of mDCS devices for wearable applications.
- To demonstrate the feasibility of a low-resource mDCS system for continuous blood flow monitoring.
Main Methods:
- A novel 1-bit autocorrelator architecture was designed, leveraging photon count binarization for reduced computational complexity.
- The 1-bit autocorrelator was implemented on a Field-Programmable Gate Array (FPGA) and tested with Single Photon Avalanche Diode (SPAD) inputs.
- Performance was compared against a conventional 5-bit baseline using a rotating diffuser for characterization and a cuff occlusion test.
Main Results:
- The 1-bit autocorrelator achieved significant reductions in FPGA resource usage: 79% in Look-Up Tables and 29.5% in Flip-Flops compared to the 5-bit baseline.
- An empirical threshold of 0.7 photon hit probability per lag bin was identified, below which the 1-bit system provides tolerable error in decay time constant estimation.
- Qualitative results from a cuff occlusion measurement demonstrated the practical viability of the proposed architecture.
Conclusions:
- The 1-bit autocorrelator presents a highly scalable and resource-efficient solution for mDCS systems-on-chip.
- This design facilitates the development of massively parallel mDCS arrays for next-generation wearable healthcare devices.
- The study validates the potential of low-bitwidth digital signal processing for efficient optical physiological monitoring.
