Field programmable gate array compression for large array multispeckle diffuse correlation spectroscopy

• Published in: Journal of biomedical optics Vol. 28; no. 5; p. 057001
• Main Authors: Della Rocca, Francescopaolo Mattioli, Sie, Edbert J., Catoen, Ryan, Marsili, Francesco, Henderson, Robert K.
• Format: Journal Article
• Language: English
• Published: United States Society of Photo-Optical Instrumentation Engineers 01.05.2023; SPIE; S P I E - International Society for
• Subjects: Algorithms; Autocorrelation functions; Avalanche diodes; Blood flow; Cameras; Cerebral blood flow; Compression; Data Compression; Data transfer (computers); Digital integrated circuits; Field programmable gate arrays; Mathematical analysis; Measuring instruments; Photon avalanches; Photons; Pixels; Real time; Sensing; Sensitivity; Sensors; Signal to noise ratio; Spectroscopy; Spectrum Analysis; Time measurement; Universal Serial Bus; field-programmable gate array compression; multispeckle; diffuse correlation spectroscopy; single-photon avalanche diode
• ISSN: 1083-3668; 1560-2281; 1560-2281
• DOI: 10.1117/1.JBO.28.5.057001

Diffuse correlation spectroscopy (DCS) is an indispensable tool for quantifying cerebral blood flow noninvasively by measuring the autocorrelation function (ACF) of the diffused light. Recently, a multispeckle DCS approach was proposed to scale up the sensitivity with the number of independent speckle measurements, leveraging the rapid development of single-photon avalanche diode (SPAD) cameras. However, the extremely high data rate from advanced SPAD cameras is beyond the data transfer rate commonly available and requires specialized high-performance computation to calculate large number of autocorrelators (ACs) for real-time measurements. We aim to demonstrate a data compression scheme in the readout field-programmable gate array (FPGA) of a large-pixel-count SPAD camera. On-FPGA, data compression should democratize SPAD cameras and streamline system integration for multispeckle DCS. We present a SPAD array with 128 linear ACs embedded on an FPGA to calculate 12,288 ACFs in real time. We achieved a signal-to-noise ratio (SNR) gain of 110 over a single-pixel DCS system and more than threefold increase in SNR with respect to the state-of-the-art multispeckle DCS. The FPGA-embedded autocorrelation algorithm offers a scalable data compression method to large SPAD array, which can improve the sensitivity and usability of multispeckle DCS instruments.