High Frequency Sampling of TTL Pulses on a Raspberry Pi for Diffuse Correlation Spectroscopy Applications.
Diffuse Correlation Spectroscopy (DCS) is a well-established optical technique that has been used for non-invasive measurement of blood flow in tissues. Instrumentation for DCS includes a correlation device that computes the temporal intensity autocorrelation of a coherent laser source after it has undergone diffuse scattering through a turbid medium. Typically, the signal acquisition and its autocorrelation are performed by a correlation board. These boards have dedicated hardware to acquire and compute intensity autocorrelations of rapidly varying input signal and usually are quite expensive. Here we show that a Raspberry Pi minicomputer can acquire and store a rapidly varying time-signal with high fidelity. We show that this signal collected by a Raspberry Pi device can be processed numerically to yield intensity autocorrelations well suited for DCS applications. DCS measurements made using the Raspberry Pi device were compared to those acquired using a commercial hardware autocorrelation board to investigate the stability, performance, and accuracy of the data acquired in controlled experiments. This paper represents a first step toward lowering the instrumentation cost of a DCS system and may offer the potential to make DCS become more widely used in biomedical applications.
Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA. tivnan.m@husky.neu.edu.|Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA. tivnan.m@husky.neu.edu.
Matthew
M
Tivnan
Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA. Rajan.Gurjar@ll.mit.edu.|MIT Lincoln Laboratory, Lexington, MA 02421, USA. Rajan.Gurjar@ll.mit.edu.
Rajan
R
Gurjar
Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA. dwolf@pendarmedical.com.|Pendar Medical, Cambridge, MA 02138, USA. dwolf@pendarmedical.com.
David E
DE
Wolf
Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA. vishwak@miamioh.edu.|Department of Physics, 500 E Spring Street, Miami University, Oxford, OH 45056, USA. vishwak@miamioh.edu.
Karthik
K
Vishwanath
D005583:Fourier Analysis; D006801:Humans; D008128:Logic; D008297:Male; D008905:Minicomputers; D011674:Pulse; D012039:Regional Blood Flow; D013057:Spectrum Analysis / Q000379:methods*; D014173:Transistors, Electronic; D055815:Young Adult
Raspberry Pi; blood flow; coherent scattering; laser speckle; optical spectroscopy; software autocorrelation