Wavelength and code-division multiplexing in diffuse optical imaging

Luca Ascari; Gianluca Berrettini; Sandro Iannaccone; Matteo Giacalone; Davide Contini; Lorenzo Spinelli; Maria Giovanna Trivella; Antonio L'Abbate; Luca Potí

doi:10.1117/12.875132

1 March 2011 Wavelength and code-division multiplexing in diffuse optical imaging

Luca Ascari, Gianluca Berrettini, Sandro Iannaccone, Matteo Giacalone, Davide Contini, Lorenzo Spinelli, Maria Giovanna Trivella, Antonio L'Abbate, Luca Potí

Author Affiliations +

Proceedings Volume 7896, Optical Tomography and Spectroscopy of Tissue IX; 789620 (2011) https://doi.org/10.1117/12.875132
Event: SPIE BiOS, 2011, San Francisco, California, United States

Abstract

We recently applied time domain near infrared diffuse optical spectroscopy (TD-NIRS) to monitor hemodynamics of the cardiac wall (oxy and desoxyhemoglobin concentration, saturation, oedema) on anesthetized swine models. Published results prove that NIRS signal can provide information on myocardial hemodynamic parameters not obtainable with conventional diagnostic clinical tools.1 Nevertheless, the high cost of equipment, acquisition length, sensitivity to ambient light are factors limiting its clinical adoption. This paper introduces a novel approach, based on the use of wavelength and code division multiplexing, applicable to TD-NIRS as well as diffuse optical imaging systems (both topography and tomography); the approach, called WS-CDM (wavelength and space code division mltiplexing), essentially consists of a double stage intensity modulation of multiwavelength CW laser sources using orthogonal codes and their parallel correlation-based decoding after propagation in the tissue; it promises better signal to noise ratio (SNR), higher acquisition speed, robustness to ambient light and lower costs compared to both the conventional systems and the more recent spread spectrum approach based on single modulation with pseudo-random bit sequences (PRBS).2 Parallel acquisition of several wavelengths and from several locations is achievable. TD-NIRS experimental results guided Matlab-based simulations aimed at correlating different coding sequences, lengths, spectrum spreading factor, with the WS-CDM performances on such tissues (achievable SNR, acquisition and reconstruction speed, robustness to channel inequalization, ...). Simulations results and preliminary experimental validation confirm the significant improvements that WS-CDM could bring to diffuse optical imaging (not limited to cardiac functional imaging).

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Luca Ascari, Gianluca Berrettini, Sandro Iannaccone, Matteo Giacalone, Davide Contini, Lorenzo Spinelli, Maria Giovanna Trivella, Antonio L'Abbate, and Luca Potí "Wavelength and code-division multiplexing in diffuse optical imaging", Proc. SPIE 7896, Optical Tomography and Spectroscopy of Tissue IX, 789620 (1 March 2011); https://doi.org/10.1117/12.875132

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