title: Ultrafast wavelength multiplexed broad bandwidth digital diffuse optical spectroscopy for in vivo extraction of tissue optical properties.
abstract: Frequency-domain diffuse optical spectroscopy (FD-DOS) utilizes intensity-modulated light to characterize optical scattering and absorption in thick tissue. Previous FD-DOS systems have been limited by large device footprints, complex electronics, high costs, and limited acquisition speeds, all of which complicate access to patients in the clinical setting. We have developed a new digital DOS (dDOS) system, which is relatively compact and inexpensive, allowing for simplified clinical use, while providing unprecedented measurement speeds. The dDOS system utilizes hardware-integrated custom board-level direct digital synthesizers and an analog-to-digital converter to generate frequency sweeps and directly measure signals utilizing undersampling at six wavelengths modulated at discrete frequencies from 50 to 400 MHz. Wavelength multiplexing is utilized to achieve broadband frequency sweep measurements acquired at over 97 Hz. When compared to a gold-standard DOS system, the accuracy of optical properties recovered with the dDOS system was within 5.3% and 5.5% for absorption and reduced scattering coefficient extractions, respectively. When tested in vivo, the dDOS system was able to detect physiological changes throughout the cardiac cycle. The new FD-dDOS system is fast, inexpensive, and compact without compromising measurement quality.
authors.affiliation: Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Torjesen
authors.affiliation: Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States.
authors.forename: Raeef
authors.initials: R
authors.lastname: Istfan
authors.affiliation: Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States.
authors.forename: Darren
authors.initials: D
authors.lastname: Roblyer
mesh_terms: D003952:Diagnostic Imaging / Q000295:instrumentation*; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D055096:Optical Devices; D013057:Spectrum Analysis