title: Time-domain diffuse correlation spectroscopy.
abstract: Physiological monitoring of oxygen delivery to the brain has great significance for improving the management of patients at risk for brain injury. Diffuse correlation spectroscopy (DCS) is a rapidly growing optical technology able to non-invasively assess the blood flow index (BFi) at the bedside. The current limitations of DCS are the contamination introduced by extracerebral tissue and the need to know the tissue's optical properties to correctly quantify the BFi. To overcome these limitations, we have developed a new technology for time-resolved diffuse correlation spectroscopy. By operating DCS in the time domain (TD-DCS), we are able to simultaneously acquire the temporal point-spread function to quantify tissue optical properties and the autocorrelation function to quantify the BFi. More importantly, by applying time-gated strategies to the DCS autocorrelation functions, we are able to differentiate between short and long photon paths through the tissue and determine the BFi for different depths. Here, we present the novel device and we report the first experiments in tissue-like phantoms and in rodents. The TD-DCS method opens many possibilities for improved non-invasive monitoring of oxygen delivery in humans.
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Sutin
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Zimmerman
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Danil
authors.initials: D
authors.lastname: Tyulmankov
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA; Dipartimento di Elettronica, Informazione e Bioingegneria at Politecnico di Milano, Milano, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Tamborini
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Kuan Cheng
authors.initials: KC
authors.lastname: Wu
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Juliette
authors.initials: J
authors.lastname: Selb
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria at Politecnico di Milano, Milano, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Gulinatti
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria at Politecnico di Milano, Milano, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Rech
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria at Politecnico di Milano, Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Tosi
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Boas
authors.affiliation: Optics Division at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: Franceschini