title: Towards next-generation time-domain diffuse optics for extreme depth penetration and sensitivity.
abstract: Light is a powerful tool to non-invasively probe highly scattering media for clinical applications ranging from oncology to neurology, but also for molecular imaging, and quality assessment of food, wood and pharmaceuticals. Here we show that, for a paradigmatic case of diffuse optical imaging, ideal yet realistic time-domain systems yield more than 2-fold higher depth penetration and many decades higher contrast as compared to ideal continuous-wave systems, by adopting a dense source-detector distribution with picosecond time-gating. Towards this aim, we demonstrate the first building block made of a source-detector pair directly embedded into the probe based on a pulsed Vertical-Cavity Surface-Emitting Laser (VCSEL) to allow parallelization for dense coverage, a Silicon Photomultiplier (SiPM) to maximize light harvesting, and a Single-Photon Avalanche Diode (SPAD) to demonstrate the time-gating capability on the basic SiPM element. This paves the way to a dramatic advancement in terms of increased performances, new high impact applications, and availability of devices with orders of magnitude reduction in size and cost for widespread use, including quantitative wearable imaging.
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Italy ; These authors contributed equally to this work.
authors.forename: Alberto Dalla
authors.initials: AD
authors.lastname: Mora
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Italy ; These authors contributed equally to this work.
authors.forename: Davide
authors.initials: D
authors.lastname: Contini
authors.affiliation: Department of Computer Science, University College London, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Arridge
authors.affiliation: Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Martelli
authors.affiliation: Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Tosi
authors.affiliation: Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Boso
authors.affiliation: Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Farina
authors.affiliation: ICFO-Institut de Cències Fotòniques, Spain.
authors.forename: Turgut
authors.initials: T
authors.lastname: Durduran
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Martinenghi
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Italy ; alessandro.torricelli@polimi.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Torricelli
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Italy ; Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pifferi
keywords: (170.3660) Light propagation in tissues; (170.5280) Photon migration; (170.6960) Tomography; (230.6046) Smart pixel systems; (290.7050) Turbid media