Arridge, S.

Boso, G.

Contini, D.

Dalla Mora, A.

Durduran, T.

Farina, A.

Martelli, F.

Martinenghi, E.

Pifferi, A.

Torricelli, A.

Tosi, A.

DALLA MORA, ALBERTO

MARTINENGHI, EDOARDO

CONTINI, DAVIDE

TOSI, ALBERTO

BOSO, GIANLUCA

FARINA, ANDREA

TORRICELLI, ALESSANDRO

PIFFERI, ANTONIO GIOVANNI

Archivio istituzionale della ricerca - Politecnico di Milano

Time-Domain Diffuse Optics: the Dawn of Next-Generation Devices  A. Dalla Mora1, E. Martinenghi1, D. Contini1, A. Tosi2, G. Boso3, A. Farina4, S. Arridge5, F. Martelli6, T. Durduran7, A. Torricelli1, A. Pifferi1,4 1. Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 2. Politecnico di Milano, Dipartimento di Elettronica Informazione e Bioingegneria, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 3. University of Geneva, Group of Applied Physics, Chemin de Pinchat 22, CH-1211, Genève 4, Switzerland 4. Consiglio Nazionale delle Ricerche, Istituto di Fotonica e Nanotecnologie, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 5. University College London, Department of Computer Science, Gower Street, London WC1E 6BT, United Kingdom 6. Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy 7. ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain   Diffuse Optics (DO) is a powerful tool to probe scattering media avoiding invasive techniques, hosting the potential to revolutionize clinical applications from oncology to neurology and also many other fields [1, 2]. The traditional Continuous-Wave (CW) approach has never reached the required performance being severely hampered by the strong interplay between absorption and scattering and the need to detect reemitted light at some centimetres from the injection point, thus lowering the useful signal and impairing the spatial resolution. Time-Domain (TD) approaches are potentially more effective in terms of quantitation, penetration depth and sensitivity, but traditionally affected by the need to use bulky, expensive and fragile instrumentation, thus strongly limiting the number of injection and detection points. We demonstrated with simulations that TD-DO must face three main challenges to reach a ultimate performance breakthrough: i) the use of a dense arrangement of pulsed sources directly hosted into the optical probe (C1); ii) an equivalent arrangement of large area time-resolved single-photon detectors (C2); iii) the fast-gating capability of each detector to increase the dynamic range by orders of magnitude, thus allowing small source-detector distances (C3) [3]. In this ideal case DO will reach a 6 cm penetration depth (Fig. 1 left), thus opening to novel applications like the lung or heart monitoring.  Fig. 1. (left) Simulation of the contrast produced in a realistic case using ideal CW and TD systems. (centre) Experimental results on contrast-to-noise ratio obtained using TD probes. (right) Probe positioning example for functional brain imaging. Since technology is still far from allowing C1+C2+C3, we separately demonstrated these concepts using emerging technologies able to replace the traditional bulky instrumentation, thus allowing the direct hosting onto the probe and a large number of channels thanks to the low cost. We realized: i) a first probe (#1) using a pulsed Vertical-Cavity Surface-Emitting Laser (VCSEL) to potentially allow a dense arrangement (C1) and a time-resolved Silicon Photomultiplier (SiPM, never used in TD-DO) to fulfil the large area requirement of C2; ii) a second probe (#2) using a VCSEL and a gated Single-Photon Avalanche Diode (SPAD) to demonstrate the on-probe gating capability of the SiPM basic building block towards C3. Pulse generators and timing electronics are still external, yet full on-board integration using already proven technologies is feasible. Measurements showed that both probes yield already comparable contrast and better contrast-to-noise ratio (Fig. 1 centre) as compared to a state-of-the-art TD instrument. We also increased 100 times the source power using an external laser to simulate the potential improvement coming from a dense arrangement of many VCSELs (C1). The path is now opened, with the possibility of rapid progress thanks to the use of technologies developed for parallel fields like positron emission tomography systems. We are at the dawn of a new era for Diffuse Optics. References1 T. Durduran et al., "Diffuse optics for tissue monitoring and tomography," Reports Prog. Phys. 73, 076701 (2010).  T. O’Sullivan, "Diffuse optical imaging using spatially and temporally modulated light," J. Biomed. Opt. 17, 071311 (2012).  A. Dalla Mora et al., "Fast-gated single-photon avalanche diode for wide dynamic range near infrared spectroscopy," IEEE J. Sel. Top. Quantum Electron. 16, 1023 (2010).

Time-Domain Diffuse Optics: the Dawn of Next-Generation Devices

https://re.public.polimi.it/retrieve/handle/11311/984170/108490/SPW_2015_Dalla%20Mora.pdf

Time-Domain Diffuse Optics: the Dawn of Next-Generation Devices

Abstract

Similar works

Full text

Available Versions

Archivio istituzionale della ricerca - Politecnico di Milano