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Dipartimento di Fisica - Politecnico di Milano

Time-Domain Broadband Diffuse Optics for non-invasive Spectroscopy of Biological Tissues

Time-Domain Broadband Diffuse Optics for non-invasive Spectroscopy of Biological Tissues

Diffuse Optics studies photon migration through highly scattering media (e.g. biological tissues). In the spectral range 600-1100 nm, for most human tissues, elastic scattering interactions are prevalent over absorption events, producing a random walk of photons in the medium. Diffuse Optical Spectroscopy (DOS) permits to recover the absorption and scattering spectra through the diffusive medium retrieving information on chemical composition (absorption) and microstructure (scattering). Due to the intrinsic non-invasiveness, this technique is particularly attractive to identify new physiological or pathological biomarkers, to study the link of nutrition and lifestyle with health status, to design novel diagnostic techniques.

The DOS laboratory is based on the time-domain approach which permits to disentangle absorption from scattering contributions based on the distribution of photon time-of-flights in the medium. The laboratory is equipped with broadband pulsed tuneable laser sources and time-resolved single-photon detectors, leading to record performances in terms of spectral coverage, sensitivity and acquisition time.

The thesis activity can be focalised on some of the following aspects: 1) system development with emphasis on spectral extension, increased automation, parallel acquisition; 2) models for the analysis of photon migration in particular for heterogeneous structures based on analytical (e.g. Diffusion Equation) or numerical (e.g. Monte Carlo) methods; 3) validation of novel techniques on tissue-equivalent phantoms; 4) exploration of novel applicative fields mostly for in vivo human diagnostics.