We performed reflectance measurements with a time-resolved white-light spectroscopy system to monitor concentrations changes in a two-layer liquid phantom with optical properties similar to human tissues. By varying the concentrations of three inks with different spectral features, we changed the absorption coefficient of the upper and lower layer to simulate either haemodynamics changes in the muscle covered by adipose layer, or functional brain activation with systemic response in the scalp. Data were analyzed by a time-resolved spectrally constrained fitting method based on a homogeneous model of photon diffusion. Although this approach is based on a homogeneous model and employs a single 2cm source-detector distance, the technique is able to monitor changes in the lower layer, while it is scarcely affected by variation in the upper layer. Preliminary in vivo measurements have been performed on one healthy volunteer to monitor oxy- and deoxy-haemoglobin changes in the muscle during arterial occlusion and in the brain during a motor task. Even if the overall sensitivity of the technique is reduced, in vivo results are in general agreement with the findings of dedicated system for tissue oximetry.
The sensitivity to collagen may be useful for diagnostic purposes in mammography, as collagen seems to be involved in
the development of breast cancer. Moreover, collagen content is expected to be related to breast density (i.e. breast
parenchymal pattern) and its quantification could allow the classification of breast type. Thus we have measured the
absorption properties of collagen from 610 to 1040 nm. Absorption spectra of breast from healthy volunteers were then
interpreted adding collagen to the other absorbers previously considered (i.e. oxy- and deoxyhemoglobin, water, and
lipids). A significant amount of collagen, depending on breast type, is estimated to be present and seems to correlate with
breast type. Moreover, adding collagen to the fitting procedure affects remarkably the estimated values of blood content
and oxygenation. We have also upgraded our time-resolved multi-wavelength optical mammograph, adding a long
wavelength (1060 nm) to improve the spectral information and, in particular, the sensitivity to collagen. Breast
measurements on volunteers have recently started.
We demonstrate the feasibility of white-light time-resolved optical mammography. The instrumentation is based on supercontinuum light generated in photonic crystal fiber and 32-channel parallel time-correlated single-photon-counting detection. Total measurement time is of the order of 10 min for typical clinical applications. Preliminary measurements performed on volunteers show the ability of the system to determine tissue constituent concentrations and structure over the entire breast area. Furthermore, measurements on a tissue-like sample demonstrate detection and characterization of inclusions.
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