Chromophore decomposition in multispectral time-resolved diffuse optical tomography

Abstract

Multicomponent phantom measurements are carried out to evaluate the ability of multispectral time domain diffuse optical tomography in reflectance geometry to quantify the position and the composition of small heterogeneities at depths of 1-1.5 cm in turbid media. Time-resolved data were analyzed with the Mellin-Laplace transform. Results show good localization and correct composition gradation of objects but still a lack of absolute material composition accuracy when no a priori geometry information is known.

The Use of Supercontinuum Laser Sources in Biomedical Diffuse Optics: Unlocking the Power of Multispectral Imaging

“…A team in Grenoble has explored the use of the Mellin-Laplace transform to reconstruct 3D images of the chromophores inside phantoms and for the non-invasive assessment of flap viability in rats' models. There instrumentation was based on commercial SCL, coupled with either an AOTF or an interferential filter, for the source and a TCPSC scheme for the detection [86,87].…”

The SiPM revolution in time-domain diffuse optics

“…To give an idea of the improvement in the signal level given by SiPMs, it is worth mentioning that the R of TD DO systems based on a 1 mm 2 probe-hosted SiPM can overcome the value of previous state-of-the-art devices by 1-2 orders of magnitude, and obviously the use of a 9 mm 2 can lead to a gain approaching the 3 orders of magnitude. SiPMs were in the following validated in different scenarios of possible TD DO applications like: i) the accurate measurement of optical properties of homogeneous media (highlighting in particular the capability to linearly follow changes in optical properties and proper uncoupling of absorption from reduced scattering coefficients), where they showed performance in line with the state of the art [57], ii) the capability of detecting localized perturbations inside the medium in depth, where they showed improved performances thanks to their increased efficiency in the collection of diffused light, thus allowing the detection of a larger number of late-arriving photons [40], iii) the possibility of exploitation in diffuse optical tomography (DOT) systems at a single wavelength to reconstruct 3D maps of optical properties [58], as well as in multispectral DOT to reconstruct 3D maps of different chemical constituents of the sample under investigation [59], in both cases showing impressive performances. Three different parallel branches of SiPM exploitation started: i) replacing PMTs or hybrid PMTs in state-of-the-art bulky systems; ii) designing hybrid systems (still fiber based) between the previous and the next-generation, taking advantage of parallel development of compact laser sources; iii) designing innovative wearable detection chains with high performance thanks to the use of SiPMs directly embedded in the probe in contact with the medium under investigation.…”

Improving Localization of Deep Inclusions in Time-Resolved Diffuse Optical Tomography

“…Background absorption was set to µ a = 0.018 cm −1 and the reduced scattering was µ s = 14.7 cm −1 over all the domain. An inclusion of 0.5 cm radius was included whose optical properties were µ a = 0.337 cm −1 and µ s = 14.7 cm −1 (these values were taken from the experiment performed at [43] using 550 nm wavelength light and are of similar order as found at several types of human tissue). The setup of source and detectors was moved along the top boundary to scan the phantom at multiple positions.…”