Experimental tests of a simple diffusion model for the estimation of scattering and absorption coefficients of turbid media from time-resolved diffuse reflectance measurements

Abstract

When a picosecond light pulse is incident upon a turbid medium such as tissue, the temporal distribution of diffusely reflected and transmitted photons depends on the optical absorption and scattering properties of the medium. From diffusion theory it is possible to derive analytic expressions for the pulse shape in terms of the optical interaction coefficients of a homogeneous semi-infinite medium. Experimental tests of this simple model in tissue-simulating liquid phantoms of different geometries are presented here. The results of these tests show that, in a semi-infinite phantom, the application of the diffusion model provides estimates of the absorption and transport-scattering coefficients that are accurate to better than 10%. Comparable accuracy was also obtained with this simple model for finite slab, cylindrical, and spherical volumes as long as the objects were of sufficient size. For smaller volumes the absorption coefficient was overestimated because of the significant loss of photons at the bounda ries of the object.

Computer simulation of time-resolved optical imaging of objects hidden in turbid media

“…Table 5 Same as Table 4, except that the dimensions of the sample are¸V"10 mm,¸W"70 mm and¸X"55 mm Differences in these results may at least in part be attributed to a difference in the composition of intralipid-10% [159,160]. Moreover, the absorption factor of intralipid seems difficult to determine accurately [163]. Fig.…”

In vivo local determination of tissue optical properties: applications to human brain

“…The relatively small errors that we found here are typical of errors found when different techniques for measuring turbid-media optical properties are compared. 28 Such errors could be avoided by multiple calibrations on several turbid samples of different known optical properties. However, the accuracy of tissue measurements is subject to other major limitations due to, for example, their structure and heterogeneity.…”

Direct imaging of turbid media using long-time back-scattered photons, a numerical study

“…It is shown here that the relevant part of this signature is the decaying one. Literature [14][15][16][17] reports results along this line about properties characterization of ho- mogeneous or layered media. However, in the case presented here, the information sought deals with the determination of the position of an embedded heterogeneous layer and not the optical properties of the material.…”

“…They provide a lot of information on the inside optical properties distribution. Theoretical investigations have opened the way of exploiting the asymptotic logarithmic slope (ALS) of the decaying part of the transient signature in reflectance or transmittance [14][15][16] for homogeneous material characterization. By fitting time-resolved measurements against solutions obtained from the diffusion approximation for Dirac-pulse light transport in turbid 1-D media, importance of the time-decaying log-slope of emerging reflected and transmitted signals for the retrieval of optical properties has been confirmed.…”