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Sesto Fiorentino, Italy

Sassaroli A.,Tufts University | Martelli F.,DellUniversity Firenze
Journal of the Optical Society of America A: Optics and Image Science, and Vision

In the field of photon migration in turbid media, different Monte Carlo methods are usually employed to solve the radiative transfer equation. We consider four different Monte Carlo methods, widely used in the field of tissue optics, that are based on four different ways to build photons' trajectories. We provide both theoretical arguments and numerical results showing the statistical equivalence of the four methods. In the numerical results we compare the temporal point spread functions calculated by the four methods for a wide range of the optical properties in the slab and semi-infinite medium geometry. The convergence of the methods is also briefly discussed. © 2012 Optical Society of America. Source

Di Ninni P.,DellUniversity Firenze | Berube-Lauziere Y.,Universite de Sherbrooke | Mercatelli L.,National Research Council Italy | Sani E.,National Research Council Italy | Martelli F.,DellUniversity Firenze
Applied Optics

Intralipid 20% was recently suggested as a diffusive reference standard for tissue simulating phantoms. In this work, we extend previously obtained results to other fat emulsions, specifically Intralipid 10%, Intralipid 30%, Lipovenoes 10%, Lipovenoes 10% PhosphoLipid Reduced, Lipovenoes 20%, Lipofundin S 10%, and Lipofundin S 20%. Of particular importance for practical applications, our measurements carried out at a wavelength of 751 nm show the following features. First, these products show high stability and small batch-to-batch variations in their diffusive optical properties, similar to Intralipid 20%. Second, the absorption coefficient of Intralipid, Lipovenoes, and Lipofundin S are very similar and their measured values are within the experimental errors; moreover the reduced scattering coefficient of Intralipid 20%, Lipovenoes 20%, and Lipofundin S 20% are similar and their measured values are within 5%. Third, the reduced scattering coefficient of Intralipid 10% and Intralipid 30% can be scaled from that of Intralipid 20% with an error of 9% and 2%, respectively. A similar scaling property is valid for Lipovenoes and Lipofundin S. We have verified that this scaling property depends on the composition of the fat emulsions: If the ingredients exactly scale with the concentration then the reduced scattering coefficient almost exactly scale as well. © 2012 Optical Society of America. Source

Martelli F.,DellUniversity Firenze | Bianco S.D.,DellUniversity Firenze | Bianco S.D.,CNR Institute of Applied Physics Nello Carrara | Zaccanti G.,DellUniversity Firenze
Physics in Medicine and Biology

We propose the use of a retrieval procedure for time-resolved near-infrared tissue spectroscopy based on the optimal estimation method. The aim of this retrieval method is to obtain an improved estimate of the target parameters compared with standard nonlinear least-squares routines, since the inverse problem dedicated to retrieve the optical properties of tissue is ill posed. A priori information on target and forward model parameters is used, so that a larger number of target parameters can be retrieved, and/or a better accuracy and precision can be achieved on the retrieved target parameters. The procedure has been tested on time-resolved simulated experiments generated, using solutions of the diffusion equation and with solutions of the radiative transfer equation reconstructed with Monte Carlo simulations. The results obtained show that, by using a priori information on target parameters, we have a smaller difference between retrieved values and true values, and lower retrieved error bars. Similarly, a more correct estimate of the errors of the forward model parameters improves the retrieval of the target parameters. © 2012 Institute of Physics and Engineering in Medicine. Source

Di Ninni P.,DellUniversity Firenze | Martelli F.,DellUniversity Firenze | Zaccanti G.,DellUniversity Firenze
Progress in Biomedical Optics and Imaging - Proceedings of SPIE

A reference standard for tissue-simulating phantoms, i.e., a phantom with well known and stable optical properties, reproducible, and easy to be found, would be very useful for many applications based on measurements of diffused light. Although many tissue-equivalent phantoms have been proposed, to our knowledge none of them has been characterized sufficiently well to be suggested as a reference standard. Based on the results of measurements of optical properties we carried out at visible and NIR wavelengths, the use of Intralipid 20% diluted in water as diffusive medium, and of India ink as absorber, is here suggested as a first step towards a diffusive reference standard for tissue-simulating phantoms. As for Intralipid 20%, measurements carried out on samples from nine different batches with expiry dates spreading over ten years showed surprisingly small batch-to-batch variations. For the reduced scattering coefficient the maximum deviation from the value averaged over the nine batches was of about 2%, and the results for the absorption coefficient were very close to those for pure water. As for India ink measurements on samples from different batches and from five different brands showed large inter-brand and inter-batch variations for both the absorption and the extinction coefficient. On the contrary, small variations have been observed for the ratio between the absorption and the extinction coefficient. Intralipid 20% and Indian ink can be therefore easily mixed to obtain liquid phantoms with well known optical properties. This phantom can be a first step towards a reference standard for optical tissue phantoms. Source

Straulino S.,DellUniversity Firenze | Cartacci A.,DellUniversity Firenze | Gambi C.M.C.,DellUniversity Firenze
Nuovo Cimento della Societa Italiana di Fisica B

We describe some of the educational experiments carried out in the framework of the "OpenLab" at the Florence University. In particular we focus our attention on three measurements, which can be carried out in a laboratory of the secondary school and concern the electromagnetism: the determination of the Earth's magnetic field in two methods, the construction of a simple electrometer and some measurements showing the operation of a moving-iron ammeter. The described measurements are quantitative and well reproducible, and have been tested with students and teachers. © Società Italiana di Fisica. Source

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