The monitoring and characterization of agricultural products before harvest or during ripening, storage, and shelf life has recently been increasingly explored in the literature. The analysis of biospeckle activity has potential for the determination of the optimal harvest window, the monitoring of the fruit ripening process, and the detection of diseases and bruising. In this technique, the specimen is illuminated with coherent light and speckle intensity fluctuations are analyzed using diverse methodologies. Prior work shows that biospeckle activity is strongly correlated to physiological indexes conventionally used to evaluate fruit texture and composition. Here, we scrupulously investigate the biospeckle activity of Gala apple fruits during postharvest stages. We simulate realistic conditions for shelf-life monitoring, namely an unknown history of the fruit and storage in an uncontrolled atmosphere. Scattering spot images are acquired with multiple exposure times using a simple optical setup. The contrast, reflecting biospeckle activity, is computed after eliminating inhomogeneous zones. The results show, for the first time, speckle activity at short time scales. The retrieved correlations between speckle parameters and the ratio of apples' firmness to their soluble solids content reveal significant links despite the unknown fruit's origin, harvest date, and storage history.

The non-contact evaluation of dynamical properties of media presents several medical, biological, and industrial applications. Diverse optical methods, operating at different scales with various targeted applications, are currently being considered as alternatives to traditional mechanical testing devices. However, the accuracy of most optical techniques upon multiple scattering is compromised by the influence of the medium’s optical properties, namely scattering and absorption. Therefore, in order to accurately estimate dynamical properties, that are related to mechanical features, it is of pivotal importance to determine the medium’s optical properties. In this paper, we present a new simple scheme for the assessment of optical as well as dynamical properties of viscoelastic media. We demonstrate, for the first time, the possibility of estimating absorption, scattering, and dynamical properties using scattering spot imaging with a standard CCD camera at multiple exposure times and with a monochromatic continuous wave (CW) illuminance.

A polyol method was used to obtain ultrasmall ZnO nanoparticles (NPs) doped with iron ions and coated with a low molecular weight fucoidan in order to perform in vivo MR and ex vivo fluorescence imaging of athrothrombosis. During the synthesis, the early elimination of water by azeotropic distillation with toluene allowed us to produce NPs which size, determined by XRD and TEM, decreased from 7 nm to 4 nm with the increase of iron/zinc ratios from 0.05 to 0.50 respectively. For the highest iron content (NP-0.50) NPs were evidenced as a mixture of nanocrystals made of wurtzite and cubic phase with a molar ratio of 2.57:1, although it was not possible to distinguish one from the other by TEM. NP-0.50 were superparamagnetic and exhibited a large emission spectrum at 470 nm when excited at 370 nm. After surface functionalization of NP-0.50 with fucoidan (fuco-0.50), the hydrodynamic size in the physiological medium was 162.0 ± 0.4 nm, with a corresponding negative zeta potential of −48.7 ± 0.4 mV, respectively. The coating was evidenced by FT-IR spectra and thermogravimetric analysis. Aqueous suspensions of fuco-0.50 revealed high transverse proton relaxivities (T2) with an r2 value of 173.5 mM−1 s−1 (300 K, 7.0 T) and remained stable for more than 3 months in water or in phosphate buffer saline without evolution of the hydrodynamic size and size distribution. No cytotoxic effect was observed on human endothelial cells up to 48 h with these NPs at a dose of 0.1 mg/mL. After injection into a rat model of atherothrombosis, MR imaging allowed the localization of diseased areas and the subsequent fluorescence imaging of thrombus on tissue slices.

The assessment of materials viscoelastic properties often represents a means of diagnosis or characterization of biological tissues and biomaterials. In this paper, we introduce a new optical method for the evaluation of dynamical properties of viscoelastic media. The approach is based on time-resolved spatial speckle imaging, using a continuous wave CW illumination and a standard CCD detector. We demonstrate that an estimation of viscoelastic properties is possible, by analyzing intensity and contrast profiles of scattering spot images acquired over multiple exposure times. The accuracy of this approach is evaluated using simulated tissue mimicking media having well known optical and dynamical properties.

We propose to analyze in details the performances of an ASIC dedicated to the real-time analysis of speckle patterns statistics. This IC calculates average statistical values over the whole pixel array, and outputs only these values instead of a whole image: such on-chip calculation achieves the high acquisition rates required to follow speckle patterns from thick living tissue, without additional noises usually associated with fast data transfer. We want to assess if our device can reach its shot-noise limit, which is the shot-noise limit on one pixel divided by the square root of the number of pixels.

We developed a fluorescence imaging microscope system intended for the localization within artery slices of a gadolinium-based macromolecular biospecific magnetic resonance (MR) contrast agent used for the visualization of atherothrombosis. As the contrast agent is not initially fluorescent, we substitute some gadolinium ions for terbium ions to make them fluorescent while preserving their chemical characteristics. A long fluorescence emission time constant enables us to have a suitable signal-to-noise ratio, despite a low intensity, using pulsed illumination and time-gated imaging. Images of rat arteries show that the contrast agent is indeed localized on the specific regions of the tissues. We currently have a tool that allows us to understand and optimize the MR contrast agent.

We report acousto-optic imaging (AOI) into a scattering medium using a Fourier Transform (FT) analysis to achieve axial resolution. The measurement system was implemented using a CMOS smart-pixels sensor dedicated to the real-time analysis of speckle patterns. This first proof-of-principle of FT-AOI demonstrates some of its potential advantages, with a signal-to-noise ratio comparable to the one obtained without axial resolution, and with an acquisition rate compatible with a use on living biological tissue.

This paper describes a simple and original method to generate short UWB pulses, obtained by the transient response of a notch filter. Whose the first principle is based on a technique On-Off Keying signal with a carrier frequency centered at the rejection frequency (requires a very fast switch and a sinusoidal carrier). Now, we propose an all-digital solution, using a Phase-Shift Keying modulation to produce short pulses. We compare the both methods and show that pulses with a spectrum satisfying the FCC indoor regulatory mask in USA. The second method (without fast switch) which can be applied to the generation of pulses matched to any type of available spectrum mask (European, Asia, imaging, medical, outdoor, radar, ...). In both cases, circuits are realized at FCC to demonstrate these principles. It is shown that the measurements are in good agreement with the theory.

Diffuse Correlation Spectroscopy (DCS) is based on the temporal correlations of the speckle pattern from the light that has diffused through a biological media. Measurements must be made on a small coherence area of the size of a speckle grain. Summing independent measurement increases the SNR as the square root of the number of detectors. We present a bi-dimensionnal pixel CMOS detector array specially designed for this task, with parallel in-pixel demodulation and temporal correlations computation. Optical signals can be processed at a rate higher than 10,000 samples per second with demodulation frequencies in the MHz range.

PURPOSE:A difficulty in nonmuscle invasive bladder cancers is the diagnosis of flat and small lesions during white light cystoscopy. We assessed a prototype that measures ultraviolet laser induced autofluorescence for endoscopic detection of nonmuscle invasive bladder cancer.MATERIALS AND METHODS:We compared spectroscopic results with histological findings in 3 groups, including normal urothelium, papillary tumors and flat lesions. The developed method is based on exciting the fluorescence of molecules naturally present in tissue using ultraviolet laser pulses. The diagnostic signal was converted into the intensity ratio of the emitted light at approximately 360 and 450 nm. This ratio depends on the histopathological state of the tissue. The signal was converted into a simple color coded image, in which green indicates normal tissue and red indicates neoplasm.RESULTS:A total of 14 patients were included in analysis. At 360 and 450 nm excitation wavelengths the overall fluorescence intensity of bladder tumors was clearly decreased compared to that of normal urothelium regardless of tumor stage or grade. At the 308 nm excitation wavelength the shape of the tumor spectra, including carcinoma in situ, was markedly different from that of normal or nonspecific inflammatory mucosa. The correlation between red images and tumor in the specimen was 100%. No absolute intensity determinations were required since a definite diagnosis was established based on the fluorescence intensity ratio at 360 and 450 nm.CONCLUSIONS:This feasibility study confirms the functionality of our clinical prototype for the noncontact imaging detection of nonmuscle invasive bladder cancer via an endoscope using ultraviolet excited autofluorescence measurements.

Les méthodes optiques présentent de nombreux avantages pour le diagnostic médical. Elles permettent d’accéder à des informations essentielles sur les tissus telles que leur oxygénation (par spectroscopie) ou leur perfusion (par analyse des corrélations du speckle optique). Elles demandent en revanche la résolution de problèmes inverses complexes, résolution grâce à laquelle les mesures résolues en temps peuvent se révéler un atout. De nouveaux circuits intégrés à pixels « intelligents » pourraient par ailleurs faciliter l’analyse statistique en temps réel du speckle.

We show how time-resolved measurements of the diffuse light transmitted through a thick scattering slab can be performed with a standard CCD camera, thanks to an interferometric protocol. Time-resolved correlations measured at a fixed photon transit time are also presented. The high number of pixels of the camera allows us to attain a quite good sensitivity for a reasonably low acquisition time.

We evaluate the ultimate transverse spatial resolution that can be expected in Diffuse Optical Tomography, in the configuration of projection imaging. We show how such a performance can be approached using time-resolved measurements and reasonable assumptions, in the context of a linearized diffusion model.

Diffusing Wave Spectroscopy (DWS) consists in the measurement of temporal correlation of the electromagnetic field in the diffusion regime, allowing a scan of dynamical properties deep inside a medium. DWS is of special interest in biomedical optics, as it is sensitive to blood circulation in capillaries inside the tissue.However one main difficulty of this technique concerns data extraction which implies to perform an inverse problem taking into account the geometry and the optical coefficients of the medium. The use of time-resolved detection has been proved to be an efficient tool to discriminate the DWS information, but the photon path lengths were up to now limited to a few tens mean free paths.In order to perform time-resolved DWS for much longer photon paths, we used a new method, based on the use of an interferometer and a wavelength modulated source. We have already demonstrated that this method, in addition to its lower cost, was very efficient to perform time-resolved measurements of the light scattered by a thick scattering medium. We will show in this poster some measurements performed by transillumination through a thick medium (4cm), opening the possibility of Time-Resolved DWS measurements in the human breast.

Article Real time transformation of pre-computed Monte Carlo results for fitting optical measurements in biomedical applications was published on January 1, 2001 in the journal Monte Carlo Methods and Applications (volume 7, issue 3-4).

We have performed experiments to explore the dependence of time and space resolved reflectance measurements on the anisotropy factor g and on the shape of the phase function for a given g. The experimental results have been compared to Monte- Carlo simulations. We have deduced some rules to obtain the g value of turbid media by analyzing the backscattered light.

Hypoxia is a factor of radioresistance in the treatment of solid tumours. One way to radiosensitize these tumours is to use carbogen (95% O-2-5% CO2) and it is important to irradiate when the increase in oxygenation created by the inhalation is at the maximal level. The DADOT is a non-invasive item of equipment that allows one to evaluate the relative proportion of oxygenated and deoxygenated forms of haemoglobin in tissues. The principle used is to measure the evolution of the absorption of red or infrared light by haemoglobin. Two light-emitting diodes at respectively 0.66 and 0.94 mu m are coupled in two optical fibres the distal ends of which are applied on the tumour. These wavelengths are absorbed differently by the oxygenated and deoxygenated forms of haemoglobin. The light which is back-scattered towards the surface of the skin is detected by an amplified photodiode through a third fibre applied on the tumour. The modifications of tumour oxygenation during carbogen inhalation were followed for two tumour cell lines. They were also studied in a patient. These first results suggest that the DADOT is a reliable item of equipment that gives reproducible results and that could be used routinely to monitor changes in tumour oxygenation in patients.

Artificial media are needed for the calibration of optical diagnostic methods in order to work on reproducible, stable and well known samples. Since the scattering and absorption coefficients can easily be adjusted by using appropriate concentrations of scattering and absorbing components, the most difficult part in the design of a good tissue phantom is to obtain an actual phase function. The most common way to create phantoms is to use scattering microspheres of equal size, but the Mie phase function of such a phantom does not match the tissue's real phase function. Moreover, we show in this paper that the similarity relations often used for the analysis of the results obtained with this type of phantom may sometimes be very inaccurate. The use of a mixture of different sized scattering particles is then considered, in order to imitate the whole phase function. However, as the determination of adequate sizes and concentrations is a difficult mathematical task, we describe a simple method to solve this problem. We first demonstrate that the extreme optical complexity of real biological samples could be simulated by a mixture of spheres with a fractal diameter distribution. Then, we present a few simple rules based on the knowledge of this fractal distribution, which can be used to obtain a realistic phase function with a limited number of sphere diameters.