A. Torricelli

Spectroscopic time-resolved diffuse reflectance and transmittance measurements of the female breast at different interfiber distances

The first, to our knowledge, in-vivo broadband spectroscopic characterization of breast tissue using different interfiber distances as well as transmittance measurements is presented. Absorption and scattering properties are measured on six healthy subjects, using time-resolved diffuse spectroscopy and an inverse model based on the diffusion equation. Wavelength-tunable picosecond-pulse lasers and time-correlated single-photon counting detection are employed, enabling fully spectroscopic measurements in the range 610 to 1040 nm. Characterization of the absorption and reduced scattering coefficients of breast tissue is made with the aim of investigating individual variations, as well as variations due to different measurement geometries. Diffuse reflectance measurements at different interfiber distances (2, 3, and 4 cm) are performed, as well as measurements in transmittance mode, meaning that different sampling volumes are involved. The results show a large variation in the absorption and scattering properties depending on the subject, correlating mainly with the water versus lipid content of the breast. Intrasubject variations, due to different interfiber distances or transmittance modes, correlate with the known structures of the breast, but these variations are small compared to the subject-to-subject variation. The intrasubject variations are larger for the scattering data than the absorption data; this is consistent with different spatial localization of the measurements of these parameters, which is explained by the photon migration theory.

Fluorescence lifetime imaging: an application to the detection of skin tumors

A portable system based on fluorescence lifetime imaging has been developed and tested for the detection of skin tumors in humans. The Heme precursor /spl delta/-aminolevulinic acid, which promotes the preferential accumulation of the endogenous Protoporphyrin IX (PpIX) in proliferative tissues, is used as an exogenous marker to target the tumor, /spl delta/-aminolevulinic acid is topically administered to the patient 1 h before the measurement. Then, using a gated intensified camera, two or more images of the sample are acquired after different delays with respect to the excitation pulses. The images are processed in real time in order to calculate the spatial map of the fluorescence decay time of the sample. The localization of the tumor is based on the longer decay time detected in neoplastic tissues as a result of the stronger emission of PpIX, which has a long decay time, and the reduction in the short living natural tissue fluorescence.

Determination of VIS- NIR absorption coefficients of mammalian fat, with time- and spatially resolved diffuse reflectance and transmission spectroscopy

The objective is derived from the need for a reliable absorption spectrum of lipids for component analysis of in-vivo tissue spectra. Three independent measurement techniques were employed to determine the absorption coefficients of mammalian lipids.

Detection of internal quality in kiwi with time-domain diffuse reflectance spectroscopy

Time-domain diffuse reflectance spectroscopy (TRS), a medical sensing technique, was used to evaluate internal nkiwi fruit quality. The application of this pulsed laser spectroscopic technique was studied as a new, possible non-destructive, nmethod to detect optically different quality parameters: firmness, sugar content, and acidity. The main difference with other nspectroscopic techniques is that TRS estimates separately and at the same time absorbed light and scattering inside the nsample, at each wavelength, allowing simultaneous estimations of firmness and chemical contents. Standard tests (flesh npuncture, compression with ball, .Brix, total acidity, skin color) have been used as references to build estimative models, using na multivariate statistical approach. Classification functions of the fruits into three groups achieved a performance of 75% ncorrectly classified fruits for firmness, 60% for sugar content, and 97% for acidity. Results demonstrate good potential for nthis technique to be used in the development of new sensors for non-destructive quality assessment.

Monitoring muscle metabolic indexes by time-domain near-infrared spectroscopy during knee flex-extension induced by functional electrical stimulation

A noninvasive methodology, combining functional electrical stimulation and time-domain near-infrared spectroscopy (TD-NIRS), is developed to verify whether stroke-altered muscular metabolism on postacute patients. Seven healthy subjects and nine postacute stroke patients undergo a protocol of knee flex-extension induced by quadricep electrical stimulation. During the protocol, TD-NIRS measurements are performed on both rectus femoris to investigate whether significant differences arise between able-bodied and stroke subjects and between patients paretic and healthy legs. During baseline, metabolic parameters do not show any significant differences among subjects. During stimulation, paretic limbs produce a knee angle significantly lower than healthy legs. During recovery, patients healthy limbs show a metabolic behavior correlated to able-bodied subjects. Instead, the correlation between the metabolic behavior of the paretic and able-bodied legs allows the definition of two patients subgroups: one highly correlated (R>0.87) and the other uncorrelated (R<0.08). This grouping reflects the patient functional condition. The results obtained on the most impaired patients suggest that stroke does not produce any systemic consequences at the muscle, but the metabolic dysfunction seems to be local and unilateral. It is crucial to enlarge the sample size of the two subgroups before making these preliminary results a general finding.

Time resolved reading of DNA microarray by an intensified CCD camera

Summary form only. The DNA microarray technology is the most appealing tool for genetic investigation that has been devised in recent years. Microarrays basically consist of a matrix of thousands or even more spots of DNA fragments or oligonucleotides arranged on a microscope slide. If a probe, marked with fluorescent molecules, containing a base sequence complementary to one in the array is spread onto the slide, hybridization takes place and the hybridized spot can be easily located by fluorescent imaging. Presently, a laser scanner and a photomultiplier are used for DNA microarray reading and the discrimination between different markers is made on the basis of different absorption/emission wavelengths. In the present paper we introduce, for the first time to our knowledge, a technique to read DNA microarrays based on an intensified CCD camera having a picosecond resolution electronic shutter. This device permits to map the fluorescence intensity in a microarray in just one shot.

Methoden für die präzise obstbauliche Produktion

Der Ansatz von Precision Horticulture im Obstbau lehnt sich an das aus dem Ackerbau stammende Konzept der Prazisionslandwirtschaft bzw. der teilflachenspezifischen Bewirtschaftung an. Hierbei sollen prazise an das individuelle Geholzwachstum angepasste Pflegemasnahmen die bislang praktizierte einheitliche Behandlung aller Baume in einer Anlage ablosen. Voraussetzungen hierfur sind u. a. Bodenkarten und Informationen zum Pflanzenwachstum. Das Ziel ist es, den informationsgestutzten Obstbau voranzutreiben und durch ein raumlich und zeitlich differenziertes Management eine effizientere und nachhaltigere Bewirtschaftung zu erreichen.

Tomography of brain activation using a time-gated camera

We propose a system for 3D tomography using a single pulsed source and a time-gated camera for functional imaging studies. Reconstructions were based on a linear model based on small perturbation assumption, applying Tikhonov regularization. This approach was tested against simulations, demonstrating both detection and localization capabilities. Preliminary measurements on realistic inhomogeneous phantoms showed good detection sensibility, even for a low optical contrast, but poorer localization properties, possibly due to the still low SNR of the system. Finally, an initial in vivo test on a motor cortex activation paradigm is presented.

In vivo time-resolved multi-distance spectroscopy of human forehead: a step towards optical characterization of brain tissue

Multi-distance time-resolved spectroscopy of in-vivo human forehead was performed on five volunteers in the range 700-1000 nm. A Monte Carlo simulation based on a four-layer model was employed and compared with in vivo data.

Performance assessment of photon migration instruments: the Medphot protocol

We propose a comprehensive protocol for the performance assessment of photon migration instruments. The protocol has been developed within the European Thematic Network MEDPHOT (optical methods for medical diagnosis and monitoring of diseases) and is based on five criteria: accuracy, linearity, noise, stability, and reproducibility. This protocol was applied to a total of 8 instruments with a set of 32 phantoms, covering a wide range of optical properties.