Biomedical subjects

Cosimo D'Andrea

Publications and source records attributed to Cosimo D'Andrea.

7 recordsLinked to original sources

PubMed2006

Comparison of noncontact and fiber-based fluorescence-mediated tomography.

We present a comparative experimental phantom study of fiber-based and noncontact fluorescence tomography with respect to quantitation and localization of reconstructed fluorescent inclusions in turbid media such as tissue. Noncontact acquisition is usually considered potentially superior to fiber-based techniques because of the availability of a large number of detector readouts through a CCD. Our results indicate, however, that noncontact acquisition itself might improve the quality of reconstructions significantly, even without increasing the number of detectors and thus keeping the inverse problem moderately complex.

Equipment Design↗

PubMed2005

Dynamic time-resolved diffuse spectroscopy based on supercontinuum light pulses.

We present a detailed characterization of a system for fast time-resolved spectroscopy of turbid media based on supercontinuum generation in a photonic crystal fiber. The light source provides subpicosecond pulses in the 550-1000-nm spectral range, at 85 MHz, at an average power of up to 50 mW. Wavelength-resolved detection is accomplished by means of a spectrometer coupled to a 16-channel, multianode photomultiplier tube, giving a resolution of 4.5-35 nm/channel, depending on the grating. Time-dispersion curves are acquired with time-correlated single-photon counting, and absorption and reduced scattering coefficients are determined by fitting the data to the diffusion equation. We characterized the system by measuring the time-resolved diffuse reflectance of epoxy phantoms and by assessing the performance in terms of accuracy, linearity, noise sensitivity, stability, and reproducibility. The results were similar to those from previous systems, whereas the full-spectrum (610-810 nm) acquisition time was as short as 1 s owing to the parallel acquisition. We also present the first in vivo real-time dynamic spectral measurements showing tissue oxygenation changes in the arm of a human subject.

Algorithms↗

PubMed2005

Localization and quantification of fluorescent inclusions embedded in a turbid medium.

A set-up, based on a CCD camera, to localize fluorescent inclusions in diffusing media was developed. This set-up allows one to acquire a huge dataset along two axes. This aspect is fundamental to performing a tomographic reconstruction in order to quantify the fluorescence amplitude in each voxel of the sample. Firstly, a simple analytical approach to recover the position of a single inclusion, embedded in a turbid medium, was developed. Then, we implemented a reconstruction algorithm to recover the position of one and two inclusions and to estimate their relative concentrations. Finally, we studied the dependence of reconstructed data on the number of injection points of excitation light and the number of detection points of fluorescence emission.

Algorithms↗

PubMed2004

Time-resolved spectrophotometer for turbid media based on supercontinuum generation in a photonic crystal fiber.

We describe an instrument for the time-resolved spectroscopy of turbid media that is based on supercontinuum generation in a photonic crystal fiber. The light injected into the sample consists of subpicosecond pulses that cover 550-1000 nm at 85 MHz at an average power of as much as 40 mW. A spectrometer coupled to a multianode photomultiplier tube is used to detect the light simultaneously in 16 wavelength channels, with a resolution of 5-20 nm/channel, depending on the grating. Time-correlated single-photon counting is used to produce time-dispersion curves, which one fits to the diffusion equation to determine absorption and reduced scattering coefficients. We tested the instrument by measuring the time-resolved diffuse reflectance of epoxy phantoms and by performing in vivo measurements on volunteers. The results were similar to those obtained with previous discrete wavelength systems, whereas the full spectrum (610-810 nm) acquisition time was as short as 1 s owing to the parallel acquisition.

Abdomen↗

PubMed2004

Fluorescence lifetime imaging and spectroscopy as tools for nondestructive analysis of works of art.

A system for advanced fluorescence investigation of works of art has been assembled and integrated in a characterization procedure that allows one to localize and identify organic compounds that are present in artworks. At the beginning of the investigation, fluorescence lifetime imaging and spectroscopy address a selective microsampling of the artwork. Then analytical measurements of microsamples identify the chemical composition of the materials under investigation. Finally, on the basis of fluorescence lifetime and amplitude maps, analytical data are extended to the whole artwork. In such a way, information on the spatial distribution of organic materials can be inferred. These concepts have been successfully applied in an extensive campaign for analysis of Renaissance fresco paintings in Castiglione Olona, Italy. Residue of various types of glue and stucco left from a restoration carried out in the early 1970s was localized and classified. Insight into the technique used by the painter to make gilded reliefs was also obtained.

Journal Article↗

PubMedDate not supplied

Feasibility of white-light time-resolved optical mammography.

We demonstrate the feasibility of white-light time-resolved optical mammography. The instrumentation is based on supercontinuum light generated in photonic crystal fiber and 32-channel parallel time-correlated single-photon-counting detection. Total measurement time is of the order of 10 min for typical clinical applications. Preliminary measurements performed on volunteers show the ability of the system to determine tissue constituent concentrations and structure over the entire breast area. Furthermore, measurements on a tissue-like sample demonstrate detection and characterization of inclusions.

Adult↗

PubMedDate not supplied

Time-resolved microspectrofluorimetry and fluorescence lifetime imaging of hypericin in human retinal pigment epithelial cells.

Hypericin is the active ingredient of the off-the-shelf antidepressant St. John's Wort. It is an effective phototoxic agent and its systemic administration at therapeutic doses could induce particular damage in the eye due to continuous light exposure. Hypercin is strongly fluorescent and its fluorescence properties can be monitored to investigate noninvasively its localization and interactions. To this aim, time-resolved microspectrofluorimetry and fluorescence lifetime imaging were used to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by retinal pigment epithelium (RPE) cells treated with Hyp at concentrations in the micromolar range (0.5-10 microM). In the presence of hypericin, the emission peaks at 600-605 nm and the fluorescence decay is best fitted with three lifetimes (5.5-7 ns, 1.9-2.5 ns and <0.8 ns). Spectral and temporal differences were observed between high (> or =5 microM) and low hypericin concentrations. In particular, upon increasing concentration, the emission spectrum of the slow component broadens and its lifetime shortens. The latter change is observed also when high concentrations are reached locally, due to more efficient localization within the cell.

Anthracenes↗