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In this paper a new time-domain frequency-selective quantification algorithm is presented. Frequency-selective quantification refers to a method that analyzes spectral components in a selected frequency region, ignoring all the other components outside. The algorithm, referred to as MeFreS (Metropolis Frequency-Selective), is based on rank minimization of an opportune Hankel matrix. The minimization procedure is satisfied by the down-hill simplex method, implemented with the simulated annealing method. MeFreS does not use any preprocessing step or filter to suppress nuisance peaks, but the signal model function is directly fitted. In this manner, neither inherent signal distortions nor estimation biases to be corrected occur. The algorithm was tested with Monte Carlo simulations. A comparison with VARPRO and AMARESw algorithms was carried out. Finally, two samples of known content from NMR data were quantified.

The optical properties of controlled size latex particles suspended in water have been investigated by using two different time-resolved transmittance set-ups. Least-mean square fitting between experimental data and analytical solution to diffusion approximation equation has given values of optical parameters in good agreement with the predictions of the Mie theory. In this way, the validity of these predictions was checked in the investigated experimental conditions and the data analysis confirms that time-resolved transmittance can be a reliable technique to measure the optical properties of scattering solutions.

The possibility that a sinusoidal 50 Hz magnetic field with a magnetic flux density of 0.5 mT can induce variations in the expression of cell adhesion molecules (CAMs) in two human osteosarcoma cell lines (MG-63 and Saos-2) was investigated. In particular, the expression of two important integrins, VLA-2, the receptor for collagen, and VLA-5, the receptor for fibronectin, as well as CD44, were examined in both cell lines after these had been exposed for 7 and 14 days to a 50 Hz, 0.5 mT field. Cell surface morphology (scanning electron microscopy), cell growth characteristics (growth curves and cell cycle phase distribution), and cell death (necrosis and apoptosis) were also examined. The results demonstrate that no variations in surface morphology and cell death occurred between control and exposed cells in both MG-63 and Saos-2 cells, while significant changes were noted in cell growth and fibronectin and CD44 expression in MG-63 cells. The results are discussed in view of the important role that CAMs play in controlling various cancer cell functions, particularly proliferation and metastasis.

Objective: The aim of the present study was to evaluate the efficacy of two different computer aided detection (CAD) systems for mammography in improving radiological diagnosis in the search of microcalcification clusters. The CAD systems used are: the SecondLook™ (CADx Medical Systems, Canada) commercial system and the CALMA (computer assisted library in MAmmography) research CAD system. Three radiologists were asked to read mammographic images with and without the support of the CAD systems. Material and methods: Three radiologists with respectively 3, 5 and 7 years of practice in mammogram reading in an Italian public hospital analysed a dataset composed of 120 digitized mammograms of healthy subjects with no lesion (proven by a radiological follow up of at least 3 years) and 70 images of patients with malignant cluster of microcalcification (proven by histopathological examination) both with no CAD support as well as with the help of the SecondLook™ system. After 3 months they were asked to observe the same digitized mammograms with the assistance of the CALMA system. The radiologists worked independently and were unaware of the final diagnosis. The values of the area Az under the ROC curve, diagnostic sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were evaluated with and without the support of the CAD systems. The reading time and qualitative evaluations of each radiologist were also reported. Results: With the support of the two CAD systems an improvement in Az area was obtained ranging from 0.01 to 0.04. Sensitivity increased from +8.6 to +15.7% and specificity decreased from 0.8 to 4.2%. Conclusion: In our study, not conditioned by the dataset, the CAD systems as second reader produced an increase in overall sensitivity of up to 15.7%, with a little decrease in specificity of up to 4.2%. Based on these results both CAD systems might be used in the current practise to improve the sensitivity values of conventional reading (radiologist alone). The results of this study show that no significant differences exist in term of Az, sensitivity and specificity between CALMA and CADx.

The role of a spatially varying absorptive inhomogeneity located at different depths within a turbid material has been investigated. This inhomogeneity has been characterized by a spatially dependent Gaussian distribution of its absorption coefficient. The present study has been performed calculating the time-resolved contrast function in the framework of the first-order perturbative approach to the diffusion equation for a slab geometry and a coaxial measurement scheme. The model has allowed us to take into account different locations of the inclusion along the source-detector axis. The accuracy of time-resolved contrast predictions has been analyzed through comparisons with results of the finite element method that has been used to numerically solve the diffusion equation. Recovery of the absorption perturbation parameter of the inhomogeneity for different axial positions has also been investigated.

High resolution proton nuclear magnetic resonance ((1)H NMR) spectroscopy was used to determine if the same cell line (MG-63 human osteosarcoma cells) grown in monolayer or as small (about 50-80 microm in diameter), three-dimensional tumor spheroids with no hypoxic center has different metabolic characteristics. Consequently, the (1)H NMR spectra were obtained from both types of cultures and then compared. The results indicate that the type of cellular spatial array determines specific changes in MG-63 cells. In particular, small but significant differences in lactate and alanine indicating a perturbation in energy metabolism were observed in the two cell models. In addition, although variations in CH(2) and CH(3) groups were also seen, it is not possible at this time to establish if lipid metabolism is truly different in cells and spheroids.

The possibility of obtaining images of human organs by optical techniques for diagnostic purposes is still under intense investigation. Useful information for devising the most efficient data acquisition procedures and reconstruction algorithms can be obtained by imaging well-controlled small inhomogeneities using different reconstruction procedures. For this purpose we performed time-resolved imaging experiments by embedding in a turbid slab small inclusions with different absorption coefficients. The ability of the imaging system to detect these hidden objects strongly depends on its optical properties and on the method that is adopted to reconstruct images. To this regard, in order to construct images different procedures can be adopted. The efficiency of these different procedures has been valuated by investigating the contrast, the noise and the effective signal-to-noise ratio of constructed images. Furthermore, this data analysis has been used to study the role of the inclusion’s object contrast on the efficiency of the adopted reconstruction algorithm.

The role of protein adsorption in the forced adhesive growth of K562 leukemic cells onto a cationic surface composed of polylysine was investigated. Numerous studies have demonstrated that adhesion in anchorage-dependent cells is mediated in vitro by adsorption of serum proteins [particularly proteins of the extracellular matrix (ECM) such as fibronectin and vitronectin] present in the growth medium. Specifically, adhesion has been shown to occur when ECM proteins attach to the substratum and act as ligands for specific receptors located on the surface of cells. K562 cells are human erythroleukemic cells that normally grow in suspension. These cells are not involved in the same cell adhesion processes as anchorage-dependent cells and do not need to be attached to ECM proteins in order to survive and grow. Thus, with these systems, it is possible to better determine the role of protein adsorption in the adhesion of cells, growing in suspension such as blood cells, onto charged surfaces. The results presented show that adhesion of K562 cells onto the positively charged polylysine surface in the presence of serum is mediated through specific interactions between fibronectin receptors present on K562 cells and fibronectin adsorbed onto that cationic surface. Specifically, determination of cell adhesion under different experimental conditions indicates that nonspecific charge interactions do not take place directly between the cells and polylysine, but rather take place between polylysine and fibronectin, which adsorbs onto the cationic polymer. In addition, flow cytometric analyses reveal that only fibronectin receptors are present on these cells and, consequently, only fibronectin can be responsible for the actual adhesion of these cells onto the cationic surface. In view of the data presented, the possibility should be considered that ECM components adsorbed onto surfaces with specific charges and/or belonging to certain functional groups are involved in structural and functional modifications in cells. These cells grow in suspension and are normally not involved in adhesion phenomena, though these components should be considered. These considerations should be made especially when designing biomaterials that can modulate the response of cells growing in suspension, such as blood cells, and also in tissue engineering of blood substitutes.

The ionic environment of the cell membrane is of extreme importance in maintaining cell integrity and the numerous functions necessary for cell growth, differentiation, etc., as well as in cell-biomaterial interactions. In this study, the effects of polylysine (a basic poly-amino acid with a net positive charge which is often used to coat biomaterials surfaces) on the erythroleukemic K562 cell membrane were investigated. In particular, the effects of this polycation were evaluated using dielectric relaxation studies in the radiofrequency range with which it is possible to measure both active ionic transport across the cell membrane (membrane conductivity) and the static charge distribution present on the cell surface due to the structural components of the cell membrane (membrane permittivity). The conductivity of the cytosol can also be determined. The results demonstrate that while the conductivity of the cytosol is not significantly altered, both the conductivity and permittivity of the K562 cell membrane are varied by exposure of these cells to polylysine. These observations indicate that both active ionic transport and the type, quantity, or distribution of membrane components such as lipids, proteins, and polysaccharides may also be altered. Although the precise mechanisms by which these variations in K562 cells occur are unknown, it can be hypothesized that changes in the growth characteristics of these cells may be in part responsible. In particular, as demonstrated by light microscopic examination of K562 cells directly in the culture flasks, the cells in polylysine-coated flasks do not grow in suspension as do the controls, but rather show anchorage-dependent-like behavior. It is this important change from suspension to monolayer growth induced by polylysine that may be responsible for the changes in membrane electrical parameters.

We have recently demonstrated using dielectic relaxation studies in the radiowave frequency range that sinusoidal 50 Hz magnetic fields (with intensities ranging from 1 to 10 mT) induce a nonlinear change in both membrane conductivity and permittivity of primary chick embryo myoblasts in vitro. It was the aim of the present study to determine if a DC-induced static magnetic field is capable of generating similar variations in the membrane conductivity and/or the membrane permittivity of chick embryo myoblasts. The results indicate that when the myogenic cells are exposed to a static magnetic field of either 1, 3 or 5 mT (values comparable with the previous extremely low frequency study), no changes in the membrane electrical parameters can be observed with respect to controls. Differences in the characteristics of static and extremely low frequency fields as well as the possible mechanisms underlying the contrasting results with these two types of magnetic fields are discussed.

Membrane electrical properties of mouse embryo fibroblasts and their ionizing radiation and chemically transformed counterparts were investigated using dielectric relaxation measurements in the radio frequency range. This determination is possible because, in the radio frequency range, suspensions of cells in an electrolyte buffer show a conductivity dispersion due to interfacial polarization. An analysis of the experimental data based on a "single-shell" model showed that conductivity and permittivity of the membranes of both radiation and chemically transformed fibroblasts were lower than in normal cells. In addition, the conductivity of the cytoplasm was higher in both transformed cell types than in the normal mouse fibroblasts. We discuss the significance of these findings in view of the possible structural and functional modifications brought about by the process of neoplastic transformation.

The effects of lonidamine on membrane electrical properties of Ehrlich ascites tumor cells are investigated. Using a dielectric relaxation technique based on the Maxwell-Wagner effect and elaborated by a ‘single-shell’ fitting procedure, the data indicate that both membrane conductivity and membrane permittivity increase after treatment of these cells with lonidamine while the conductivity of the cytosol remains unchanged. Changes in membrane proteins and/for lipids are suggested which lead to altered membrane structure and/or function.

A detailed investigation of the use of time-resolved trasmittance for the optical characterization of scattering media by use of different analytical solutions to the diffusion equation has been performed. A femtosecond Ti:sapphire laser working at 800 nm and a streak camera with a time resolution of a few picoseconds were employed. Different latex and Intralipid solutions as well as biological samples were investigated. Reduced scattering coefficients were evaluated, and good agreement with the Mie predictions was found. An estimation of the order of magnitude of the absorption coefficient was obtained for the low-absorbance samples examined. These studies confirm experimentally that time-resolved trasmittance can be employed usefully for evaluating μs′ values of thick scattering samples when a proper theoretical description that takes into account realistic boundary conditions is used.