Asima Pradhan

Fluorescence spectra from cancerous and normal human breast and lung tissues

The fluorescence spectra have been measured from native chromophores in malignant and normal human breast and lung tissues. The spectra profiles were found to be different in both species. In addition, one normal breast tissue exhibited Raman spectra.

Recovery of turbidity free fluorescence from measured fluorescence: an experimental approach.

Fluorescence from fluorophores embedded in a turbid medium like biological tissue gets strongly modulated by the wavelength dependent absorption and scattering properties of tissue. This makes it extremely difficult to extract valuable biochemical information from tissue which is present in the intrinsic line shape and intensity of fluorescence from tissue fluorophores. We present an experimental approach to remove the distorting effect of scattering and absorption on intrinsic fluorescence of fluorophores embedded in a turbid medium like tissue. The method is based on simultaneous measurement of polarized fluorescence and polarized elastic scattering spectra from a turbid medium. The polarized fluorescence normalized by the polarized elastic scattering spectra (in the wavelength range of fluorescence emission) was found to be free from the distorting effect of absorption and scattering properties of the medium. The applicability range of this technique to recover intensity and line shape information of intrinsic fluorescence has been investigated by carrying out studies on a variety of tissue phantoms having different absorption and scattering properties. The results obtained show that this technique can be used to recover intrinsic line shape and intensity information of fluorescence from fluorophores embedded in a scattering medium for the range of optical transport parameters typically found in biological tissue.

Mueller decomposition images for cervical tissue: potential for discriminating normal and dysplastic states.

We report the potential of Mueller decomposition images to discriminate the normal against the dysplastic (precancerous) states in cervical tissue. It is observed that in the epithelium region, depolarization power is sensitive to morphological changes during progression from normal to dysplastic state while retardance and diattenuation do not show any significant change. These morphological changes have been correlated with the microscopic images of the tissues. In contrast, it is the retardance which reveals the morphological changes around the stromal region. Additionally, we have evaluated the arithmetic mean of depolarization power and retardance from their respective decomposed images and have shown that this parameter has a potential to discriminate normal tissues against dysplastic ones.

Pulsed and cw laser fluorescence spectra from cancerous, normal, and chemically treated normal human breast and lung tissues

The origin of the differences in the fluorescence spectra obtained from cancerous and normal human breast and lung tissues is explored experimentally. The fluorescence spectra from chemically treated normal tissues were measured to give information on the source of the spectral differences. The pulsed fluorescence spectra photoexcited by the second and third harmonic of a 10-ps pulse from Nd:glass laser are reported for normal and cancerous tissues of breast and lung.

Effects of crystallite size distribution on the Raman-scattering profiles of silicon nanostructures

Raman scattering (RS) from semiconductor nanostructures provide excellent information on the size of the crystallites. Processing history of most nanocrystalline semiconductors suggests natural incorporation of a distribution of crystallite sizes. In this paper, we report on the influence of crystallite size distribution on the shifts in RS frequencies and line shapes. A phenomenological model is developed to obtain an analytical expression for the Raman spectral profile from semiconductor nanostructures having a Gaussian distribution in the crystallite sizes. Computer simulations of RS profiles on nanocrystalline silicon (nc-Si) demonstrate the effects of a size distribution on the Raman shifts. In particular, the effects on the asymmetry in Raman line shapes are emphasized. The model is applied to the published Raman data on nc-Si samples where size distributions are known from the direct measurements. The size distribution obtained from Raman analysis is in good agreement with that reported by direct m...

Wavelet transform of breast tissue fluorescence spectra: a technique for diagnosis of tumors

Polarized fluorescence spectra of malignant, benign, and normal human breast tissues in the emission range of 500-700 nm, with an excitation wavelength of 488 nm, are analyzed through discrete wavelet transform. The multiresolution and localization properties of the wavelets are shown to be ideally suited for identifying characteristic features distinguishing these tissue types. Analysis of a number of data sets, belonging to both parallel and perpendicular polarized spectra, have led to several key distinctions between different tumors and corresponding normal breast tissues, revealing the usefulness of polarized fluorescence in the diagnosis of tumors. Wavelet transform also naturally leads to the dimensional reduction of the data set, in the form of low-pass coefficients, making it amenable for physical modeling.

Raman scattering characterization of Si(100) implanted with mega-electron-volt Sb

Dose dependent structural modifications in Si(100) due to 1.5 MeV implantation of Sb have been characterized using Raman spectroscopy and Rutherford backscattering spectrometry/channeling (RBS/C) techniques. With increasing fluence, an intensity reduction of the first order Raman peak, characteristic of crystalline Si, is observed. The amorphicity in Si lattice appears at a dose of 1×1013 ions/cm2 and it increases with each dose. For a dose of 5×1014 ions/cm2 the Raman spectrum resembles that of amorphous Si. RBS/C studies also support a fully amorphized lattice at this dose though for smaller doses it suggests lower disorder. For the fluences of 1×1013 and 1×1014 ions/cm2 a coexistence of undamaged crystalline Si regions and amorphous zones is observed. Consequently, phonon confinement is observed. Lattice recovery achieved by subsequent annealing has also been investigated using Raman spectroscopy. By annealing at 600 °C, sample crystallinity is fully recovered in all the cases up to the fluence of 5×10...

Probing multifractality in tissue refractive index: prospects for precancer detection

Multiresolution analysis on the spatial refractive index inhomogeneities in the epithelium and connective tissue regions of a human cervix reveals a clear signature of multifractality. Importantly, the derived multifractal parameters, namely, the generalized Hurst exponent and the width of the singularity spectrum, derived via multifractal detrended fluctuation analysis, shows interesting differences between tissues having different grades of precancers. The refractive-index fluctuations are found to be more anticorrelated, and the strength of multifractality is observed to be considerably stronger in the higher grades of precancers. These observations on the multifractal nature of tissue refractive-index variations may prove to be valuable for developing light-scattering approaches for noninvasive diagnosis of precancer and early-stage cancer.

Microwave synthesis and characterization of doped ZnS based phosphor materials

We report here the synthesis and characterization of a host of ZnS-based phosphor materials employing microwave radiation. Activator ions such as Cu, Ag and Mn have been successfully doped. Microwave method enables higher doping percentage of Cu, upto 10% in ZnS. These materials have been characterized using XRD, SEM, EPMA, and the emission spectral studies. The effect of higher doping concentrations and narrow particle size distribution of the microwave-prepared samples is clearly reflected in the emission spectra.

Wavelet-based characterization of spectral fluctuations in normal, benign, and cancerous human breast tissues

Fluorescence intensity fluctuations in the visible wavelength regime in normal, benign, and cancerous human breast tissue samples are studied through wavelet transform. The analyses have been carried out in unpolarized, parallel and perpendicularly polarized channels, for optimal tissue characterization. It has been observed that polarized fluorescence data, particularly the perpendicular components, differentiate various tissue types quite well. Wavelet transform, because of its ability for multiresolution analysis, provides the ideal tool to separate and characterize fluctuations in the fluorescence spectra at different scales. We quantify these differences and find that the fluctuations in the perpendicular channel of the cancerous tissues are more randomized as compared to their normal counterparts. Furthermore, for cancerous tissues, the same is very well described by the normal distribution, which is not the case for normal and benign samples. It has also been observed that, up to a certain point, fluctuations at larger scales are more sensitive to tissue types. The differences in the average, low-pass wavelet coefficients of normal, cancerous, pericanalicular, and intracanalicular benign tissues are also pointed out.