A systematic investigation of the polarization characteristics of the auto-fluorescence of normal and benign human
breast tissues is carried out complementing our earlier studies on normal and cancer tissues. Co- and
cross-polarized auto-fluorescence are collected in the 500 to 700nm range through excitation at 488nm using
laser as excitation source. A number of parameters, capturing spectral variations are extracted in the co- and
cross-polarized channels through singular value decomposition and wavelet decomposition, which differentiate
normal and benign tissues. The correlation matrix differs significantly in normal and benign tissues reflecting
the presence of different fluorophores. The eigenvectors corresponding to the dominant eigenvalues reveal
differences between tissue types. The co-polarized component being sensitive to intrinsic fluorescence shows
different behavior for normal and benign tissues in the emission domain of known fluorophores. Interestingly, the
benign tissue samples show correlation properties intermediate to malignant and normal cases. In the wavelet
domain the standard deviation of percentage fluctuation reveal differences between tissues type. The correlation
characteristics manifest prominently in the wavelet low pass (average) domain.
Properties of spectral fluctuations and prominent spectral features of fluorescence spectra in visible region using
laser as an excitation source of normal, benign and cancer human breast tissues are studied through wavelet
transform and principal component analysis.
A systematic investigation of the fluorescence characteristics of normal and cancerous human breast tissues is
carried out, using laser and lamp as excitation sources. It is found that earlier observed subtle differences between
these two tissue types in the wavelet domain are absent, when lamp is used as excitation source. However, singular
value decomposition of the average spectral profile in the wavelet domain yields strong correlation for the cancer
tissues in the 580-750 nm regimes indicating weak fluorophore activity in this wavelength range.
We study the spectral correlation properties of the polarized fluorescence spectra of normal and cancerous human breast tissues, corresponding to patients belonging to diverse age groups and socioeconomic backgrounds. The emission range in the visible wavelength regime of 500 to 700 nm is analyzed, with the excitation wavelength at 488 nm, where flavin is one of the active fluorophores. The correlation matrices for parallel and perpendicularly polarized fluorescence spectra reveal correlated domains, differing significantly in normal and cancerous tissues. These domains can be ascribed to different fluorophores and absorbers in the tissue medium. The spectral fluctuations in the perpendicular component of the cancerous tissue clearly reveal randomization not present in the normal channel. Random matrix-based predictions for the spectral correlations match quite well with the observed behavior. The eigenvectors of the correlation matrices corresponding to large eigenvalues clearly separate out different tissue types and identify the dominant wavelengths, which are active in cancerous tissues.
The statistical and characteristic features of the polarized fluorescence spectra from cancer, normal and benign
human breast tissues are studied through wavelet transform and singular value decomposition. The discrete
wavelets enabled one to isolate high and low frequency spectral fluctuations, which revealed substantial randomization
in the cancerous tissues, not present in the normal cases. In particular, the fluctuations fitted well
with a Gaussian distribution for the cancerous tissues in the perpendicular component. One finds non-Gaussian
behavior for normal and benign tissues' spectral variations. The study of the difference of intensities in parallel
and perpendicular channels, which is free from the diffusive component, revealed weak fluorescence activity in
the 630nm domain, for the cancerous tissues. This may be ascribable to porphyrin emission. The role of both
scatterers and fluorophores in the observed minor intensity peak for the cancer case is experimentally confirmed
through tissue-phantom experiments. Continuous Morlet wavelet also highlighted this domain for the cancerous
tissue fluorescence spectra. Correlation in the spectral fluctuation is further studied in different tissue types
through singular value decomposition. Apart from identifying different domains of spectral activity for diseased
and non-diseased tissues, we found random matrix support for the spectral fluctuations. The small eigenvalues of
the perpendicular polarized fluorescence spectra of cancerous tissues fitted remarkably well with random matrix
prediction for Gaussian random variables, confirming our observations about spectral fluctuations in the wavelet
domain.
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