Ms. Aleksandra Zh. Zhelyazkova Profile

Aleksandra Zh. Zhelyazkova

PhD Student at Institute of Electronics

SPIE Involvement:

Author

Publications (8)

Proceedings Article | 5 January 2017 Paper

Investigating different skin and gastrointestinal tract (GIT) pathologies ex vivo by autofluorescence spectroscopy and optical imaging

A. Zhelyazkova, I. Kuzmina, E. Borisova, N. Penkov, Ts. Genova, J. Spigulis, L. Avramov

Proceedings Volume 10226, 1022615 (2017) https://doi.org/10.1117/12.2261817

KEYWORDS: Imaging spectroscopy, Spectroscopy, Skin, Tissues, Tumors, Luminescence, Collagen, Diagnostics, Chromophores, Signal detection

Read Abstract +

Proceedings Article | 5 January 2017 Paper

Autofluorescence polarization spectroscopy of cancerous and normal colorectal tissues

Ts. Genova, E. Borisova, N. Penkov, B. Vladimirov, I. Terziev, Al. Zhelyazkova, L. Avramov

Proceedings Volume 10226, 1022618 (2017) https://doi.org/10.1117/12.2264453

KEYWORDS: Fluorescence spectroscopy, Polarization, Spectroscopy, Tissues, Colorectal cancer, Diagnostics, Luminescence, Standards development, Endoscopy, Collagen

Read Abstract +

The wide spread of colorectal cancer and high mortality rate among the patients, brings it to a level of high public health concern. Implementation of standard endoscopic surveillance proves to be effective for reduction of colorectal cancer patients’ mortality, since its early diagnosis allows eradication of the disease prior to invasive cancer development, but its application in common clinical practice is still limited. Therefore the development of complimentary diagnostic techniques of the standard white-light endoscopy is on high demand. The non-invasive and highly informative nature of the fluorescence spectroscopy allow to use it as the most realistic prospect of an add-on “red flag” technique for early endoscopy detection of colorectal cancer.

Synchronous fluorescence spectroscopy (SFS) is a steady-state approach that is used for evaluation of specific fluorescence characteristics of cancerous colorectal tissues in our studies. The feasibility of polarization fluorescence technique to enhance the contrast between normal and cancerous tissues was investigated as well. Additional linear polarizing optics was used on the way of the excitation and emission fluorescence light beams. The polarizing effects were investigated in parallel and perpendicular linear polarization modes respectively. The excitation applied was in the region of 280 – 440 nm, with 10 nm scanning step, and the fluorescence emission was detected in the region of 300 – 800 nm.

Our previous experience with SFS technique showed its great potential for accurate, highly sensitive and specific discrimination between cancerous and normal colorectal tissue. Since one of the major sources of endogenous fluorescence with diagnostic meaning is the structural protein — collagen, which is characterized with high anisotropy, we’ve expected and observed an enhancement of the spectral differences between cancerous and normal colorectal tissue, which could be beneficial for the colorectal tumour’ diagnostics using SFS.

Proceedings Article | 8 January 2015 Paper

Synchronous fluorescence spectroscopy for analysis of wine and wine distillates

Ya. Andreeva, E. Borisova, Ts. Genova, Al. Zhelyazkova, L. Avramov

Proceedings Volume 9447, 94470Z (2015) https://doi.org/10.1117/12.2178026

KEYWORDS: Luminescence, Fluorescence spectroscopy, Analytical research, Bioalcohols, Manufacturing, Monochromators, Fiber optics tests, Fiber optics, Aluminum, Electronics

Read Abstract +

Proceedings Article | 8 January 2015 Paper

Tissue fluorescence origins evaluation using excitation-emission matrices

A. Zhelyazkova, E. Borisova, L. Angelova, E. Pavlova, M. Keremedchiev, L. Avramov

Proceedings Volume 9447, 944711 (2015) https://doi.org/10.1117/12.2177795

KEYWORDS: Tissues, Luminescence, Collagen, Proteins, Skin, Tumors, Tissue optics, Polarization, Matrices, Diagnostics

Read Abstract +

Proceedings Article | 8 January 2015 Paper

Excitation-emission matrices (EEMs) and synchronous fluorescence spectroscopy (SFS) investigations of gastrointestinal tissues

Ts. Genova, E. Borisova, Al. Zhelyazkova, O. Semyachkina-Glushkovskaya, N. Penkov, M. Keremedchiev, B. Vladimirov, L. Avramov

Proceedings Volume 9447, 94470X (2015) https://doi.org/10.1117/12.2177674

KEYWORDS: Tissues, Luminescence, Fluorescence spectroscopy, Diagnostics, Signal detection, Matrices, Cancer, Proteins, Tissue optics, Biological research

Read Abstract +

In this report we will present our recent investigations of the fluorescence properties of lower part gastrointestinal tissues using excitation-emission matrix and synchronous fluorescence spectroscopy measurement modalities. The spectral peculiarities observed will be discussed and the endogenous sources of the fluorescence signal will be addressed. For these fluorescence spectroscopy measurements the FluoroLog 3 system (HORIBA Jobin Yvon, France) was used. It consists of a Xe lamp (300 W, 200-650 nm), a double mono-chromators, and a PMT detector with a work region at 220- 850 nm. Autofluorescence signals were detected in the form of excitation-emission matrices for the samples of normal mucosa, dysphasia and colon carcinoma and specific spectral features for each tissue were found. Autofluorescence signals from the same samples are observed through synchronous fluorescence spectroscopy, which is a novel promising modality for fluorescence spectroscopy measurements of bio-samples. It is one of the most powerful techniques for multicomponent analysis, because of its sensitivity. In the SFS regime, the fluorescence signal is recorded while both excitation λexc and emission wavelengths λem are simultaneously scanned. A constant wavelength interval is maintained between the λexc and λem wavelengths throughout the spectrum. The resulted fluorescence spectrum shows narrower peak widths, in comparison with EEMs, which are easier for identification and minimizes the chance for false determinations or pretermission of specific spectral feature. This modality is also faster, than EEMs, a much smaller number of data points are required.¹ In our measurements we use constant wavelength interval Δλ in the region of 10-200 nm. Measurements are carried out in the terms of finding Δλ, which results in a spectrum with most specific spectral features for comparison with spectral characteristics observed in EEMs. Implementing synchronous fluorescence spectroscopy in optical methods for analyzing biological tissues could result in a better differentiation between normal and dysplastic tissue. Thus could establish fluorescence imaging as a diagnostic modality among optical techniques applied in clinical practice.

Proceedings Article | 8 May 2014 Paper

Polarization effects in cutaneous autofluorescent spectra

E. Borisova, L. Angelova, Al. Jeliazkova, Ts. Genova, E. Pavlova, P. Troyanova, L. Avramov

Proceedings Volume 9129, 91292G (2014) https://doi.org/10.1117/12.2050886

KEYWORDS: Luminescence, Skin, Polarization, Polarizers, Signal detection, Tissues, Fluorescence spectroscopy, Collagen, In vivo imaging, Tissue optics

Read Abstract +