We explore the application of structured vortex laser beams, or shaped light with orbital angular momentum (OAM), in the diagnosis of cell and cell cultures and the quantitative characterization of biological tissues. To examine the conservation of spin and orbital angular momenta during propagation, we constructed a Mach-Zehnder-like interferometer, equipped with a spatial light modulator (SLM), to generate Laguerre-Gaussian (LG) beams with varying momenta. As the LG beam traverses tissue samples, its interference with a reference plane wave is captured by a camera. Our findings reveal that the OAM of the LG beam is maintained through both normal and cancerous tissue samples, exhibiting a distinct phase shift – or twist of light – which is significantly more sensitive (up to ~1000 times) to changes in the tissue's refractive indices compared to conventional methods. We conclude that leveraging OAM in biomedical diagnosis presents exciting prospects for both groundbreaking biological research and enhanced clinical applications.
In turbid tissue-like scattering medium the conventional polarised light, scattered multiple number of times, is depolarised, and the depolarisation rate depends strongly on the size and shape of scattering particles, as well as on the number of scattering events. In fact, the structure of light can be more complicated when the polarisation of light across the laser beam can be radially or azimuthally polarised and carry orbital angular momentum (OAM). We use both conventional polarisation and shaped light with OAM for characterisation of biological tissues and their structural malformations associated with dangerous diseases, including cancer, dementia, diabetes and other.
SignificanceMueller-matrix polarimetry is a powerful method allowing for the visualization of malformations in biological tissues and quantitative evaluation of alterations associated with the progression of various diseases. This approach, in fact, is limited in observation of spatial localization and scale-selective changes in the poly-crystalline compound of tissue samples.AimWe aimed to improve the Mueller-matrix polarimetry approach by implementing the wavelet decomposition accompanied with the polarization-singular processing for express differential diagnosis of local changes in the poly-crystalline structure of tissue samples with various pathology.ApproachMueller-matrix maps obtained experimentally in transmitted mode are processed utilizing a combination of a topological singular polarization approach and scale-selective wavelet analysis for quantitative assessment of the adenoma and carcinoma histological sections of the prostate tissues.ResultsA relationship between the characteristic values of the Mueller-matrix elements and singular states of linear and circular polarization is established within the framework of the phase anisotropy phenomenological model in terms of linear birefringence. A robust method for expedited (up to ∼15 min) polarimetric-based differential diagnosis of local variations in the poly-crystalline structure of tissue samples containing various pathology abnormalities is introduced.ConclusionsThe benign and malignant states of the prostate tissue are identified and assessed quantitatively with a superior accuracy provided by the developed Mueller-matrix polarimetry approach.
Laser Speckle Contrast Imaging (LSCI) is a powerful low-cost method for visualization of flow, microcirculation and blood perfusion. Due to the fact that diseased and healthy tissues has different blood perfusion, LSCI can be a perspective tool for cancer diagnostics and discrimination between different types of tissues. Previously, multispectral diffuse reflectance imaging method for melanoma diagnostics has been introduced. In this work, multi-wavelength (532-, 655- and 850- nm) LSCI technique combined with hyperspectral camera and diffuse reflectance imaging method will be used for assessment of tissues with different skin perfusion properties. An in vivo experiment with occlusion in human finger was performed serving as a model of tissues with different perfusion properties. The proposed method still requires further development and improvements to become a real clinical laboratory tool for non-invasive skin cancer diagnostics.
Diagnosis and treatment of acute destructive pancreatitis is one of the most urgent problems of abdominal surgery. To obtain additional diagnostic information about the microcirculation state and metabolic processes, various imaging techniques are widely used during surgical interventions. One of the most perspective techniques for in vivo microcirculation assessment is laser speckle-contrast imaging (LSCI), allowing for evaluation of blood perfusion. The experimental results showed the possibility to evaluate the blood perfusion of the mouse pancreas in the simulation of ischemia using the LSCI method.
Optical clearing agents (OCAs) and many chemicals are widely used in functional diagnosis of skin tissues. Numerous studies are associated with the transcutaneous diffusion of OCA in epidermal, dermal, and hypodermal tissues, which results in changing their optical properties. In addition, an objective approach that is suitable for screening the influence of utilized OCA, as well as various chemical agents, synthetics, and nanomaterials, on blood and lymph flows is highly desirable. In our study, a highly sensitive laser speckle imaging (LSI) system and fluorescent intravital microscopy (FIM) were used team-wise to inspect the acute skin vascular permeability reaction in mouse ear during the local application of OCA on the skin surface. Fluorescent contrast material administrated intravenously was used for quantitatively assessing the intensity of vascular permeability reaction and the strength of skin irritation. The obtained results suggest that a combined use of LSI and FIM is highly effective for monitoring the cutaneous vascular permeability reaction, with great potential for assessment of allergic reactions of skin in response to interactions with chemical substances.
Laser speckle contrast imaging (LSCI) is a simple and quite powerful method for visualization of flow, microcirculation and perfusion. In current study the speckle contrast variations towards breaking ergodicity conditions are considered with a final aim of envision a practical approach allowing real-time imaging of variations in dynamic properties of complex fluids with an opportunity of quantitative interpretation of the obtained flowing map. As example of systems with static to dynamic transition, melting of Intralipid samples were studied. Also, investigation of influence of static layer thickness above the dynamic sample on the ergodicity condition has been studied.
We report the results on in ovo application of developed Laser Doppler Anemometer (LDA) device. The chorioallantoic membrane (CAM) of 9-13 days chicken embryos was used as a biological model that allows an easy access to both arterial and venous vessels of different size. The key point of our study was to find out how the periodic and aperiodic pulsations of blood flow (which are inevitable in living organism) will affect the LDA functions and measuring capability. Specifically, we (i) developed the technique to extract and refine the pulse rhythm from the signal received from a vessel, and (ii) analyzed the changes in power spectra of LDA signal that are caused by heart beating and considerably complicate the reliable measurement of Doppler shift. Our main conclusion is that the algorithm of LDA data processing need to be improved, and this possibly can be done by counting the information on current phase of cardiac cycle.
Particularities of interference signal shaping in white-light interferometer with uncompensated dispersive layer are discussed. We especially attended to dependence of interference pulse position on the dispersive layer properties. Phase refractive index of the layer tends to be substantially nonlinear function of wavelength within the wide emission band of ultra-low coherence thermal light source. In this case, it is the group refractive index dispersion that is beginning to exert an influence on interference signal formation. It is shown experimentally that influence consists in nonlinear dependence of interference pulse position on geometrical thickness of the dispersive layer. The results show that mismatch of the dispersive layer and compensator refractive indices in the third place can produce interference signal shift on the order of pulse width.
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