“…The polarization-sensitive THz SI microscopy can be further aided by the Mueller matrix formalism 57 , 58 , that employs a 4 × 4-matrix for describing transformation of the electromagnetic-wave polarization upon its interaction with a turbid medium. Decomposition of the Muller matrix gives a reasonable estimate for such polarization parameters of a turbid medium, as optical rotation and linear retardance 59 , 60 . Different instrumental realizations of the polarization imaging have been proposed in the visible and infrared ranges, including the classic approach (it requires 36 measurements with different combinations of polarizer and analyzer to estimate the 4 × 4 Mueller matrix), or the rotating retarder approach (it reduces the number of measurements down to 24) 61 .…”
Terahertz (THz) technology offers a variety of applications in label-free medical diagnosis and therapy, majority of which rely on the effective medium theory that assumes biological tissues to be optically isotropic and homogeneous at the scale posed by the THz wavelengths. Meanwhile, most recent research discovered mesoscale ($$\sim \lambda $$
∼
λ
) heterogeneities of tissues; $$\lambda $$
λ
is a wavelength. This posed a problem of studying the related scattering and polarization effects of THz-wave–tissue interactions, while there is still a lack of appropriate tools and instruments for such studies. To address this challenge, in this paper, quantitative polarization-sensitive reflection-mode THz solid immersion (SI) microscope is developed, that comprises a silicon hemisphere-based SI lens, metal-wire-grid polarizer and analyzer, a continuous-wave 0.6 THz ($$\lambda = 500$$
λ
=
500
µm) backward-wave oscillator (BWO), and a Golay detector. It makes possible the study of local polarization-dependent THz response of mesoscale tissue elements with the resolution as high as $$0.15 \lambda $$
0.15
λ
. It is applied to retrieve the refractive index distributions over the freshly-excised rat brain for the two orthogonal linear polarizations of the THz beam, aimed at uncovering the THz birefringence (structural optical anisotropy) of tissues. The most pronounced birefringence is observed for the Corpus callosum, formed by well-oriented and densely-packed axons bridging the cerebral hemispheres. The observed results are verified by the THz pulsed spectroscopy of the porcine brain, which confirms higher refractive index of the Corpus callosum when the THz beam is polarized along axons. Our findings highlight a potential of the quantitative polarization THz microscopy in biophotonics and medical imaging.
“…The polarization-sensitive THz SI microscopy can be further aided by the Mueller matrix formalism 57 , 58 , that employs a 4 × 4-matrix for describing transformation of the electromagnetic-wave polarization upon its interaction with a turbid medium. Decomposition of the Muller matrix gives a reasonable estimate for such polarization parameters of a turbid medium, as optical rotation and linear retardance 59 , 60 . Different instrumental realizations of the polarization imaging have been proposed in the visible and infrared ranges, including the classic approach (it requires 36 measurements with different combinations of polarizer and analyzer to estimate the 4 × 4 Mueller matrix), or the rotating retarder approach (it reduces the number of measurements down to 24) 61 .…”
Terahertz (THz) technology offers a variety of applications in label-free medical diagnosis and therapy, majority of which rely on the effective medium theory that assumes biological tissues to be optically isotropic and homogeneous at the scale posed by the THz wavelengths. Meanwhile, most recent research discovered mesoscale ($$\sim \lambda $$
∼
λ
) heterogeneities of tissues; $$\lambda $$
λ
is a wavelength. This posed a problem of studying the related scattering and polarization effects of THz-wave–tissue interactions, while there is still a lack of appropriate tools and instruments for such studies. To address this challenge, in this paper, quantitative polarization-sensitive reflection-mode THz solid immersion (SI) microscope is developed, that comprises a silicon hemisphere-based SI lens, metal-wire-grid polarizer and analyzer, a continuous-wave 0.6 THz ($$\lambda = 500$$
λ
=
500
µm) backward-wave oscillator (BWO), and a Golay detector. It makes possible the study of local polarization-dependent THz response of mesoscale tissue elements with the resolution as high as $$0.15 \lambda $$
0.15
λ
. It is applied to retrieve the refractive index distributions over the freshly-excised rat brain for the two orthogonal linear polarizations of the THz beam, aimed at uncovering the THz birefringence (structural optical anisotropy) of tissues. The most pronounced birefringence is observed for the Corpus callosum, formed by well-oriented and densely-packed axons bridging the cerebral hemispheres. The observed results are verified by the THz pulsed spectroscopy of the porcine brain, which confirms higher refractive index of the Corpus callosum when the THz beam is polarized along axons. Our findings highlight a potential of the quantitative polarization THz microscopy in biophotonics and medical imaging.
“…Moreover, the intercellular substance exhibits birefringence with a value of 0.003, and its optical axis is aligned along the x-axis. In our simulations, we employ incident light with a wavelength of 633 nm, and the total number of simulated photons is set to 10*1e7, ensuring a comprehensive evaluation of the light-tissue interaction 19 .…”
Section: Monte Carlo Simulationmentioning
confidence: 99%
“…Despite with lower dimensions, some polarization information extracted from Stokes vectors is equally effective as methods based on the Mueller matrix 16,17 . In our previous work, we developed a fast Stokes imaging system and applied it to monitor the tissue optical clearing process 18,19 . Experimental results demonstrate that in this dynamic process, Stokes imaging exhibits advantages and effectiveness over Mueller matrix imaging.…”
“…Compared to conventional optical detection methods, polarization measurement techniques can provide higher dimensional polarization information that is more sensitive to microstructures at sub-wavelength scale, and has become a favorable tool for characterizing biological tissues and cells [6,7] . Specifically, the Mueller matrix can comprehensively evaluate the polarization properties of biological samples, and some polarization parameters derived from the Mueller matrix have shown potential in cancer diagnosis [8,9,10] , the analysis of biological tissues [11,12] , and the monitoring of the dynamic process in biological tissues [13,14] . In recent years, some researchers applied polarization imaging to investigate morphological changes of cells and used polarization parameters for qualitative or quantitative characterization.…”
In the clinic, certain diseases caused by genetic mutations or viral infections can alter the morphology and size of cells. Mueller matrix polarimetry is highly sensitive to microscale structural changes and can be utilized to detect cellular morphological alterations. Moreover, the extracting parameters from the Mueller matrix can serve as a key indicator for characterizing anomalous changes in cell morphology, demonstrating promising potential for application in disease analysis and diagnosis. Based on full polarization Mueller matrix imaging, this study proposes a characterization method for assessing red blood cell morphological changes induced by osmotic pressure. The results indicate significant variations in polarization parameters reflecting the morphological changes of red blood cells under different osmotic pressure regulations from sodium chloride solutions with different mass fractions. In addition, there are some differences in the sensitivity of different polarization parameters to cell deformation.
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