Polarization birefringence measurements for characterizing the myocardium, including healthy, infarcted, and stem-cell-regenerated tissues

Abstract

Abstract. Myocardial infarction leads to structural remodeling of the myocardium, in particular to the loss of cardiomyocytes due to necrosis and an increase in collagen with scar formation. Stem cell regenerative treatments have been shown to alter this remodeling process, resulting in improved cardiac function. As healthy myocardial tissue is highly fibrous and anisotropic, it exhibits optical linear birefringence due to the different refractive indices parallel and perpendicular to the fibers. Accordingly, changes in myocardial structure associated with infarction and treatment-induced remodeling will alter the anisotropy exhibited by the tissue. Polarization-based linear birefringence is measured on the myocardium of adult rat hearts after myocardial infarction and compared with hearts that had received mesenchymal stem cell treatment. Both point measurement and imaging data show a decrease in birefringence in the region of infarction, with a partial rebound back toward the healthy values following regenerative treatment with stem cells. These results demonstrate the ability of optical polarimetry to characterize the micro-organizational state of the myocardium via its measured anisotropy, and the potential of this approach for monitoring regenerative treatments of myocardial infarction.

Comparative study of differential matrix and extended polar decomposition formalisms for polarimetric characterization of complex tissue-like turbid media

“…4)]} via Eqs. (24) and (25), thus establishing self-consistency between the two formalisms. One can also notice that for this nonscattering phantom, the differential matrix-derived uncertainties in the parameters (Δδ log -M , ΔΨ log -M obtained from the matrix logarithm L u ) are quite small and physically insignificant.…”

“…19 Once again, the estimation of Ψ-parameter using the retarder polar decomposition which assumes sequential occurrence of linear and circular retardance leads to an overestimation; self-consistency is established by using retarder polar decomposition for simultaneous occurrence of linear retardance and optical rotation effects [Eqs. (24) and (25)]. Interestingly, Table 2 The values for the polarization parameters extracted using Eqs.…”

“…Mueller matrix images were recorded in the transmission geometry, from these 1-mm-thick ex vivo tissue samples. 24 …”

“…(24) and (25) in combination with polar decomposition has been tested on experimental Mueller matrices from optical phantoms exhibiting simultaneous linear retardance, optical rotation and depolarization effects and on analogous MC-generated Mueller matrices. These results are presented subsequently.…”

“…19,23 To investigate the utility of linear retardance measurements and quantification (using differential matrix decomposition) for monitoring regenerative treatments, samples from a rat model of myocardial infarction and regeneration were used. 23,24 All animal studies were carried out under institutional approval from the University Health Network, Toronto, Canada. Myocardial infarctions were induced in Lewis rats through coronary artery ligation.…”