With the incidence rate exceeding 11% in the United States and 15%¹ in the developing countries, preterm birth (PTB), defined as labor prior to 37 weeks of gestation, is the leading cause of infant death worldwide. PTB is reported to be responsible for infant neurological disorders,² long-term cognitive impairment,³ as well as chronic health issues involving the auditory, visual, digestive, and respiratory systems.⁴ In expectant mothers, causes for PTB can include infection, inflammation,⁵ vascular disease,⁶ short intervals between pregnancies,⁷ multiple gestations,⁶ and genetic factors.⁸

The use of polarized light in clinical and preclinical applications is expanding,¹ and several recent reviews by Tuchin,² Ghosh and Vitkin,³ Qi and Elson,⁴ de Boer et al.,⁵ and Baumann⁶ have illustrated the fast progress of this approach in the medical field.

Significance: Obesity is a worldwide epidemic contributing directly to several cardiovascular risk factors including hypertension and type 2 diabetes. Wearable devices are becoming better at quantifying biomarkers relevant for the management of health and fitness. Unfortunately, both anecdotal evidence and recent studies indicate that some wearables have higher levels of error when utilized by populations with darker skin tones and high body mass index (BMI). There is an urgent need for a better evaluation of the limits of wearable health technologies when used by obese individuals. Aims: (1) To review the current know-how on changes due to obesity in the skin epidermis, dermis, and subcutis that could affect the skin optical properties; (2) for the green wavelength range, to evaluate the difference in absorption and scattering coefficients from the abdominal skin between individuals with and without elevated BMI. The changes include alterations in layer thickness and cell size, as well as significant differences in chromophores and scatterer content, e.g., water, hemoglobin, collagen, and lipids. Approach: We have summarized literature pertaining to changes in skin and its components in obesity and report the results of our search using articles published between years 1971 and 2020. A linear model was used to demonstrate the absorption and reduced scattering coefficient of the abdominal skin of individuals with and without elevated BMI in the green wavelength range (530 to 550 nm) that is typically found in most wearables. Results: The general trends indicate a decrease in absorption for both dermis and subcutis and an increase in reduced scattering for both epidermis and dermis. At 544-nm wavelength, a typical wavelength used for photoplethysmography (PPG), the absorption coefficient’s relative percentage difference between high and low BMI skin, was 49% in the subcutis, 19% in the dermis, and negligible in the epidermis, whereas the reduced scattering coefficient relative difference was 21%, 29%, and 165% respectively. Conclusions: These findings suggest that there could be significant errors in the output of optical devices used for monitoring health and fitness if changes due to obesity are not accounted for in their design.

Preterm birth (PTB) presents a serious medical health concern throughout the world. There is a high incidence of PTB in both developed and developing countries ranging from 11% to 15%, respectively. Recent research has shown that cervical collagen orientation and distribution changes during pregnancy may be useful in predicting PTB. Polarization imaging is an effective means to measure optical anisotropy in birefringent materials, such as the cervix’s extracellular matrix. Noninvasive, full-field Mueller matrix polarimetry (MMP) imaging methodologies, and optical coherence tomography (OCT) imaging were used to assess cervical collagen content and structure in nonpregnant porcine cervices. We demonstrate that the highly ordered structure of the nonpregnant porcine cervix can be observed with MMP. Furthermore, when utilized ex vivo, OCT and MMP yield very similar results with a mean error of 3.46% between the two modalities.

A Mueller matrix can completely characterize the polarimetric properties of a medium, where the parameters of depolarization, retardance and diattenuation can be obtained by decomposing a Mueller matrix with existing decomposition methods. The introduction of polarization sensitive cameras with integrated wire-grid polarizers has allowed for the fast acquisition and analysis of four linear states within a single snapshot. Moreover, these cameras provide the opportunity to capture a reduced 3 × 4 Mueller matrix with the acquisition of generated states polarization in the illumination arm. In order to measure and characterize samples using a reduced 3 × 4 Mueller matrix, a 3 × 4 decomposition algorithm is introduced. This new algorithm is compared and validated against established 4 × 4 decompositions. The validation of this algorithm is shown using a previously reported Mueller matrix of polyacrylamide phantom, and experimental Mueller matrices of quarter-wave plates, silicone phantoms and a skin model sample. The 3 × 4 decomposition compares well to established decompositions and is capable of characterizing the samples based on the calculation of depolarization, retardance and orientation.

Cervical cancer is the fourth most common cancer in women worldwide, with an estimated half a million new cases and 311,000 deaths each year.¹ Developing countries suffer about 84% of the global burden of disease and 80% of the mortality due to a lack of effective screening programs. The hardest-hit regions are among the world’s poorest with incidence rates over 35 per 100,000 women compared with 3 per 100,000 women or lower in North America and Europe.² Because the disease progresses over many years, an estimated 1.4 million women worldwide are living with cervical cancer, and two to five times more—up to 7 million—may have precancerous conditions that should be identified and treated.³ While several prophylactic human papillomavirus (HPV) vaccines are now available in more than 100 countries for primary prevention,⁴ they do not target all 15 high-risk HPV types, ergo there is still a need for screening.⁵ Moreover, due to cost-effectiveness issues of vaccination in low- and middle-income countries, it is often seen that the only available prevention method is regular screening and treatment of precancerous lesions.⁶