Optical Breast Spectroscopy (OBS) has been shown to predict mammographic breast density, a strong breast cancer risk factor. OBS is a low-cost technique applicable at any age. OBS information may be useful for personalizing breast cancer screening programs based on risk to improve consensus on and adherence to screening guidelines. To facilitate the use of OBS in population-wide studies, a research prototype OBS device was modified to make it portable and cheaper and to require less operator interaction. Two major changes were made: (1) the broadband light source was replaced with a laser module with 13 individual wavelengths turned on sequentially, enabling the use of photodiode detectors instead of a spectrometer, and (2) the light sources and detectors were placed in fixed positions within 4 sizes of cup, eliminating the need for placement by the operator. Wavelengths were selected using data from two previous studies. The reduction in spectral content did not significantly reduce the ability to distinguish between different risk groups. Positions for the light sources and detectors were chosen based on Monte Carlo simulations to match the optically interrogated volumes of the original device. Two light sources and six detectors per cup were used in the final design.

Formed almost exclusively during development, arterial elastic fibers must function for the lifetime of the animal. We have observed dramatic structural and mechanical changes in aortic elastic tissue during gestational and postnatal development. Elastic tissue was isolated from bovine aortas: (i) during late pregnancy and (ii) in adults. Changes in the relative content of aortic elastic tissue were assessed, as were the viscoelastic properties and residual strains of purified aortic elastic tissue rings. As aortic elastic tissue content increased during development, its circumference and thickness increased-but with circumference rising faster than wall thickness, causing a relative thinning of the elastic tissue. At the same time, elastic tissue stiffness increased while viscoelastic behavior decreased. Much of these changes were concentrated during late gestational development, such that the changes observed during the short span of late gestation examined (~60 days) were similar in magnitude to those occurring over the much longer postnatal period (approximately 1-2 years). Finally, we observed an approximately threefold increase in residual strain in aortic elastic tissue from fetal to adult life, with most of this increase again occurring in late gestation. These results suggest that rapid remodeling, as well as accumulation, of aortic elastic tissue occurs during late gestation. These changes significantly alter both fetal aortic mechanical properties and residual stresses.

A 12-laser-wavelength, fixed source-detector position, cup-based optical breast spectroscopy (OBS) device was developed for use in large-scale, multicenter trials as a mammographic breast density (MBD) quantification and breast cancer (BC) risk prescreening tool. In this study, the device was evaluated in comparison with a spectrometer-based device used in previous studies. The devices were compared on their ability to predict mammographic percent density (MPD) and to identify women with high MBD from optical spectra. OBS measurements were made on 60 women, (age 29-73), using both devices. Recent mammograms were collected for all women and MPD quantified from the mammograms. Principal components (PCs) analysis was performed on both sets of OBS spectra, and multivariate logistic regression analysis of the resulting PC scores was used to identify women with high MBD. Both devices are able to identify high MBD with very high sensitivity and specificity. Partial least-squares regression of the spectra was used to predict MPD. Both devices show a strong correlation between OBS-predicted MPD and MPD read from mammograms, however, the correlation is stronger for the continuous-spectrum device (r = 0.74, P = .001) than for the 12-wavelength device (r = 0.62, P = .004). Improvements to the cup-based device to reduce detector saturation should improve the prediction of MPD from the spectra.

Mechanical loading conditions are important factors in the gestational development of fetal tissues. However, little is known about how mechanical loading during development modulates the structure and function of elastic tissues. We hypothesized that developing elastic tissues functionally adapt to their loading conditions. To test this hypothesis, we assessed the changes in the composition, viscoelasticity, and thermoelastic properties of elastic tissue from bovine aortas (functional during gestation) and nuchal ligaments (nonfunctional during gestation). Clear differences in the developmental timeline of elastic tissue structure and function were observed between aortic and ligament elastic tissue. Elastic tissue in the aorta developed earlier than that of the nuchal ligament, indicating a role for loading conditions in the timeline of development. Ligament elastic tissue, however, underwent rapid remodeling in late gestation-likely as a preadaptation to the sudden-onset of tensile load it experiences at birth. Finally, while the same fundamental structure-mechanical relationships were seen in both tissues, there was a clear difference in mechanical properties between the elastic tissues from the adult nuchal ligament and the adult aorta, indicating that postnatal loading conditions continue to influence tissue structure and mechanical properties, tailoring them to their functional roles in adult life.

This study compared different approaches to measuring breast density and breast tissue composition (BTC) in adolescent girls (n = 42, aged 14–16 years) and their mothers (n = 39, aged 36–61 years) from a cohort in Santiago, Chile. Optical spectroscopy (OS) was used to measure collagen, water, and lipid concentrations, which were combined into a percent breast density index (%BDI). A clinical dual-energy X-ray absorptiometry (DXA) system calibrated to measure breast density provided percent fibroglandular volume (%FGV) from manually delineated images. After digitizing mammogram films, the percent mammographic breast density (%MBD) was measured using computer-assisted software. Partial correlation coefficients (rpartial) were used to evaluate associations between breast density measures and BTC from these three different measurement approaches, adjusting for age and body mass index. %BDI from OS was associated with %FGV from DXA in adolescent girls (rpartial = 0.46, p-value = 0.003), but not in mothers (rpartial = 0.17, p-value = 0.32). In mothers, %FGV from DXA was associated with %MBD from mammograms (rpartial = 0.60, p-value < 0.001). These findings suggest that data from OS, DXA, and mammograms provide related but distinct information about breast density and BTC. Future studies should explore how the information provided by these different devices can be used for breast cancer risk prediction in cohorts of adolescent girls and women.