With the growing demand for vital signs monitoring using wearables, there is a gap between what is offered and the desire for clinical accuracy. Advancements in electronic miniaturization, materials and signal processing have increased possibilities for wearable technology. Optical sensing using photoplethysmography (PPG) is prominent within the field of wearable healthcare due to the non-invasive and versatile nature of the modality. Different aspects related to cardiovascular health can be screened and monitored with PPG, such as oxygen saturation (SPO2), heart rate (HR), heart rate variability (HRV) and possibly blood pressure. Although the principles and possibilities for vital sign monitoring with PPG are present, there is only sparse evidence of clinically relevant signals from commercial optical sensors. Furthermore, there is still a big challenge regarding motion artifact within a wearable device. Currently three wavelengths are commonly used within commercial wearables; green (550nm), red (660nm) and infrared (850nm). There is increased research on including shorter wavelengths (blue) potentially providing increased robustness to motion artifacts during wear.
Within this study, the design challenges for a universal wearable optic patch for improved signal accuracy were investigated. A dual-photodiode and multi-wavelength flexible wearable optic patch was fabricated using hybrid printed electronics. The design was evaluated as a function of patch-skin contact pressure during motion. Our preliminary results show a more robust PPG signal with increased patch-skin contact pressure. In addition, this study demonstrates the capability of our wearable and flexible optical patch at measuring simultaneous multi-wavelength PPG.
In recent years, several commercial systems relying on picosecond pulses have been introduced into the field of cutaneous interventions. In parallel with this development, a somewhat distinct research prototype also operating in the picosecond regime was described in literature. Albeit both market-available products and the investigational device employ laser beams of nearly the same pulse duration and were reported to cause laser-induced optical breakdown (LIOB), they are different in terms of wavelength, applied fluence, laser beam quality, optical architecture and related focusing optics, resulting in different histomorphological features (such as e.g. lesion size, location, expression of collagen). Understanding the differences between these systems in relation to implications for clinical results raises a need in highlighting the nuances behind interaction of picosecond pulses with biological tissue. To achieve this, we accentuate the interplay of irradiance levels of picosecond pulses in W/cm2 , absorption properties of a target tissue at a wavelength of a light source and resulting interaction mechanisms with biological object. We also relate these nuances to potential consequences for cutaneous interventions.
Distinct lineages of human dermal fibroblasts play complementary roles in skin rejuvenation and wound healing, which
makes them a target of phototherapy. However, knowledge about differential responses of specific cell lineages to
different light parameters and moreover the actual molecular targets remain to be unravelled.
The goal of this study was to investigate the impact of a range of parameters of light on the metabolic activity, collagen
production, and cell migration of distinct lineages of human dermal fibroblasts. A rational approach was used to identify
parameters with high therapeutic potential.
Fibroblasts exhibited both inhibitory and cytotoxic change when exposed to a high dose of blue and cyan light in tissue
culture medium containing photo-reactive species, but were stimulated by high dose red and near infrared light.
Cytotoxic effects were eliminated by refreshing the medium after light exposure by removing potential ROS formed by
extracellular photo-reactive species.
Importantly, distinct lineages of fibroblasts demonstrated opposite responses to low dose blue light treatment when
refreshing the medium after exposure. Low dose blue light treatment also significantly increased collagen production by
papillary fibroblasts; high dose significantly retarded closure of the scratch wound without signs of cytotoxicity, and this
is likely to have involved effects on both cell migration and proliferation.
We recommend careful selection of fibroblast subpopulations and their culture conditions, a systematic approach in
choosing and translating treatment parameters, and pursuit of fundamental research on identification of photoreceptors
and triggered molecular pathways, while seeking effective parameters to address different stages of skin rejuvenation and
wound healing.
An increasing number of applications, including non- or minimally invasive diagnostics and treatment as well as various cosmetic procedures, has resulted in a need to determine the optical properties of hair and its structures. We report on the measurement of the total attenuation coefficient of the cortex and the medulla of blond, gray, and Asian black human scalp hair at a 633-nm wavelength. Our results show that for blond and gray hair the total attenuation coefficient of the medulla is more than 200 times higher compared to that of the cortex. This difference is only 1.5 times for Asian black hair. Furthermore, we present the total attenuation coefficient of the cortex of blond, gray, light brown, and Asian black hair measured at wavelengths of 409, 532, 633, 800, and 1064 nm. The total attenuation coefficient consistently decreases with an increase in wavelength, as well as with a decrease in hair pigmentation. Additionally, we demonstrate the dependence of the total attenuation coefficient of the cortex and the medulla of Asian black hair on the polarization of incident light. A similar dependence is observed for the cortex of blond and gray hair but not for the medulla of these hair types.
We demonstrate a significant improvement of depth selectivity when using obliquely oriented fibers for near-infrared (NIR) diffuse reflectance spectroscopy. This is confirmed by diffuse reflectance measurements of a two-layer tissue-mimicking phantom across the spectral range from 1000 to 1940 nm. The experimental proof is supported by Monte Carlo simulations. The results reveal up to fourfold reduction in the mean optical penetration depth, twofold reduction in its variation, and a decrease in the number of scattering events when a single fiber is oriented at an angle of 60 deg. The effect of reducing the mean optical penetration depth is enhanced by orienting both fibers inwardly. Using outwardly oriented fibers enables more selective probing of deeper layers, while reducing the contribution from surface layers. We further demonstrate that the effect of an inward oblique arrangement can be approximated to a decrease in fiber-to-fiber separation in the case of a perpendicular fiber arrangement. This approximation is valid in the weak- or absorption-free regime. Our results assert the advantages of using obliquely oriented fibers when attempting to specifically address superficial tissue layers, for example, for skin cancer detection, or in noninvasive glucose monitoring. Such flexibility could be further advantageous in a range of minimally invasive applications, including catheter-based interventions.
Singular value decomposition was applied to the set of the
non-resonant Raman spectra, recorded during Raman imaging of the
single apoptotic cell. The basis vectors and the corresponding
singular values were assessed in terms of their statistical
significance. The noise-containing basis vectors were rejected
while keeping the meaningful ones. In this way the Raman images of
the apoptotic cell were successfully reconstructed from the
spectrally-filtered data matrix. The results are demonstrated on
the spatial distribution of the DNA, protein and phospholipids,
present in the fragments of the apoptotic cell.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.