Accurate and repeatable epidermal thickness (ET) measurement is essential for assessing and quantifying cutaneous characteristics in dermatological disease, skin injury, and cosmetic research. Here, we investigated the integration of pressure sensors with optical coherence tomography (OCT) for improved epidermal thickness (ET) measurements. Traditional contact imaging techniques could induce variations in measurement due to inconsistent pressure. By using pressure sensors, real-time monitoring of applied pressure during OCT imaging provides stable and consistent ET mapping, improving repeatability. The result further demonstrates that increased compression forces can lead to significant deformation of the epidermis. This study demonstrates a pressure sensor integration to allow more accurate ET measurements and offers improved imaging quality, with potential applications in dermatology and cosmetics, underscoring the need for controlled pressure in contact imaging.
Pulsatile signals from the cutaneous blood flow could be informative for evaluating the health condition of an individual. One of the popular optical measuring devices, photoplethysmogram (PPG) is often used to detect the pulse signal from skin. However, the origin of the PPG signal still remains controversial. Benefiting from the non-invasive, label-free, 3D imaging tool, optical coherence tomography (OCT) is able to capture the intrinsic tissue signals at different penetration depth in high spatial and temporal resolution. Periodic pulse signal was observed by taking advantage of the optical microangiography (OMAG) algorithm which is sensitive to the motion of blood flow. The pulsatile pattern from the capillary and arteriole was successfully differentiated and their morphology showed distinct property at different local blood pressure. The pulse signal from the arteriole is more consistent and has similar waveform as the PPG signals. The result indicated that the PPG signal could be deceive by the mixing signal from the capillary bed and arterioles since it measures the total blood volume change in the plexuses. This study may shed some new light on understanding the mechanical property of how blood travel through different types of vasculature networks and elucidate its potential application in disease assessments.
The dynamic properties of subcellular organism are important biomarkers of health. Imaging subcellular level dynamics provides effective solutions for evaluating cell metabolism, and moreover, testing the responses of cells to pathogens and drugs in pharmaceutical engineering. In this paper, we demonstrate an innovative approach to contrast the subcellular motions by using eigen decomposition (ED) based variance analysis of time-dependent complex optical coherence tomography (OCT) signals. This method reveals superior contrast to noise advantage compared with intensity-based dynamic imaging regime. Further validation experiments were performed with B-mode imaging sections crossing a wide range of sampling frequencies, and on the patterned samples of yeast powder mixed with gelatin/TiO2-water solution. In addition, the proposed method was further used to image mouse cerebral cortex in vivo, suggesting the promising of ED based correlation power mapping in analyzing coupled dynamics of neuron activity and cerebral blood flow. The proposed technique promises efficient measurement of subcellular motions with high sensitivity and low artifact involvement, suggesting high potential for in vivo and in situ applications.
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