Nonlinear beamforming for intracardiac echocardiography: a comparative study.

Intracardiac echocardiography (ICE) enables cardiac imaging with a wide field of view, deep imaging depth, and high frame rate during surgery. However, strong sidelobe and grating lobe artifacts created by the ultra-compact transducer degrade its image quality, making diagnosis and monitoring of treatment difficult. Conventionally, aperture apodization algorithms are often used to suppress sidelobe and grating lobe artifacts at the expense of lateral resolution, which is undesirable in ICE. In this study, we present comparative results of the beamforming methods specifically in ICE application. We demonstrate and compare five nonlinear beamforming algorithms in ICE: nonlinear pth root delay and sum (NL-p-DAS), nonlinear pth root spectral magnitude scaling (NL-p-SMS), delay-and-sum with coherence factors (DAS + SCF), delay and sum with apodization (DAS + apodization) and delay and sum (DAS). Phantom and ex-vivo experiment compare the performance of each algorithm in static and dynamic conditions. DAS + SCF shows the best lateral resolution, and all four algorithms improve the image contrast and sidelobe suppression over conventional DAS. NL-p-SMS stands out for the best axial resolution and suppression of grating lobe artifacts. For motion tracking, NL-p-SMS shows better temporal resolution than other methods. Overall, all the beamforming algorithms other than DAS showed improved image quality. Among them, NL-p-SMS, which has a high temporal resolution, showed the potential for providing more accurate information regards movement tracking. Supplementary Information: The online version contains supplementary material available at 10.1007/s13534-024-00352-9.

X-ray free-electron laser induced acoustic microscopy (XFELAM).

The X-ray free-electron laser (XFEL) has remarkably advanced X-ray imaging technology and enabled important scientific achievements. The XFEL's extremely high power, short pulse width, low emittance, and high coherence make possible such diverse imaging techniques as absorption/emission spectroscopy, diffraction imaging, and scattering imaging. Here, we demonstrate a novel XFEL-based imaging modality that uses the X-ray induced acoustic (XA) effect, which we call X-ray free-electron laser induced acoustic microscopy (XFELAM). Initially, we verified the XA effect by detecting XA signals from various materials, then we validated the experimental results with simulation outcomes. Next, in resolution experiments, we successfully imaged a patterned tungsten target with drilled various-sized circles at a spatial resolution of 7.8 ± 5.1 µm, which is the first micron-scale resolution achieved by XA imaging. Our results suggest that the novel XFELAM can expand the usability of XFEL in various areas of fundamental scientific research.

An ultrasensitive and broadband transparent ultrasound transducer for ultrasound and photoacoustic imaging in-vivo.

Transparent ultrasound transducers (TUTs) can seamlessly integrate optical and ultrasound components, but acoustic impedance mismatch prohibits existing TUTs from being practical substitutes for conventional opaque ultrasound transducers. Here, we propose a transparent adhesive based on a silicon dioxide-epoxy composite to fabricate matching and backing layers with acoustic impedances of 7.5 and 4-6 MRayl, respectively. By employing these layers, we develop an ultrasensitive, broadband TUT with 63% bandwidth at a single resonance frequency and high optical transparency ( > 80%), comparable to conventional opaque ultrasound transducers. Our TUT maximises both acoustic power and transfer efficiency with maximal spectrum flatness while minimising ringdowns. This enables high contrast and high-definition dual-modal ultrasound and photoacoustic imaging in live animals and humans. Both modalities reach an imaging depth of > 15 mm, with depth-to-resolution ratios exceeding 500 and 370, respectively. This development sets a new standard for TUTs, advancing the possibilities of sensor fusion.

Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma.

This study investigated the effect of temperature on the aspect-ratio etching of SiO2 in CF4/H2/Ar plasma using patterned samples of a 200 nm trench in a low-temperature reactive-ion etching system. Lower temperatures resulted in higher etch rates and aspect ratios for SiO2. However, the plasma property was constant with the chuck temperature, indicated by the line intensity ratio from optical emission spectroscopy monitoring of the plasma. The variables obtained from the characterization of the etched profile for the 200 nm trench after etching were analyzed as a function of temperature. A reduction in the necking ratio affected the etch rate and aspect ratio of SiO2. The etching mechanism of the aspect ratio etching of SiO2 was discussed based on the results of the surface composition at necking via energy-dispersive X-ray spectroscopy with temperature. The results suggested that the neutral species reaching the etch front of SiO2 had a low sticking coefficient. The bowing ratio decreased with lowering temperature, indicating the presence of directional ions during etching. Therefore, a lower temperature for the aspect ratio etching of SiO2 could achieve a faster etch rate and a higher aspect ratio of SiO2 via the reduction of necking than higher temperatures.

Panoramic volumetric clinical handheld photoacoustic and ultrasound imaging.

Photoacoustic (PA) imaging has gained much attention, providing structural and functional information in combination with clinical ultrasound (US) imaging systems. 2D PA and US imaging is easily implemented, but its heavy dependence on operator skills makes 3D imaging preferable. In this study, we propose a panoramic volumetric clinical PA and US imaging system equipping a handheld imaging scanner weighing 600 g and measuring 70 × 62 × 110 mm3. Multiple PA/US scans were performed to cover a large field-of-view (FOV), and the acquired PA/US volumes were mosaic-stitched after manually correcting the positions and rotations in a total of 6 degrees of freedom. PA and US maximum amplitude projection images were visualized online, while spectral unmixed data was quantified offline. The performance of the system was tested via tissue-mimicking phantom experiments. The system's potential was confirmed in vivo by panoramically imaging vascular networks in human arms and necks, with FOVs of 331 × 38 and 129 × 120 mm2, respectively. Further, we quantified hemoglobin oxygen saturation levels in the radial artery, brachial artery, carotid artery, and jugular vein. We hope that this system can be applied for various clinical fields such as cardiovascular imaging, dermatology, vascular surgery, internal medicine, and oncology.

Benefits of leaders' pleasurable recovery activities on follower performance via emotional contagion.

Recovery research has amply documented the benefits of employee recovery for their well-being and performance. However, most research to date has mainly focused on intraindividual benefits, so that we know relatively little about how focal employees' recovery activities might affect others at work. Bridging the gaps in the recovery and leadership literatures, this study focuses on leader-follower dyads and examines the interpersonal effects of leaders' recovery activities on followers' daily performance quality. In particular, our proposed model-which is informed by the conservation of resource and emotional contagion theories-explains the spillover-crossover process by which leaders' pleasurable recovery activity at home influences their positive affect (PA) displays at work, their followers' PA, and ultimately followers' task performance and creative behavior. We conducted two experience sampling method studies that relied on leader-member dyads of full-time working adults who responded to multiple online surveys for five workdays (n1 = 511 daily observations) and 10 workdays (n2 = 576 daily observations). In both studies, multilevel path analyses showed that leaders' previous-night pleasurable recovery activity leads to increased morning PA displays at work (observed by followers), which in turn crosses over to followers' midday PA and positive work outcomes. In particular, the affective crossover from leaders to followers was stronger when followers were in an inadequate morning recovery state and, therefore, more in need of resource replenishment. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The influence of different hinge position on PTS during HTO: comparison between open-wedge and closed-wedge HTO.

PURPOSE: The purpose of this study was to determine the significance of hinge position through comparison between open-wedge and closed-wedge high tibial osteotomy (HTO) and to determine the ideal hinge position to minimize the effect of HTO on the posterior tibial slope (PTS) and medial proximal tibial angle (MPTA). METHODS: Procedures were performed on 32 cadaveric knees using open-wedge HTO with the standard hinge position or a low hinge position or closed-wedge HTO with the standard hinge position or a low hinge position. To define the standard hinge position in open wedge HTO, we drew a line 3-cm inferior to the medial tibial plateau toward the fibular head and located the intersection of this line with a longitudinal line 1-cm medial to fibular shaft. The low hinge position was then defined as the point 1-cm inferior to the standard position. For the standard hinge position for closed-wedge HTO, we drew a line parallel with joint line from 2-cm inferior to the lateral tibial plateau. The low hinge position was then defined as the point 1-cm inferior to the standard position. RESULTS: For the open-wedge procedure, osteotomy through the low hinge position resulted in a significantly greater PTS compared to osteotomy through the standard hinge position. MPTA was also significantly greater for the low hinge position compared to standard hinge position. In the closed-wedge HTO, neither the PTS nor MPTA was significantly different for the low and standard hinge positions. CONCLUSIONS: Hinge position significantly affects changes in the PTS and MPTA following open-wedge but not closed-wedge HTO. Understanding how to hinge position affects the PTS and MPTA is critical for surgeons performing open-wedge HTO procedures. Adopting an accurate hinge position is crucial for preventing complications, especially in open-wedge osteotomy, due to postoperative changes in the PTS and MPTA.

Performance comparison of high-speed photoacoustic microscopy: opto-ultrasound combiner versus ring-shaped ultrasound transducer.

Photoacoustic microscopy (PAM) embedded with a 532 nm pulse laser is widely used to visualize the microvascular structures in both small animals and humans in vivo. An opto-ultrasound combiner (OUC) is often utilized in high-speed PAM to confocally align the optical and acoustic beams to improve the system's sensitivity. However, acoustic impedance mismatch in the OUC results in little improvement in the sensitivity. Alternatively, a ring-shaped ultrasound transducer (RUT) can also accomplish the confocal configuration. Here, we compare the performance of OUC and RUT modules through ultrasound pulse-echo tests and PA imaging experiments. The signal-to-noise ratios (SNRs) of the RUT-based system were 15 dB, 12 dB, and 7 dB higher when compared to the OUC-based system for ultrasound pulse-echo test, PA phantom imaging test, and PA in-vivo imaging test, respectively. In addition, the RUT-based system could image the microvascular structures of small parts of a mouse body in a few seconds with minimal loss in SNR. Thus, with increased sensitivity, improved image details, and fast image acquisition, we believe the RUT-based systems could play a significant role in the design of future fast-PAM systems.

Three-dimensional Multistructural Quantitative Photoacoustic and US Imaging of Human Feet in Vivo.

Background Monitoring the microcirculation in human feet is crucial in assessing peripheral vascular diseases, such as diabetic foot. However, conventional imaging modalities are more focused on diagnosis in major arteries, and there are limited methods to provide microvascular information in early stages of the disease. Purpose To investigate a three-dimensional (3D) noncontrast bimodal photoacoustic (PA)/US imaging system that visualizes the human foot morphologically and also reliably quantifies podiatric vascular parameters noninvasively. Materials and Methods A clinically relevant PA/US imaging system was combined with a foot scanner to obtain 3D PA and US images of the human foot in vivo. Healthy participants were recruited from September 2020 to June 2021. The collected 3D PA and US images were postprocessed to present structural information about the foot. The quantitative reliability was evaluated in five repeated scans of 10 healthy feet by calculating the intraclass correlation coefficient and minimal detectable change, and the detectability of microvascular changes was tested by imaging 10 healthy feet intentionally occluded with use of a pressure cuff (160 mm Hg). Statistically significant difference is indicated with P values. Results Ten feet from six healthy male volunteers (mean age ± standard deviation, 27 years ± 3) were included. The foot images clearly visualized the structure of the vasculature, bones, and skin and provided such functional information as the total hemoglobin concentration (HbT), hemoglobin oxygen saturation (SO2), vessel density, and vessel depth. Functional information from five independent measurements of 10 healthy feet was moderately reliable (intraclass correlation coefficient, 0.51-0.74). Significant improvements in HbT (P = .006) and vessel density (P = .046) as well as the retention of SO2 were observed, which accurately described the microvascular change due to venous occlusion. Conclusion Three-dimensional photoacoustic and US imaging was able to visualize morphologic and physiologic features of the human foot, including the peripheral microvasculature, in healthy volunteers. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Mezrich in this issue.

Does a healthy lifestyle matter? A daily diary study of unhealthy eating at home and behavioral outcomes at work.

With abundant health-related information, the modern workforce is advised to engage in health-promoting behaviors such as good sleep, physical activities, and a healthy diet to stay productive at work. However, no study has provided a theoretical framework or empirical evidence on the association between employees' unhealthy eating behavior and the quality of their performance. Drawing from the stress and coping literature, the current study proposes a moderated mediation model to investigate the day-specific roles of (un)healthy lifestyle in regard to personal well-being and performance at work. We used daily diary data collected from 97 full-time employees and employed an experience sampling method (ESM) to examine this within-person phenomenon for 2 weeks. Our multilevel path analysis reveals that employees' unhealthy eating behavior in the evening led to emotional strain (e.g., guilt) as well as physical strain (e.g., stomachache, diarrhea) on the next morning; the emotional and physical strains experienced in the morning served as key mediators resulting in decreased quality of performance (i.e., less helping and more withdrawal behaviors) in the afternoon. Furthermore, emotional stability was found to moderate the relationship between unhealthy eating behavior and morning strains, such that employees with higher emotional stability tended to experience less negative emotions and fewer physical symptoms. The theoretical and practical implications of these findings are discussed, along with suggestions for future studies on health-related behaviors. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Daily microbreaks in a self-regulatory resources lens: Perceived health climate as a contextual moderator via microbreak autonomy.

Grounded in self-regulatory resources and conservation of resources theories, the current research examines poor self-regulatory capacity as a precursor to microbreaks and their possible outcomes at work. Full-time employees completed multiple online surveys for 10 (n1 = 779 daily observations) and 5 workdays (n2 = 1,024 daily observations). In Study 1, multilevel path analysis results showed that on days when employees had poorer recovery at home (i.e., poor sleep quality), they experienced higher fatigue in the next morning (low self-regulatory capacity) and thus took microbreaks more frequently at work. In turn, their engagement in microbreaks was related to higher work engagement during the day and lower end-of-work fatigue. Furthermore, perceived health climate was found to moderate the path from morning fatigue to microbreaks. In Study 2, we replicated and confirmed the serial mediation paths found in Study 1 (poor sleep quality → morning fatigue → microbreaks → work engagement and end-of-work fatigue). Building on Study 1, Study 2 also identified microbreak autonomy as a mechanism by which perceived health climate moderates the path between morning fatigue and microbreaks (i.e., mediated moderation effect). Exploratory analyses discovered intriguing patterns of socialization microbreaks versus other microbreaks, providing further implications for the theoretical perspective. Overall, the findings support the theoretical resource perspective of microbreaks as an effective energy management strategy while at work. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Prescription patterns of herbal medicine for menopausal disorders in major Korean medicine hospitals: a multicenter retrospective study.

BACKGROUND: This study aimed to obtain the symptom, prescription and therapeutic patterns for the treatment of patients with menopausal syndrome in major Korean medicine (KM) hospitals. METHODS: We used a retrospective chart review of climacteric disorder and postmenopausal syndrome patients by examining medical records (ICD-10, menopausal and female climacteric states: N95.1, Menopausal and perimenopausal disorder, unspecified: N95.9) from eight university KM hospitals in South Korea. RESULTS: The main symptoms of 1,682 patients with menopausal disorders visiting eight college-affiliated oriental medicine hospitals were hot flush, hyperhidrosis, fatigue, insomnia, and chest tightness. Guipi decoction, Si-wu guipi decoction, Qing-xin lianzi-yin, Jiawei xiao-yao-san and Guipi wen-dan decoction were the most commonly prescribed treatments for menopausal disorders. Patients were most often treated with a combination of herbal medicine and acupuncture. CONCLUSION: Our study shows that the current prescribed herbal medicines were used for treating menopausal disorders in Korean medicine hospitals. However, the objectivity of the efficacy assessment should be studied further.

12-Year longitudinal study linking within-person changes in work and family transitions and workplace injury risk.

INTRODUCTION: Despite the rich tradition of research on predictors of workplace injury, most studies rely on cross-sectional, between-person designs. Furthermore, prior research has often overlooked the possibility that factors outside the work domain can influence the occurrence of actual injuries at work. To address these limitations, the current study examined the effects of work and family demands on the occurrence of workplace injury. Drawing on the intuition of the work-home resources model (W-HR), we investigated how within-person level changes in demands and resources from both domains influence work injuries over a 12-year period. METHOD: We used 12 years of longitudinal data (N = 7,820) to study the long-term within-person changes in work and family domains and to capture the event of low frequency incidence such as workplace injury. Specifically, we conducted multilevel analyses to study the links between within-person change in time and energy resources both in work and family domains and within-person change in the likelihood of experiencing a workplace injury. RESULTS AND CONCLUSION: The findings showed that within-person changes in work hours, spousal work hours, income and number of children, were significantly associated with changes in the likelihood of experiencing a workplace injury. We conclude with a discussion of implications for theory and future research of workplace injuries. Practical application: The research provided useful insights on the intimate association between work and family domains in the context of safety management.

Nonlinear pth root spectral magnitude scaling beamforming for clinical photoacoustic and ultrasound imaging.

A recently introduced nonlinear pth root delay-and-sum (NL-p-DAS) beamforming (BF) technique for ultrasound (US) and photoacoustic (PA) imaging, achieving better spatial and contrast resolution compared to a conventional delay and sum (DAS) technique. While the method is advantageous for better resolution, it suffers from grainy speckles and dark areas in the image mainly due to the interference of non-sinusoidal functions. In this Letter, we introduce a modified NL-p-DAS technique called nonlinear pth root spectral magnitude scaling (NL-p-SMS), which performs the pth root on the spectral magnitude instead of the temporal amplitude. We evaluated the US and PA images of NL-p-SMS against those of NL-p-DAS by comparing the axial and lateral line profiles, contrasts, and contrast-to-noise ratios (CNRs) in both phantom and in vivo imaging studies with various p values. As a result, we found that the NL-p-SMS has better axial resolution and CNR than the NL-p-DAS, and reduces the grainy speckles and dark area artifacts. We believe that, with this enhanced performance, our proposed approach could be an advancement compared to the existing nonlinear BF algorithms.

Daily effects of continuous ICT demands on work-family conflict: Negative spillover and role conflict.

Growing concerns about intensive information and communication technology (ICT) use led to abundant research on its debilitating effects on employees' abilities to meet family demands. Drawing on the stressor-strain model, we conducted a daily diary study to investigate how different types of daily ICT demands experienced during work hours and after work influence work-family conflict (WFC) in the evening. We collected data from 98 full-time employees (793 day-level observations) for 10 consecutive workdays to understand employees' work-nonwork interface experiences, namely, negative spillover and role conflict. First, we examined a multilevel mediation model to test the negative spillover effect of on-the-job ICT demands on WFC in the evening via negative affect (NA) at the end of the workday. Second, we investigated the effects of off-the-job ICT demands on WFC to provide evidence of role conflict in the nonwork domain. Further, we tested the protective role of boundary control in these phenomena. The multilevel analysis results revealed that different types of ICT demands experienced at work have idiosyncratic impacts on WFC. Also, while extended availability after work hours yields greater WFC, this link was weaker for the employees who perceive high boundary control.

An examination of the temporal order of helping behaviours and emotional exhaustion.

An emerging body of research has investigated the relationship between helping (as a type of organizational citizenship behaviour) and emotional exhaustion (as an aspect of employee health). Research has demonstrated a significant relationship between helping and emotional exhaustion, but the theoretical arguments for the causal direction vary across studies. Specifically, some researchers have conceptualized helping as an outcome of emotional exhaustion, while others have regarded helping as a predictor of emotional exhaustion. This lack of theoretical clarity in directionality hinders the field's ability to summarize existing empirical findings cohesively and elucidate theoretical mechanisms. Therefore, this study attempts to clarify the theoretical directionality between helping and emotional exhaustion using four waves of data collected at 6-month intervals. Autoregressive cross-lagged analyses with auto-correlations revealed that more helping was associated with less future emotional exhaustion from Wave 1 to Wave 2, but from Wave 2 to Wave 3, the directionality reversed, as less emotional exhaustion significantly predicted more future helping, and from Wave 3 to Wave 4, both prediction directions were no longer significant. The findings suggest that helping and emotional exhaustion reciprocally affect each other, though the reciprocal pattern may disappear across time. The present study sheds light on the theoretical relationship between helping and emotional exhaustion, and provides theoretical and practical implications.

3D PHOVIS: 3D photoacoustic visualization studio.

Photoacoustic (PA) imaging (or optoacoustic imaging) is a novel biomedical imaging method in biological and medical research. This modality performs morphological, functional, and molecular imaging with and without labels in both microscopic and deep tissue imaging domains. A variety of innovations have enhanced 3D PA imaging performance and thus has opened new opportunities in preclinical and clinical imaging. However, the 3D visualization tools for PA images remains a challenge. There are several commercially available software packages to visualize the generated 3D PA images. They are generally expensive, and their features are not optimized for 3D visualization of PA images. Here, we demonstrate a specialized 3D visualization software package, namely 3D Photoacoustic Visualization Studio (3D PHOVIS), specifically targeting photoacoustic data, image, and visualization processes. To support the research environment for visualization and fast processing, we incorporated 3D PHOVIS onto the MATLAB with graphical user interface and developed multi-core graphics processing unit modules for fast processing. The 3D PHOVIS includes following modules: (1) a mosaic volume generator, (2) a scan converter for optical scanning photoacoustic microscopy, (3) a skin profile estimator and depth encoder, (4) a multiplanar viewer with a navigation map, and (5) a volume renderer with a movie maker. This paper discusses the algorithms present in the software package and demonstrates their functions. In addition, the applicability of this software to ultrasound imaging and optical coherence tomography is also investigated. User manuals and application files for 3D PHOVIS are available for free on the website (www.boa-lab.com). Core functions of 3D PHOVIS are developed as a result of a summer class at POSTECH, "High-Performance Algorithm in CPU/GPU/DSP, and Computer Architecture." We believe our 3D PHOVIS provides a unique tool to PA imaging researchers, expedites its growth, and attracts broad interests in a wide range of studies.

Super Wide-Field Photoacoustic Microscopy of Animals and Humans In Vivo.

Acoustic-resolution photoacoustic micro-scopy (AR-PAM) is an emerging biomedical imaging modality that combines superior optical sensitivity and fine ultrasonic resolution in an optical quasi-diffusive regime (~1-3 mm in tissues). AR-PAM has been explored for anatomical, functional, and molecular information in biological tissues. Heretofore, AR-PAM systems have suffered from a limited field-of-view (FOV) and/or slow imaging speed, which have precluded them from routine preclinical and clinical applications. Here, we demonstrate an advanced AR-PAM system that overcomes both limitations of previous AR-PAM systems. The new AR-PAM system demonstrates a super wide-field scanning that utilized a 1-axis water-proofing microelectromechanical systems (MEMS) scanner integrated with two linear stepper motor stages. We achieved an extended FOV of 36 ×80 mm2 by mosaicking multiple volumetric images of 36 ×2.5 mm2 with a total acquisition time of 224 seconds. For one volumetric data (i.e., 36 ×2.5 mm2), the B-scan imaging speed over the short axis (i.e., 2.5 mm) was 83 Hz in humans. The 3D volumetric image was also provided by using MEMS mirror scanning along the X-axis and stepper-motor scanning along the Y-axis. The super-wide FOV mosaic image was realized by registering and merging all individual volumetric images. Finally, we obtained multi-plane whole-body in-vivo PA images of small animals, illustrating distinct multi-layered structures including microvascular networks and internal organs. Importantly, we also visualized microvascular networks in human fingers, palm, and forearm successfully. This advanced MEMS-AR-PAM system could potentially enable hitherto not possible wide preclinical and clinical applications.

How to benefit from weekend physical activities: Moderating roles of psychological recovery experiences and sleep.

This study examines the short-term recovery benefits of weekend physical activity on reduced negative affective state (NA) on Monday morning, using a weekly diary method from 70 employees across four weekends (repeated pre- and post-weekend measures). The first hypothesis tests the within-person relationship between weekend physical activity and post-weekend NA. The results of multilevel path analysis show that the main effect of weekend physical activity on reduced Monday NA is not significant. In addition, the study tests weekend recovery experiences (i.e., psychological detachment, relaxation, mastery, and control) and sleep hours as possible moderators. The findings support the moderating effects of psychological detachment and sleep hours. Specifically, weekend physical activity is related to lower Monday NA only if workers achieve high psychological detachment from work during the weekend. If not, their weekend physical activity is associated with higher NA. Also, the benefit of weekend physical activity occurs only when workers sleep longer on the weekend nights. The findings suggest that physical activity has important boundary conditions-psychological detachment and sleep duration-that influence its recovery effects on NA. The complex relationship between exercise and recovery is discussed, along with the implications of the findings for future research.

High-Contrast Imaging of Cholesterol Crystals in Rabbit Arteries Ex Vivo Using LED-Based Polarization Microscopy.

Detection of cholesterol crystals (Chcs) in atherosclerosis disease is important for understanding the pathophysiology of atherosclerosis. Polarization microscopy (PM) has been in use traditionally for detecting Chcs, but they have difficulty in distinguishing Chcs with other crystalline materials in tissue, such as collagens. Thus, most studies using PM have been limited to studying cell-level samples. Although various methods have been proposed to detect Chcs with high specificity, most of them have low signal-to-noise ratios, a high system construction cost, and are difficult to operate due to a complex protocol. To address these problems, we have developed a simple and inexpensive universal serial bus (USB) PM system equipped with a 5700 K cool-white light-emitting diode (LED). In this system, Chcs are shown in a light blue color while collagen is shown in a yellow color. More importantly, the contrast between Chcs and collagens is improved by a factor of 2.3 under an aqueous condition in these PM images. These imaging results are well-matched with the ones acquired with two-photon microscopy (TPM). The system can visualize the features of atherosclerosis that cannot be visualized by the conventional hematoxylin and eosin and oil-red-o staining methods. Thus, we believe that this simple USB PM system can be widely used to identify Chcs in atherosclerosis.