Ultraviolet photoacoustic microscopy (UV-PAM) has emerged as a promising medical imaging technique for alternative histopathology, relying on the inherent optical absorption of DNA/RNA. However, traditional UV-PAM faces resolution challenges compared to clinical histological methods, limiting the observation of cellular structures. This limitation stems from the constraints of conventional reflection-mode UV-PAM systems, utilizing opto-ultrasound beam combiners or ring-shaped ultrasound transducers. These components impose constraints on numerical apertures (NA), thereby limiting spatial resolution. On the flip side, transmission-mode UV-PAM encounters difficulties in imaging thick specimens due to signal attenuation. In this study, we introduce an innovative solution – the development of an ultraviolet-transparent ultrasound transducer (UV-TUT) – overcoming these limitations and enabling high-resolution UV-PAM system. The UV-TUT significantly enhances both NA and lateral resolution, outperforming previous reflection-mode UV-PAM systems. With an impressive light transmission efficiency in the UV region and sensitivity four times greater than traditional ring-shaped ultrasound transducers, the UV-TUT lays the foundation for improved imaging capabilities. Leveraging the capabilities of the UV-TUT, we exploited a UV-PAM system, showcasing superior performance for imaging mouse brain tissue sections compared to conventional opto-ultrasound beam combiner-based UV-PAM. Furthermore, our application of photoacoustic histopathology on uterine cancer tissue sections demonstrated image quality comparable to microscopy images, providing valuable insights for accurate histopathological analysis. This work signifies a significant advancement in UV-PAM system, holding the promise to enhance the clinical utility of alternative histopathology with unprecedented resolution and imaging capabilities.
Blood glucose (BG) level is one of the cardiovascular indicators that must be kept within a certain range. The importance of BG management is rising as clinical results have recently been reported that a vicious cycle of spikes and drops in BG levels, called a BG roller coaster, causes vascular dysfunction, increasing the risk of cardiovascular diseases. To investigate how elevated BG affects blood vessels, we photoacoustically monitored time-dependent changes in vascular diameters after intraperitoneal glucose injection in normal rats. Every five minutes, vascular networks were visualized using high-speed photoacoustic microscopy, their vascular diameters were calculated, and finally, the changes in vascular diameter were quantified. Arterioles constricted as the BG level increased, and then recovered as the BG level saturated. In the meantime, venules maintained their diameters. These results show that sudden transition to a hyperglycemic state may cause the arterioles to be constricted. The first direct observation of arterioles’ rapid vasoconstriction due to acute hyperglycemia and spontaneous recovery in this study would be used as meaningful evidence to study the effects of BG level on the cardiovascular system.
Fusion sensors, including photoplethysmograms, cameras, microphones, ultrasound sensors, and accelerometers, are commonly used in mobile and wearable healthcare electronics to measure bio-signals. However, small size is in high demand, but integrating multiple sensors into small mobile or wearable devices is challenging. This study presents two new opto-ultrasound sensors: (1) a wearable device with both photoplethysmography (PPG) and ultrasound (US) capabilities, and (2) a PPG sensor built-in mobile smartphone with an integrated US sensor using a transparent ultrasound transducer (TUT). The TUT has a center frequency of 6 MHz, a 50% bandwidth, and is 82% transparent in the visible and near-infrared ranges. To demonstrate its potential, we developed a wearable device combining photoplethysmography and ultrasound capabilities and fused the TUT to the smartphone. We used this setup to measure heart rates optically and acoustically in human subjects and to calculate oxygen saturation optically through the TUT. This proof-of-concept represents a unique fusion of sensors for small mobile and wearable devices that aim to improve digital healthcare. The results of this research can serve as a basis for innovative development of sensor-based high-tech industrial applications such as healthcare, automobiles, robots, and drones.
Corticosteroids are commonly used medications for dermatological diseases. The main mechanisms of corticosteroids are vasoconstriction and anti-inflammatory. In medical field, its effectiveness is determined based on the degree of skin whitening caused by vasoconstriction. In this study, we first quantitatively evaluate the vasoconstriction induced by corticosteroids using photoacoustic microscopy (PAM). We longitudinally monitor vascular density and observe vasoconstriction by corticosteroids. Further, the changes in vascular density are quantified in each skin layer. From these results, we believe that PAM could potentially be a useful evaluation tool to predict the effectiveness of the corticosteroids in dermatology.
SignificanceCorticosteroids—commonly prescribed medications for skin diseases—inhibit the secretion of vasodilators, such as prostaglandin, thereby exerting anti-inflammatory action by constricting capillaries in the dermis. The effectiveness of corticosteroids is determined by the degree of vasoconstriction followed by skin whitening, namely, the blanching effect. However, the current method of observing the blanching effect indirectly evaluates the effects of corticosteroids.AimIn this study, we employed optical-resolution photoacoustic (PA) microscopy (OR-PAM) to directly visualize the blood vessels and quantitatively evaluate vasoconstriction.ApproachUsing OR-PAM, the vascular density in mice skin was monitored for 60 min after performing each experimental procedure for four groups, and the vasoconstriction was quantified. Volumetric PA data were segmented into the papillary dermis, reticular dermis, and hypodermis based on the vascular characteristics obtained through OR-PAM. The vasoconstrictive effect of each skin layer was quantified according to the dermatological treatment method.ResultsIn the case of corticosteroid topical application, vasoconstriction was observed in the papillary (56.4 ± 10.9 % ) and reticular (45.1 ± 4.71 % ) dermis. For corticosteroid subcutaneous injection, constriction was observed solely in the reticular (49.5 ± 9.35 % ) dermis. In contrast, no vasoconstrictions were observed with nonsteroidal topical application.ConclusionsOur results indicate that OR-PAM can quantitatively monitor the vasoconstriction induced by corticosteroids, thereby validating OR-PAMs potential as a practical evaluation tool for predicting the effectiveness of corticosteroids in dermatology.
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