High-Resolution Photoacoustic Microscopy Based on a Transparent Ultrasonic Transducer

We present high-resolution and high-SNR in vivo vascular imaging of the mouse eye, brain, and ear with photoacoustic microscopy (PAM) integrated with a transparent ultrasound transducer. We observed microvessels in a chemically damaged mouse eye. Particularly, the performance of PAM as a comprehensive eye disease diagnosis tool was demonstrated by observing not only corneal neovascularization, but also iris blood vessels and hemorrhages in a cloudy state of the corneal. Second, we delineated in vivo mouse brain vascular imaging at high resolution with a depth encoding. Third, we monitored the ears of tumor-bearing mice to observe for angiogenesis over time. © 2022 SPIE.1

Handheld photoacoustic detector and its potential application for sentinel lymph node sensing

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Recent Advances in Ultrasound and Photoacoustic Analysis for Thyroid Cancer Diagnosis

Abstract Thyroid cancer is one of the most commonly diagnosed cancers worldwide, with a continuously increasing incidence rate in recent decades. Although ultrasonography, which is the current screening method in clinical workflows, has successfully triaged cancerous nodules for biopsy, overdiagnosis has also grown due to the relatively low specificity of the method. Studies are conducted to overcome this overdiagnosis issue by complementing ultrasonography with additional image‐based analysis techniques. This review presents an overview of the current advances in clinical trials using advanced ultrasound (US) and photoacoustic (PA) imaging techniques for thyroid nodules in humans. A summary of initial trials by Doppler US and US elastography to improve the classification accuracy of thyroid nodules is presented. Furthermore, recent PA techniques with multispectral analyses utilizing clinically available machines are explored. By amending the existing ultrasonography, the advanced US and PA techniques can enhance the triaging accuracy by analyzing both structural and functional information of thyroid nodules in vivo

A Deep Learning-Based Model That Reduces Speed of Sound Aberrations for Improved In Vivo Photoacoustic Imaging

Photoacoustic imaging (PAI) has attracted great attention as a medical imaging method. Typically, photoacoustic (PA) images are reconstructed via beamforming, but many factors still hinder the beamforming techniques in reconstructing optimal images in terms of image resolution, imaging depth, or processing speed. Here, we demonstrate a novel deep learning PAI that uses multiple speed of sound (SoS) inputs. With this novel method, we achieved SoS aberration mitigation, streak artifact removal, and temporal resolution improvement all at once in structural and functional in vivo PA images of healthy human limbs and melanoma patients. The presented method produces high-contrast PA images in vivo with reduced distortion, even in adverse conditions where the medium is heterogeneous and/or the data sampling is sparse. Thus, we believe that this new method can achieve high image quality with fast data acquisition and can contribute to the advance of clinical PAI.11Nsciescopu

Functional photoacoustic imaging: from nano- and micro- to macro-scale

Abstract Functional photoacoustic imaging is a promising biological imaging technique that offers such unique benefits as scalable resolution and imaging depth, as well as the ability to provide functional information. At nanoscale, photoacoustic imaging has provided super-resolution images of the surface light absorption characteristics of materials and of single organelles in cells. At the microscopic and macroscopic scales. photoacoustic imaging techniques have precisely measured and quantified various physiological parameters, such as oxygen saturation, vessel morphology, blood flow, and the metabolic rate of oxygen, in both human and animal subjects. This comprehensive review provides an overview of functional photoacoustic imaging across multiple scales, from nano to macro, and highlights recent advances in technology developments and applications. Finally, the review surveys the future prospects of functional photoacoustic imaging in the biomedical field

3D multi-structural foot imaging using dual-modal photoacoustic and ultrasound imaging

We demonstrate an agent-free multi-structural peripheral angiography technique based on the volumetric photoacoustic (PA) and ultrasound (US) images. The volumetric images are obtained by stacking B-mode PA/US images along the elevational direction using a motorized scanner. Three structural features such as skin, bone, and vasculature are extracted from the volumetric US image and combined with the PA microvasculature image to provide a multi-structural vascular image of the foot. For quantitative PA imaging, we have tested the reliability of the PA images. The method can be used to provide a comprehensive anatomic and functional analysis of the extremity. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.1

Dual-pulse photoactivated atomic force microscopy

Photoactivated atomic force microscopy (pAFM), which integrates light excitation and mechanical detection of the deflections of a cantilever tip, has become a widely used tool for probing nanoscale structures. Raising the illuminating laser power is an obvious way to boost the signal-to-noise ratio of pAFM, but strong laser power can damage both the sample and cantilever tip. Here, we demonstrate a dual-pulse pAFM (DP-pAFM) that avoids this problem by using two laser pulses with a time delay. The first laser heats the light absorber and alters the local Gruneisen parameter value, and the second laser boosts the mechanical vibration within the thermal relaxation time. Using this technique, we successfully mapped the optical structures of small-molecule semiconductor films. Of particular interest, DP-pAFM clearly visualized nanoscale cracks in organic semiconductor films, which create crucial problems for small-molecule semiconductors. DP-pAFM opens a promising new optical avenue for studying complex nanoscale phenomena in various research fields.11Nsciescopu

Bi-modal near-infrared fluorescence and ultrasound imaging via a transparent ultrasound transducer for sentinel lymph node localization (vol 47, 393, 2022)

In [1], the funding section was inadvertently left out of the published paper. The article was corrected online on 17 January 2022. © 2022 Optica Publishing Group.11Nsciescopu

Opto-ultrasound biosensor for wearable and mobile devices: realization with a transparent ultrasound transducer

Mobile and wearable healthcare electronics are widely used for measuring bio-signals using various fusion sensors that employ photoplethysmograms, cameras, microphones, ultrasound (US) sensors, and accelerometers. However, the consumer demand for small form factors has significantly increased as the integration of multiple sensors is difficult in small mobile or wearable devices. This study proposes two novel opto-US sensors, namely (1) a wearable photoplethysmography (PPG)-US device and (2) a PPG sensor built-in mobile smartphone with a US sensor, seamlessly integrated using a transparent ultrasound transducer (TUT). The TUT exhibits a center frequency of 6 MHz with a 50% bandwidth and 82% optical transparency in visible and near-infrared regions. We developed an integrated wearable PPG-US device to demonstrate its feasibility and coupled the TUT sensor with a smartphone. We measured the heart rates optically and acoustically in human subjects and quantified the oxygen saturation optically by passing light through the TUT. The proposed proof-of-concept is a novel sensor fusion for mobile and wearable devices that require a small form factor and aim to improve digital healthcare. The results of this study can form the basis for innovative developments in sensor-based high-tech industrial applications, such as automobiles, robots, and drones, in addition to healthcare applications. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement11Nsciescopu

Super-resolution Photoacoustic Microscopy Using a Localized Near-field of a Plasmonic Nanoaperture: A Three-dimensional Simulation Study

Super-resolution microscopy has been increasingly important to delineate nanoscale biological structures or nanoparticles. With these increasing demands, several imaging modalities, including super-resolution fluorescence microscope (SRFM) and electron microscope (EM), have been developed and commercialized. These modalities achieve nanoscale resolution, however, SRFM cannot image without fluorescence, and sample preparation of EM is not suitable for biological specimens. To overcome those disadvantages, we have numerically studied the possibility of super-resolution photoacoustic microscopy (SR-PAM) based on near-field localization of light. Photoacoustic (PA) signal is generally acquired based on optical absorption contrast; thus it requires no agents or pre-processing for the samples. The lateral resolution of the conventional photoacoustic microscopy is limited to similar to 200 nm by diffraction limit, therefore reducing the lateral resolution is a major research impetus. Our approach to breaking resolution limit is to use laser pulses of extremely small spot size as a light source. In this research, we simulated the PA signal by constructing the three dimensional SR-PAM system environment using the k-Wave toolbox. As the light source, we simulated ultrashort light pulses using geometrical nanoaperture with near-field localization of surface plasmons. Through the PA simulation, we have successfully distinguish cuboids spaced 3 nm apart. In the near future, we will develop the SR-PAM and it will contribute to biomedical and material sciences.1