We present a novel implementation of high-speed photoacoustic microscopy with an ultrawide field of view (FOV). Existing photoacoustic microscopy systems have limitations in resolution, FOV, and speed. To address these challenges, we improved our previous immersible-polygon-scanner-based photoacoustic microscopy and developed a dual-view photoacoustic microscopy system using two facets of the same scanner. The system has achieved high resolutions of ~10 µm (lateral) and 35 µm (axial) with a B-scan rate of 500 Hz. We have demonstrated the imaging performance on freely-moving zebrafish and hypoxia challenge of a pair of mice.
Traditional deconvolution methods can improve the spatial resolution of photoacoustic computed tomography (PACT) systems but are often sensitive to noise. We propose a novel approach to enhance the resolution of PACT, by modeling the system’s point spread function (PSF) and performing deep-learning-based deconvolution. We train a robust deep learning model without the need for ground truth, using a self-supervised method on a mixed dataset of simulation, phantom, and in vivo data, in combination with various data augmentation techniques. We demonstrate that our deep learning deconvolution achieves superior spatial resolution, image contrast, and artifact suppression, when compared to traditional deconvolution methods.
We present an experimental ischemic stroke study using our newly-developed multimodal imaging system that integrates photoacoustic computed tomography (PACT), high-frequency ultrasound imaging, and acoustic angiographic tomography, or PAUSAT. PAUSAT is capable of three-dimensional high-frequency ultrasound imaging of the brain morphology, micro-bubble-enabled acoustic angiography of the brain blood perfusion, and multispectral PACT of brain blood oxygenation. PAUSAT was able to clearly show the brain vascular changes after ischemic stroke, including significantly reduced blood perfusion and oxygenation. Using PAUSAT, stroke infarct volume was reliably measured. The PAUSAT results were confirmed by laser speckle imaging and histology.
Our study exploits Rhodopseudomonas palustris BphP1 bacterial phytochrome to generate a near-infrared (NIR) loxP-BphP1 photoswitchable transgenic mouse model that enables deep-tissue optogenetics and photoacoustic tomography (PAT). BphP1 incorporates biliverdin and reversibly switches between the ground state and activated state, with distinct optical absorption spectra in the NIR window. We validated the optogenetic performance of the BphP1-encoded mouse model to trigger gene transcription, and demonstrated its superior capability of deep-tissue optogenetics. Then, taking advantage of BphP1's photoswitching properties, we can suppress the non-switching signals from background blood and improve the molecular detection sensitivity of PAT by three orders of magnitude.
A unique deep learning network, Deep-E, is proposed, which utilizes 2D training data to solve a 3D problem. The novelty of this simulation method is to generate a 2D matrix in the axial-elevational plane using an arc-shaped transducer element, instead of generating a 3D matrix using the linear transducer arrays. Deep-E exhibited significant resolution improvement on the in vivo human breast data. In addition, we were able to restore deeper vascular structures and remove the noise artifact. We envision that Deep-E will have a significant impact in linear-array-based photoacoustic imaging studies by providing high-speed and high-resolution image enhancement.
Optical-resolution photoacoustic microscopy (OR-PAM) can image biological tissues at micrometer level resolution. However, the imaging speed of traditional OR-PAM is often too slow for capturing dynamic information. In this work, we demonstrate a high-speed OR-PAM system using a water-immersible two-axis torsion-bending scanner, in which the fast axis employs the torsion scanning while the slow axis works at the bending mode. The system has achieved a cross-sectional frame rate of 400 Hz, and a volumetric imaging speed of 1 Hz over a field of view of 1.5 × 2.5 mm2. We have demonstrated high-speed OR-PAM of fast hemodynamic changes in vivo.
We present a new functional photoacoustic microscopy system with the highest imaging speed and ultrawide field of view. The high imaging speed is enabled by a 12-facets polygon for fast scanning and a Raman-shifter system for fast dual-wavelength measurement of oxygen saturation in vivo. we imaged the dynamic functions in mouse brains in response to hypoxia challenge, sodium nitroprusside (SNP), and ischemic stroke. The experimental results have demonstrated that the high-speed photoacoustic microscopy system can be a powerful tool for studying the rapid hemodynamics in the mouse brains of a wide range of pathological and physiological models.
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