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Noncontact photoacoustic angiography with an air-coupled ultrasonic transducer for evaluation of burn injury
摘要： In vivo identi?cation of viable and thermally coagulated blood in a burn wound can be used to pro?le the type, extent, and site of the burn, thus assisting the removal of necrotic tissue in preparation for skin grafts. Recently, intensive research on photoacoustic imaging (PAI) has been conducted to evaluate burn injury. However, most PAI systems usually take the approach of direct physical contact of an acoustic detector or an impedance matching medium with the vulnerable burned skin, which exposes signi?cant limitations on the diagnosis of burn injuries. Here, we present a noncontact PAI system, based on a custom designed air-coupled ultrasonic transducer, enabling in vivo noncontact vasculature to be imaged without contrast agents. Using the natural difference in light absorption between coagulated and non-coagulated blood at the wavelength of 532 nm, this PAI system possesses an immanent advantage to discriminate viable and thermally coagulated blood in burned tissues. Phantom experiments and burned rabbit’s skin imaging have been implemented to demonstrate that the noncontact PAI technique could be valuable in the adjuvant diagnosis and observation of burns.
关键词： air-coupled ultrasonic transducer,noncontact,photoacoustic imaging,burn injury,vasculature
更新于2025-09-11 14:15:04
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Biodegradable Bi <sub/>2</sub> O <sub/>2</sub> Se Quantum Dots for Photoacoustic Imaging-Guided Cancer Photothermal Therapy
摘要： As new 2D layered nanomaterials, Bi2O2Se nanoplates have unique semiconducting properties that can benefit biomedical applications. Herein, a facile top-down approach for the synthesis of Bi2O2Se quantum dots (QDs) in a solution is described. The Bi2O2Se QDs with a size of 3.8 nm and thickness of 1.9 nm exhibit a high photothermal conversion coefficient of 35.7% and good photothermal stability. In vitro and in vivo assessments demonstrate that the Bi2O2Se QDs possess excellent photoacoustic (PA) performance and photothermal therapy (PTT) efficiency. After systemic administration, the Bi2O2Se QDs accumulate passively in tumors enabling efficient PA imaging of the entire tumors to facilitate imaging-guided PTT without obvious toxicity. Furthermore, the Bi2O2Se QDs which exhibit degradability in aqueous media not only have sufficient stability during in vivo circulation to perform the designed therapeutic functions, but also can be discharged harmlessly from the body afterward. The results reveal the great potential of Bi2O2Se QDs as a biodegradable multifunctional agent in medical applications.
关键词： biodegradable,Bi2O2Se,2D layered materials,photothermal agents,photoacoustic imaging
更新于2025-09-11 14:15:04
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Impact of depth-dependent optical attenuation on wavelength selection for spectroscopic photoacoustic imaging
摘要： An optical wavelength selection method based on the stability of the absorption cross-section matrix to improve spectroscopic photoacoustic (sPA) imaging was recently introduced. However, spatially-varying chromophore concentrations cause the wavelength- and depth-dependent variations of the optical fluence, which degrades the accuracy of quantitative sPA imaging. This study introduces a depth-optimized method that determines an optimal wavelength set minimizing an inverse of the multiplication of absorption cross-section matrix and fluence matrix to minimize the errors in concentration estimation. This method assumes that the optical fluence distribution is known or can be attained otherwise. We used a Monte Carlo simulation of light propagation in tissue with various depths and concentrations of deoxy-/oxy-hemoglobin. We quantitatively compared the developed and current approaches, indicating that the choice of wavelength is critical and our approach is effective especially when quantifying deeper imaging targets.
关键词： Spectroscopic photoacoustic imaging,Spectral unmixing,Optimal wavelength selection,Oxygen saturation estimation
更新于2025-09-11 14:15:04
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1064 nm acoustic resolution photoacoustic microscopy
摘要： Photoacoustic imaging is a non-invasive imaging technique having the advantages of high optical contrast and good acoustic resolution at improved imaging depths. Light transport in biological tissues is mainly characterized by strong optical scattering and absorption. Photoacoustic microscopy is capable of achieving high resolution images at greater depth compared to conventional optical microscopy methods. In this work, we have developed a high-resolution, acoustic resolution photoacoustic microscopy (AR-PAM) system in the near infra-red (NIR) window II (NIR-II, e.g., 1064 nm) for deep tissue imaging. Higher imaging depth is achieved as the tissue scattering at 1064 nm is lesser compared to visible or near infrared window-I (NIR-I). Our developed system can provide a lateral resolution of 130 μm, axial resolution of 57 μm, and image up to 11 mm deep in biological tissues. This 1064-AR-PAM system was used for imaging sentinel lymph node and the lymph vessel in rat. Urinary bladder of rat filled with black ink was also imaged to validate the feasibility of the developed system to study deeply seated organs.
关键词： photoacoustic imaging,deep tissue imaging,urinary bladder,sentinel lymph node,Acoustic resolution photoacoustic microscopy
更新于2025-09-10 09:29:36
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Photoacoustic microscopy for evaluating a lipopolysaccharide-induced inflammation model in mice
摘要： Photoacoustic microscopy (PAM) is a noninvasive imaging technique and is excellent to study structural and functional changes in the microcirculation. In this work, a lipopolysaccharide (LPS)-induced inflammation model in mice is noninvasively evaluated by PAM. PAM is used to image the microvascular structural changes in mice for 8 hours after the LPS with different concentrations is applied. Quantitative analysis of five vessel parameters is conducted, which shows that the rate of reduction in microvasculature is highly dependent on the applied LPS concentrations. For low-concentration LPS, changes in the microvasculature are not obvious over the observation period, while for high-concentration LPS, quick and marked reduction in the microvasculature is observed. In addition, changes in capillaries are more significant than those in relatively large vessels. The results show that PAM is able to evaluate the inflammation mouse model by studying structural (and potentially functional) changes in the microcirculation. Further, PAM may have potential for early intervention and treatment plan optimization of sepsis by monitoring the microcirculation and inflammatory response.
关键词： inflammatory response,photoacoustic imaging,photoacoustic microscopy,sepsis,microcirculation
更新于2025-09-10 09:29:36
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Investigation on Reconstruction for Frequency Domain Photoacoustic Imaging via TVAL3 Regularization Algorithm
摘要： Photoacoustic imaging (PAI) has been widely investigated by researchers from a range of areas. According to the differences between excitation laser sources, PAI can be categorized into two main types, namely the time-domain and frequency-domain PAI. Although the frequency-domain approach is more portable and economic than the other alternative, the low intensity of excitation source may lead to a lower signal-to-noise ratio (SNR). This paper aiming to propose the suitable scheme for image reconstruction, we focus on the model-based PAI system and make great efforts to reduce the impact of noise algorithmically. Three regularization algorithms, i.e., Least Square QR-factorization, Tikhonov, and Total Variation minimization by Augmented Lagrangian and alternating direction algorithms (TVAL3) are studied. By choosing three important parameters as criteria, i.e., the peak SNR, image quality index, and time consumption during different situations, the most effective regularization algorithm amongst has been selected. Based on simulation results and detailed discussions, TVAL3 algorithm performs better than the other two for model-based signal reconstruction. The result is pivotal for effective PAI in high quality and highly ef?cient biomedical tomography and microimaging.
关键词： imaging parameters,Photoacoustic imaging (PAI),regularization algorithms,white Gaussian noise (WGN),stochastic noise (SN)
更新于2025-09-10 09:29:36
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Hybrid multi-wavelength photoacoustic imaging
摘要： Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength-tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this paper, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on combination of single-wavelength pulsed and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling laser illumination sequence (pulse-CW-pulse), and extracting the PA signals’ difference before and after heating of CW lasers, the optical absorption property of multi-wavelength CW lasers could be obtained. Compared with conventional PA imaging, the proposed hPAI shows much lower system cost due to the usage of single-wavelength pulsed laser and cheap CW lasers. Theoretical analysis and analytical model are presented in this paper, followed by proof-of-concept experimental results.
关键词： photoacoustic imaging,continuous-wave laser,multi-wavelength,pulsed laser,hybrid imaging
更新于2025-09-10 09:29:36
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Comparative Quantification of Arterial Lipid by Intravascular Photoacoustic-Ultrasound Imaging and Near-Infrared Spectroscopy-Intravascular Ultrasound
摘要： Intravascular photoacoustic-ultrasound (IVPA-US) imaging and near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) are two hybrid modalities that detect arterial lipid, with comparison necessary to understand the relative advantages of each. We performed in vivo and ex vivo IVPA-US imaging of the iliac arteries of Ossabaw swine with metabolic syndrome (MetS) and lean swine to investigate sensitivity for early-stage atherosclerosis. We repeated imaging ex vivo with NIRS-IVUS for comparison to IVPA-US and histology. Both modalities showed significantly greater lipid in MetS vs. lean swine, but only IVPA-US localized the lipid as perivascular. To investigate late-stage atherosclerosis, we performed ex vivo IVPA-US imaging of a human coronary artery with comparison to NIRS-IVUS and histology. Two advanced fibroatheromas were identified, with agreement between IVPA-measured lipid area and NIRS-derived lipid content. As confirmed histologically, IVPA-US has sensitivity to detect lipid content similar to NIRS-IVUS and provides additional depth resolution, enabling quantification and localization of lipid cores within plaques.
关键词： Swine,Lipid core plaque,Near-infrared spectroscopy,Human,Intravascular imaging,Photoacoustic imaging,Atherosclerosis,Perivascular adipose tissue
更新于2025-09-10 09:29:36
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An FPGA-Based Backend System for Intravascular Photoacoustic and Ultrasound Imaging
摘要： The integration of intravascular ultrasound (IVUS) and intravascular photoacoustic (IVPA) imaging produces an imaging modality with high sensitivity and specificity which is particularly needed in interventional cardiology. Conventional side-looking IVUS imaging with a single-element ultrasound (US) transducer lacks forward-viewing capability, which limits the application of this imaging mode in intravascular intervention guidance, Doppler-based flow measurement, and visualization of nearly or totally blocked arteries. For both side-looking and forward-looking imaging, the necessity to mechanically scan the US transducer limits the imaging frame rate, and therefore array-based solutions are desired. In this paper, we present a low-cost, compact, high-speed, and programmable imaging system based on a field-programmable gate array (FPGA) suitable for dual-mode forward-looking IVUS/IVPA imaging. The system has 16 US transmit and receive channels and functions in multiple modes including interleaved photoacoustic (PA) and US imaging, hardware-based high-frame-rate US imaging, software-driven US imaging, and velocity measurement. The system is implemented in the register-transfer level, and the central system controller is implemented as a finite state machine. The system was tested with a capacitive micromachined ultrasonic transducer (CMUT) array. A 170-frames-per-second (FPS) US imaging frame rate is achieved in the hardware-based high-frame-rate US imaging mode while the interleaved PA and US imaging mode operates at a 60-FPS US and a laser-limited 20-FPS PA imaging frame rate. The performance of the system benefits from the flexibility and efficiency provided by low-level implementation. The resulting system provides a convenient backend platform for research and clinical IVPA and IVUS imaging.
关键词： software/hardware co-design,velocity measurement,ultrasound imaging,Photoacoustic imaging,FPGA,data acquisition,finite state machine
更新于2025-09-10 09:29:36
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Indocyanine Green labeling for optical and photoacoustic imaging of Mesenchymal Stem Cells after in vivo transplantation
摘要： The transplantation of Mesenchymal Stem Cells (MSCs) holds great promise for the treatment of a plethora of human diseases, but new non-invasive procedures are needed to monitor the cell fate in vivo. Already largely used in medical diagnostics, the fluorescent dye Indocyanine Green (ICG) is an established dye to track limited numbers of cells by optical imaging, but it can be visualized also by Photoacoustic Imaging (PAI), which provides a higher spatial resolution than pure near infrared fluorescence imaging (NIRF). Because of its successful use in clinical and preclinical examinations, we chose ICG as PAI cell labeling agent. Optimal incubation conditions were defined for an efficient and clinically translatable MSC labeling protocol, such that no cytotoxicity or alterations of the phenotypic profile were observed, and a consistent intracellular uptake of the molecule was achieved. Suspensions of ICG-labeled cells were both optically and optoacoustically detected in vitro, revealing a certain variability in the photoacoustic spectra acquired by varying the excitation wavelength from 680 to 970 nm. Intramuscular engraftments of ICG-labeled MSCs were clearly visualized by both PAI and NIRF over few days after transplantation in the hindlimb of healthy mice, suggesting that the proposed technique retains a considerable potential in the field of transplantation-focused research and therapy.
关键词： Indocyanine Green,Near Infrared Fluorescence Imaging,Photoacoustic Imaging,Cell tracking,Stem Cells
更新于2025-09-10 09:29:36