Photoacoustic Imaging Research Articles

Técnicas de Imagenología Óptica Aplicadas a Dermatología

The use of optical imaging technology in recent years has improved diagnostics in the dermatology area. The techniques that can be named are optical coherence tomography, Raman spectroscopy, and optoacoustic imaging. Each technique has applications in general medicine and dermatology but with their respective limitations and focus. This work reviews the imaging techniques in general, prioritizing the theoretical background that allows the technique to operate, and then an image example obtained with the technique is shown. Then, an extensive review of the techniques of hyperspectral imaging and hyperspectral polarized dermatoscope is made. Finally, we talk about new trends in optical imaging future.

Robotic Repositioning of Photoacoustic Tomography for Reproducible Long-Term Monitoring of Peripheral Artery In Vivo

Robotic Repositioning of Photoacoustic Tomography for Reproducible Long-Term Monitoring of Peripheral Artery <i>In Vivo</i>

Fourier Finite Difference Migration Based Heterogeneous Photoacoustic Imaging in Irregular Layered Media

Fourier Finite Difference Migration Based Heterogeneous Photoacoustic Imaging in Irregular Layered Media

Skin Imaging Using Optical Coherence Tomography and Photoacoustic Imaging: A Mini-Review

This article provides an overview of the progress made in skin imaging using two emerging imaging modalities, optical coherence tomography (OCT) and photoacoustic imaging (PAI). Over recent years, these technologies have significantly advanced our understanding of skin structure and function, offering non-invasive and high-resolution insights previously unattainable. The review begins by briefly describing the fundamental principles of how OCT and PAI capture images. It then explores the evolving applications of OCT in dermatology, ranging from diagnosing skin disorders to monitoring treatment responses. This article continues by briefly describing the capabilities of PAI imaging, and how PAI has been used for melanoma and non-melanoma skin cancer detection and characterization, vascular imaging, and more. The third section describes the development of multimodal skin imaging systems that include OCT, PAI, or both modes. A comparative analysis between OCT and PAI is presented, elucidating their respective strengths, limitations, and synergies in the context of skin imaging.

An AND-Gate Photoacoustic Probe for Cys and H2S Precise Photoacoustic Sensing in Localized Tumors.

Photoacoustic (PA) tomography has shown many promising aspects in noninvasive and precise imaging of deep-localized biomarkers. However, these traditional single-locked PA probes always face challenges in precise PA imaging with high specificity. Here, we report a novel AND-gate photoacoustic probe, BAE, to improve tumor imaging accuracy via the combination of two tumor-associated biomarkers, cysteine (Cys) and hydrogen sulfide (H2S). Only when Cys and H2S are concurrently introduced into the detection system does the absorption of BAE red-shift from the initial 680 to 810 nm, thereby showing a 5.29-fold enhancement in its PA signal at 810 nm. The good specificity of BAE is proven, since an obvious PA signal could be observed only in the solution containing both Cys and H2S and was not affected by other reactive sulfur species. After being taken up by tumors with the assistance of a nanomicelle, the AND-gate PA probe BAE was applied for dynamic real-time monitoring of Cys and H2S in vivo, achieving precise identification of tumors. This AND-gate PA probe provides a potential technical tool for precise sensing analysis of deep-seated diseases.

A “Transformers”‐like nanochain for precise navigation and efficient cancer treatment

AbstractIntegrated multimodal imaging in theranostics nanomaterials offers extensive prospects for precise and noninvasive cancer treatment. Precisely controlling the structural evolution of plasmonic nanoparticles is crucial in the development of photothermal agents. However, previous successes have been limited to static assemblies and single‐component structures. Here, an activatable plasmonic theranostics system utilizing self‐assembled 1D silver‐coated gold nanochains (1D nanochains) is presented for precise tumor diagnosis and effective treatment. The absorbance of the adaptable core–shell chain structure can shift from visible to near‐infrared (NIR) regions due to the fusion between nearby Au@Ag nanoparticles induced by elevated H2O2 levels in the tumor microenvironment (TME), resulting in the creation of a novel 3D aggregates with strong NIR absorption. With a high photothermal conversion efficiency of 60.2% at 808 nm, nanochains utilizing the TME‐activated characteristics show remarkable qualities for photoacoustic imaging and significantly limit tumor growth in vivo. This study may pave the way for precise tumor diagnosis and treatment through customizable, optically tunable adaptive plasmonic nanostructures.

Ultrasmall copper-based nanoplatforms for NIR-II light-triggered photothermal/ photodynamic and amplified nanozyme catalytic therapy of hypoxic tumor

The clinical applications of the photothermal therapy (PTT) and photodynamic therapy (PDT) are restricted by the limited tissue penetration depth of excitation light, while the enzyme catalysis therapy is hindered on account of the low treatment efficiency. Herein, we modify artificial nanozyme Pt nanoparticles on the surface of CuCo2S4 nanoparticles to prepare ultrasmall copper-based ternary bimetallic chalcogenides CuCo2S4-Pt-PEG nanocomposites for PTT/PDT/enzyme catalysis synergistic therapy. The as-fabricated CuCo2S4-Pt-PEG nanocomposites display peroxidase (POD)-like and catalase (CAT)-like activities, which can catalyze hydrogen peroxide to emerge highly toxic hydroxyl radicals and oxygen, respectively. The integration of Pt nanozyme significantly improves the POD-like and CAT-like activity of CuCo2S4 −PEG that can produce more hydroxyl radicals and oxygen to improve the effects of PDT. Furthermore, the nanocomposites exhibit outstanding photothermal properties derived from the enhanced photothermal conversion efficiency (η = 78.46 %) exposed to 1064 nm NIR-II light irradiation with a low power density (0.8 W cm−2). In particular, the photothermal performance of CuCo2S4-Pt-PEG significantly enhances the enzyme-like activity. Additionally, the T1-weighted magnetic resonance and photoacoustic imaging endow CuCo2S4-Pt-PEG with the advantages of guiding the treatment process. The synergistic treatment demonstrates significant anticancer treatment efficiency while also elicits immune response that suppressed metastasis. This study could further promote the application of ternary bimetallic chalcogenides in cancer diagnosis and treatment.

Engineering Cyanine- and Hemicyanine-Based Probes for Optical Imaging of Kidney Diseases.

Molecular optical probes play pivotal roles in in vivo imaging of biomarkers associated to kidney diseases. Relying on structural tunability and high fluorescence quantum yields, versatile optical probes have been constructed on cyanine or hemicyanine-based scaffold in recent years. This review summaries the recent progress on the development of optical probes for imaging of kidney diseases, particularly through near-infrared fluorescence, chemiluminescence and photoacoustic imaging modalities. The chemical design and sensing mechanisms are discussed along with applications in the detection of renal cell carcinoma and acute kidney injury. This progress provides insights and directions for the development of next generation kidney-targeted probes and for pushing their further applications in preclinical and clinical research.

Photoacoustic lifetime oxygen imaging of radiotherapy-induced tumor reoxygenation In Vivo

PurposeEarly detection and diagnosis of cancer is critical for achieving positive therapeutic outcomes. Biomarkers that can provide clinicians with clues to the outcome of a given therapeutic course are highly desired. Oxygen is a small molecule that is nearly universally present in biological tissues and plays a critical role in the effectiveness of radiotherapies by reacting with DNA radicals and subsequently impairing cellular repair of double strand breaks.Techniques for measuring oxygen in biological tissues often use blood oxygen saturation to approximate the oxygen partial pressure in surrounding tissues despite the complex, nonlinear, and dynamic relationship between these two separate oxygen populations. Methods and materialsWe combined a directly oxygen-sensitive, tumor-targeted, chemical contrast nanoelement with the photoacoustic lifetime-based (PALT) oxygen imaging technique to obtain image maps of oxygen in breast cancer tumors in vivo. The oxygen levels of patient-derived xenografts in a mouse model were characterized before and after a course of radiotherapy. ResultsWe show that, independent of tumor size, radiotherapy induced an increase in the overall oxygenation levels of the tumor. Further, this increase in the oxygenation of the tumor significantly correlated with a positive response to radiotherapy, as demonstrated by a reduction in tumor volume over the twenty-day monitoring period following therapy and histological staining. ConclusionOur PALT imaging presented here is simple, fast, and non-invasive. Facilized by the PALT approach, imaging of tumor reoxygenation may be utilized as a simple, early indicator for evaluating cancer response to radiotherapy. Further characterization of the reoxygenation degree, temporal onset, and possible theragnostic implications are warranted.

Near-Infrared Absorbing BODIPY-Xanthene Hybrids for Multiplexed Photoacoustic Imaging.

We report a series of ethenylene-bridged D-π-A BODIPY-xanthene hybrid dyes with precisely regulated absorption bands ranging from the far-red to the near-infrared region (NIR, 700-1000 nm) through rational molecular design. These dyes have excellent photoacoustic properties, and their biocompatibility can be significantly improved by facilely introducing water-soluble groups. In vivo two-channel multiplexed photoacoustic imaging demonstrated their high-resolution imaging capabilities, making them promising candidates for future NIR bioimaging applications.

Acceleration of the Iterative Procedure for Correction of Optoacoustic Images

Acceleration of the Iterative Procedure for Correction of Optoacoustic Images

Endogenous Melanin and Hydrogen-Based Specific Activated Theranostics Nanoagents: A Novel Multi-Treatment Paradigm for Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by excessive proliferation of rheumatoid arthritis synovial fibroblasts (RASFs) and accumulation of inflammatory cytokines. Exploring the suppression of RASFs and modulation of the RA microenvironment is considered a comprehensive strategy for RA. In this work, specifically activated nanoagents (MAHI NGs) based on the hypoxic and weakly acidic RA microenvironment are developed to achieve a second near-infrared fluorescence (NIR-II FL)/photoacoustic (PA) dual-model imaging-guided multi-treatment. Due to optimal size, the MAHI NGs passively accumulate in the diseased joint region and undergo rapid responsive degradation, precisely releasing functionalized components: endogenous melanin-nanoparticles (MNPs), hydrogen gas (H2), and indocyanine green (ICG). The released MNPs play a crucial role in ablating RASFs within the RA microenvironment through photothermal therapy (PTT) guided by accurate PA imaging. However, the regional hyperthermia generated by PTT may exacerbate reactive oxygen species (ROS) production and inflammatory response following cell lysis. Remarkably, under the acidic microenvironment, the controlled release of H2 exhibits precise synergistic antioxidant and anti-inflammatory effects with MNPs. Moreover, the ICG, the second near-infrared dye currently approved for clinical use, possesses excellent NIR-II FL imaging properties that facilitate the diagnosis of deep tissue diseases and provide the right time-point for PTT.

Extractor-attention-predictor network for quantitative photoacoustic tomography

Quantitative photoacoustic tomography (qPAT) holds great potential in estimating chromophore concentrations, whereas the involved optical inverse problem, aiming to recover absorption coefficient distributions from photoacoustic images, remains challenging. To address this problem, we propose an extractor-attention-predictor network architecture (EAPNet), which employs a contracting–expanding structure to capture contextual information alongside a multilayer perceptron to enhance nonlinear modeling capability. A spatial attention module is introduced to facilitate the utilization of important information. We also use a balanced loss function to prevent network parameter updates from being biased towards specific regions. Our method obtains satisfactory quantitative metrics in simulated and real-world validations. Moreover, it demonstrates superior robustness to target properties and yields reliable results for targets with small size, deep location, or relatively low absorption intensity, indicating its broader applicability. The EAPNet, compared to the conventional UNet, exhibits improved efficiency, which significantly enhances performance while maintaining similar network size and computational complexity.

Compressed Sensing for Biomedical Photoacoustic Imaging: A Review.

Photoacoustic imaging (PAI) is a rapidly developing emerging non-invasive biomedical imaging technique that combines the strong contrast from optical absorption imaging and the high resolution from acoustic imaging. Abnormal biological tissues (such as tumors and inflammation) generate different levels of thermal expansion after absorbing optical energy, producing distinct acoustic signals from normal tissues. This technique can detect small tissue lesions in biological tissues and has demonstrated significant potential for applications in tumor research, melanoma detection, and cardiovascular disease diagnosis. During the process of collecting photoacoustic signals in a PAI system, various factors can influence the signals, such as absorption, scattering, and attenuation in biological tissues. A single ultrasound transducer cannot provide sufficient information to reconstruct high-precision photoacoustic images. To obtain more accurate and clear image reconstruction results, PAI systems typically use a large number of ultrasound transducers to collect multi-channel signals from different angles and positions, thereby acquiring more information about the photoacoustic signals. Therefore, to reconstruct high-quality photoacoustic images, PAI systems require a significant number of measurement signals, which can result in substantial hardware and time costs. Compressed sensing is an algorithm that breaks through the Nyquist sampling theorem and can reconstruct the original signal with a small number of measurement signals. PAI based on compressed sensing has made breakthroughs over the past decade, enabling the reconstruction of low artifacts and high-quality images with a small number of photoacoustic measurement signals, improving time efficiency, and reducing hardware costs. This article provides a detailed introduction to PAI based on compressed sensing, such as the physical transmission model-based compressed sensing method, two-stage reconstruction-based compressed sensing method, and single-pixel camera-based compressed sensing method. Challenges and future perspectives of compressed sensing-based PAI are also discussed.

Structural and functional imaging of psoriasis for severity assessment and quantitative monitoring of treatment response using high-resolution optoacoustic imaging

Psoriasis is a chronic inflammatory skin disease, characterized by thick scaly plaques. It imposes a notable disease burden with varying levels of severity affecting the quality of life significantly. Current disease severity assessment relies on semi-objective visual inspection based on the Psoriasis Area and Severity index (PASI) score that might not be sensitive to sub-clinical changes. Histology of psoriasis skin lesions necessitate invasive skin biopsies. This indicates an unmet need for a non-invasive, objective and quantitative approach to assess disease severity serially. Herein, we employ multispectral Raster-Scanning Optoacoustic Mesoscopy (ms-RSOM) derived structural and microvascular functional imaging metrics to examine the lesional and non-lesional skin in psoriasis subjects across different severities and also evaluate the treatment outcome in a subject with topical steroids and biologics, such as adalimumab. ms-RSOM derived structural metrics like epidermal thickness and total blood volume (TBV) and microvascular functional information such as oxygen saturation (sO2) are evaluated by spectrally resolving the endogenous chromophores like melanin, oxy-, and deoxy-hemoglobin. Initial findings reveal an elevated sO2 and TBV with severity in lesional and non-lesional psoriasis skin, thus representing increasing inflammation. An increase in epidermal thickness is also noted with the degree of severity, corresponding to the inflammation and increased abnormal cell growth. As a marker to evaluate the treatment response, we observed a decrease in epidermal thickness, sO2, and TBV in a psoriasis patient post-treatment, which is consistent with the decrease in the PASI score from 4.1 to 1.9. We envision that ms-RSOM has a huge potential to be translated into routine clinical setting for the diagnosis of severity and assessment of treatment monitoring in psoriasis subjects.

Promising two-dimensional rhenium diselenide nanosheets: Facile Preparation, characterization, in vivo tumor photoacoustic imaging and photothermal therapy

Nanoagent-mediated photothermal therapy (PTT) has been considered as an useful strategy for curing cancer. Nonetheless, identifying high-quality photothermal nanoagents with excellent biocompatibility testing, superior photothermal conversion efficiency (PTCE), and high treatment efficacy, is still a key dilemma for performing practical application in biomedicine field. In our work, a novel photothermal nanoagent named two-dimensional (2D) colloidal rhenium diselenide (ReSe2) nanosheets was exfoliated via a facile liqiud-assisted exfoliation approach. Owing to surface functionalization with poly-ethylene glycol (PEG), the obtained PEG-ReSe2 nanosheets demonstrated good solubility and excellent biocompatibility. Notably, the PEG-ReSe2 nanosheets showed excellent near infrared (NIR) photothermal activity. For the radiation of an NIR laser at 808 nm, an ultrahigh PTCE of 81.3% was demonstrated. Owing to its high Re element and good photoacoustic effect, the PEG-ReSe2 nanosheets can serve as good contrast nanoagents for in vivo photoacoustic (PA) imaging. Furthermore, the PEG-ReSe2 nanosheets acted as excellent photothermal agents (PTAs) for performing PTT. Thanks to high photothermal effects of PEG-ReSe2 nanosheets, in vitro photothermal effects showed that, the mortality rate of 4T1 cells was almost 100%. Meanwhile, in vivo experiments showed that mouse tumors were 100% ablated. More importantly, the PEG-ReSe2 nanosheets exhibited negligible levels of toxicity, as demonstrated by in vivo cytotoxicity assays and histological analysis. Finally, changes in micro-RNA expression level was proposed to assess PTT treatment efficacy of PEG-ReSe2 nanoagent. Interestingly, the miRNAs such as miR-125b-5p, miR-20a-5p, miR-214–3p, miR-221–3p, miR-212–3p and miR-27b-3p, were down-regulated. In addiiton, the miRNAs including miR-451a, miR200c-3p, and miR-let-7d-3p, were up-regulated. More importantly, these obtained miRNAs can work as typical indicators for screening PTT outcomes of PEG-ReSe2 nanosheets-involved PTT. Our research suggested that, the PEG-ReSe2 nanoagent may represent potential therapeutic nanoagents for in vivo photoacoustic imaging and cancer therapy.

Design, implementation, and analysis of a compressed sensing photoacoustic projection imaging system.

Compressed sensing (CS) uses special measurement designs combined with powerful mathematical algorithms to reduce the amount of data to be collected while maintaining image quality. This is relevant to almost any imaging modality, and in this paper we focus on CS in photoacoustic projection imaging (PAPI) with integrating line detectors (ILDs). Our previous research involved rather general CS measurements, where each ILD can contribute to any measurement. In the real world, however, the design of CS measurements is subject to practical constraints. In this research, we aim at a CS-PAPI system where each measurement involves only a subset of ILDs, and which can be implemented in a cost-effective manner. We extend the existing PAPI with a self-developed CS unit. The system provides structured CS matrices for which the existing recovery theory cannot be applied directly. A random search strategy is applied to select the CS measurement matrix within this class for which we obtain exact sparse recovery. We implement a CS PAPI system for a compression factor of 4:3, where specific measurements are made on separate groups of 16 ILDs. We algorithmically design optimal CS measurements that have proven sparse CS capabilities. Numerical experiments are used to support our results. CS with proven sparse recovery capabilities can be integrated into PAPI, and numerical results support this setup. Future work will focus on applying it to experimental data and utilizing data-driven approaches to enhance the compression factor and generalize the signal class.

Biosustainable Hybrid Nanoplatforms as Photoacoustic Agents.

The development of biosafe theranostic nanoplatforms has attracted great attention due to their multifunctional behavior, reduced potential toxicity, and improved long-term safety. When considering photoacoustic contrast agents and photothermal conversion tools, melanin and constructs like melanin are highly appealing due to their ability to absorb optical energy and convert it into heat. Following a sustainable approach, in this study, silver-melanin like-silica nanoplatforms are synthesized exploiting different bio-available and inexpensive phenolic acids as potential melanogenic precursors and exploring their role in tuning the final systems architecture. The UV-Vis combined with X-Ray Diffraction investigation proves metallic silver formation, while Transmission Electron Microscopy analysis reveals that different morphologies can be obtained by properly selecting the phenolic precursors. By looking at the characterization results, a tentative formation mechanism is proposed to explain how phenolic precursors' redox behavior may affect the nanoplatforms' structure. The antibacterial activity experiments showed that all synthesized systems have a strong inhibitory effect on Escherichia coli, even at low concentrations. Furthermore, very sensitive Photoacoustic Imaging capabilities and significant photothermal behavior under laser irradiation are exhibited. Finally, a marked influence of phenol nature on the final system architecture is revealed resulting in a significant effect on both biological and photoacoustic features of the obtained systems. These melanin-based hybrid systems exhibit excellent potential as triggerable nanoplatforms for various biomedical applications.

Inversion of Sound Speed Field in Photoacoustic Imaging Based on Root Mean Square Propagation Algorithm

Inversion of Sound Speed Field in Photoacoustic Imaging Based on Root Mean Square Propagation Algorithm

Depth-Specific Hypoxic Responses to Spreading Depolarizations in Gyrencephalic Swine Cortex Unveiled by Photoacoustic Imaging.

Spreading depolarizations (SDs) are a marker of brain injury and have a causative effect on ischemic lesion progression. The hemodynamic responses elicited by SDs are contingent upon the metabolic integrity of the affected tissue, with vasoconstrictive reactions leading to pronounced hypoxia often indicating poor outcomes. The stratification of hemodynamic responses within different cortical layers remains poorly characterized. This pilot study sought to elucidate the depth-specific hemodynamic changes in response to SDs within the gray matter of the gyrencephalic swine brain. Employing a potassium chloride-induced SD model, we utilized multispectral photoacoustic imaging (PAI) to estimate regional cerebral oxygen saturation (rcSO2%) changes consequent to potassium chloride-induced SDs. Regions of interest were demarcated at three cortical depths covering up to 4mm. Electrocorticography (ECoG) strips were placed to validate the presence of SDs. Through PAI, we detected 12 distinct rcSO2% responses, which corresponded with SDs detected in ECoG. Notably, a higher frequency of hypoxic responses was observed in the deeper cortical layers compared to superficial layers, where hyperoxic and mixed responses predominated (p < 0.001). This data provides novel insights into the differential oxygenation patterns across cortical layers in response to SDs, underlining the complexity of cerebral hemodynamics post-injury.