A review of clinical photoacoustic imaging: Current and future trends

Dual-modality ultrasound/photoacoustic tomography for mapping tissue oxygen saturation distribution in intestinal strangulation

The strangulation of intestinal obstruction (IO) presents challenges in the assessment of disease progression and surgical decision-making. Intraoperatively, an accurate evaluation of the status of the IO is critical for determining the extent of surgical resection. Dual-modality ultrasound/photoacoustic tomography (US/PAT) imaging has the potential to provide spatially resolved tissue oxygen saturation (SO₂), serving as a valuable marker for IO diagnosis. In this study, US/PAT was utilized for imaging rat models of IO, with the data used for reconstruction, statistical analysis, and distribution evaluation. Results showed that SO₂ decreased with increasing strangulation severity. Notably, the kurtosis and skewness of the SO₂ distribution outperformed SO₂ itself in diagnosis, as they more effectively capture the heterogeneity of SO₂ distribution. Kurtosis reflects distribution concentration, while skewness measures asymmetry, both achieving areas under the receiver operating characteristic curve (AUROC) of 0.969. In conclusion, US/PAT offers a rapid and convenient method for assessing strangulation in IO.

Image restoration for ring-array photoacoustic tomography based on an attention mechanism driven conditional generative adversarial network

Ring-Array photoacoustic tomography (PAT) systems have shown great promise in non-invasive biomedical imaging. However, images produced by these systems often suffer from quality degradation due to non-ideal imaging conditions, with common issues including blurring and streak artifacts. To address these challenges, we propose an image restoration method based on a conditional generative adversarial network (CGAN) framework. Our approach integrates a hybrid spatial and channel attention mechanism within a Residual Shifted Window Transformer Module (RSTM) to enhance the generator's performance. Additionally, we have developed a comprehensive loss function to balance pixel-level accuracy, detail preservation, and perceptual quality. We further incorporate a gamma correction module to enhance the contrast of the network's output. Experimental results on both simulated and in vivo data demonstrate that our method significantly improves resolution and restores overall image quality.

Nanomedical Strategies for Kidney Disease: Diagnostic Innovations and Therapeutic Advancements

Kidney diseases, posing significant global public health challenges due to their complex pathogenesis and diagnostic/therapeutic difficulties, have seen emerging advancements through nanomedicine. In diagnostics, nanoparticles leverage unique physicochemical properties to enhance imaging precision. Superparamagnetic iron oxide nanoparticles improve magnetic resonance imaging sensitivity by amplifying T2-weighted contrast, while microbubbles/nanobubbles enhance ultrasound resolution via signal reflection. Quantum dots and gold nanoparticles optimize photoacoustic imaging with superior fluorescence and photostability. Therapeutically, nanoparticle-based drug delivery systems demonstrate targeted delivery, reduced systemic toxicity, and improved drug stability and bioavailability in preclinical studies. Nanocarrier-integrated stem cell and gene therapies further show potential in repairing renal cells and mitigating kidney injury. This review systematically examines nanomedicine's dual diagnostic and therapeutic roles in kidney diseases, compares strengths and limitations of various nanodelivery platforms, and addresses current challenges in clinical translation. By exploring novel nanotechnology-driven strategies, it aims to guide future research toward effective, tailored therapies for improved renal disease management.

Photoacoustic endoscopic probe based on lens scanning using a laterally tunable electrowetting liquid lens

Most existing photoacoustic endoscopies (PAEs) rely on external scanning methods, which can result in a bulky and complex probe. We propose a laterally tunable liquid lens that enables direct focal point shifting, eliminating the need for an external scanning mirror. This reduces system size and enhances endoscopic applications. Ray tracing analysis and experiments confirmed the lens's tunability, achieving 20 mm axial shifting and 4.42° lateral tilting at 45.3 Vrms. Integrated into a probe, the lens significantly improved photoacoustic imaging, yielding nearly four times the signal intensity of conventional stage scanning. Therefore, the proposed lens holds great potential for compact PAE.

Breaking the Chains of Therapeutic Blockade: Pyroptosis-Induced Photothermal-Chemotherapy with Targeted Nanoprobes in Triple-Negative Breast Cancer

There is an important clinical need and social significance, especially for young patients, to explore a new breast-conserving strategy that is not dependent on biomarkers for anti-triple-negative breast cancer. Disulfiram, historically employed for the treatment of chronic alcoholism, has recently emerged as a promising antitumor agent in combination with Cu2+. However, reported disulfiram-Cu2+ codelivery regimens often suffer from instability as well as inadequate drug metabolism, which is detrimental to the production and action of the antitumor active ingredient copper(II) bis(diethyldithiocarbamate). To address this obstacle, this study tested nanosystems ICG-CuET@PLGA-CS-HA (IC@PCH) nanoparticles (NPs) carrying the chemotherapeutic agent copper(II) bis(diethyldithiocarbamate) and photosensitizer indocyanine green for the efficient delivery of antitumor drugs. Benefiting from the involvement of hyaluronic acid, the prepared IC@PCH NPs not only targeted CD44 on the surface of tumor cells but also showed a longer in vivo circulation time. The in vitro and in vivo results demonstrated that IC@PCH NP-mediated photothermal-chemotherapy treatment led to pyroptosis via the NLRP3/caspase-1 classical pathway, which had a significant therapeutic effect on triple-negative breast cancer. In addition, targeting IC@PCH NPs allows photoacoustic-magnetic resonance-fluorescence trimodal imaging, which is capable of detecting more insidious cancer foci and opens up new avenues for precise cancer diagnosis and treatment.

Next generation gold nanomaterials for photoacoustic imaging

Photoacoustic (PA) imaging integrates ultrasound with the molecular contrast afforded by optical imaging, enabling noninvasive, real-time visualization of tissue structures and contrasts. Gold nanoparticles (GNPs) have been extensively studied as contrast agents for PA imaging due to their strong optical absorption derived from localized surface plasmon resonance, particularly when engineered to absorb in the near-infrared (NIR) region to enhance tissue penetration. However, the use of conventional anisotropic nanoparticles that absorb the NIR wavelengths is limited by their poor photostability under pulsed lasing conditions, which restricts their applicability in longitudinal in vivo imaging studies. This review first outlines the fundamental principles of PA imaging and introduces conventional GNP-based contrast agents, emphasizing their applications and inherent limitations. Subsequently, recent advances in GNP engineering are discussed, with particular focus on strategies to improve photostability, and a future perspective on the development of GNP-based PA contrast agents is provided.

Photoacoustic contrast agents: a review focusing on image-guided therapy

Photoacoustic (PA) imaging is a burgeoning imaging modality that has a broad range of applications in the early diagnosis of cancer, detection of various diseases, and relevant scientific research. It is a non-invasive imaging modality that relies on the absorption coefficient of the imaging tissue and the injected PA-imaging contrast agent. Nevertheless, PA imaging exhibits weak imaging depth due to its exponentially decaying signal intensity with increasing tissue depth. To improve the depth and heighten the contrast of imaging, a series of PA contrast agents has been developed based on nanomaterials. In this review, we present a comprehensive overview of recent advancements in contrast agents for photoacoustic (PA) imaging, encompassing the emergence of first near-infrared region (NIR-I, 700-950 nm) PA contrast agents, second near-infrared region (NIR-II, 1000-1700 nm) PA contrast agents, and ratiometric PA contrast agents. Subsequently, the latest advances in PA image-guided cancer therapy were introduced, such as photothermal therapy (PTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), and PTT-based synergistic therapy. Finally, the prospects of PA contrast agents and their biomedical applications were also discussed. This review provides a systematic summary of the development and utilization of the cutting-edge photoacoustic agents, which may inspire fresh thinking in the fabrication and application aspects of imaging agents.

Photoacoustic Imaging of Metabolic Activities across Biological Length Scales

Imaging is ubiquitous with biomedical research and discovery. This article surveys the role of imaging in our understanding of metabolism and introduces photoacoustic imaging as a compelling candidate for providing high-resolution, label-free, and real-time insights into metabolic processes. As a rapidly evolving modality, photoacoustics holds promising preclinical and clinical potential in imaging of metabolism as well as metabolism-related changes.

Future prospects for the advancement of treatment of men with NOA: focus on gene editing, artificial sperm, stem cells, and use of imaging

ABSTRACT

Nonobstructive azoospermia (NOA) affects about 60% of men with azoospermia, representing a severe form of male infertility. The current approach to manage NOA primarily involves testicular sperm retrieval methods such as conventional testicular sperm extraction (c-TESE) and microdissection testicular sperm extraction (micro-TESE). While combining testicular sperm retrieval with intracytoplasmic sperm injection (ICSI) offers hope for patients, the overall sperm retrieval rate (SRR) stands at around 50%. In cases where micro-TESE fails to retrieve sperm, limited options, like donor sperm or adoption, can be problematic in certain cultural contexts. This paper delves into prospective treatments for NOA management. Gene editing technologies, particularly clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) protein 9 (CRISPR/Cas9), hold potential for correcting genetic mutations underlying testicular dysfunction. However, these technologies face challenges due to their complexity, potential off-target effects, ethical concerns, and affordability. This calls for research to address key challenges associated with NOA management within the clinical settings. This also necessitate ongoing research essential for developing more sensitive diagnostic tests, validating novel treatments, and customizing current treatment strategies for individual patients. This review concluded that the future of NOA management may entail a combination of these treatment options, tailored to each patient's unique circumstances, providing a comprehensive approach to address NOA challenges.

Frequency-aware denoising using a diffusion model for enhanced band-limited and white noise removal in x-ray acoustic computed tomography

BACKGROUND

Radiation therapy delivers precise doses to tumors, but accurately measuring internal tissue doses remains a challenge. Current methods, such as ionization chambers and radiographic films, rely on external measurements, which cannot provide direct, in vivo dose feedback. X-ray acoustic computed tomography (XACT) was developed to generate thermoacoustic signals when x-rays deposit energy into water or tissue, enabling the reconstruction of dose distribution patterns through acoustic signals. However, the longer pulse width of x-rays from linear accelerators reduces the efficiency of thermoacoustic signal conversion, lowering the signal-to-noise ratio (SNR) of radiofrequency (RF) signals. This noise significantly affects the quality of reconstructed XACT images. Overcoming the impact of noise is essential for advancing XACT toward accurate dose detection.

PURPOSE

This study aims to develop a frequency-aware denoising (FAD) method for overcoming the impact of band-limited and white noise in RF signals for XACT.

METHODS

Real RF signals were acquired from an XACT system using radiotherapy megavoltage (MV) x-rays, a water tank, and an ultrasound transducer. To capture the frequency characteristics of these RF signals, we first estimated the probability density function (PDF) of their frequency spectrum. To generate synthetic RF data that closely approximates realistic noisy signals for model training, noise was sampled from this PDF, incorporating both magnitude and random phase components, and combined with simulated signals and white noise. A conditional diffusion model was trained on these synthetic signals to obtain the FAD model. A total of 3150 frequency-aware RF data samples were used to train the FAD model. For testing, acoustic RF signal data excited by five different x-ray shapes were measured, denoised by the FAD model, and finally reconstructed into XACT. The performance of the method was evaluated based on XACT image quality using SNR analysis and γ passing rate, and compared with results from Raw-RF and background noise-removed (BNR-RF) methods.

RESULTS

The FAD-RF method produced XACT images with clearer structural details and fewer artifacts. It achieved the highest SNR among the tested methods, with a mean SNR of 27.6 ± 5.0, outperforming both Raw-RF (22.9 ± 2.2, p < 0.05) and BNR-RF (22.0 ± 3.0, p < 0.05). In terms of spatial accuracy, the FAD-RF method also outperformed in γ analysis, achieving a mean γ passing rate of 79.0% ± 2.4%, significantly higher than Raw-RF (50.2% ± 20.0%, p < 0.05) and BNR-RF (73.5% ± 3.6%, p = 0.078).

CONCLUSION

The FAD-RF method relies solely on the RF signals for denoising, making it practical and efficient for real-world applications. It demonstrates effective noise suppression and enhanced spatial accuracy in XACT image reconstruction.

Photoacoustic-Based Intra- and Peritumoral Radiomics Nomogram for the Preoperative Prediction of Expression of Ki-67 in Breast Malignancy

RATIONALE AND OBJECTIVES

This study investigated the preoperative predictive efficiency of radiomics derived from photoacoustic (PA) imaging, integrated with the clinical features of Ki-67 expression in malignant breast cancer (BC), with a focus on both intratumoral and peritumoral regions.

METHODS

This study involved 359 patients, divided into a training set (n = 251) and a testing set (n = 108). Radiomic features were extracted from intratumoral and peritumoral regions using PA imaging. Multivariate logistic regression was employed to identify significant clinical factors. LASSO regression was used to select the features extracted from the training set. The selected radiomics features were combined with clinical features to develop a radiomics nomogram. The predictive efficiency of the model was assessed using the area under the receiver operating characteristic curve (AUC), and its clinical utility and accuracy were evaluated through decision curve analysis and calibration curves, respectively.

RESULTS

The developed nomogram combined 6 mm peritumoral data with intratumoral and clinical features and showed excellent diagnostic performance, achieving an AUC of 0.899 in the testing set. They both showed good calibrations. The outperformed models based solely on clinical features or other radiomics methods, with the 6 mm surrounding tumor area proving most effective in identifying Ki-67 status in BC patients.

CONCLUSION

Integrating PA radiomics with clinical features offers a robust preoperative tool for predicting Ki-67 status in BC, optimizing the delineation of peritumoral regions for enhanced diagnostic precision. The model's strong performance supports its potential as a non-invasive adjunct to traditional biopsy methods, aiding in the personalized management of BC treatment.

Development of cysteine-sensitive bimodal probes for in situ monitoring of early-stage pulmonary fibrosis progression and therapeutic effects

Pulmonary fibrosis (PF) is a chronic interstitial lung disease characterized by excessive extracellular matrix deposition and lung scarring, leading to impaired lung function, severe respiratory distress, and potentially fatal outcomes. Early diagnosis of PF is crucial for optimizing treatment strategies to improve patient prognosis. However, an activated near-infrared fluorescent (NIRF) and photoacoustic (PA) bimodal probe for non-invasive in situ imaging of PF is still lacking. In this study, we developed a novel cysteine-sensitive NIRF/PA dual-modal probe, MR-Cys, for in situ monitoring of early progression and the therapeutic response in a mouse model of PF. The probe MR-Cys selectively detects cysteine (Cys) levels in vivo, thereby activating both NIRF and PA signals. Using NIRF/PA dual-modal imaging technology, MR-Cys successfully tracked fluctuations in Cys levels within the PF mouse model. After treatment with nintedanib (OFEV), a notable decrease in both PA and NIRF signal intensities was observed in the treated mice, indicating that MR-Cys can be used to assess the therapeutic efficacy for PF. Therefore, MR-Cys not only holds great promise for early detection of pulmonary fibrosis progression, but also offers a precise monitoring tool for the optimization of personalized treatment plans.

Illuminating Hope for Tumors: The Progress of Light-Activated Nanomaterials in Skin Cancer

Skin cancer is a common malignant tumor that poses significant global health and economic burdens. The main clinical types include malignant melanoma and non-melanoma. Complications such as post-surgical recurrence, wound formation, or disfigurement can severely impact the patient's mental well-being. Traditional treatments such as surgery, chemotherapy, radiation therapy, and immunotherapy often face limitations. These challenges not only reduce the effectiveness of treatments but also negatively impact patients' quality of life. Phototherapy, a widely used and long-standing method in dermatology, presents a promising alternative for skin cancer treatment. Light-triggered nanomaterials further enhance the potential of phototherapy by offering advantages such as improved therapeutic precision, controlled drug release, minimal invasiveness, and reduced damage to surrounding healthy tissues. This review summarizes the application of light-triggered nanomaterials in skin cancer treatment, focusing on the principles, advantages, and design strategies of photodynamic therapy (PDT), photothermal therapy (PTT), and photoacoustic therapy (PAT). In this manuscript we have an in-depth discussion on overcoming translational barriers, including strategies to enhance light penetration, mitigate toxicity, reduce production costs, and optimize delivery systems. Additionally, we discuss the challenges associated with their clinical translation, including limited light penetration in deep tissues, potential toxicity, high production costs, and the need for advanced delivery systems.

Biomimetic Co-delivery of Lenvatinib and FePt Nanoparticles for Enhanced Ferroptosis/Apoptosis Treatment of Hepatocellular Carcinoma

Lenvatinib, endorse as a first-line targeted therapy, has demonstrated efficacy in extending the survival span of individuals afflicted with advanced Hepatocellular carcinoma (HCC). However, its therapeutic effect wears off with time, which is ascribed to the cancer cell's tendency to evade and tamper with its usual modes of action, severely limiting its clinical use. This study devises an innovative therapeutic modality involving the synergistic co-delivery of FePt nanoparticles (NPs) and Lenvatinib via poly lactic-co-glycolic acid (PLGA) NPs encase in HCC cell membranes (Len/FePt@CMP NPs). The investigation explores the mechanism through which Lenvatinib induces ferroptosis in HCC, notably by dampening the glutathione peroxidase 4 (GPX4) through the inhibition of fibroblast growth factor receptor 4. FePt NPs are engineered to enhance the efficacy of ferroptosis and apoptosis for HCC treatment. Concurrently, the incorporation of the cancer cell membrane facilitates the targeted accumulation of NPs at the tumor site, leveraging mechanisms of immune evasion and homologous targeting. This enhances ferroptosis/apoptosis treatment efficacy, triggeres by Len/FePt@CMP NPs, is convincingly demonstrated both in vitro and in vivo. The proposed approach has the potential to redefine HCC therapeutic paradigms by overcoming mono-therapeutic limitations in current clinical treatments, showcasing the improved efficacy of a comprehensive strategy.

Enhanced clinical photoacoustic vascular imaging through a skin localization network and adaptive weighting

Photoacoustic tomography (PAT) is an emerging imaging modality with widespread applications in both preclinical and clinical studies. Despite its promising capabilities to provide high-resolution images, the visualization of vessels might be hampered by skin signals and attenuation in tissues. In this study, we have introduced a framework to retrieve deep vessels. It combines a deep learning network to segment skin layers and an adaptive weighting algorithm to compensate for attenuation. Evaluation of enhancement using vessel occupancy metrics and signal-to-noise ratio (SNR) demonstrates that the proposed method significantly recovers deep vessels across various body positions and skin tones. These findings indicate the method's potential to enhance quantitative analysis in preclinical and clinical photoacoustic research.

Normal and melanoma skin visualized, quantified and compared by in vivo photoacoustic imaging

Photoacoustic imaging (PAI) shows promise for skin cancer diagnosis by detecting chromophores like melanin, hemoglobin, lipids, and collagen. While most studies focus on malignant lesions, understanding normal skin variability across anatomical regions is crucial for validating PAI's clinical application and its use in melanoma diagnosis. We assessed normal skin in 20 healthy volunteers from three different body locations using a clinical PAI system and compared suspicious looking pigmented skin lesions, including melanomas, to adjacent normal skin (n = 74). Higher deoxyhemoglobin levels were observed in the ankle compared to the cheek and volar forearm, while melanin, lipids, and collagen showed minimal variation. Patients with malignant lesions had significantly higher deoxyhemoglobin levels (p = 0.001) than adjacent normal skin, a difference not seen in benign lesions. These findings suggest that PAI may help diagnose malignancies by identifying increased vascularity in skin cancers, while anatomical differences should be considered during diagnostic work-up.

Raster Scan Optoacoustic Mesoscopy for detecting microvascular complications in diabetes mellitus: A narrative brief review

Diabetes mellitus (DM) may lead to microvascular and macrovascular complications. Screening for these complications is crucial, and so non-invasive methods with high-dissemination potential are needed. Diabetic peripheral neuropathy (DPN) is particularly challenging to screen due to the lack of reliable clinical markers and endpoints. In this context, Raster Scan Optoacoustic Mesoscopy (RSOM) emerges as a highly promising technique that offers hybrid, non-invasive imaging of optical absorption using light-induced ultrasound waves within tissue without the use of contrast agents. RSOM provides high-resolution visualisation of micro-vasculature and other tissue structures along with functional information. The technique has already assessed microvasculature loss as a function of diabetes progression and used it to characterise DPN severity. RSOM has also shown that cutaneous vessels in the mesoscopic range (mean diameters of 30-40 µm) are most prominently affected by DM and that the mean number of cutaneous vessels was lower in subjects with DM than in healthy participants (p < 0.001 and p < 0.05, respectively). Although experience is still limited, we present an overview of the novel technique in relation to its potential for detecting early DM onset and development of microvascular complications.

Nanophotonic-enhanced photoacoustic imaging for brain tumor detection

Photoacoustic brain imaging (PABI) has emerged as a promising biomedical imaging modality, combining high contrast of optical imaging with deep tissue penetration of ultrasound imaging. This review explores the application of photoacoustic imaging in brain tumor imaging, highlighting the synergy between nanomaterials and state of the art optical techniques to achieve high-resolution imaging of deeper brain tissues. PABI leverages the photoacoustic effect, where absorbed light energy causes thermoelastic expansion, generating ultrasound waves that are detected and converted into images. This technique enables precise diagnosis, therapy monitoring, and enhanced clinical screening, specifically in the management of complex diseases such as breast cancer, lymphatic disorder, and neurological conditions. Despite integration of photoacoustic agents and ultrasound radiation, providing a comprehensive overview of current methodologies, major obstacles in brain tumor treatment, and future directions for improving diagnostic and therapeutic outcomes. The review underscores the significance of PABI as a robust research tool and medical method, with the potential to revolutionize brain disease diagnosis and treatment.

Guided Multispectral Optoacoustic Tomography for 3D Imaging of the Murine Colon

Multispectral optoacoustic tomography is a promising medical imaging modality that combines light and sound to provide molecular imaging information at depths of several centimeters, based on the optical absorption of endogenous chromophores, such as hemoglobin. Assessment of inflammatory bowel disease has emerged as a promising clinical application of optoacoustic tomography. In this context, preclinical studies in animal models are essential to identify novel disease-specific imaging biomarkers and understand findings from emerging clinical pilot studies, however to-date, these studies have been limited by the precise identification of the bowel wall. Herein, a transrectal-absorber guide is applied, serving as a high-contrast landmark for 3D optoacoustic tomography of the colon. This study shows that guided multispectral optoacoustic tomography is able to measure changes in blood oxygenation status over the course of acute, chemically-induced colitis in mice and correlates with standard disease activity scores. This novel approach depicts intestinal hemoglobin composition non-invasively during murine inflammation. These results underscore the potential for optoacoustic imaging in translational inflammatory bowel disease research.

Anatomical analysis of the periosteal blood supply system of the fibula using fresh cadavers

A vascularized free fibula flap is often used to reconstruct bone defects. However, bone resorption within the osteotomized segment is often observed. This may be attributed to damage to bone blood flow supplied by nonpenetrating periosteal vessels (NPPVs); however, there are few studies on NPPVs in the fibula. In this study, we investigated dissection methods to assess the vascular network in the fibula and performed a detailed anatomical investigation of NPPVs using fresh cadavers provided by the Clinical Anatomy Laboratory at the Keio University. Three dissection methods were compared to assess the vascular network, and data on the branching, distribution, and number of NPPVs from the peroneal artery were collected. A method involving the elevation of the periosteal bone flap was found to be the most acceptable for assessing fibular NPPVs with less vascular damage. A total of 13 limbs from 7 male and 2 female cadavers were dissected. The number of detected NPPVs was 12-23 per limb (median: 17). No nutrient vessels were detected 5 cm from the proximal and distal ends of the fibula. Fibular NPPVs were distributed in the anterior and posterior directions along the peroneal artery trunk, with more NPPVs toward the posterior. Among the osteotomized segments of 1.0 cm, 30% did not contain any NPPVs, whereas segmentations of 1.5, 2.0, and 3.0 cm resulted in 87%, 95%, and 99% of the segments with at least one NPPV, respectively. These findings for the vascular network in the fibula may help to improve the graft blood supply and prognosis.

Study on the use of black phosphorus quantum dots in the treatment of atherosclerosis

Atherosclerosis is the pathological basis of cardiovascular disease, and there are no clinical drugs that can safely and efficiently remove atherosclerotic plaques. In this study, black phosphorus quantum dots (BPQDs) were applied to the treatment of atherosclerosis in high fat diet ApoE-/- model mice that BPQDs were given every other day for 3 weeks without changing the high-fat diet. 45.3% atherosclerotic plaque was cleared efficiently within 3 weeks in BPQDs intravenous administration way every other day. The treatment was more effective than traditional statins. The findings suggest that BPQDs have great potential to be applied for clinical prevention and treatment of AS that does not require dietary changes.

Biodegradable semiconducting polymer nanoparticles for phototheranostics

Semiconducting polymer nanoparticles (SPNs) have been widely applied for phototheranostics. However, the disadvantage of in vivo long-term metabolism greatly suppresses the clinical application of SPNs. To improve the metabolic rate and minimize the long-term toxicity of SPNs, biodegradable semiconducting polymers (BSPs), whose backbones may be degraded under certain conditions, have been designed. This review summarizes recent advances in BSP-constructed nanoparticles (BSPNs) for phototheranostics. BSPs are divided into two categories: conjugated backbone degradable BSPs (CBD-BSPs) and non-conjugated backbone degradable BSPs (NCBD-BSPs), based on the feature of chemical structure. The biological applications, including cancer imaging and combination therapy, of these BSPNs are described. Finally, the conclusion and future perspectives of this field are discussed.

A promising mesoporous silica carrier material for the diagnosis and treatment of liver diseases: recent research advances

The therapeutic diagnosis of liver diseases has garnered significant interest within the medical community. In recent years, mesoporous silica nanoparticles (MSNs) have emerged as crucial nanocarriers for the treatment of liver ailments. Their remarkable diagnostic capabilities enable them to be used in techniques such as high-throughput mass spectrometry (MS), magnetic resonance imaging (MRI), near-infrared (NIR) fluorescence imaging, photoacoustic imaging (PAI), and ultrasonography (US), attracting considerable attention. Furthermore, the introduction of amino and carboxyl group modifications in MSNs has facilitated their use as drug delivery carriers for treating liver diseases, including hepatocellular carcinoma. This paper reviews the preparation methods, in vitro diagnostic capabilities, and in vivo therapeutic delivery systems of MSNs for liver disease treatment. It also summarizes relevant toxicity studies, aiming to provide a comprehensive overview of the diagnostic and therapeutic applications of MSNs in the treatment of liver diseases, particularly hepatocellular carcinoma. Through this review, we seek to offer theoretical insights into the potential of MSNs for diagnostic and therapeutic applications in liver disease treatment.

Emerging Wearable Acoustic Sensing Technologies

Sound signals not only serve as the primary communication medium but also find application in fields such as medical diagnosis and fault detection. With public healthcare resources increasingly under pressure, and challenges faced by disabled individuals on a daily basis, solutions that facilitate low-cost private healthcare hold considerable promise. Acoustic methods have been widely studied because of their lower technical complexity compared to other medical solutions, as well as the high safety threshold of the human body to acoustic energy. Furthermore, with the recent development of artificial intelligence technology applied to speech recognition, speech recognition devices, and systems capable of assisting disabled individuals in interacting with scenes are constantly being updated. This review meticulously summarizes the sensing mechanisms, materials, structural design, and multidisciplinary applications of wearable acoustic devices applied to human health and human-computer interaction. Further, the advantages and disadvantages of the different approaches used in flexible acoustic devices in various fields are examined. Finally, the current challenges and a roadmap for future research are analyzed based on existing research progress to achieve more comprehensive and personalized healthcare.

Dichroism-sensitive photoacoustic imaging for in-depth estimation of the optic axis in fibrous tissue

Photoacoustic imaging (PAI) is a developing image modality that benefits from light-matter interaction and low acoustic attenuation to provide functional information on tissue composition at relatively large depths. Several studies have reported the potential of dichroism-sensitive photoacoustic (DS-PA) imaging to expand PAI capabilities by obtaining morphological information of tissue regarding anisotropy and predominant orientation. However, most of these studies have limited their analysis to superficial scanning of samples, where fluence effects are negligible. Herein, we present a mathematical model for the in-depth analysis of the DS-PA signal of biological samples, focusing on estimating tissue orientation. Our model is validated with a B-scan setup for DS-PA imaging in ex-vivo porcine tendon samples, for which collagen displays optical anisotropy. Results show that for in-depth DS-PA imaging, the accumulative fluence modulation due to dichroism overcomes the effect of absorption dichroism affecting the measured signals; however, this effect can be corrected based on the presented model for determining fiber orientation.

Current issues in optical monitoring of drug delivery via hair follicles

Drug delivery via hair follicles has attracted much research attention due to its potential to serve for both local and systemic therapeutic purposes. Recent studies on topical application of various particulate formulations have demonstrated a great role of this delivery route for targeting numerous cell populations located in skin and transporting the encapsulated drug molecules to the bloodstream. Despite a great promise of follicle-targeting carriers, their clinical implementation is very rare, mostly because of their poorer characterization compared to conventional topical dosage forms, such as ointments and creams, which have a history spanning over a century. Gathering as complete information as possible on the intrafollicular penetration depth, storage, degradation/metabolization profiles of such carriers and the release kinetics of drugs they contain, as well as their impact on skin health would significantly contribute to understanding the pros and cons of each carrier type and facilitate the selection of the most suitable candidates for clinical trials. Optical imaging and spectroscopic techniques are extensively applied to study dermal penetration of drugs. Current paper provides the state-of-the-art overview of techniques, which are used in optical monitoring of follicular drug delivery, with a special focus on non-invasive in vivo methods. It discusses key features, advantages and limitations of their use, as well as provide expert perspectives on future directions in this field.

Investigating the Impact of Chronical Prenatal Alcohol Exposure on Fetal Vascular Development Across Pregnancy Stages Using Photoacoustic Tomography

Prenatal alcohol exposure (PAE) is a major contributor to fetal alcohol spectrum disorder (FASD), resulting in neurodevelopmental abnormalities. This study utilizes photoacoustic tomography (PAT) to investigate the effects of PAE on fetal brain vasculature in mice. PAT imaging was conducted from embryonic Day 10 (E10) to Day 20 (E20), aimed to compare two alcohol-exposed groups with a control group. Key vascular parameters, including blood vessel diameter and density, and oxygen saturation (sO2), were analyzed. Results show significant reductions in vessel size and density, as well as reduced sO2 levels, in alcohol-exposed groups, especially from E14 onward, compared to controls. These findings underscore the vulnerability of the fetal brain to alcohol exposure during early development and highlight the potential of PAT as a valuable tool for investigating FASD-related vascular changes.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

A Review on Ultrasound-based Methods to Image the Distribution of Magnetic Nanoparticles in Biomedical Applications

Magnetic nanoparticles (MNPs) have gained significant attention in biomedical engineering and imaging applications due to their unique magnetic and mechanical properties. With their high magnetization and small size, MNPs serve as excitation sources for magnetically heating to destroy tumors (magnetic hyperthermia) and magnetically controlled drug carriers in magnetic drug targeting. However, effectively visualizing the distribution of MNPs during research or potential clinical use with low-cost modalities remains a critical challenge. Although magnetic resonance imaging provides pre- and post-procedural imaging, it is considered to be high cost, and real-time imaging during clinical procedures is limited. In contrast, ultrasound-based imaging methods offer the advantage of providing the potential for immediate feedback during clinical use and are considered to be a low-cost modality. Ultrasound-based imaging techniques, including magnetomotive ultrasound, magnetoacoustic tomography, and thermoacoustic imaging, emerged as promising approaches for imaging the distribution of MNPs. These techniques offer the potential for real-time imaging, facilitating precise therapy monitoring. By exploring the strengths and limitations of various ultrasound-based imaging techniques for MNPs, this review seeks to provide comprehensive insights that can guide researchers in selecting suitable ultrasound-based modalities and inspire further advancements in this exciting field.

Multifunctional drug delivery nanoparticles for combined chemotherapy/chemodynamic/photothermal therapy against colorectal cancer through synergistic cuproptosis/ferroptosis/apoptosis

The use of combination therapies that employ a variety of cell death mechanisms has emerged as a promising avenue of research in the treatment of cancer. However, the optimization of therapeutic synergies when integrating different modes remains a significant challenge. To this end, we developed a multifunctional intelligent drug-carrying nanoparticle (DFMTCH NPs) based on the metal-organic framework MIL-100, loaded with doxorubicin (DOX) and disulfiram (DSF), coated with a Cu-tannic acid (Cu-TA) network and hyaluronic acid (HA), for the purpose of combined chemotherapy/chemodynamic/photothermal anti-cancer therapy. On the one hand, the DFMTCH NPs exhibited a range of therapeutic capabilities, including chemotherapy, photothermal therapy (PTT), and chemodynamic therapy (CDT), which collectively enhanced the anti-tumor efficacy of chemotherapeutic agents. In addition, DFMTCH NPs proved sensitive photoacoustic imaging (PAI) in image-guided therapy. On the other hand, DFMTCH NPs could produce reactive oxygen species (ROS) and consume glutathione (GSH) by amplifying cellular oxidative stress, while causing intracellular mitochondrial dysfunction, inducing effective cuproptosis/ferroptosis/apoptosis to inhibit tumor growth. Collectively, this work provided an innovative strategy for designing multifunctional nanoparticles for effective combination therapies to combat colorectal cancer (CRC).

Enhancing signal-to-noise ratio in real-time LED-based photoacoustic imaging: A comparative study of CNN-based deep learning architectures

Recent advances in Light Emitting Diode (LED) technology have enabled a more affordable high frame rate photoacoustic imaging (PA) alternative to traditional laser-based PA systems that are costly and have slow pulse repetition rate. However, a major disadvantage with LEDs is the low energy outputs that do not produce high signal-to-noise ratio (SNR) PA images. There have been recent advancements in integrating deep learning methodologies aimed to address the challenge of improving SNR in LED-PA images, yet comprehensive evaluations across varied datasets and architectures are lacking. In this study, we systematically assess the efficacy of various Encoder-Decoder-based CNN architectures for enhancing SNR in real-time LED-based PA imaging. Through experimentation with in vitro phantoms, ex vivo mouse organs, and in vivo tumors, we compare basic convolutional autoencoder and U-Net architectures, explore hierarchical depth variations within U-Net, and evaluate advanced variants of U-Net. Our findings reveal that while U-Net architectures generally exhibit comparable performance, the Dense U-Net model shows promise in denoising different noise distributions in the PA image. Notably, hierarchical depth variations did not significantly impact performance, emphasizing the efficacy of the standard U-Net architecture for practical applications. Moreover, the study underscores the importance of evaluating robustness to diverse noise distributions, with Dense U-Net and R2 U-Net demonstrating resilience to Gaussian, salt and pepper, Poisson, and Speckle noise types. These insights inform the selection of appropriate deep learning architectures based on application requirements and resource constraints, contributing to advancements in PA imaging technology.

Monitoring of microvascular calcification by time-resolved photoacoustic microscopy

Monitoring of microvascular calcification (MC) is essential for the understanding of pathophysiological processes and the characterization of certain physiological states such as drug abuse, metabolic abnormality, and chronic nephrosis. In this work, we develop a novel and effective time-resolved photoacoustic microscopy (TR-PAM) technology, which can observe the obvious microvascular bio-elastic change in the development process of the MC owing to the calcium deposition along vascular walls.The feasibility of the TR-PAM imaging was validated using a group of agar phantoms and ex vivo tissues. Furthermore, MC pathological animal models were constructed and imaged in situ and in vivo by the TR-PAM to demonstrate its capability for the bio-mechanical monitoring and characterization of MC, and experimental results were consistent with the pathological knowledge. The feasibility study of monitoring MC by the TR-PAM proves that this technique has potential to be developed as a superficial microvascular bio-mechanical assessment method to supplement current clinical strategy for prediction and monitoring of some diseases.

Ultrasound-guided photoacoustic image annotation toolkit in MATLAB (PHANTOM) for preclinical applications

Depth-dependent fluence-compensation in photoacoustic (PA) imaging is paramount for accurate quantification of chromophores from deep tissues. Here we present a user-friendly toolkit named PHANTOM (PHotoacoustic ANnotation TOolkit for MATLAB) that includes a graphical interface and assists in the segmentation of ultrasound-guided PA images. We modelled the light source configuration with Monte Carlo eXtreme and utilized 3D segmented tissues from ultrasound to generate fluence maps to depth compensate PA images. The methodology was used to analyze PA images of phantoms with varying blood oxygenation and results were validated with oxygen electrode measurements. Two preclinical models, a subcutaneous tumor and a calcified placenta, were imaged and fluence-compensated using the PHANTOM toolkit and the results were verified with immunohistochemistry. The PHANTOM toolkit provides scripts and auxiliary functions to enable biomedical researchers not specialized in optical imaging to apply fluence correction to PA images, enhancing accessibility of quantitative PAI for researchers in various fields.

Multi-parametric Photoacoustic Imaging Combined with Acoustic Radiation Force Impulse Imaging for Applications in Tissue Engineering

Tissue engineering is a dynamic field focusing on the creation of advanced scaffolds for tissue and organ regeneration. These scaffolds are customized to their specific applications and are often designed to be complex, large structures to mimic tissues and organs. This study addresses the critical challenge of effectively characterizing these thick, optically opaque scaffolds that traditional imaging methods fail to fully image due to their optical limitations. We introduce a novel multi-modal imaging approach combining ultrasound, photoacoustic, and acoustic radiation force impulse imaging. This combination leverages its acoustic-based detection to overcome the limitations posed by optical imaging techniques. Ultrasound imaging is employed to monitor the scaffold structure, photoacoustic imaging is employed to monitor cell proliferation, and acoustic radiation force impulse imaging is employed to evaluate the homogeneity of scaffold stiffness. We applied this integrated imaging system to analyze melanoma cell growth within silk fibroin protein scaffolds with varying pore sizes and therefore stiffness over different cell incubation periods. Among various materials, silk fibroin was chosen for its unique combination of features including biocompatibility, tunable mechanical properties, and structural porosity which supports extensive cell proliferation. The results provide a detailed mesoscale view of the scaffolds' internal structure, including cell penetration depth and biomechanical properties. Our findings demonstrate that the developed multimodal imaging technique offers comprehensive insights into the physical and biological dynamics of tissue-engineered scaffolds. As the field of tissue engineering continues to advance, the importance of non-ionizing and non-invasive imaging systems becomes increasingly evident, and by facilitating a deeper understanding and better characterization of scaffold architectures, such imaging systems are pivotal in driving the success of future tissue-engineering solutions.

Three-dimensional diffractive acoustic tomography

Acoustically probing biological tissues with light or sound, photoacoustic and ultrasound imaging can provide anatomical, functional, and/or molecular information at depths far beyond the optical diffusion limit. However, most photoacoustic and ultrasound imaging systems rely on linear-array transducers with elevational focusing and are limited to two-dimensional imaging with anisotropic resolutions. Here, we present three-dimensional diffractive acoustic tomography (3D-DAT), which uses an off-the-shelf linear-array transducer with single-slit acoustic diffraction. Without jeopardizing its accessibility by general users, 3D-DAT has achieved simultaneous 3D photoacoustic and ultrasound imaging with optimal imaging performance in deep tissues, providing near-isotropic resolutions, high imaging speed, and a large field-of-view, as well as enhanced quantitative accuracy and detection sensitivity. Moreover, powered by the fast focal line volumetric reconstruction, 3D-DAT has achieved 50-fold faster reconstruction times than traditional photoacoustic imaging reconstruction. Using 3D-DAT on small animal models, we mapped the distribution of the biliverdin-binding serpin complex in glassfrogs, tracked gold nanoparticle accumulation in a mouse tumor model, imaged genetically-encoded photoswitchable tumors, and investigated polyfluoroalkyl substances exposure on developing embryos. With its enhanced imaging performance and high accessibility, 3D-DAT may find broad applications in fundamental life sciences and biomedical research.

Ppb-Level Photoacoustic Detection of Chloroform Using Four-Microphone Array

The photoacoustic spectroscopy (PAS) system commonly enhances the efficiency of optical-acoustic-electrical energy conversion by increasing the laser power, optimizing the resonance characteristics of the photoacoustic cell (PAC), and improving the sensitivity of acoustic sensors. However, conventional systems using a single-microphone or a dual-microphone differential setup for point sampling of the photoacoustic signal fail to account for its spatial distribution, leading to a loss of spatial gain. Drawing on microphone array theory derived from sonar technology, this study, for the first time, presents a PAS sensing system based on a four-microphone array, which is applied to detect chloroform gas. The microphones are positioned at 90° intervals around the PAC resonance chamber wall, enhancing the spatial sampling rate of the signals. A digital phase-locked algorithm demodulates the combined signals from the four microphones into the concentration data. Experimental results show that, compared to a single-microphone system, the four-microphone array system increases sensitivity by a factor of 4, doubles the signal-to-noise ratio, and achieves a minimum detection limit of 69 ppb, demonstrating a significant improvement in sensitivity by capturing the spatial distribution of PA signals.

Nanomaterial-based synergistic strategies for combating dental caries: progress and perspectives

Dental caries, as the predominant global oral disease, remains a critical public health issue worldwide, particularly in socioeconomically disadvantaged communities. However, common caries prevention approaches (e.g., oral health education, mechanical plaque removal, and delivery of fluoride agents) are still insufficient for optimal caries management, and therefore, alternative regimens that can supplement existing strategies are highly warranted. Nanomaterials exhibit considerable potential in combating cariogenic pathogens and biofilms owing to their promising antimicrobial capacity, improved penetration into biofilms, targeted precision delivery, and versatile physicochemical properties. As unifunctional materials are limited in caries management, this review underscores the latest advancement in multifunctional anti-caries nanomaterials/nanomedicines. It highlights the cutting-edge materials developed or engineered to (i) incorporate diagnostic capabilities to prevent caries at an early stage, thus enhancing treatment efficiency, (ii) integrate mechanical "brushing" with anti-caries approaches to mechanochemically eradicate biofilms, (iii) exert antimicrobial/antibiofilm effects while preserving dental hard tissue. The current work also outlines future directions for optimizing nanosystems in the management of dental caries while emphasizing the need for innovative solutions to improve preventive and therapeutic efficacies.

Carbon-based Nanomaterials in Photothermal Therapy Guided by Photoacoustic Imaging: State of Knowledge and Recent Advances

Carbon-based nanomaterials (CBNM) have been widely used in various fields due to their excellent physicochemical properties. In particular, in the area of tumor diagnosis and treatment, researchers have frequently reported them for their potential fluorescence, photoacoustic (PA), and ultrasound imaging performance, as well as their photothermal, photodynamic, sonodynamic, and other therapeutic properties. As the functions of CBNM are increasingly developed, their excellent imaging properties and superior tumor treatment effects make them extremely promising theranostic agents. This review aims to integrate the considered and researched information in a specific field of this research topic and systematically present, summarize, and comment on the efforts made by authoritative scholars. In this review, we summarized the work exploring carbon-based materials in the field of tumor imaging and therapy, focusing on PA imaging-guided photothermal therapy (PTT) and discussing their imaging and therapeutic mechanisms and developments. Finally, the current challenges and potential opportunities of carbon-based materials for PA imaging-guided PTT are presented, and issues that researchers should be aware of when studying CBNM are provided.

Focal point technology: Controlling treatment depth and pattern of skin injury by a novel highly focused laser

BACKGROUND

Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550 nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis.

OBJECTIVE

To characterize the conical thermal zones in vivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications.

METHODS

A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in ex vivo human skin and subsequently on the backs of 21 human subjects.

RESULTS

Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae.

LIMITATIONS

Clinical data are currently being collected to further explore the safety and efficacy of the device.

CONCLUSION

The 1550 nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects.

Melanin and Light

Melanin is responsible, in Nature, for photoprotection, for this reason it is expected to be poorly photoreactive. However, the photo-reactivity of melanin and related materials is well documented. Here we discuss some relevant recent examples to demonstrate that, indeed, the actual mechanism of interaction of melanin with light is complex and still not completely understood. Photochemical and photothermal processes are involved, giving a contribution that strongly depends on light wavelength and intensity. Moreover, some interesting experiments demonstrated that photochemical reactivity of melanin related compounds is likely to be indirect, in the sense that the effect of light is to increase the number of radical species rather than creating photoreactive excited state. These suggestions open-up new perspectives in the interpretation of the role of melanin in photoprotection and in the design of new melanin based photoactive materials for energy conversion, environmental remediation, and nanomedicine. Further complication is given by the role of atmospheric oxygen and humidity in the photoinduced processes. Beside this complexity of behavior makes it difficult a systematic understanding of the interaction of melanin with light, it surely strongly contributes to make the properties of melanin and related materials unique.

Advances in Injectable Hydrogels Based on Diverse Gelation Methods for Biomedical Imaging

The injectable hydrogels can deliver the loads directly to the predetermined sites and form reservoirs to increase the enrichment and retention of the loads in the target areas. The preparation and injection of injectable hydrogels involve the sol-gel transformation of hydrogels, which is affected by factors such as temperature, ions, enzymes, light, mechanics (self-healing property), and pH. However, tracing the injection, degradation, and drug release from hydrogels based on different ways of gelation is a major concern. To solve this problem, contrast agents are introduced into injectable hydrogels, enabling the hydrogels to be imaged under techniques such as fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, and radionuclide imaging. This review details methods for causing the gelation of imageable hydrogels; discusses the application of injectable hydrogels containing contrast agents in various imaging techniques, and finally explores the potential and challenges of imageable hydrogels based on different modes of gelation.

In Vivo Assessment of Deep Vascular Patterns in Murine Colitis Using Optoacoustic Mesoscopic Imaging

The analysis of vascular morphology and functionality enables the assessment of disease activity and therapeutic effects in various pathologies. Raster-scanning optoacoustic mesoscopy (RSOM) is an imaging modality that enables the visualization of superficial vascular networks in vivo. In murine models of colitis, deep vascular networks in the colon wall can be visualized by transrectal absorber guide raster-scanning optoacoustic mesoscopy (TAG-RSOM). In order to accelerate the implementation of this technology in translational studies of inflammatory bowel disease, an image-processing pipeline for TAG-RSOM data has been developed. Using optoacoustic data from a murine model of chemically-induced colitis, different image segmentation methods are compared for visualization and quantification of deep vascular patterns in terms of vascular network length and complexity, blood volume, and vessel diameter. The presented image-processing pipeline for TAG-RSOM enables label-free in vivo assessment of changes in the vascular network in murine colitis with broad applications for inflammatory bowel disease research.

Unveiling placental development in circadian rhythm-disrupted mice: A photo-acoustic imaging study on unstained tissue

INTRODUCTION

Circadian rhythm disruption has garnered significant attention for its adverse effects on human health, particularly in reproductive medicine and fetal well-being. Assessing pregnancy health often relies on diagnostic markers such as the labyrinth zone (LZ) proportion within the placenta. This study aimed to investigate the impact of disrupted circadian rhythms on placental health and fetal development using animal models.

METHODS AND RESULTS

Employing unstained photo-acoustic microscopy (PAM) and hematoxylin and eosin (HE)-stained images, we found them mutually reinforcing. Our images revealed the role of maternal circadian rhythm disrupted group (MCRD) on the LZ and fetus weight: a decrease in LZ area from 5.01 (4.25) mm2 HE (PAM) to 3.58 (2.62) mm2 HE (PAM) on day 16 and 6.48 (5.16) mm2 HE (PAM) to 4.61 (3.03) mm2 HE (PAM) on day 18, resulting in 0.71 times lower fetus weights. We have discriminated a decrease in the mean LZ to placenta area ratio from 64 % to 47 % on day 18 in mice with disrupted circadian rhythms with PAM.

DISCUSSION

The study highlights the negative influence of circadian rhythm disruption on placental development and fetal well-being. Reduced LZ area and fetal weights in the MCRD group suggest compromised placental function under disrupted circadian rhythms. PAM imaging proved to be an efficient technique for assessing placental development, offering advantages over traditional staining methods. These findings contribute to understanding the underlying mechanisms of circadian disruption on reproductive health and fetal development. Further research is needed to explore interventions to mitigate these effects and improve pregnancy outcomes.

High speed innovations in photoacoustic microscopy

Photoacoustic microscopy (PAM) is a key implementation of photoacoustic imaging (PAI). PAM merges rich optical contrast with deep acoustic detection, allowing for broad biomedical research and diverse clinical applications. Recent advancements in PAM technology have dramatically improved its imaging speed, enabling real-time observation of dynamic biological processes in vivo and motion-sensitive targets in situ, such as brain activities and placental development. This review introduces the engineering principles of high-speed PAM, focusing on various excitation and detection methods, each presenting unique benefits and challenges. Driven by these technological innovations, high-speed PAM has expanded its applications across fundamental, preclinical, and clinical fields. We highlight these notable applications, discuss ongoing technical challenges, and outline future directions for the development of high-speed PAM.

Deep tissue photoacoustic imaging with light and sound

Photoacoustic computed tomography (PACT) can harvest diffusive photons to image the optical absorption contrast of molecules in a scattering medium, with ultrasonically-defined spatial resolution. PACT has been extensively used in preclinical research for imaging functional and molecular information in various animal models, with recent clinical translations. In this review, we aim to highlight the recent technical breakthroughs in PACT and the emerging preclinical and clinical applications in deep tissue imaging.

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Controlling the sound of light: photoswitching optoacoustic imaging

Optoacoustic (photoacoustic) imaging advances allow high-resolution optical imaging much deeper than optical microscopy. However, while label-free optoacoustics have already entered clinical application, biological imaging is in need of ubiquitous optoacoustic labels for use in ways that are similar to how fluorescent proteins propelled optical microscopy. We review photoswitching advances that shine a new light or, in analogy, 'bring a new sound' to biological optoacoustic imaging. Based on engineered labels and novel devices, switching uses light or other energy forms and enables signal modulation and synchronous detection for maximizing contrast and detection sensitivity over other optoacoustic labels. Herein, we explain contrast enhancement in the spectral versus temporal domains and review labels and key concepts of switching and their properties to modulate optoacoustic signals. We further outline systems and applications and discuss how switching can enable optoacoustic imaging of cellular or molecular contrast at depths and resolutions beyond those of other optical methods.

Masked cross-domain self-supervised deep learning framework for photoacoustic computed tomography reconstruction

Accurate image reconstruction is crucial for photoacoustic (PA) computed tomography (PACT). Recently, deep learning has been used to reconstruct PA images with a supervised scheme, which requires high-quality images as ground truth labels. However, practical implementations encounter inevitable trade-offs between cost and performance due to the expensive nature of employing additional channels for accessing more measurements. Here, we propose a masked cross-domain self-supervised (CDSS) reconstruction strategy to overcome the lack of ground truth labels from limited PA measurements. We implement the self-supervised reconstruction in a model-based form. Simultaneously, we take advantage of self-supervision to enforce the consistency of measurements and images across three partitions of the measured PA data, achieved by randomly masking different channels. Our findings indicate that dynamically masking a substantial proportion of channels, such as 80%, yields meaningful self-supervisors in both the image and signal domains. Consequently, this approach reduces the multiplicity of pseudo solutions and enables efficient image reconstruction using fewer PA measurements, ultimately minimizing reconstruction error. Experimental results on in-vivo PACT dataset of mice demonstrate the potential of our self-supervised framework. Moreover, our method exhibits impressive performance, achieving a structural similarity index (SSIM) of 0.87 in an extreme sparse case utilizing only 13 channels, which outperforms the performance of the supervised scheme with 16 channels (0.77 SSIM). Adding to its advantages, our method can be deployed on different trainable models in an end-to-end manner, further enhancing its versatility and applicability.

The Utility of Indocyanine Green Angiography in Breast Reconstruction to Detect Mastectomy Skin Flap Necrosis and Free Flap Perfusion: An Umbrella Review

Two of the greatest challenges in breast reconstruction are mastectomy skin flap necrosis (MSFN) and autologous flap failure. This review summarizes current evidence regarding the usage of indocyanine green angiography (ICGA) in breast reconstruction, identifies knowledge gaps, and provides directions for future studies. An umbrella review was conducted to identify related syntheses in Embase, Ovid Medline, Scopus, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Clinical Trials databases. Data were extracted from systematic reviews (SRs) and meta-analyses (MAs) that discussed the use of ICGA in breast reconstruction. Sixteen syntheses were included (10 SRs and 6 MAs). Syntheses showed much evidence that ICGA usage typically reduces MSFN rates. However, it tends to overpredict necrosis and is best utilized in high-risk patients or those with an unclear clinical picture. ICGA is also useful in autologous breast reconstruction by reducing rates of breast fat necrosis (BFN), total flap loss, and reoperation. ICGA usage may also aid in perforator mapping and selection intraoperatively, with minimal complication risk. Most syntheses had moderate quality scores; however, they were small with significant heterogeneity in protocols and complication definitions. The use of ICGA in breast reconstruction is safe and useful in decreasing rates of MSFN, BFN, and reoperation after free flap reconstruction.