Photoacoustic-enabled automatic vascular navigation:accurate and naked-eye real-time visualization of deep-seated vessels

Accurate localization of blood vessels with image navigation is a key element in vascular-related medical research and vascular surgery.However,current vascular navigation techniques cannot provide naked-eye visualization of deep vascular information noninvasively and with high resolution,resulting in inaccurate vascular anatomy and diminished surgical success rates.Here,we introduce a photoacousticenabled automatic vascular navigation method combining photoacoustic computed tomography with augmented and mixed reality,for the first time,to our knowledge,enabling accurate and noninvasive visualization of the deep microvascular network within the tissues in real time on a real surgical surface.This approach achieves precise vascular localization accuracy(<0.89 mm)and tiny vascular relocation latency(<1 s)through a zero-mean normalization idea-based visual tracking algorithm and a curved surfacefitting algorithm.Further,the subcutaneous vessels of minimum diameter(∼0.15 mm)in rabbit thigh and the maximum depth(∼7 mm)in human arm can be vividly projected on the skin surface with a computer visionbased projection tracking system to simulate preoperative and intraoperative vascular localization.Thereby,this strategy provides a way to visualize deep vessels without damage on the surgical surface and with precise image navigation,opening an avenue for the application of photoacoustic imaging in surgical operations.

Prospects of microwave-induced thermoacoustic imaging

Microwave-induced thermoacoustic imaging(MTAI)has advantages including the large imaging depth,high imaging resolution,high imaging contrast,and fast imaging speed.The thermoacoustic(TA)group of South China Normal University has dedicated to developing TA imaging for more than a decade and has made many breakthroughs.This review introduces these breakthroughs from two aspects including the improvement in techniques and the exploration of applications.On the technological level,there are ultrashort microwave pulse(USMP)-inducedTA imaging that can improve the imaging resolution,nonlinear thermoacoustic imaging(NTAI)that can improve the imaging contrast,polarized microwave-inducedthermoacoustic imaging(P-MTAI)that can obtain cellular-level alignment information,and more convenient and accurate handheld and multimodal probes.On the application side,the optimization and expansion have been carried out,mainly concentrating on breast and myocardial imaging.Finally,several current research directions are introduced,including the application of P-MTAI on joint imaging and research on whole-body imaging of small animals.

Automated apoptosis identification in fluorescence imaging of nucleus based on histogram of oriented gradients of high-frequency wavelet coefficients

The automatic and accurate identification of apoptosis facilitates large-scale cell analysis.Most identification approaches using nucleus fluorescence imaging are based on specific morphological parameters.However,these parameters cannot completely describe nuclear morphology,thus limiting the identification accuracy of models.This paper proposes a new feature extraction method to improve the performance of the model for apoptosis identification.The proposed method uses a histogram of oriented gradient(HOG)of high-frequency wavelet coefficients to extract internal and edge texture information.The HOG vectors are classified using support vector machine.The experimental results demonstrate that the proposed feature extraction method well performs apoptosis identification,attaining 95:7% accuracy with low cost in terms of time.We confirmed that our method has potential applications to cell biology research.

Quantitative tracing of bioprobes by simultaneously monitoring radiative and nonradiative relaxations

Bioprobe based on fluorescence is widely used in biological and medical research due to its high sensitivity and selectivity.Yet,its quantification in vivo is complicated and often compromised by the interaction between the fluorophore with the environmental factors,as well as the optical scattering and absorption by the tissue.A high florescence quantum yield and minimal interference by the environment are key requirements for designing an effective bioprobe,and the prerequisitions severely limit the available options.We propose that a comprehensive evaluation of potential bioprobe can be achieved by simultaneously measuring both radiative and nonradiative transitions,the two fundamental and complementary pathways for the energy de-excitation.This approach will not only improve the accuracy of the quantification by catching the information from a broader spectrum of the energy,but also provide additional information of the probe environment that often impacts the balance between the two forms of the energy transition.This work first analyzes the underlying mechanism of the hypothesis.The practical feasibility is then tested by means of simultaneous measurements of photoacoustic signal for the non-radiative and fluorescence for the radiative energy processes,respectively.It is demonstrated that the systematic evaluation of the probe energy de-excitation results in an improved quantitative tracing of a bioprobe in complex environment.

Spatial weight matrix in dimensionality reduction reconstruction for microelectromechanical system-based photoacoustic microscopy

A micro-electromechanical system(MEMS)scanning mirror accelerates the raster scanning of optical-resolution photoacoustic microscopy(OR-PAM).However,the nonlinear tilt angular-voltage characteristic of a MEMS mirror introduces distortion into the maximum back-projection image.Moreover,the size of the airy disk,ultrasonic sensor properties,and thermal effects decrease the resolution.Thus,in this study,we proposed a spatial weight matrix(SWM)with a dimensionality reduction for image reconstruction.The three-layer SWM contains the invariable information of the system,which includes a spatial dependent distortion correction and 3D deconvolution.We employed an ordinal-valued Markov random field and the Harris Stephen algorithm,as well as a modified delay-and-sum method during a time reversal.The results from the experiments and a quantitative analysis demonstrate that images can be effectively reconstructed using an SWM;this is also true for severely distorted images.The index of the mutual information between the reference images and registered images was 70.33 times higher than the initial index,on average.Moreover,the peak signal-to-noise ratio was increased by 17.08%after 3D deconvolution.This accomplishment offers a practical approach to image reconstruction and a promising method to achieve a real-time distortion correction for MEMS-based OR-PAM.

Microwave-induced thermoacoustic imaging with functional nanoparticles

As an emerging hybrid imaging modality,microwave-induced thermoacoustic imaging(MTAI),using microwaves as the excitation source and ultrasonic signals as the information carrier for combining the characteristics of high contrast of electromagnetic imaging and high resolution of ultrasound imaging,has shown broad prospects in biomedical and clinical applications.The imaging contrast depends on the microwave-absorption coe±cient of the endogenous imaged tissue and the injected MTAI contrast agents.With systemically introduced functional nanoparticles,MTAI contrast and sensitivity can be further improved,and enables visualization of biological processes in vivo.In recent years,functional nanoparticles for MTAI have been developed to improve the performance and application range of MTAI in biomedical applications.This paper reviews the recent progress of functional nanoparticles for MTAI and their biomedical applications.The challenges and future directions of microwave thermoacoustic imaging with functional nanoparticles in theeld of translational medicine are discussed.

Correction to: Spatial weight matrix in dimensionality reduction reconstruction for micro-electromechanical system-based photoacoustic microscopy

Following publication of the original article[1],the keywords are missing in the article.Keywords:Photoacoustic microscopy,Spatial weight matrix,Dimensionality reduction,Distortion correction,Mutual information The original article has been updated.

High-fidelity SIM reconstruction-based super-resolution quantitative FRET imaging

Structured illumination-based super-resolution Förster resonance energy transfer microscopy(SIM-FRET)provides an approach to resolving molecular behavior localized in intricate biological structures in living cells.However,SIM reconstruction artifacts will decrease the quantitative analysis fidelity of SIMFRET signals.To address these issues,we have developed a method called HiFi spectrum optimization SIM-FRET(HiFi-SO-SIM-FRET),which uses optimized Wiener parameters in the two-step spectrum optimization to suppress sidelobe artifacts and achieve super-resolution quantitative SIM-FRET.We validated our method by demonstrating its ability to reduce reconstruction artifacts while maintaining the accuracy of FRET signals in both simulated FRET models and live-cell FRET-standard construct samples.In summary,HiFi-SO-SIM-FRET provides a promising solution for achieving high spatial resolution and reducing SIM reconstruction artifacts in quantitative FRET imaging.

In vivo volumetric monitoring of revascularization of traumatized skin using extended depth-of-field photoacoustic microscopy

Faster and better wound healing is a critical medical issue.Because the repair process of wounds is closely related to revascularization,accurate early assessment and postoperative monitoring are very important for establishing an optimal treatment plan.Herein,we present an extended depth-of-field photoacoustic microscopy system(E-DOF-PAM)that can achieve a constant spatial resolution and relatively uniform excitation efficiency over a long axial range.The superior performance of the system was verified by phantom and in vivo experiments.Furthermore,the system was applied to the imaging of normal and trauma sites of volunteers,and the experimental results accurately revealed the morphological differences between the normal and traumatized skin of the epidermis and dermis.These results demonstrated that the E-DOF-PAM is a powerful tool for observing and understanding the pathophysiology of cutaneous wound healing.

Polarization microwave-induced thermoacoustic imaging for quantitative characterization of deep biological tissue microstructures

Polarization optical imaging can be used to characterize anisotropy in biological tissue microstructures and has been demonstrated to be a powerful tool for clinical diagnosis. However, the approach is limited by an inability to image targets deeper than ~1 mm due to strong optical scattering in biological tissues. As such, we propose a novel polarization microwave-induced thermoacoustic imaging(P-MTAI) technique to noninvasively detect variations in deep tissue by exploiting the thermoacoustic signals induced by four pulsed microwaves of varying polarization orientations. The proposed P-MTAI method overcomes the penetration limits of conventional polarization optical imaging and provides submillimeter resolution over depths of several centimeters. As part of the paper, the structural characteristics of tissues were quantified using a new parameter, the degree of microwave absorption anisotropy. P-MTAI was also applied to the noninvasive detection of morphological changes in cardiomyocytes as they transitioned from ordered to disordered states, providing a potential indication of myocardial infarction.

Collagen fiber anisotropy characterization by polarized photoacoustic imaging for just-in-time quantitative evaluation of burn severity

Just-in-time burn severity assessment plays a vital role in burn treatment and care.However,it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed.As an elastic skeleton of skin,the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner.Herein,the polarized photoacoustic technique(PPAT)for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed.First,phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage.Then,the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95,validated by burn skin samples.The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

Tomography-assisted Doppler photoacoustic microscopy:proof of concept

The previous methods to measure flow speed by photoacoustic microscopy solely focused on either the transverse or the axial flow component, which did not reflect absolute flow speed. Here, we present absolute flow speed maps by combining Doppler bandwidth broadening with volumetric photoacoustic microscopy. Photoacoustic Doppler bandwidth broadening and photoacoustic tomographic images were applied to measure the transverse flow component and the Doppler angle, respectively. Phantom experiments quantitatively demonstrated that ranges of 55° to 90° Doppler angle and 0.5 to 10 mm/s flow speed can be measured. This tomography-assisted method provides the foundation for further measurement in vivo.

The suppression of cervical cancer ferroptosis by macrophages:The attenuation of ALOX15 in cancer cells by macrophages-derived exosomes

Induction of cancer cell ferroptosis has been proposed as a potential treatment in several cancer types.Tumor-associated macrophages(TAMs)play a key role in promoting tumor malignant progression and therapy resistance.However,the roles and mechanisms of TAMs in regulating tumor ferroptosis is still unexplored and remains enigmatic.This study shows ferroptosis inducers has shown therapeutic outcomes in cervical cancer in vitro and in vivo.TAMs have been found to suppress cervical cancer cells ferroptosis.Mechanistically,macrophage-derived miRNA-660-5p packaged into exosomes are transported into cancer cells.In cancer cells,miRNA-660-5p attenuates ALOX15 expression to inhibit ferroptosis.Moreover,the upregulation of miRNA-660-5p in macrophages depends on autocrine IL4/IL13-activated STAT6 pathway.Importantly,in clinical cervical cancer cases,ALOX15 is negatively associated with macrophages infiltration,which also raises the possibility that macrophages reduce ALOX15 levels in cervical cancer.Moreover,both univariate and multivariate Cox analyses show ALOX15 expression is independent prognostic factor and positively associated with good prognosis in cervical cancer.Altogether,this study reveals the potential utility of targeting TAMs in ferroptosis-based treatment and ALOX15 as prognosis indicators for cervical cancer.

High-fluence relay-based disposable photoacoustic-ultrasonic endoscopy for in vivo anatomical imaging of gastrointestinal tract

Photoacoustic endomicroscopy combined with ultrasound(PAEM-US)has been a long-standing expectation for gastrointestinal tumor examination.Here,we introduce a prototype disposable PAEM-US catheter and corresponding power interface unit,featuring catheter switchability,self-internal three-dimensional scanning,and system repeatability for gastrointestinal endoscopy.By utilizing high-fluence relays,cascade insertion loss of the optical waveguide is minimized to 0.6 dB with a high performance of power resistance,and a focus-customizable acousto-optic coaxial probe is designed for high-sensitivity optical-resolution photoacoustic imaging.Imaging capability was demonstrated with in vivo anatomical imaging at 30 frames per second.Imaging results showed co-registered microscopic visualization of the microvascular and stratification of the rat colorectum with lateral resolution of 18μm and axial resolution of 63μm,holding great potential in the clinical detection of gastrointestinal diseases.

An intravascular needle coated by ZnO nanoflowers for in vivo elimination of circulating tumor cells

Circulating tumor cells(CTCs)are recognized as the main source of tumor recurrence and metastasis.Eliminating the CTCs in peripheral blood provides a new strategy to reduce the probability of recurrence or metastasis.Here,we proposed a concept to eliminate CTCs by inserting a needle in the superficial blood vessel.Using the property of ZnO and the structure of nanoflowers,we designed a medical needle coated with ZnO nanoflowers(ZNFs),which killed about 90%of captured CTCs in vitro and prevented the injecting CTCs from spreading to lung tissue in BABL/c mouse model.Results in vitro and in vivo demonstrated that the CTCs not only were captured and killed,but also detached from the needle surface after dead,enabling the ZNFs needle continually eliminate CTCs.Furthermore,a theoretical model was presented to explain the penetration mechanism of cells by nanostructures,which indicated that nanoflowers structure can puncture CTCs more easily than vertical nanowire structure.The concept of inserting an intravascular needle provides a potential strategy to lower the concentration of CTCs in blood and reduce the probability of tumor recurrence or metastasis.

Advancing insights into in vivo meningeal lymphatic vessels with stereoscopic wide-field photoacoustic microscopy

Meningeal lymphatic vessels(mLVs)play a pivotal role in regulating metabolic waste from cerebrospinal fluid(CSF).However,the current limitations in field of view and resolution of existing imaging techniques impede understanding the stereoscopic morphology and dynamic behavior of mLVs in vivo.Here,we utilized dual-contrast functional photoacoustic microscopy to achieve wide-field intravital imaging of the lymphatic system,including mLVs and glymphatic pathways.The stereoscopic photoacoustic microscopy based on opto-acoustic confocal features has a depth imaging capability of 3.75 mm,facilitating differentiation between mLVs on the meninges and glymphatic pathways within the brain parenchyma.Subsequently,using this imaging technique,we were able to visualize the dynamic drainage of mLVs and identify a peak drainage period occurring around 20–40 min after injection,along with determining the flow direction from CSF to lymph nodes.Inspiringly,in the Alzheimer’s disease(AD)mouse model,we observed that AD mice exhibit a~70%reduction in drainage volume of mLVs compared to wild-type mice.With the development of AD,there is be continued decline in mLVs drainage volume.This finding clearly demonstrates that the AD mouse model has impaired CSF drainage.Our study opens up a horizon for understanding the brain’s drainage mechanism and dissecting mLVs-associated neurological disorders.

Towards in vivo photoacoustic human imaging:Shining a new light on clinical diagnostics

Multiscale visualization of human anatomical structures is revolutionizing clinical diagnosis and treatment.As one of the most promising clinical diagnostic techniques,photoacoustic imaging(PAI),or optoacoustic imaging,bridges the spatial-resolution gap between pure optical and ultrasonic imaging techniques,by the modes of optical illumination and acoustic detection.PAI can non-invasively capture multiple optical contrasts from the endogenous agents such as oxygenated/deoxygenated hemoglobin,lipid and melanin or a variety of exogenous specific biomarkers to reveal anatomy,function,and molecular for biological tissues in vivo,showing significant potential in clinical diagnostics.In 2001,the worldwide first clinical prototype of the photoacoustic system was used to screen breast cancer in vivo,which opened the prelude to photoacoustic clinical diagnostics.Over the past two decades,PAI has achieved monumental discoveries and applications in human imaging.Progress towards preclinical/clinical applications includes breast,skin,lymphatics,bowel,thyroid,ovarian,prostate,and brain imaging,etc.,and there is no doubt that PAI is opening new avenues to realize early diagnosis and precise treatment of human diseases.In this review,the breakthrough researches and key applications of photoacoustic human imaging in vivo are emphatically summarized,which demonstrates the technical superiorities and emerging applications of photoacoustic human imaging in clinical diagnostics,providing clinical translational orientations for the photoacoustic community and clinicians.The perspectives on potential improvements of photoacoustic human imaging are finally highlighted.

Defect-rich titanium nitride nanoparticle with high microwaveacoustic conversion efficiency for thermoacoustic imaging-guided deep tumor therapy

Pulse microwave excite thermoacoustic(TA)shockwave to destroy tumor cells in situ.This has promising applications for precise tumor therapy in deep tissue.Nanoparticle(NP)with high microwave-acoustic conversion is the key to enhance the efficiency of therapy.In this study,we firstly developed defect-rich titanium nitride nanoparticles(TiN NPs)for pulse microwave excited thermoacoustic(MTA)therapy.Due to a large number of local structural defects and charge carriers,TiN NPs exhibit excellent electromagnetic absorption through the dual mechanisms of dielectric loss and resistive loss.With pulsed microwave irradiation,it efficiently converts the microwave energy into shockwave via thermocavitation effect,achieving localized mechanical damage of mitochondria in the tumor cell and yielding a precise antitumor effect.In addition to the therapeutic function,the NP-mediated TA process also generates images that provide valuable information,including tumor size,shape,and location for treatment planning and monitoring.The experimental results showed that the TiN NPs could be efficiently accumulated in the tumor via intravenous infusion.With the deep tissue penetration characteristics of microwave,the proposed TiN-mediated MTA therapy effectively and precisely cures tumors in deep tissue without any detectable side effects.The results indicated that defect-rich TiN NPs are promising candidates for tumor therapy.

Light-responsive charge-reversal nanovector for high-efficiency in vivo CRISPR/Cas9 gene editing with controllable location and time

Controllably and efficaciously localized CRISPR/Cas9 plasmids transfection plays an essential role in genetic editing associated with various key human diseases.We employed near-infrared(NIR)light-responsive CRISPR/Cas9 plasmids delivery via a charge-reversal nanovector to achieve highly efficient and site-specific gene editing.The nanovector with abundant positive charges was fabricated on the basis of an ultraviolet-sensitive conjugated polyelectrolyte coated on an upconversion nanomaterial(UCNP-UVP-P),which can convert into negative charges upon 980 nm light irradiation.Using the as-prepared nanovector,we demonstrated the plasmids could be efficiency transfected into tumor cells(~63%±4%)in a time-contolled manner,and that functional CRISPR/Cas9 proteins could be successfully expressed in a selected NIR-irradiated region.Particularly,this strategy was successfully applied to the delivery of CRISPR/Cas9 gene to tumor cells in vivo,inducing high efficiency editing of the target gene PLK-1 under photolrradiation.Therefore,this precisely controlled gene regulation strategy has the potential to serve as a new paradigm for gene engineering in complex biological systems.

Photosensitizer conjugate-functionalized poly(hexamethylene guanidine) for potentiated broad-spectrum bacterial inhibition and enhanced biocompatibility

Pathogen infection is the main cause of human morbidity and death.Traditional antibiotics usually sterilize bacteria in chemical ways,which tends to develop serious antibiotic resistance.Cationic polymers exhibit good bacterial inhibition with less resistance,but often face severe cytotoxicity toward normal cells.The optimization of polymeric antimicrobials for enhanced bactericidal capacity and improved biocompatibility is quite meaningful.In addition,photodynamic therapy(PDT) is a therapeutic modality with less susceptibility to develop resistance.Herein,a typical commercial polymeric antimicrobial,polyhexamethylene guanidine(PHMG) was selected for current proof-of-concept optimization due to its excellent bactericidal capacity but moderate biocompatibility.Eosin-Y(EoS)was copolymerized to afford EoS-labeled polymer conjugates,poly(2-(dimethylamino) ethyl methacrylate-co-eosin),P(DMAEMA-co-EoS),which was conjugated with PHMG to afford a novel polymeric antimicrobial,P(DMAEMA-co-EoS)-b-PHMG-b-P(DMAEMA-co-EoS),noted as PEoS-PHMG.It could efficiently kill broad-spectrum bacteria by physical damage and photodynamic therapy.Compared with PHMG,the bacterial inhibition of PEoS-PHMG was potentiated after the functionalization.Furthermore,PEoS-PHMG exhibited low cytotoxicity and minimal hemolysis,which was demonstrated by cell viability assays toward LO2 cells and RAW 264.7 cells as well as hemolytic assays against red blood cells.These results confirmed that the resultant PEoS-PHMG could act as promising alternative antibacterial materials with excellent broad-spectrum bacterial inhibition and favorable biocompatibility.