Commentary on“The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in the early phase of cutting maneuvers in female athletes”

1.Introduction For decades,substantial disagreement has persisted as to whether dynamic knee valgus is the cause of the majority of anterior cruciate ligament(ACL)injuries or rather the result of the ACL rupture.1 Consequently,great effort and expense has gone into capturing 3-dimensional kinetics and kinematics from live athletes to drive in vitro and in silico models of ACL injury in order to elucidate the actual mechanism of injury,as these factors have been demonstrated to be surrogates of intraarticular structural loading on the ACL.2,3 The elucidation of injury mechanisms for non-contact ACL injuries is of great medical value as such knowledge consequently permits quantified examination and validation of interventions and their respective effectiveness in both prevention and rehabilitation of these traumatic knee injuries.

Wideband frequency-dependent dielectric properties of rat tissues exposed to low-intensity focused ultrasound in the microwave frequency range

Tissue dielectric properties can vary upon the incident of an acoustic wave.The goal of this study is to quantify this change due to the acoustoelectric effect(AE),and to obtain the frequency-dependent dielectric properties of tissues exposed to low-intensity focused ultrasound(LIFU).The dielectric properties of the blood,brain,chest muscle,heart,kidney,leg muscle,liver,lung,pancreas,and spleen of rats were measured by an open-ended coaxial probe method.The acoustic intensity of LIFU focus was 2.97 MPa(67.6 W/cm^(2)),3.95 MPa(120 W/cm^(2)),and 5.17 MPa(204 W/cm^(2)),respectively,and the measurement frequency band was 0.1–7.08 GHz.The measurement results show that with the LIFU modulation,the conductivity and dielectric constant decreased in the high-frequency band,and on the contrary,they increased in the lowfrequency band,and the larger the acoustic intensity was,the more obvious the phenomenon was.This work contributes to a better understanding of the mechanisms by which ultrasound acts on the dielectric properties of biological tissues.It is expected that the findings from this study will provide a basis that the response of tissue to LIFU modulation can be monitored by noninvasive techniques such as microwave-induced thermoacoustic imaging(MTI)and microwave imaging,present a new idea for improving the endogenous contrast between different biological tissues in MTI and acoustoelectric imaging,and possibly lead to the development of a new imaging method based on the relaxation time of tissue after LIFU modulation.

Microwave-induced thermoacoustic imaging of joints

Due to the complexity of joint structures and the diversity of disorders in the joints,the diagnosis of joint diseases is challenging.Current clinical diagnostic techniques for evaluating joint diseases,such as arthritis,have strengths and weaknesses.New imaging techniques need to be developed for the diagnosis or auxiliary diagnosis of arthritis.As an emerging nonintrusive low-cost imaging method,microwave-induced thermoacoustic imaging(TAI)can present tissue morphology while providing the tissue microwave energy absorption density distribution related to dielectric properties.TAI is currently in development to potentially visualize joint anatomic structures and to detect arthritis.Here,we offer a mini review to summarize the status of research on TAI of joints and present an outlook to the future development of TAI in the detection of joint diseases.

Thermoacoustic tomography of in vivo rat brain

We present for the¯rst time in vivo imaging of rat brain using microwave-induced thermoacoustic tomography(TAT).The in vivo imaging of rat brain was realized through an unconventional delivery of microwave energy from the front of rat brain(while the transducer was scanned along coronal plane of the animal brain),which maximized the microwave penetration into the brain.In addition,we found that the imaging contrast was highly dependent on the direction of the electric¯eld polarization(EFP)and that more tissue structures/compositions could be revealed when both X-and Y-EFPs were used for TAT.The in vivo TAT images of rat brain obtained were compared with the 3.0 T MRI images and histological photographs,and numerous important brain anatomical structures were identi¯ed.An example of our TAT approach for imaging a foreign object embedded in a rat brain was also demonstrated.This study suggests that TAT has a great potential to be used in neuroscience studies and in noninvasive imaging of brain disorders.

A comparative study on water and dry coupling in photoacoustic tomography of the finger joints

We present a systematical study on comparison between water and dry coupling in photoacoustic tomography of the humanfinger joints.Compared to the direct water immersion of thefinger for water coupling,the dry coupling is realized through a transparent PDMSfilm-based water bag,which ensures water-free contact with the skin.The results obtained suggest that the dry cou-pling provides image quality comparable to that by water coupling while eliminating the wrin-kling of thefinger joint caused by the water immersion.In addition,the dry coupling offers more stable hemodynamic images than the water coupling as the water immersion of thefinger joint causes reduction in blood vessel size.

Optical neuroimaging:advancing transcranial magnetic stimulation treatments of psychiatric disorders

Transcranial magnetic stimulation(TMS)has been established as an important and effective treatment for various psychiatric disorders.However,its effectiveness has likely been limited due to the dearth of neuronavigational tools for targeting purposes,unclear ideal stimulation parameters,and a lack of knowledge regarding the physiological response of the brain to TMS in each psychiatric condition.Modern optical imaging modalities,such as functional near-infrared spectroscopy and diffuse optical tomography,are promising tools for the study of TMS optimization and functional targeting in psychiatric disorders.They possess a unique combination of high spatial and temporal resolutions,portability,real-time capability,and relatively low costs.In this mini-review,we discuss the advent of optical imaging techniques and their innovative use in several psychiatric conditions including depression,panic disorder,phobias,and eating disorders.With further investment and research in the development of these optical imaging approaches,their potential will be paramount for the advancement of TMS treatment protocols in psychiatry.

Thermoacoustic assessment of hematocrit changes in human forearms

Abnormal hematocrit(Hct)is associated with an increased risk of pre-hypertension and all-cause death in general population,and people with a high Hct value are susceptible to arterial cardiovascular disease and venous thromboembolism.In this study,we report for the first time on the ability of thermoacoustic imaging(TAI)for in vivo evaluating Hct changes in human forearms.In vitro blood samples with different Hct values from healthy volunteers(n=3)were prepared after centrifugation.TAI was performed using these samples in comparison with the direct measurements of conductivity.In vivo TAI was conducted in the forearm of healthy volunteers(n=7)where Hct changes were produced through a vascular occlusion stimulation over a period of time.The results of in vitro blood samples obtained from the 3 healthy subjects show that the thermoacoustic(TA)signals changes due to the variation of blood conductivity are closely related to the changes in Hct.In addition,the in vivo TA signals obtained from the 7 healthy subjects consistently increase in the artery/muscle and decrease in the vein during venous or arterial occlusion because of the changed Hct value in their forearms.These findings suggest that TAI has the potential to become a new tool for monitoring Hct changes for a variety of pre-clinical and clinical applications.

Biomedical microwave-induced thermoacoustic imaging

Microwave induced thermoacoustic imaging(MTAI)has emerged as a potential biomedical imaging modality with over 20-year growth.MTAI typically employs pulsed microwave as the pumping source,and detects the microwave-induced ultrasound wave via acoustic transducers.Therefore,it features high acoustic resolution,rich elect romagnetic contrast,and large imaging depth.Benefiting from these unique advantages,MTAI has been extensively applied to various fields including pathology,biology,material and medicine.Till now,MTAI has been deployed for a wide range of biomedical applications,including cancer diagnosis,joint evaluation,brain in-vestigation and endoscopy.This paper provides a comprehensive review on(1)essential physics(endogenous/exogenous contrast mechanisms,penetration depth and resolution),(2)hardware configurations and software implementations(excit ation source,antenna,ultrasound detector and image recovery algorithm),(3)animal studies and clinical applications,and(4)future directions.

基于微波热声层析成像定量重建生物组织电导率的改进方法

目的生物电磁学参数中的电导率与组织的功能性信息直接相关,精准重建生物组织电导率在医学成像技术和医学诊断领域中有着重要意义。本文改进定量微波热声层析成像(microwave-induced thermoacoustic tomography,MTAT)算法,使组织电导率的重建精度提高。方法本文在利用有限元离散法求解热声波动方程和亥姆霍兹方程的基础之上,提出了一种基于正则化牛顿迭代法(regularized Newton iteration method,RNIM)定量重建组织电导率的改进方法。结果通过数值模拟实验和含不同浓度NaCl溶液的仿体实验,验证了算法改进的有效性。组织仿体实验结果表明,目标在不同位置、不同大小、不同对比度情况下,相比于定量微波热声层析成像采用拟合(fitting)的方法,采用正则化牛顿法定量重建的仿体电导率相对误差明显降低,重建目标精度提高。在仿体实验中采用RNIM方法重建相同浓度的单目标在不同位置的电导率变化幅度更小,以及重建多目标电导率的相对比值与实际更接近,实验结果验证了改进方法的稳定性。结论研究结果表明优化算法能更加准确地定量重建组织仿体的电导率,这对于肿瘤的定位和分期的早期筛查及精准诊疗,预防疾病恶化具有重要意义。

微波热声成像技术用于人体甲状腺检测

本文首次通过人体实验验证了微波热声成像技术用于人体甲状腺检测的可行性.文章首先讨论了该技术用于人体甲状腺检测的可行性;然后对3名志愿者的健康甲状腺进行了微波热声成像实验.结果表明:微波热声成像能够对人体健康甲状腺进行清晰成像,能够真实反映皮肤、甲状腺和气管等不同组织的结构特征;并且一次完整的检测过程时间约5 s,系统操作简单成像快速.综上所述,微波热声成像技术有望为甲状腺疾病的基础研究和临床诊断提供一种新的影像学参考.

一种低成本、高性价比的穿戴式扩散光学断层人脑成像系统

现有扩散光学断层成像(diffuse optical tomography,DOT)系统常采用高档光探测器和放大器,令系统成本居高不下、性价比较低.本文旨在使用全新技术降低系统成本、增加成像深度,研发一套可实用于人脑成像的新型扩散光学断层成像系统.为此采用了成本较低的新型光探测器和一款自主设计研制的光电二极管前置放大器.相较于实验室原有DOT系统,新系统整体成本节约了40%以上.其次,设计了一款具有弹性并可适应多种不规则待测物(subject)外形的无光纤穿戴式脑-机接口(brain computer interface,BCI)装置.本文首次将手持式3D激光扫描仪应用于待测物外形结构和光源-探测器位置信息的精确获取.最后综合应用上述技术装备于人脑形状仿体成像实验中,新系统的目标成像深度提升至35 mm.验证结果说明本系统已具备了实际人脑功能成像能力.

多波长光声层析成像技术用于人体气管探测

目的通过多波长光声层析成像技术对气管结构进行重建成像。方法基于阵列换能器的光声成像技术对7名志愿者的气管进行了多波长光声层析成像实验,研究光声层析成像技术对气管不同呼吸相、不同层面的高分辨率(高达150μm)图像特征,并对该技术的成像优劣性进行评价。结果光声层析成像技术能对人体气管进行清晰成像,能够真实反映气管及气管周围组织的结构特征。结论光声层析成像技术可作为一种无创便捷、无电离辐射的成像方式,对气管解剖和功能状态进行实时评估。

基于Renyi熵滤波的光声图像重建算法设计与实现

针对光声图像重建过程中存在的原始光声信号信噪比差、重建图像对比度低、分辨率不足等问题,提出了基于Renyi熵的光声图像重建滤波算法.该算法首先根据原始光声信号的Renyi熵分布情况,确定分割阈值,并滤除杂波信号;再利用滤波后的光声数据进行延时叠加光声图像重建.利用该滤波算法分别处理铅笔芯横截面(零维)、头发丝(一维)以及小鼠大脑皮层血管(二维)等不同维度样本的光声信号,实验结果表明:相比Renyi熵处理之前,重建图像对比度平均增强了32.45%,分辨率平均提高了30.78%,信噪比提高了47.66%,均方误差降低了35.01%;相比典型的滤波处理算法(模极大值法和阈值去噪法),本研究中图像的对比度、分辨率和信噪比分别提高了25.94%/10.60%、27.90%/19.48%、35.21%/10.60%,均方误差减小了28.57%/16.66%.因此,选择利用Renyi熵滤波算法处理光声信号,从而使光声图像重建质量得到大幅改善.

Photoacoustic molecular imaging using combined acupuncture and gold nanorods as a composite contrast agent

In this study,we developed a novel photoacoustic imaging technique based on poly(ethyleneglycol)-coated(PEGylated)gold nanorods(PEG-GNRs)(as the contrast agent)combined with traditional Chinese medicine(TCM)acupuncture(as the auxiliary method)for quantitatively monitoring contrast enhancement in the vasculature of a mouse brain in vivo.This study takes advantage of the strong near-infrared absorption(peak at
700 nm)of GNRs and the ability to adjust the hemodynamics of acupuncture.Experimental results show that photoacoustic tomography(PAT)successfully reveals the optical absorption variation of the vasculature of the mouse brain in response to intravenous administration of GNRs and acupuncture at the Zusanli acupoint(ST36)both individually and combined.The quantitative measurement of contrast enhancement indicates that the composite contrast agents(integration of acupuncture and GNRs)would greatly enhance the photoacoustic imaging contrast.The quantitative results also have the potential to estimate the local concentration of GNRs and even the real-time effects of acupuncture.

一种提高乳腺扩散光学层析成像分辨率的方式

目的 扩散光学层析成像(diffuse optical tomography,DOT)在女性大尺寸乳腺检测时因信噪比低,导致其成像分辨率较低。本文基于计算机断层扫描激光乳腺成像系统(computed tomography laser mammography,CTLM),提出一种提高乳腺扩散光学层析成像分辨率的方式。方法 本文首先通过仿体实验探讨仿体直径和目标深度对扩散光学层析成像分辨率的影响;其次,本文使用高透性的光敏树脂通过3D打印制作外壳定位件,在验证其对扩散光学层析成像分辨率无显著影响后,利用外壳定位件对被测物进行约束压缩,以减小被测物直径来提高信噪比,优化扩散光学层析成像分辨率。结果 本文通过仿体实验验证了仿体直径的增加和目标深度的变化均会在一定程度上影响成像分辨率,随着仿体直径的增加,其感兴趣区(region of interests,ROIs)宽轴和长轴半高宽基本属于上升趋势;随着目标深度的增加,也会对ROIs宽轴和长轴半高宽产生影响。同时发现仿体直径对ROIs长轴半高宽有显著影响,目标深度对ROIs宽轴半高宽有显著影响。另外通过仿体实验结果验证了外壳定位件对扩散光学层析成像分辨率无显著影响,利用外壳定位件约束压缩后ROIs长轴半高宽降幅明显,降幅达到30%以上,远大于宽轴半高宽的降幅,达到了提高成像分辨率的作用。结论 本文所提出的方式能够达到提高乳腺扩散光学层析成像分辨率的作用,且所使用的材料和方法简单,具有较强的可实施性,为提高乳腺扩散光层析成像分辨率提供了新思路。

Deep learning for image reconstruction in thermoacoustic tomography

Microwave-induced thermoacoustic tomography(TAT)is a rapidly-developing noninvasive imaging technique that integrates the advantages of microwave imaging and ultrasound imaging.While an image reconstruction algorithm is critical for the TAT,current reconstruction methods often creates significant artifacts and are computationally costly.In this work,we propose a deep learning-based end-to-end image reconstruction method to achieve the direct reconstruction from the sinogram data to the initial pressure density image.We design a new network architecture TAT-Net to transfer the sinogram domain to the image domain with high accuracy.For the scenarios where realistic training data are scarce or unavailable,we use the finite element method(FEM)to generate synthetic data where the domain gap between the synthetic and realistic data is resolved through the signal processing method.The TAT-Net trained with synthetic data is evaluated through both simulations and phantom experiments and achieves competitive performance in artifact removal and robustness.Compared with other state-of-the-art reconstruction methods,the TAT-Net method can reduce the root mean square error to 0.0143,and increase the structure similarity and peak signal-to-noise ratio to 0.988 and 38.64,respectively.The results obtained indicate that the TAT-Net has great potential applications in improving image reconstruction quality and fast quantitative reconstruction.

Convolutional neural network for breast cancer diagnosis using diffuse optical tomography

We have developed a computer-aided diagnosis system based on a convolutional neural network that aims to classify breast mass lesions in optical tomographic images obtained using a diffuse optical tomography system,which is suitable for repeated measurements in mass screening.Sixty-three optical tomographic images were collected from women with dense breasts,and a dataset of 12602D gray scale images sliced from these 3D images was built.After image preprocessing and normalization,we tested the network on this dataset and obtained 0.80 specificity,0.95 sensitivity,90.2%accuracy,and 0.94 area under the receiver operating characteristic curve(AUC).Furthermore,a data augmentation method was implemented to alleviate the imbalance between benign and malignant samples in the dataset.The sensitivity,specificity,accuracy,and AUC of the classification on the augmented dataset were 0.88,0.96,93.3%,and 0.95,respectively.

双频微波热声成像方法及应用研究

为解决传统微波热声成像技术对含有骨骼的复杂生物组织难以完整清晰重建的问题,本文提出新型双频微波热声成像技术.即利用两个不同中心频率短脉宽微波激励组织得到两组单频微波热声数据,两组数据利用区域像素均值与区域吸收系数补偿进行能量校准后,以骨骼在不同频率下微波能量吸收系数的比值进行加权相减,最后得到减小骨骼副作用的双频微波热声图像.本文首先对双频微波热声成像方法的原理进行了研究,然后介绍了搭建的双频微波热声成像系统,最后进行了兔膝关节与鸡跖骨成像实验,并对成像结果进行了定性观察与半定量量化分析.实验结果表明,与单频微波热声成像相比,双频微波热声成像中的组织估算尺寸和微波热声信号趋势与相应的组织实际尺寸和理论分析更加符合.双频微波热声成像技术能够减小骨骼的“负造影”作用带来的影响,从而使受此作用影响的半月板、交叉韧带和骨髓腔清晰完整重建.综上,此方法能够提高微波热声成像技术对含骨复杂生物组织的成像能力,从而推动相关应用研究的进展,并为需要缓解骨骼副作用的其他影像学方法提供参考.

类血红细胞状氧化铁纳米颗粒在小鼠大脑皮层光声成像中的应用

制备了盐酸多巴胺修饰的类血红细胞状氧化铁纳米颗粒(DA@Fe_2O_3),基于其良好的光吸收特性,讨论了其作为光声造影剂的可能性.对DA@Fe_2O_3进行了体外细胞毒性测试,不同浓度材料光声信号响应和体外光声造影增强特性测试等;在此基础上,研究了其对小鼠大脑皮层血管的光声造影效果.结果表明,DA@Fe_2O_3生物兼容性良好、体外光声性能和造影效果优异,在小鼠大脑皮层血管中能起到较好的光声造影增强作用,具有成为高性能光声造影剂的潜质.

Thin ceramic PZT dual-and multi-frequency pMUT arrays for photoacoustic imaging

Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging(PAI)systems to achieve high spatial resolution and large imaging depth for biomedical applications.In this article,we report on the development of ceramic thin-film PZT-based dual-and multi-frequency piezoelectric micromachined ultrasonic transducer(pMUT)arrays and the demonstration of their PAI applications.With chips sized 3.5mm in length or 10mm in diameter,square and ring-shaped pMUT arrays incorporating as many as 2520 pMUT elements and multiple frequencies ranging from 1 MHz to 8 MHz were developed for endoscopic PAI applications.Thin ceramic PZT with a thickness of 9μm was obtained by wafer bonding and chemical mechanical polishing(CMP)techniques and employed as the piezoelectric layer of the pMUT arrays,whose piezoelectric constant d_(31)was measured to be as high as 140 pm/V.Benefiting from this high piezoelectric constant,the fabricated pMUT arrays exhibited high electromechanical coupling coefficients and large vibration displacements.In addition to electrical,mechanical,and acoustic characterization,PAI experiments with pencil leads embedded into an agar phantom were conducted with the fabricated dual-and multi-frequency pMUT arrays.Photoacoustic signals were successfully detected by pMUT elements with different frequencies and used to reconstruct single and fused photoacoustic images,which clearly demonstrated the advantages of using dual-and multi-frequency pMUT arrays to provide comprehensive photoacoustic images with high spatial resolution and large signal-to-noise ratio simultaneously.