光声层析成像技术在骨坏死早期诊断中的应用

骨坏死是骨科临床常见的疾病,严重地影响人类健康及生存质量,临床研究表明骨坏死治疗效果取决该病的早期诊断．X线成像、计算机断层摄影(CT)及同位素骨扫描等一些传统的检查方法难以对骨坏死进行早期诊断,即使应用核磁共振成像(MRI)检测也存在很大的局限性,所以寻求一种简单易行、无创、价廉的早期诊断骨坏死的方法具有重要临床意义．光声层析成像是近年来发展起来的新技术,对哺乳动物组织可产生高对比、高分辨率影像．为探讨光声层析成像对骨坏死早期诊断的可行性,应用脉冲激光产生的光声成像技术对早期动物股骨头坏死模型及人股骨头坏死标本进行图像重建分析,实验结果显示,重建图像和股骨头坏死标本的部位、形状及尺寸完全吻合,成像系统空间分辨率为0.3 mm,表明光声层析成像技术有望成为一种有效的诊断早期骨坏死的新方法．     

光声成像在光动力疗法研究中的应用

组织氧合作用和光敏剂应用在疾病诊治中都有着重要的作用,因此其实时在体无损检测很有意义。光动力疗法涉及光敏剂、光和氧分子三大要素,其疗效受组织氧合作用影响。本文对光声成像(PAI)、光声寿命成像(PALI)和多光谱光声层析成像(MSOT)等光声成像技术在光动力疗法的研究和应用中的使用现状进行了综述。对相关设备系统在检测光敏剂、组织氧分压和微血管损伤等方面的应用原理和技术分别进行了介绍,并总结了这些技术的应用前景。     

基于样品及点源光声信号逆卷积的光声成像方法

光声成像是一种新的生物组织成像方法,在目前的光声成像中,都是通过样品光声信号和超声探测器的脉冲响应来计算样品光吸收的投影,但是由于无法获得超声探测器较准确的脉冲响应,影响重建图像质量。提出一种新的计算样品光吸收投影的方法,从理论上给出了样品光吸收投影和样品及点源光声信号的关系,由样品及点源光声信号的逆卷积可直接计算样品光吸收的投影,点源光声信号通过聚焦入射激光直接测得。试验结果显示,重建图像和样品的相对位置、形状及尺寸完全吻合,成像系统空间分辨率达到0．3mm,证明这是一种有效的光声成像方法。     

全光学光声/OCT双模态成像系统及其应用

本文提出了一种新型的全光学光声/OCT双模态成像系统。该系统利用同一个低相干迈克尔逊干涉仪即可实现非接触式光声成像和OCT于一体,系统装置结构简单,可同时获取生物组织的吸收与散射结构信息。通过模拟实验证明了该双模态成像系统的可行性及成像能力,并对活体小鼠耳朵同时进行光声/OCT成像测试,实验结果表明非接触式光声/OCT双模态成像系统可以实现生物组织内的微血管及散射结构的高分辨率成像。进一步地,我们将光声/OCT双模态成像系统应用于基底细胞癌的检测中,获得了初步的研究结果,表明了该系统在皮肤肿瘤诊断中的具有潜在的应用价值。     

基于压缩感知理论的光声成像方法研究现状

光声成像是一种新兴的无损生物医学成像方法,因其兼具高灵敏的光学对比度和超声能够对深层组织进行高分辨成像的优点,已经成为当前生物医学成像领域发展最快的技术之一。光声成像的光吸收对比度能够反映生物组织微小的组织病变,与血氧饱和度等多种功能和生理信息紧密相关,目前已被证明在肿瘤血管新生研究、早期癌症检测和心血管疾病诊断等方面有很大的应用潜力。基于超声阵列探测的常规光声计算层析成像系统,数据采集量大,由此导致的较低数据采集和成像速度成为制约该技术临床应用和转化的重要因素。压缩感知理论可以在远低于Nyquist采样定理的欠采样方式下,高质量重建信号,已被广泛用于信号处理和传统的医学图像重建领域。自2009年压缩感知理论被应用于光声成像以来,已有的研究结果表明,该方法为解决目前大区域光声成像的数据采集和成像速度问题提供了一条有效的途径。本文将重点介绍压缩感知理论用于光声成像的基本原理、研究现状、面临的问题和应用前景。     

热声、光声双模态早期乳腺肿瘤成像系统

本文提出一种热声、光声双模态乳腺肿瘤检测成像系统。本装置中,脉冲微波和脉冲激光分别为热声、光声激发源,产生的热声、光声信号被同一个超声探测器、同一套数据采集装置接收,用同一种成像算法重建出图像。该系统可同时获取多种互补的诊断参数,提高检测早期乳腺肿瘤的准确率。     

不同探测距离对光声成像的影响

为了研究不同探测距离对光声成像的影响,采用了线性扫描和滤波反投影算法,得出了吸收体间距相对探测距离越大,则成像亮度差异明显,吸收体远离探测器,则重建图像变形很明显.采用了光声信号衰减补偿的方法,对前者重建图像取域值,对后者采用旋转扫描重建,均得到了较好的图像质量.该研究结果对光声成像探测距离的合理选择和成像效果评估具有...     

基于阵列式换能器的光声成像系统的实现

目的:本文设计了一套光声成像(photoacoustic imaging,PAI)系统,由脉冲激光、阵列换能器、临床超声(ultrasound,US)主机、软件平台以及成像样品组成。系统的图像质量、最大成像深度等重要参数需通过实验进行确定。方法:使用本系统对黑色头发丝横截面进行成像,比较、分析光声(photoacoustic,PA)信号幅值的半极大处全宽度以量化图像分辨率。此外,使用系统对特定的光吸收体和鸡胸肉组织进行成像,确定系统的成像深度。结果:实验结果证明了PAI系统的实现,其PA图像的平均轴向和横向分辨率分别约为0.18 mm和1.44mm,系统的最大成像深度达到4.6 cm。结论:本PAI系统PA图像分辨率优于US主机获得的US图像分辨率,系统最大成像深度与其他国际研究组的系统成像深度的数量级一致。通过进一步优化与活体组织实验的开展,本PAI系统将有望实现临床成像诊断。     

热声成像技术及其在生物医学中的研究进展

摘要：成像技术在疾病的诊断、治疗和监测中起着重要的作用。热声成像作为一种非电离和非侵入性的新型生物医学成像技术,结合了微波成像高对比度和超声成像高分辨率的优点。因其具有利用内源性对比剂（如水和离子）或多种外源性对比剂（或两者兼有）提供结构、功能、和分子信息的能力,在预临床和临床应用中显示出了巨大的潜力。近几十年来,由于微波辐射源和超声硬件的不断发展,热声成像技术已被广泛用于生物医学成像领域。本文阐述了热声成像的基本原理及成像特点,介绍了近年来热声成像技术在生物医学上的应用、当前在解决相应临床问题应用中的优势及研究现状,最后针对热声成像技术在现有生物医学中面临的挑战对该技术进行了展望。     

不同方位探测对光声成像的影响

为了研究在不同方位探测光声信号对光声层析成像的影响,采用了数值仿真计算,得出了在有限角度扫描的情况下,吸收体分布与探测方向呈45度夹角时,成像效果较好;在条件允许的情况下,采用全方位探测扫描,其成像效果最好。该研究结果对光声成像扫描轨迹的设计、成像效果评估具有较好的参考价值。     

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150 μm)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...     

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging technologies. Existing retinal imaging modalities, such as fundus photography¹, confocal scanning laser ophthalmoscopy (cSLO)², and optical coherence tomography (OCT)³, have significant contributions in monitoring disease onsets and progressions, and developing new therapeutic strategies. However, they predominantly rely on the back-reflected photons from the retina. As a consequence, the optical absorption properties of the retina, which are usually strongly associated with retinal pathophysiology status, are inaccessible by the traditional imaging technologies.Photoacoustic ophthalmoscopy (PAOM) is an emerging retinal imaging modality that permits the detection of the optical absorption contrasts in the eye with a high sensitivity^4-7 . In PAOM nanosecond laser pulses are delivered through the pupil and scanned across the posterior eye to induce photoacoustic (PA) signals, which are detected by an unfocused ultrasonic transducer attached to the eyelid. Because of the strong optical absorption of hemoglobin and melanin, PAOM is capable of non-invasively imaging the retinal and choroidal vasculatures, and the retinal pigment epithelium (RPE) melanin at high contrasts ^6,7. More importantly, based on the well-developed spectroscopic photoacoustic imaging^5,8 , PAOM has the potential to map the hemoglobin oxygen saturation in retinal vessels, which can be critical in studying the physiology and pathology of several blinding diseases ⁹ such as diabetic retinopathy and neovascular age-related macular degeneration.Moreover, being the only existing optical-absorption-based ophthalmic imaging modality, PAOM can be integrated with well-established clinical ophthalmic imaging techniques to achieve more comprehensive anatomic and functional evaluations of the eye based on multiple optical contrasts^6,10 . In this work, we integrate PAOM and spectral-domain OCT (SD-OCT) for simultaneously in vivo retinal imaging of rat, where both optical absorption and scattering properties of the retina are revealed. The system configuration, system alignment and imaging acquisition are presented.     

用侧向光源进行前列腺光声扫描成像的研究

光声成像技术是近年来兴起的前列腺早期检测与成像的新技术.前列腺组织的结构特征需要一种无创的且光穿透深度足够大的光声激发方式.本文设计了一种可用于经由尿道对前列腺光辐照的侧向光源,并结合直肠处长焦区聚焦式超声换能器的光声探测展开了前列腺仿体的光声扫描成像.结果表明,侧向光源有利于单侧吸收体的定位和成像,具有较好的成像范围和深度,结合侧向光源的旋转可实现全方位成像.因此该侧向光源有望成为早期前列腺肿瘤光声成像技术中一种新型的光源结构,具有重要意义.     

生物组织光声粘弹显微成像

提出一种反演生物组织粘弹信息的新型无损光声粘弹显微成像方法,它是以强度调制激光作为激发源,通过检测光声（Photoacoustic,PA）信号的相位重建组织粘弹特性分布的成像方法.实验利用不同浓度的琼脂样品来验证光声粘弹显微测量中相位随浓度变化的依赖关系.利用埋有头发丝的琼脂样品来测试这种显微方法的成像分辨率.利用具有不同粘弹性的离体生物组织来验证系统的成像能力.实验结果表明,这种新方法能够高分辨率和高对比度地重建出具有不同粘弹性的生物组织的光声粘弹显微图像,有望实现组织结晶类病变水平的显微在体检测.     

Photoacoustic and ultrasound (PAUS) dermoscope with high sensitivity and penetration depth by using a bimorph transducer

A bimorph transducer was proposed to improve the detection sensitivity and imaging depth of photoacoustic and ultrasound (PAUS) dermoscope. By applying the bimorph transducer, the imaging depth and sensitivity of PAUS dermoscope were enhanced by simultaneously improving excitation efficiency and reception bandwidth. The integrated design of the imaging head of the dermoscope makes it highly convenient for detecting human skin. The PAUS imaging performance was demonstrated via visualizing subcutaneous tumor and depicting full structures of different skin layers from epidermis to subcutaneous tissue. The results confirm that the dermoscope with the bimorph transducer is well suited for PA and US dual‐modality imaging, which can provide multi‐information for skin disease.     

Wideband Optical Detector of Ultrasound for Medical Imaging Applications

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic imaging. In medical applications, one of the major limitations of optical sensing technology is its susceptibility to environmental conditions, e.g. changes in pressure and temperature, which may saturate the detection. Additionally, the clinical environment often imposes stringent limits on the size and robustness of the sensor. In this work, the combination of pulse interferometry and fiber-based optical sensing is demonstrated for ultrasound detection. Pulse interferometry enables robust performance of the readout system in the presence of rapid variations in the environmental conditions, whereas the use of all-fiber technology leads to a mechanically flexible sensing element compatible with highly demanding medical applications such as intravascular imaging. In order to achieve a short sensor length, a pi-phase-shifted fiber Bragg grating is used, which acts as a resonator trapping light over an effective length of 350 µm. To enable high bandwidth, the sensor is used for sideway detection of ultrasound, which is highly beneficial in circumferential imaging geometries such as intravascular imaging. An optoacoustic imaging setup is used to determine the response of the sensor for acoustic point sources at different positions.     

Perspectives,potentials and trends of ex vivo and in vivo optical molecular pathology

It is pivotal for medical applications, such as noninvasive histopathologic characterization of tissue, to realize label‐free and molecule‐specific representation of morphologic and biochemical composition in real‐time with subcellular spatial resolution. This unmet clinical need requires new approaches for rapid and reliable real‐time assessment of pathologies to complement established diagnostic tools. Photonic imaging combined with digitalization offers the potential to provide the clinician the requested information both under in vivo and ex vivo conditions. This report summarizes photonic approaches and their use in combination with image processing, machine learning and augmented virtual reality that might solve current challenges in modern medicine. Details are given for pathology, intraoperative diagnosis in head and neck cancer and endoscopic diagnosis in gastroenterology.      

Integrated photoacoustic and diffuse optical tomography system for imaging of human finger joints in vivo

In this study, we developed a dual‐modality tomographic system that integrated photoacoustic imaging (PAI) and diffuse optical tomography (DOT) into a single platform for imaging human finger joints with fine structures and associated optical properties. In PAI, spherical focused transducers were utilized to collect acoustic signals, and the concept of virtual detector was applied in a conventional back‐projection algorithm to improve the image quality. A finite‐element based reconstruction algorithm was employed to quantitatively recover optical property distribution in the objects for DOT. The phantom results indicate that PAI has a maximum lateral resolution of 70 µm in resolving structures of targets. DOT was able to recover both optical absorption and reduced scattering coefficients of targets accurately. To validate the potential of this system in clinical diagnosis of joint diseases, the distal interphalangeal (DIP) joints of 4 healthy female volunteers were imaged. We successfully obtained high‐resolution images of the phalanx and the surrounding soft tissue via PAI, and recovered both optical absorption and reduced scattering coefficients of phalanx using DOT. The in vivo results suggest that this dual‐modality system has the potential for the early diagnosis of joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA).

Integrated PAI/DOT imaging interface (top) and typical reconstruction of structures and associated optical properties of a female finger joint via PAI and DOT (bottom).