光学相干断层成像在临床医学中的应用

光学相干断层成像(OCT)是一种基于弱相干光学断层成像技术,可以对生物组织活体断层成像,是继计算机X射线摄影(CR)和数字X射线摄影(DR)、超声、电子计算机断层扫描(CT)、磁共振成像(MRI)之后又一新的生物组织成像方法。OCT在眼科、皮肤科、心血管科、肿瘤科、骨科、口腔科、妇科等对组织病变的早期光学诊断和实时动态监测方面具有广泛的应用及重要的临床价值。本文就OCT的基本原理、研究现状、主要的临床应用和应用过程中存在的问题进行综述并展望未来相关的发展趋势。     

高动态光学血管造影成像

我们提出一种高动态光学血管造影成像(HDOA)方法来实现活体生物样本血管造影成像.该方法通过设置高动态范围曝光时间,依据动态积分效应和吸收效应以实现高动态积分时间调制.通过该方法,不仅能够同时获得各级血管清晰的造影图像,还能消除样品厚度不均、吸收系数不同对成像造成的影响.论文以仿体和活体金鱼为样品,通过实验验证了HDOA方法根据动态积分调制效应和吸收效应,能有效实现各级血管同时成像.     

金纳米棒-聚苯胺核壳纳米材料的光学相干层析成像能力研究

对比试剂的使用能够显著提升光学相干层析(OCT)的成像效果。聚苯胺(PANI)是一种有机导电聚合物,在近红外(NIR)区有着很强的光吸收。本文采用PANI对常见的OCT成像对比试剂--金纳米棒(GNRs)进行修饰,合成了PANI/GNRs核壳粒子,并对其OCT成像对比能力进行了研究。PANI/GNRs展现出良好的NIR光吸收特性;同时,PANI对GNRs的包裹也显著提升了金纳米结构的稳定性、降低了GNRs原有的毒性。选用离体猪肝组织作为检测样本,发现纳米材料使用能够显著提升OCT的成像效果。与未修饰的GNRs及PANI粒子相比,PANI/GNRs的OCT成像对比效果明显更好。因此,PANI包裹的GNRs核壳纳米材料有望成为一种低毒性且效果良好的OCT对比试剂用于生物组织成像。     

生物光子成像专题序言

本专题刊由八篇有关生物组织光学成像方面的邀稿 (Invited papers)及一些常规文章组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 (OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术、漫射光断层成像等等方面。另一方面 ,荧光标记成像、单分子探测等等手段 ,拓展了研究范围 ,提供了更多的处理方法…     

采用OCT系统对组织光学通透的研究

组织通透方法采用高折射率化学试剂对生物组织进行渗透,改变组织的光学均匀性,可以有效地改善光学成像的穿透深度,受到生物医学光学研究领域的重视。利用光学相干层析成像技术,测量通透过程中不同测量深度下组织的散射特征的变化。通过采用系统信号对数的梯度值近似地表征光学散射系数,研究了通透过程中组织的散射特征随渗透时间和测量深度的动态关系。实验证明了组织通透可以有效地增加光子的穿透深度,并改善成像质量。研究发现:不同测量深度处组织的散射系数及其变化幅度、变化过程和变化趋势等均存在一定的差异性,并与组织的微观结构、其通透效果,化学试剂在组织中的渗透行为等有密切关系,有助于组织通透过程的理解,并为组织通透机制提供可能的实验依据。     

光声成像及其在生物医学中的应用

光声成像是一种新近迅速发展起来、基于生物组织内部光学吸收差异、以超声作媒介的无损生物光子成像方法,它结合了纯光学成像的高对比度特性和纯超声成像的高穿透深度特性的优点,以超声探测器探测光声波代替光学成像中的光子检测,从原理上避开了光学散射的影响,可以提供高对比度和高分辨率的组织影像,为研究生物组织的结构形态、生理特征、代谢功能、病理特征等提供了重要手段,在生物医学临床诊断以及在体组织结构和功能成像领域具有广泛的应用前景.对光声成像技术的机理、光声成像技术和方法、光声图像重建算法以及光声成像在生物医学上的应用情况作一个简单介绍,希望有助于推动我国在该领域的科研和开发应用工作的迅速发展.     

生物光学成像专刊征文通知

本专刊主要由有关生物组织光学成像方面的邀稿和投稿组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 ( OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术等等方面。在这些技术中 ,相干光断层成像具有较高的空间分辨率 ,技术相对比较成熟 ,但其检测深度有限。漫射光断层成像的空间分辨率是比较低的 …     

生物光学成像专题征文通知

本专刊主要由有关生物组织光学成像方面的邀稿和投稿组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 ( OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术等等方面。在这些技术中 ,相干光断层成像具有较高的空间分辨率 ,技术相对比较成熟 ,但其检测深度有限。漫射光断层成像的空间分辨率是比较低的 …     

生物组织的超声调制光学成像技术

具有超声定位的高空间分辨率和光学检测的高灵敏度的超声调制光学成像技术是一种有前途的无损的生物组织成像技术。文章阐述了该技术的成像原理,评述了前人在散射介质中声光作用机制的理论研究;介绍了该领域在技术路线上的最新研究进展;最后总结了超声调制光学成像技术的优点并展望了其在生物医学领域的应用前景。     

高动态光学血管造影成像（英文）

我们提出一种高动态光学血管造影成像(HDOA)方法来实现活体生物样本血管造影成像.该方法通过设置高动态范围曝光时间,依据动态积分效应和吸收效应以实现高动态积分时间调制.通过该方法,不仅能够同时获得各级血管清晰的造影图像,还能消除样品厚度不均、吸收系数不同对成像造成的影响.论文以仿体和活体金鱼为样品,通过实验验证了HDOA方法根据动态积分调制效应和吸收效应,能有效实现各级血管同时成像.     

Tissue-simulating Phantoms for Assessing Potential Near-infrared Fluorescence Imaging Applications in Breast Cancer Surgery

Inaccuracies in intraoperative tumor localization and evaluation of surgical margin status result in suboptimal outcome of breast-conserving surgery (BCS). Optical imaging, in particular near-infrared fluorescence (NIRF) imaging, might reduce the frequency of positive surgical margins following BCS by providing the surgeon with a tool for pre- and intraoperative tumor localization in real-time. In the current study, the potential of NIRF-guided BCS is evaluated using tissue-simulating breast phantoms for reasons of standardization and training purposes.Breast phantoms with optical characteristics comparable to those of normal breast tissue were used to simulate breast conserving surgery. Tumor-simulating inclusions containing the fluorescent dye indocyanine green (ICG) were incorporated in the phantoms at predefined locations and imaged for pre- and intraoperative tumor localization, real-time NIRF-guided tumor resection, NIRF-guided evaluation on the extent of surgery, and postoperative assessment of surgical margins. A customized NIRF camera was used as a clinical prototype for imaging purposes.Breast phantoms containing tumor-simulating inclusions offer a simple, inexpensive, and versatile tool to simulate and evaluate intraoperative tumor imaging. The gelatinous phantoms have elastic properties similar to human tissue and can be cut using conventional surgical instruments. Moreover, the phantoms contain hemoglobin and intralipid for mimicking absorption and scattering of photons, respectively, creating uniform optical properties similar to human breast tissue. The main drawback of NIRF imaging is the limited penetration depth of photons when propagating through tissue, which hinders (noninvasive) imaging of deep-seated tumors with epi-illumination strategies.     

时间分辨反射确定生物组织光学性质的方法研究

通过考虑吸收系数对漫射常数的影响,改进了时间分辨反射中两点测量生物组织光学性质的方法,对约化散射系数与吸收系数之比较小的生物组织进行了模型测量,结果表明此种不仅减小了测量的系统误差,而且扩展了两点测量法的应用范围。同时也较为详细地讨论了有效时间的选择和光源与探测点间的距离对测量结果的影响。     

Characterization of the optical properties of color pastes for the design of optical phantoms mimicking biological tissue

Clinicians need a way to rapidly and reliably test the correct functioning of near‐infrared spectroscopy (NIRS)–based oximeters. Therefore, optical phantoms for quality assessment of NIRS oximeters are needed. The fabrication of such phantoms that mimic the optical properties of biological tissue in the NIR range represents a challenge. To enable their development, the aim was to characterize the absorption and scattering spectra of different dyes. The optical properties of silicone SILPURAN 2420 with 11 color pastes of type ELASTOSIL were measured in the 500 to 1000 nm range by a spectrometer with an integrating sphere. In addition, two commercial frequency‐domain NIRS devices, the ISS OxiplexTS and the ISS Imagent, were used to assess the optical properties at specific wavelengths. The evaluated colors present mostly features in the visible range below 650 nm, but two colors include peaks in the near‐infrared region, simulating low tissue oxygenation values. These colors were used to create an optical phantom, which matched the designed StO₂ value within an error of only 4%. This set of dyes already enables simulating many different spectra, thus achieving a first step on the way to a long‐term stable comparison and validation method.      

Optical coherence tomography for ultrahigh resolution in vivo imaging

Optical coherence tomography (OCT) is an emerging biomedical optical imaging technique that performs high-resolution, cross-sectional tomographic imaging of microstructure in biological systems. OCT can achieve image resolutions of 1-15 microm, one to two orders of magnitude finer than standard ultrasound. The image penetration depth of OCT is determined by the optical scattering and is up to 2-3 mm in tissue. OCT functions as a type of 'optical biopsy' to provide cross-sectional images of tissue structure on the micron scale. It is a promising imaging technology because it can provide images of tissue in situ and in real time, without the need for excision and processing of specimens.     

A spatial resolution evaluation method of endoscopic optical coherence tomography system using the annular phantom

As an important biomedical imaging method, endoscopic optical coherence tomography (OCT) is necessary to check its performance regularly. The ordinary plane phantoms are only able to evaluate part of image tangent to the probe. In this research, a spatial resolution estimate method of the endoscope OCT system is proposed. The annular phantom, made by uniformly distributing golden scattered microparticles in polydimethylsiloxane (PDMS), can provide dynamic scanning imaging evaluation of endoscopic OCT system, closer to its actual working status. The point spread function analysis method is used to analyze the imaging results of the annular phantom with the endoscopic OCT system. And many scattered particles are statistically analyzed to determine the spatial resolution of the endoscope OCT system. The method is low in cost, simple and convenient. It is valuable for the development of test standards for endoscope OCT systems.     

Changes in the optical properties of cotyledons of Cucurbits pepo during the first seven days of their development

Abstract. We recently discussed a method for measuring optical properties of light scattering and absorbing plant tissue ( Seyfried, Fukshansky & Schafer, 1983 ). This method has been used to measure the changes in optical properties of cotyledons between 360 and 1000 run during the first 7d of development. The seedlings were either etiolated or grown under continuous white light, the latter either herbicide-treated (SAN 9789 = Norflurazon) or untreated. Some of the observed changes in seedlings grown under white light are due to chlorophyll accumulation. This accumulation leads to an increase in absorption coefficients at all wavelengths except in the 750 to 850 nm region. Reflectance, transmittance, and the scattering coefficient decreased markedly. Other changes seem to be independent of light conditions since they occur in much the same way under all treatments. These are a generally decreasing reflectance and scattering coefficient and an even stronger decrease of reflectance from the upper face of the cotyledon as compared to the reflectance from the lower face, in particular in the blue region of the spectrum. The observed changes are discussed in terms of light gradients and the resulting problems for in vivo spectroscopy.     

The influence of the blood vessel diameter on the full scattering profile from cylindrical tissues: experimental evidence for the shielding effect

Optical methods for detecting physiological state based on light–tissue interaction are noninvasive, inexpensive, simplistic, and thus very useful. The blood vessels in human tissue are the main cause of light absorbing and scattering. Therefore, the effect of blood vessels on light–tissue interactions is essential for optically detecting physiological tissue state, such as oxygen saturation, blood perfusion and blood pressure. We have previously suggested a new theoretical and experimental method for measuring the full scattering profile, which is the angular distribution of light intensity, of cylindrical tissues. In this work we will present experimental measurements of the full scattering profile of heterogenic cylindrical phantoms that include blood vessels. We show, for the first time that the vessel diameter influences the full scattering profile, and found higher reflection intensity for larger vessel diameters accordance to the shielding effect. For an increase of 60% in the vessel diameter the light intensity in the full scattering profile above 90° is between 9% to 40% higher, depending on the angle. By these results we claim that during respiration, when the blood‐vessel diameter changes, it is essential to consider the blood‐vessel diameter distribution in order to determine the optical path in tissues.

A CT scan of the measured silicon‐based phantoms. The phantoms contain the same blood volume in different blood‐vessel diameters.     

Wavelength Optimization for Quantitative Spectral Imaging of Breast Tumor Margins

A wavelength selection method that combines an inverse Monte Carlo model of reflectance and a genetic algorithm for global optimization was developed for the application of spectral imaging of breast tumor margins. The selection of wavelengths impacts system design in cost, size, and accuracy of tissue quantitation. The minimum number of wavelengths required for the accurate quantitation of tissue optical properties is 8, with diminishing gains for additional wavelengths. The resulting wavelength choices for the specific probe geometry used for the breast tumor margin spectral imaging application were tested in an independent pathology-confirmed ex vivo breast tissue data set and in tissue-mimicking phantoms. In breast tissue, the optical endpoints (hemoglobin, β-carotene, and scattering) that provide the contrast between normal and malignant tissue specimens are extracted with the optimized 8-wavelength set with <9% error compared to the full spectrum (450–600 nm). A multi-absorber liquid phantom study was also performed to show the improved extraction accuracy with optimization and without optimization. This technique for selecting wavelengths can be used for designing spectral imaging systems for other clinical applications.