人离体乳腺癌肿瘤新生血管的同步辐射成像实验研究

目的:探讨同步辐射类同轴相衬成像在人乳腺癌离体标本中的应用。方法:12例乳腺癌标本经4%甲醛溶液固定后,在上海同步辐射光源(Shanghai Synchrotron Radiation Facility,SSRF)X线成像与生物医学应用光束线站(BL13W)上进行同步辐射类同轴相位衬度二维及三维成像,最后行病理学及免疫组化检查,将所得影像学资料与病理学资料进行对比研究。结果:物像距为100 cm、能量为13 ke V时,图像具有较高的空间分辨率和衬度分辨率。类同轴相位衬度二维及三维成像均可在无对比剂条件下清晰显示肿瘤新生血管,最小肿瘤血管直径约9μm。结论:同步辐射类同轴相位衬度成像可检测人乳腺癌标本中的肿瘤新生血管,清晰观察肿瘤血管的形态特征和空间分布,为研究肿瘤新生血管的形成机制及各种干预或治疗措施对肿瘤血管的影响提供了检测和监测方法,具有很高的医学应用价值。     

比较同步辐射衍射增强与同轴技术小鼠肾脏成像

目的 通过评价同步辐射相位衬度成像技术在小鼠肾脏微细结构的成像过程,比较同轴成像技术(IOXI)与衍射增强成像(DEI)的差异,探索相位成像技术的应用价值。方法 在北京同步辐射装置(BSRF)形貌站4W1A和上海光源(SSRF)成像线站BL13W上,分别对小鼠肾脏进行成像,以组织衬度与空间分辨力作为评价指标。结果 肾脏微细结构在IOXI与DEI中均得以显示,尤其是IOXI可显示肾小球。通过显微放大法获得的图像空间分辨力达10 μm。结论 包括IOXI与DEI在内的相位衬度成像技术在软组织及血管结构的显示中均具有较高的应用价值。IOXI由于获得成像信息更多,且光路较为简单、图像可直接获得,在生物医学应用研究中的价值可能更高。     

衍射增强成像(DEI)动物实验研究

目的通过动物样品的衍射增强成像(DEI),获得衬度及分辨率,并与常规吸收成像比较,对DEI方法进行分析和评价。方法在北京高能物理研究所同步辐射装置(BSRF)形貌站(4W1A束线)上,取大鼠脏器在摇摆曲线上进行扫描,并与常规吸收像进行比较,通过放大法获得分辨率。结果大鼠的肝脏、肾脏样本的DEI均显示较好的衬度和分辨率,并且扫描位置对图像显示具有较大影响。结论DEI从相位衬度角度进行成像,是一种有望开发运用于临床的先进成像技术。     

兔下肢淋巴水肿模型微米级三维成像:基于同步辐射类同轴技术的可行性

背景:目前国内外应用类同轴相位衬度技术对生物组织的成像多为多血管成像,很少有对淋巴管的成像研究.另外对淋巴水肿常规影像学检查的分辨率为毫米级,不利于早期诊断,而类同轴相位衬度成像技术可以实现对软组织的微米级成像.目的:利用类同轴相位成像技术实现对兔下肢淋巴水肿模型的微观成像,以观察早期水肿的病变程度.设计、时间及地点:样本于2009-05/06在首都医科大学医学图像实验室制作完成,成像实验于2009-06在上海光源BL13W1线站完成.材料:采用5只新西兰兔制备下肢淋巴水肿模型.方法:利用淋巴结根治术实现实验动物的下肢淋巴水肿,应用类同轴相位衬度CT实现对实验样本的投影成像.对所得投影数据利用滤波反投影法、表面绘制技术进行三维重建.主要观察指标:淋巴管的病变程度,管壁厚度变化.结果:利用同步辐射光相位衬度成像技术得到的下肢淋巴水肿三维衬度图像可以明显的观察到淋巴管道有扩张、弯曲、变形现象发生,并可清晰地观察到淋巴管和静脉血管为促进淋巴回流所支生的细小侧支.结论:利用同步辐射类同轴相衬成像可以实现对淋巴水肿模型的微米级成像,并可观察到样本的早期病变,对临床诊断有一定的意义.     

衍射增强技术应用于医学成像的实验研究

目的本实验通过各类样品的DEI成像，获得衬度及分辨率，并与常规吸收成像比较，对衍射增强成像（DEI）方法进行分析和评价。方法在北京高能物理研究所同步辐射装置（BSRF）形貌站（4W1A束线）上，取人及动物脏器在摇摆曲线上进行扫描，并与常规吸收像进行比较，通过显微放大法获得分辨率。结果不同组织之间存在不同的衍射增强，DEI均显示较好的衬度和分辨率，图像分辨率达到微米级，并且扫描位置对图像显示具有较大影响。结论DEI从相位衬度角度进行成像，极大地改进了成像质量，理论上来说是安全的，有望运用于临床。     

同步辐射技术应用于冠状动脉成像的实验初探

目的比较衍射增强成像（DEI）和单色光成像两种方法冠状动脉成像效果,评价同步辐射方法在冠状动脉成像上的意义。方法DEI装置及白光成像装置下,分别对大鼠心脏进行成像,在DEI成像时,采用离体心脏样品;在单色光成像时,采用活体大鼠,并静注60%碘造影剂1ml,迅速采集图像,以图像衬度和空间分辨率作为评价指标。结果两种方法均能显示大鼠的冠状动脉。虽然DEI不用造影剂,从成像效果上来说稍差于单色光技术效果,但两种成像方法获得的图像没有显著性差异。结论DEI用于冠状动脉成像是可行的,但受成像条件和方法的限制,同步辐射的优良特性尚未得到充分利用。     

兔股骨头软骨缺损同步辐射X线相衬成像研究

目的采用同步辐射X线相衬成像技术进行兔股骨头软骨组织缺损的观察.方法取新西兰大白兔双侧股骨头,一侧制成软骨缺损,对侧股骨头未缺损作为对照.以同步辐射宽带光对股骨头进行类同轴全息相衬成像.所有标本行普通X线成像以对比观察.结果同步辐射相衬X线成像技术可见清晰的50 μm左右软骨微缺损.结论同步辐射相衬X线成像技术可检测到普通X线成像技术无法检测到的软骨微缺损,并可进一步分析病变的细微结构.     

同轴X射线位相衬度成像实验研究

目的研究利用类点光源的同轴X射线位相衬度成像技术。方法在北京同步光源4W1A光束线上,分别利用白光束X射线和14keV单色X射线,采用同轴方式开展生物样品的位相衬度成像实验。结果位相衬度图像比吸收衬度的图像分辨率更高、衬度更好。结论对于X射线吸收很弱的样品,位相衬度成像能够得到更好衬度和更高分辨率的图像。利用类点源X射线同轴相位衬度成像技术相对比较容易地被用于临床。     

大鼠肾X线衍射增强成像

目的探讨高衬度成像技术--同步辐射衍射增强成像(DEI)对肾脏成像的可能性.方法在北京同步辐射装置(BSRF)采用X线衍射增强成像法对离体的大鼠肾样品进行成像,成像样品的厚度分别为2 mm和120 μm.成像后的样品进行组织学切片,其结果和DEI结果进行对比分析.结果离体大鼠肾衍射增强成像可清晰显示常规成像方法无法观察到的走向清晰的髓质区直集合管和乳头管,以及常规需经造影处理才可见的小叶间动、静脉,最细可分辨直径为30μm的管道结构.结论同步辐射衍射增强成像法具有早期观察肾脏髓质病变及血管微细病变的潜力,该方法为目前影像学尚不能观察到的生物样品结构的成像提供了一种新的研究手段.     

超分辨超声造影成像技术在人体肾脏上的初步应用

目的：应用超分辨技术提高肾脏血流超声造影成像的空间分辨率。方法：提出一种基于造影图像序列统计变换的超声衍射衰减显微镜,并应用到人体肾脏超声造影的图像重建中。通过与最大强度投影成像结果相对比,来探究超分辨成像对于空间分辨率的改善效果。结果：与最大强度投影结果相比,超分辨成像对于肾脏血流显示的空间分辨率从视觉上显著提高。结论：超声衍射衰减显微镜可以对临床采集的肾血流造影视频进行重建并提高成像的空间分辨率,为观察微小血流结构提供了新的有效手段。     

离体生物软组织同步辐射相衬CT成像

目的 探讨同步辐射相衬CT对离体生物软组织成像的可行性。方法 将手术切除人贲门标本3块、食管及食管癌标本各2块及自尸体标本提取的大脑中动脉组织2块固定并自然干燥,之后行同步辐射相衬CT成像,观察成像显示的软组织结构,并与病理结果进行对照。结果 同步辐射相衬CT图像清晰显示正常贲门及食管壁3层结构,即黏膜层、黏膜下层及肌层,黏膜面光整;在食管癌标本则显示癌组织浸润食管壁;对大脑中动脉组织可清晰显示脑动脉管壁及血管腔内状况。结论 同步辐射相衬CT成像能清晰显示离体生物软组织的细微结构。     

Field-portable reflection and transmission microscopy based on lensless holography

We demonstrate a lensfree dual-mode holographic microscope that can image specimens in both transmission and reflection geometries using in-line transmission and off-axis reflection holography, respectively. This field-portable dual-mode holographic microscope has a weight of ~200 g with dimensions of 15 x 5.5 x 5cm, where a laser source is powered by two batteries. Based on digital in-line holography, our transmission microscope achieves a sub-pixel lateral resolution of ≤2 μm over a wide field-of-view (FOV) of ~24 mm(2) due to its unit fringe magnification geometry. Despite its simplicity and ease of operation, in-line transmission geometry is not suitable to image dense or connected objects such as tissue slides since the reference beam gets distorted causing severe aberrations in reconstruction of such objects. To mitigate this challenge, on the same cost-effective and field-portable assembly we built a lensless reflection mode microscope based on digital off-axis holography where a beam-splitter is used to interfere a tilted reference wave with the reflected light from the object surface, creating an off-axis hologram of the specimens on a CMOS sensor-chip. As a result of the reduced space-bandwidth product of the off-axis geometry compared to its in-line counterpart, the imaging FOV of our reflection mode is reduced to ~9 mm(2), while still achieving a similar sub-pixel resolution of ≤2 μm. We tested the performance of this compact dual-mode microscopy unit by imaging a US-air force resolution test target, various micro-particles as well as a histopathology slide corresponding to skin tissue. Due to its compact, cost-effective, and lightweight design, this dual-mode lensless holographic microscope might especially be useful for field-use or for conducting microscopic analysis in resource-poor settings.     

Clinical application of low-dose phase contrast breast CT: methods for the optimization of the reconstruction workflow

Results are presented of a feasibility study of three-dimensional X-ray tomographic mammography utilising in-line phase contrast. Experiments were performed at SYRMEP beamline of Elettra synchrotron. A specially designed plastic phantom and a mastectomy sample containing a malignant lesion were used to study the reconstructed image quality as a function of different image processing operations. Detailed evaluation and optimization of image reconstruction workflows have been carried out using combinations of several advanced computed tomography algorithms with different pre-processing and post-processing steps. Special attention was paid to the effect of phase retrieval on the diagnostic value of the reconstructed images. A number of objective image quality indices have been applied for quantitative evaluation of the results, and these were compared with subjective assessments of the same images by three experienced radiologists and one pathologist. The outcomes of this study provide practical guidelines for the optimization of image processing workflows in synchrotron-based phase-contrast mammo-tomography.OCIS codes: (100.5070) Phase retrieval, (110.3000) Image quality assessment, (340.6720) Synchrotron radiation, (170.6960) Tomography, (170.7440) X-ray imaging, (170.3880) Medical and biological imaging, (170.3010) Image reconstruction techniques, (170.3830) Mammography     

In Vitro Superharmonic Contrast Imaging Using a Hybrid Dual-Frequency Probe

Superharmonic imaging is an ultrasound contrast imaging technique that differentiates microbubble echoes from tissue through detection of higher-order bubble harmonics in a broad frequency range well above the excitation frequency. Application of superharmonic imaging in three dimensions allows specific visualization of the tissue microvasculature with high resolution and contrast, a technique referred to as acoustic angiography. Because of the need to transmit and receive across a bandwidth that spans up to the fifth harmonic of the fundamental and higher, this imaging approach requires imaging probes comprising dedicated transducers for transmit and receive. In this work, we report on a new dual-frequency probe including two 1.7-MHz rectangular transducers positioned one on each side of a 20-MHz 256-element array. Finite element modeling-based design, fabrication processes and assembly of the transducer are described, as is integration with a high-frequency ultrasound imaging platform. Dual-frequency single-plane-wave imaging was performed with a microbubble contrast agent in flow phantoms and compared with conventional high-frequency B-mode imaging, and resolution and contrast-to-tissue ratio were quantified. This work represents an intermediate but informative step toward the development of dual-frequency imaging probes based on array technology, specifically designed for clinical applications of acoustic angiography.     

同步辐射装置(BSRF)上的衍射增强医学成像实验

目的：利用衍射增强成像（DEI）技术成像机制的特异性，进行医学样品的成像研究，并进行分析评价。方法：使用衍射增强成像（DEI）技术对肝、肾样本进行成像，通过显微放大法获得图像分辨率，并对摇摆曲线上的不同位置成像结果进行分析，与病理和常规吸收像图像进行比较。结果：获得的成像具有较高的分辨率、可以显示更多的微细结构，摇摆曲线上的不同位置对成像具有较大的影响。结论：DEI对样品，尤其是弱吸收组织（软组织）显示具有较强的特异性，可望在临床上具有广阔的应用前景。     

Objective measurements of image quality in synchrotron radiation phase-contrast imaging versus digital mammography

Purpose

Phase-contrast mammography with synchrotron radiation is an innovative X-ray imaging practice that improves the identification of breast lesions. Previous studies have proven the superiority of the mammography images taken in the phase-contrast modality using synchrotron radiation beams as compared with images taken in conventional mammography by subjective analyses. However, to our knowledge, no previous study has compared different acquisition systems in order to quantify this improvement by means of objective robust indicators. In this research, we intend to quantify the superiority of phase-contrast imaging by means of objective metrics of image quality.

Methods

Images from the American College of Radiology Mammographic Accreditation Phantom were obtained at hospitals, in two digital mammography equipment and at the Elettra synchrotron radiation facility (Trieste, Italy), using free space propagation phase-contrast modality. Regions of interest were selected to analyze image quality at the fibers (phase object) and masses (area object) simulated on the phantom by means of the signal-to-noise ratio, the figure of merit, the contrast and the edge visibility.

Results

The image contrast and edge visibility were significantly higher at the phase-contrast modality as compared with digital mammography equipment. The figure of merit using phase-contrast modality was higher for the fibers and comparable for the masses.

Conclusion

The results showed an improvement of the contrast and edge visibility in phase-contrast images. These improvements may be important in the detection of small lesions and details.

     

Analysis of contrast in images generated with transient acoustic radiation force

Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force in tissue and correlation-based US methods to detect the resulting tissue displacements. Local displacements reflect relative mechanical properties of tissue. The resolution of these images is comparable with that of conventional B-mode imaging. The response of tissue to focused radiation force excitation is complex and depends upon tissue geometry, forcing function geometry (i.e., region of excitation, or ROE) and tissue mechanical and acoustic properties. Finite element method (FEM) simulations using an experimentally validated model and phantom experiments have been performed using varying systems, system configurations and tissue-mimicking phantoms to determine their impact on image quality. Image quality is assessed by lesion contrast. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally-dependent. Contrast of spherical inclusions is highest immediately after force cessation, decreases with time postforce and then reverses, due to shear wave interaction with internal boundaries, differences in shear modulus between lesions and background and inertial effects. In images generated immediately after force cessation, contrast does not vary with applied force, increases with lesion stiffness and increases as the ROE size decreases relative to the size of the structure being imaged. These studies indicate that improved contrast in radiation force-generated images will be achieved as ROE size decreases; however, frame rate and thermal considerations present trade-offs with small ROE size.