X‐ray fluorescent CT imaging of cerebral uptake of stable‐iodine perfusion agent iodoamphetamine analog IMP in mice

Using X‐ray fluorescent computed tomography (XFCT), the in vivo and ex vivo cerebral distribution of a stable‐iodine‐labeled cerebral perfusion agent, iodoamphetamine analog (¹²⁷I‐IMP), has been recorded in the brains of mice. In vivo cerebral perfusion in the cortex, hippocampus and thalamus was depicted at 0.5 mm in‐plane spatial resolution. Ex vivo XFCT images at 0.25 mm in‐plane spatial resolution allowed the visualisation of the detailed structures of these regions. The quality of the XFCT image of the hippocampus was comparable with the ¹²⁵I‐IMP autoradiogram. These results highlight the sensitivity of XFCT and its considerable potential to evaluate cerebral perfusion in small animals without using radioactive agents.     

Imaging of subcutaneous blood vessels and flow velocity profiles by optical coherence tomography

We have applied a compact low power rapid scanning Doppler Optical Coherence Tomography system to monitor multi-dimensional velocity profiles within the complex vessels and simultaneous real-time non-invasive imaging of skin tissues morphology in vivo, in the wavelength range of 1.3–1.5 nm. Optical clearing of skin tissues has been utilized to achieve depth of OCT images up to 1.7 mm. Current approach enables applying low-power (0.4–0.5 mW) and low-noise broadband near-infrared light sources and obtaining OCT images with down to 12 μm spatial resolution. Two-dimensional time-domain OCT images of complex flow velocity profiles in blood vessel phantom and in vivo subcutaneous human skin tissues are presented. The effect of optical clearing on in vivo images is demonstrated and discussed.     

Early commissioning results for spectroscopic X‐ray Nano‐Imaging Beamline BL 7C sXNI at PLS‐II

For spectral imaging of chemical distributions using X‐ray absorption near‐edge structure (XANES) spectra, a modified double‐crystal monochromator, a focusing plane mirrors system and a newly developed fluorescence‐type X‐ray beam‐position monitoring and feedback system have been implemented. This major hardware upgrade provides a sufficiently stable X‐ray source during energy scanning of more than hundreds of eV for acquisition of reliable XANES spectra in two‐dimensional and three‐dimensional images. In recent pilot studies discussed in this paper, heavy‐metal uptake by plant roots in vivo and iron's phase distribution in the lithium–iron–phosphate cathode of a lithium‐ion battery have been imaged. Also, the spatial resolution of computed tomography has been improved from 70 nm to 55 nm by means of run‐out correction and application of a reconstruction algorithm.     

Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity

We have developed a novel phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system that uses phase information derived from a Hilbert transformation to image blood flow in human skin with fast scanning speed and high velocity sensitivity. Using the phase change between sequential scans to construct flow-velocity imaging, this technique decouples spatial resolution and velocity sensitivity in flow images and increases imaging speed by more than 2 orders of magnitude without compromising spatial resolution or velocity sensitivity. The minimum flow velocity that can be detected with an axial-line scanning speed of 400 Hz and an average phase change over eight sequential scans is as low as 10 microm/s, while a spatial resolution of 10 microm is maintained. Using this technique, we present what are to our knowledge the first phase-resolved OCT/ODT images of blood flow in human skin.     

Birefringence imaging of human skin by polarization-sensitive spectral interferometric optical coherence tomography

We have developed a spectral interferometric optical coherence tomography (OCT) system with polarization sensitivity that is able to measure a two-dimensional tomographic image by means of one-dimensional mechanical scanning. Our system, which has an axial resolution of 32 mum , calculates the distribution of each element of the Müller matrix of a measured object from 16 OCT images. The OCT system successfully reveals the birefringent nature of human skin tissue.     

Microvascular imaging using synchrotron radiation

In vascular diseases, the involvement of small vessels can be very crucial physiologically. Morphological changes of vasculature and alterations may be promising characteristic criteria for investigating disease progression and for evaluating therapeutic effects. Visualization of microvasculatures is an important step in understanding the mechanism of early vessel disorders and developing effective therapeutic strategies. However, the microvessels involved are beyond the detection limit of conventional angiography, i.e. 200 µm. Thus, faster and higher‐resolution imaging technologies are desired to capture the early anatomical structure changes of vasculatures in study of the disease. A new angiography system, synchrotron radiation microangiography, has been developed in this study. It allows for enhanced sensitivity to contrast agents and superior image quality in spatial resolution. Iodine and barium sulfate were used as blood vessel contrast agents. Physiological features of whole‐body mouse microvasculature were investigated using synchrotron radiation for the first time. The intracranial vascular network and other blood vessels were observed clearly, and the related anatomy and vessel diameters were studied. Dynamic angiography in mouse brain was performed with a high spatial image resolution of around 20–30 µm. Future research will focus on the development of novel specific targeting contrast agents for blood vessel imaging in vivo with a long half‐life and fewer side effects.     

Polarization-resolved second-harmonic-generation optical coherence tomography in collagen

We describe a novel imaging technique, second-harmonic-generation optical coherence tomography (SHOCT). This technique combines the spatial resolution and depth penetration of optical coherence tomography (OCT) with the molecular sensitivity of second-harmonic-generation spectroscopy. As a consequence of the coherent detection required for OCT, polarization-resolved images arise naturally. We demonstrate this new technique on a skin sample from the belly of Icelandic salmon, acquiring polarization-resolved SHOCT and OCT images simultaneously.     

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680–940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.     

First experimental result with fluorescent X‐ray CT based on sheet‐beam geometry

Fluorescent X‐ray computed tomography (FXCT) enables us to reveal the cross‐sectional distribution of very low concentration of specific elements, e.g. I, Gd, or Au, in biomedical samples at a spatial resolution of several hundred micrometers, and it has been used to evaluate the states of cerebral perfusion and fatty acid metabolic function of small animals in vivo and ex vivo. However, since the current system employs the data‐acquisition scheme of the first‐generation type of CT, it requires a huge amount of time to obtain a whole set of projections. In order to overcome the problem, we propose a novel imaging geometry using a sheet incident beam. We performed a proof‐of‐concept experiment using a preliminary imaging system constructed at beam line BLNE‐5A, KEK. The efficacy of the proposed method is demonstrated by the reconstructed images of a physical phantom containing various concentrations of iodine solution and a mouse brain that is extracted after intravenous injection of ¹²⁷I‐IMP for observing the cerebral perfusion and then fixed with formalin. Copyright © 2009 John Wiley & Sons, Ltd.     

Adaptive optics optical coherence tomography for retina imaging

When optical coherence tomography (OCT) is used for human retina imaging, its transverse resolution is limited by the aberrations of human eyes. To overcome this disadvantage, a high resolution imaging system for living human retina, which consists of a time domain OCT system and a 37-elements adaptive optics (AO) system, has been developed. The AO closed loop rate is 20 frames per second, and the OCT has a 6.7-μm axial resolution. In this paper, this system is introduced and the high resolution imaging results for retina are presented.     

Double fusion filtering based multi-view face recognition

Two-dimensional (2D) face recognition by correlation is a key challenge of telecommunication and optical information processing. Although this issue has been the focus of intense research, its utilization still has some drawbacks especially when the face is in rotation. In this paper, we propose an alternative method based on a newly designed optical correlation filter which allows recognizing faces with different view angles. This filter called “Multi-View Binary Phase-Only Filter” is based on a double fusion of reference images allowing an optimisation of the use of the spatial-bandwidth product (SBWP) in the filter Fourier plane. The first fusion is performed in the image (space) domain, and the second one is conducted in the spectral domain. Simulations results with the Pointing Head Pose Image Database illustrate the performance of the designed correlation filter for multi-view face recognition.     

Optical Coherence Tomographic Features of Macular Diseases

Optical coherence tomography (OCT) is a new diagnostic technology which allows visualization of a cross-sectional image of the anterior eye and the retina in vivo with a high resolution similar to a histological section by light microscopy. Although the fundus can be examined at the semihistologic level by a biomicroscope, histopathologic study has been difficult because of the rare opportunity for retinal biopsy or enucleation. OCT reveals the intraretinal structure of macular diseases on the histopathologic level. In this article, we review the research on various macular diseases using OCT at Gunma University School of Medicine.     

Three‐Dimensional,Time‐Resolved Profiling of Ferroelectric Domain Wall Dynamics by Spectral‐Domain Optical Coherence Tomography

We apply here spectral‐domain optical coherence tomography (SD‐OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium‐doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ～ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3‐dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs’ polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD‐OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high‐speed SD‐OCT setup for the real‐time DW tracking upon ferroelectric domain switching under high external fields.     

Comparison of molecular images as defined by Raman spectra between normal mucosa and squamous cell carcinoma in the oral cavity

Raman spectroscopy has been effectively applied to clinically differentiate normal and cancerous mucosal tissues. Micro‐Raman spectroscopy provides a tool to better understand the molecular basis for the Raman clinical signal. The objective of the current study was to utilize micro‐Raman spectroscopy to define the molecular/spectral differences between normal and abnormal squamous cell carcinoma (SCC) in oral mucosa (in vitro). Understanding this may help in identifying unique spectra or may be useful for in vivo application of this technology. Micro‐Raman (confocal) spectroscopy was used to obtain molecular images of normal and SCC cells of human oral mucosa. Four fresh flashed‐frozen tumor and four matched normal tongue specimens were studied. The spectra covered a wavenumber range from 300 to 4000 cm⁻¹ with a spectral resolution of 8 cm⁻¹ and a spatial resolution of 1.0 µm. The cells were located within thin sections of tongue mucosa biopsies. The excitation wavelength of 515 nm was used. We were able to obtain Raman images with rich information about the spectroscopic and structural features within the cytoplasm, cell membrane, and cell nuclei. Significant spectral differences were observed between the Raman images of normal and malignant squamous cells. The heterogeneity of tumor cells within the abnormal tissue was also demonstrated. Spectral differences demonstrated between both tissue types have provided important information regarding the origins of specific signals within the cells of each tissue type. In our search for specific spectral biomarkers, we believe that a cell surface protein, greatly upregulated in SCC cells, was discovered at 1583 cm⁻¹. Copyright © 2010 John Wiley & Sons, Ltd.     

多尺度条件卷积的OCT视网膜图像降噪研究

散斑噪声存在于光学相干层析成像(OCT)中,影响OCT图像质量.在使用OCT设备诊断各种常见眼科疾病时,高质量的OCT图像是极为重要的.利用深度神经网络对OCT图像进行降噪处理,使图像在保留空间结构细节的基础上能展示更多的信息.提出了一种基于残差学习网络的新型OCT图像降噪网络-CMCNN,其具有多尺度、多权重和多层次...     

高分辨率快速数字化光声CT乳腺肿瘤成像

提出了一种基于聚焦线性阵列探测器的快速光声计算机断层成像技术（光声CT）.在光声二维图像重建中,根据阵列探测器机械扫描和电子扫描相结合的组合扫描模式,提出了改进的有限场滤波反投影重建算法.一方面该算法适合多元探测器旋转扫描模式,另一方面探测器的指向性函数作为反投影的权重因子提高了系统的横向分辨率.同时,该成像系统还利用柱面声透镜实现Z轴方向上的聚焦扫描以实现三维层析成像.实验中,这套成像系统空间分辨率达到0.2mm,Z轴方向分辨率为1.5mm,扫描一幅二维图像仅需150s,得到 关键词： 光声CT 有限场滤波反投影算法 声透镜聚焦 乳腺肿瘤检测     

Direct characterization of phase behavior and compatibility in PET/HDPE polymer blends by confocal Raman mapping

Morphology, chemical distribution and domain size in poly(ethylene terephthalate)/high‐density poly(ethylene) (PET/HDPE) polymer blends of various ratios prepared with and without maleic anhydride have been analyzed with confocal Raman mapping and SEM. The ratioimage method introduced here allows us to obtain enhanced chemical images with higher contrast and reliability. Compatibility numbers (N_c) are calculated to evaluate the compatibility of the blends. The incompatible polymer blends show heterogeneous distribution with phase separation behavior, while the semicompatible blends prepared with maleic anhydride show much smaller subphase distributions with less distinct interphases. After the blending modification by maleic anhydride of only 0.5%, the viscosity status and dispersibility between PET and HDPE could be substantially improved, and the interactions that exist between the two phases have also been proved by ATR‐FT‐IR results. High‐spatial‐resolution confocal Raman mapping coupled with the ratioimage method provides a very attractive way to characterize the compatibility and phase behavior of the polymer blend through different blending methodologies. Copyright © 2006 John Wiley & Sons, Ltd.     

High-resolution imaging characterization of bladder dynamic morphophysiology by time-lapse optical coherence tomography

We report an experimental study of the possibility of high-speed optical coherence tomography (OCT) for high-resolution imaging characterization of detrusor dynamic morphophysiology and analysis of the mechanisms that lead to geriatric incontinence (GI). The spontaneous contractility of intact fresh rabbit bladders was imaged with two-dimensional (2D) OCT ex vivo at up to 8 frames/s. The time-lapse 2D OCT images were postprocessed by image segmentation and fast-Fourier-transform analysis to characterize the dynamic morphological changes of the bladder contractility. In addition, we studied young and aging rat bladders to analyze the differences in dynamics. Preliminary results of our ex vivo study reveal that time-lapse OCT can track the contractile waves of bladders at high spatial resolution and characterize their dynamic morphophysiology in terms of amplitude, phase, and frequency. The results suggest that time-lapse OCT has the potential to act as a detrusor optical biopsy to enhance the diagnosis of detrusor dysfunction and thus of the mechanisms that lead to GI.     

Quadrature fringes wide-field optical coherence tomography and its applications to biological tissues

We propose and demonstrate quadrature fringes wide-field optical coherence tomography (QF WF OCT) to expand an optical Hilbert transformation to two-dimensions. This OCT simultaneously measures two quadrature interference images using a single InGaAs CCD camera to obtain en face OCT images. The axial and lateral resolutions are measured at 29 μm in air and 70 μm limited by a pixel size of camera using a superluminescent diode with a wavelength of 1.3 μm as the light source; the system sensitivity is determined to be −90 dB. The area of the en face OCT images is 4.0 mm × 4.0 mm (160 × 160  pixels). The OCT images are measured axially with steps of 10 μm. The en face OCT images of a in vivo human fingertip and a in situ rat brain are three-dimensionally measured up to the depth of about 3 mm with some degradations of a lateral resolution.     

Dipole‐like backscatter stimulated Raman scattering for in vivo imaging

Stimulated Raman scattering (SRS) scanning microscopy has the potential to enable label‐free in vivo imaging for research and clinical medicine. Volume SRS from focus occurs in the forward scattered direction. Therefore, multiple scattering events are required to direct the light out of the tissue, reducing imaging depth and resolution. Here, a method called Stokes interference SRS (SISRS) is introduced that operates by the addition to the standard pump and stimulated emission probe beams a third beam called the donut beam. The donut is close in wavelength to the probe beam and, after passage through a π phase plate, forms an annular beam in the focal plane with bright nodes above and below focus. The donut beats with the probe beam, and when they destructively interfere with each other, the microscope's 3‐D stimulated emission focal spot is reduced to subwavelength dimensions. A subwavelength focal volume emits a dipole pattern of SRS with forward and backscatter lobes, enabling high‐resolution single‐backscatter imaging from deep within tissues. The reduction of the focal volume also increases the resolution of the scanning image creating imaging beyond the diffraction limit. SISRS imaging may provide in vivo label‐free Raman images comparable with that achieved in stained in vitro tissues in all planes of section. Copyright © 2014 John Wiley & Sons, Ltd.