Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent

We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyanine green, a FDA-approved infrared red dye, within a stage 54 Xenopus laevis.     

Spectral-domain differential interference contrast microscopy

We present a fiber-optic low-coherence imaging technique, termed spectral-domain differential interference contrast microscopy (SD-DIC), for quantitative DIC imaging of both reflective surfaces and transparent biological specimens. SD-DIC combines the common-path nature of a Nomarski DIC interferometer with the high sensitivity of spectral-domain low-coherence interferometry to obtain high-resolution, quantitative measurements of optical pathlength gradients from a single point on the sample. Full-field imaging can be achieved by scanning the sample. A reflected-light SD-DIC system was demonstrated using a USAF resolution target as the phase object. Live cardiomyocytes were also imaged, achieving a resolution of 36 pm for pathlength gradient measurements. The dynamics of cardiomyocyte contraction were recorded with high sensitivity at selected sites on the cells.     

Compact microfiber Bragg gratings with high-index contrast

We fabricate fiber Bragg grating (FBG) in microfibers (MFs) using focused ion beam milling technique. By periodically etching 100 nm-depth grooves on the surface of silica MFs with diameters less than 2 μm, evident grating features with transmission dip up to 15 dB are obtained. Because of the high-index contrast of the gratings structure, the length of the microfiber Bragg grating (MFBG) can be reduced to 500 μm level. Using a 518 μm-length 1.8 μm-diameter MFBG, we also demonstrate sensitivity up to 660 nm per refractive index unit (RIU) for refractive index (RI) sensing. The highly compact MFBGs demonstrated here may serve as low-dimensional building blocks for miniaturized photonic components and devices.     

Molecular imaging contrast media for visualization of liver function

Background and Aims

Diagnosis of liver disease has improved because of progress in imaging technology. Among the imaging methods, magnetic resonance imaging (MRI) has the advantage of a lack of radiation exposure, but the basis of the method (imaging of hydrogen atoms in water molecules) makes it hard to detect changes in tissue or the location of the diseased tissue in the liver. The aims of this study are to develop new contrast media for visualization of functional changes in the liver and to check the effectiveness of the media.

Methods

We developed a new molecular imaging contrast media that targets the asialoglycoprotein receptor (ASGP-R), a membrane protein that is specific to hepatocytes. We first checked the contrast media diameter and the cytotoxicity. Next, we examined the interaction of the media with ASGP-R through observation of fluorescein isothiocyanate (FITC)-labeled molecular imaging contrast media bound to normal hepatocellular ASGP-R using confocal laser scanning microscopy. Finally, we used MRI to observe hepatocyte interactions with the molecular imaging contrast media.

Results

The contrast media forms a nanoparticle of about 30 nm diameter in aqueous solution and the cytotoxicity is low. In vitro, the media has high specificity for ASGP-R in normal rat hepatocyte RLN-8 cells and this interaction was blocked by lactose (which has a similar molecular structure to that of galactose) and by an anti-ASGP-R antibody. The contrast media markedly enhanced T1-weighted images in MRI of normal rat hepatocytes compared to the signal strength for rat liver cancer cells.

Conclusions

We have shown that our new contrast media for molecular imaging of hepatocytes by MRI is effective in vitro.     

Apparent contrast of molecularly thin films of water at ionic crystal surfaces

We focus the apparent contrast of water islands formed at ionic crystal surfaces in air at room temperature (RT) using the non-contact monitoring mode of a scanning force microscope (SFM). Their apparent heights of water islands formed on LiF(001), CaF₂(111) and BaF₂(111) surfaces have been measured to be about 2, 1 and 1 nm, respectively. The water growth of a NaF(001) surface has two phases (phase I and phase II). The apparent heights of phase I and phase II have been measured to be about 2 and 1.5 nm, respectively. The apparent height of water films is shown to be strongly modified by the dielectric constant of sample and water, and the true thickness of water islands is discussed.     

Spectral contrast imaging microscopy

We introduce a new technique, spectral contrast imaging microscopy (SCIM), for super-resolution microscopic imaging. Based on a novel contrast mechanism that encodes each local spatial frequency with a corresponding optical wavelength, SCIM provides a real-time high-resolution spectral contrast microscopic image with superior contrast. We show that two microscopic objects, separated by a distance smaller than the diffraction limit of the optical system, can be spatially resolved in the SCIM image as different colors. Results with numerical simulation and experiments using a high-resolution United States Air Force target are presented. The ability of SCIM for imaging biological cells is also demonstrated.     

Width determination of SiO2-films in Si-based devices using low-loss EFTEM: image contrast as a function of sample thickness

Energy filtering transmission electron microscopy (EFTEM) has become one of the most efficient tools for specimen characterization at nanometer length scales. EFTEM imaging is most often carried out in the core-loss region but image intensity becomes more and more a limiting factor with decreasing feature size. Alternatively, it is possible to record EFTEM images in the low-loss region, where intensities are essentially higher and where in many cases the images contain material specific contrasts. In this paper we investigate the influence of the important parameters on the material contrast between silicon and silicon dioxide, e.g. specimen thickness, specimen orientation, energy-loss and energy selecting slit width. We show that sample thickness plays an important role and present two methods to calculate material contrast as a function of energy-loss and sample thicknesses. The first method uses spectra taken from both materials at different sample thickness by electron energy-loss spectroscopy, the second calculates contrast directly from a series of energy filtered images. From the results we determine the ideal acquisition parameters for the Si/SiO(2) system and demonstrate imaging at sufficient resolution below 2nm with a test sample of thin SiO(2) layers on Si.     

伪装目标与背景的偏振对比特性

为解决传统光强探测手段难以有效探测和识别伪装目标这一难题,基于偏振探测技术搭建了光谱偏振探测成像系统,利用该系统在位于442.0,545.5,670.5,850.5 nm的窄波段对典型草地、土壤背景下的某型深绿色和土黄色伪装涂层进行了光谱偏振探测实验研究。并通过编制的图像处理软件对测试结果进行处理分析以提取其中的偏振信息,获得了目标与背景偏振度和偏振对比度随探测波长和探测角的变化规律。研究结果表明,合理地选择偏振成像探测条件可以使伪装涂层与背景之间存在较大的偏振对比度,可以实现对传统伪装涂层涂覆的目标的有效探测和识别。     

X‐ray analyzer‐based phase‐contrast computed laminography

X‐ray analyzer‐based phase‐contrast imaging is combined with computed laminography for imaging regions of interest in laterally extended flat specimens of weak absorption contrast. The optics discussed here consist of an asymmetrically cut collimator crystal and a symmetrically cut analyzer crystal arranged in a nondispersive (+, ?) diffraction geometry. A generalized algorithm is given for calculating multi‐contrast (absorption, refraction and phase contrast) images of a sample. Basic formulae are also presented for laminographic reconstruction. The feasibility of the method discussed was verified at the vertical wiggler beamline BL‐14B of the Photon Factory. At a wavelength of 0.0733 nm, phase‐contrast sectional images of plastic beads were successfully obtained. Owing to strong circular artifacts caused by a sample holder, the field of view was limited to about 6 mm in diameter.     

The effect of low level laser therapy in different wavelengths in the treatment of oral mucositis—proposal for extra-oral implementation

The oral mucositis is the most frequent acute oral complication resulting from antineoplastic treatment and may worsen the clinical condition of the patient and interfere with his/her quality of life. This study aimed to comparatively evaluate, from a clinical point of view, the effect of Laser Therapy λ660 nm (wavelength of the red Laser) and λ830 nm (wavelength of the infrared Laser), at extra-oral points, in remission of severity of oral mucositis and pain associated with it in pediatric oncological patients undergoing chemotherapy with the anticancer drug methotrexate, noting which of the two wavelength is the most appropriate to this new technique. The sample consisted of 13 patients placed at random in each group and subjected to sessions of Low Level Laser Therapy, at pre-determined extra-oral points for five consecutive days, starting at the beginning of the observation of mucositis injuries. It became possible to note that from the group of patients in the group of Laser λ830 nm (n = 6; 46.15%), four (n = 4; 66.67%) of these patients had remission of injuries to grade 0 (WHO), and as for pain, five patients (n = 5; 83.33%) showed no painful symptoms for mucositis injuries. In the Laser λ660 nm group (n = 7; 53.85%), only two patients (n = 2; 28.57%) achieved a regression of lesions to grade 0 (WHO), while four patients (n = 4; 57.14%) had no pain. So, the extra-oral application of Laser Therapy was effective in treating injuries of oral mucositis in the patients treated; and Laser Therapy in the infrared spectrum (λ830 nm) was more effective in the treatment of oral mucositis injuries compared to the red spectrum (λ660 nm), which can be explained by the greater power of penetration of infrared rays, acting in a more expressive way in deeper places.     

Luminescence of thulium-activated cubic boron nitride

Under high pressure and temperature conditions, we have obtained samples of thulium-activated cubic boron nitride in the form of micropowders, ceramics, and polycrystals activated by thulium in the presence of aluminum. We studied the cathodoluminescence (CL), photoluminescence (PL), and photoluminescence excitation spectra of the samples. In the luminescence spectra we observe structured bands with maxima at ∼370, ∼475, ∼660, and ∼ 800 nm, assigned to electronic transitions in the triply charged thulium ions. We have established that the most efficient method for excitation of “blue” luminescence at ∼475 nm for thulium ions in cBN is excitation by an electron beam. The cBN samples synthesized in the presence of Al have photoluminescence spectra with a more complex structure compared with samples not containing Al, with the band of dominant intensity at about 660 nm. Hypothetically, this is a consequence of incorporation of thulium ions into the crystalline phases cBN and AlN, which are equally likely to be formed during synthesis. The observed photoluminescence spectrum of the indicated samples is the superposition of the photoluminescence spectra of the Tm³⁺ ions located in the crystal fields of cBN and AlN of different symmetries. The presence in the photoluminescence excitation spectra (at 450, 490, and 660 nm) of structure, with features at wavelengths shorter than the excited photoluminescence, suggests a nonresonant mechanism for its excitation. We have established that luminescence of Tm³⁺ ions is less intense than for other rare earth elements incorporated into cubic boron nitride. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 547–555, July–August, 2008.     

Magnetic and relaxometric properties of polyethylenimine-coated superparamagnetic MRI contrast agents

Novel systems to be employed as superparamagnetic contrast agents (CA) for magnetic resonance imaging (MRI) have been synthesized. These compounds are composed of an iron oxide magnetic core coated by polyethylenimine (PEI) or carboxylated polyethylenimine (PEI-COOH). The aim of the present work was to prepare and study new nanostructured systems (with better or at least comparable relaxivities, R₁ and R₂, with respect to the commercial ones) with controlled, almost monodisperse average dimensions and shape, as candidates for molecular targeting. By means of atomic force microscopy (AFM) measurements we determined the average diameter, of the order of 200 nm, and the shape of the particles. The superparamagnetic behavior was assessed by SQUID measurements. From X-ray data the estimated average diameters of the magnetic cores were found to be 5.8 nm for PEI-COOH60 and 20 nm for the compound named PEI25. By NMR-dispersion (NMRD), we found that PEI-COOH60 presents R₁ and R₂ relaxivities slightly lower than Endorem^®. The experimental results suggest that these novel compounds can be used as MRI CA.     

Correlation between spectroscopic and morphological properties of composite P3HT/PCBM nanoparticles studied by single particle spectroscopy

We report the fabrication and characterization of composite nanoparticles consisting of a conducting polymer, poly-3-hexylthiophene (P3HT), doped with varying amounts of [6,6]-phenyl C61-butyric acid methyl ester (PCBM), a material blend that is commonly applied in bulk heterojunction organic photovoltaic devices (OPVs). Single particle spectroscopy (SPS) studies, where nanoparticles are studied one particle at a time, reveal that these nanoparticles have spectroscopic characteristics consistent with the existence of two types of crystalline nanodomains, one with a higher energy emission at 660 nm and one with a lower energy emission at 720 nm. In addition, the occurrence of emission at lower peak energy increases with increasing PCBM doping levels, and the intensity of the lower energy peak emission increases with respect to the higher energy peak emission as well. These data reveal a PCBM concentration dependent formation of two types of P3HT crystalline nanodomains in P3HT/PCBM composite nanoparticles, where the lower energy crystal structure becomes more favored with higher PCBM concentration. This work provides a molecular scale insight in the correlation between changes in morphology of conjugated polymer materials with different weight percentages of fullerene dopants.     

Elemental x-ray imaging using Zernike phase contrast

We develop an element-specific x-ray microscopy method by using Zernike phase contrast imaging near absorption edges, where a real part of refractive index changes abruptly. In this method two phase contrast images are subtracted to obtain the target element: one is at the absorption edge of the target element and the other is near the absorption edge. The x-ray exposure required by this method is expected to be significantly lower than that of conventional absorption-based x-ray elemental imaging methods. Numerical calculations confirm the advantages of this highly efficient imaging method.     

All-solid-state continuous-wave frequency doubling Nd:YAG/LBO laser with 8.2 W output power at 660 nm

An efficient and compact red laser at 660 nm is generated by intracavity frequency doubling of continuous wave (CW) laser operation of a diode pumped Nd:YAG laser at 1319 nm under the condition of suppression the higher gain transition near 1064 and 1319 nm under the condition of suppression the higher gain transition near 1064 and 1338 nm. With 40 W diode pump power and a frequency doubling crystal LBO, as high as 8.6 W of CW output power at 660 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 21.5% and the output power stability in 8 h is better than 2.73%. To the best of our knowledge, this it the highest conversion efficiency of watt-level laser at 660 nm generated by intracavity frequency doubling of a diode end pumped Nd:YAG laser at 1319 nm.     

Aptamer-conjugated multi-walled carbon nanotubes as a new targeted ultrasound contrast agent for the diagnosis of prostate cancer

Early diagnosis is primarily important for the therapeutic and prognostic outcomes of malignancies including prostate cancer (PCa). However, the visuality and veracity of ultrasound imaging for the diagnosis and prognostic prediction of PCa remains poor at present. In this study, we developed a new nanoultrasound contrast agent by modifying multi-walled carbon nanotubes (MWCNTs) with polyethylene glycol (PEG) and anti-PSMA aptamer. The result showed that the modified MWCNTs offered better visuality and veracity and were able to target PCa cells more effectively as compared with the traditional contrast agent. The zeta potential was about ??38 mv. The length of this contrast agent was about 400 nm and the diameter of it was about 30 nm. The zeta potential, TEM, and FT-IR all proved the successful preparation of the agent. The vitro cytological study revealed good cell uptake and biocompatibility of the new contrast agent. The minimum detection concentration in vitro is 10 μg/ml. The earliest stage of the detection was under the parameters of frequency?=?6.0 MHz and medical index?=?0.06. Both in vitro and in vivo ultrasound imaging demonstrated that the new nanoultrasound contrast agent had a good development effect, distribution, and metabolism, and may prove to be a good targeted ultrasound contrast agent, especially for PCa.     

Single-element objective lens for soft x-ray differential interference contrast microscopy

High-resolution soft x-ray differential interference contrast (DIC) imaging was demonstrated through the use of a single-element objective, the XOR pattern, in a full-field soft x-ray microscope. DIC images of the magnetic domains in a 59 nm thick amorphous Gd25Fe75 layer were obtained and magnetic phase contributions were directly imaged. With its elemental, chemical, and magnetic specificity, compatibility with various sample environments, and ease of implementation, we expect this soft x-ray DIC technique to become one of the standard modes of operation for existing full-field soft x-ray microscopes.     

Frequency-selective quadrupolar MRI contrast

A method for the selective detection of quadrupolar nuclei located in anisotropic environments is presented. The image contrast can be tuned to the degree of anisotropy in the sample by using frequency-swept pulsed. These methods are particularly useful in the field of sodium-MRI, where sodium signals from locally-ordered environments provide diagnostic information. In solid-state MRI, these methods could be useful for probing structural defects within the sample. We demonstrate here one-dimensional images, in which the pixel contrast indicates the presence or absence of quadrupolar coupling within a certain frequency range.     

LD侧面抽运Nd∶YAG多波长激光器

利用单根Nd∶YAG晶体棒,实现1 064 nm和1 319 nm双波长基频光振荡及其倍频光532 nm、660 nm激光的输出.采用LD侧面抽运单根Nd∶YAG晶体棒实现1 064 nm和1 319 nm基频光振荡,在此基础上使用非线性频率变换技术获得532 nm和660 nm倍频光的输出.结果表明:1 064 nm和1 319 nm基频激光同时输出时功率分别为30.5 W和8.78 W,单独输出时功率分别为35.6 W和11.2 W|在声光调Q频率分别为10.5 kHz和20.5 kHz时,获得了功率分别为5.34 W和1.353 W的532 nm激光和660 nm激光两路同时运转输出、功率分别为6.72 W和1.902 W各路单独输出,两种情况下倍频转换效率均为17.5%和15.4%,不稳定度小于2%.