Long-Duration Soft X-Ray Pulses by XeCl Laser Driven Plasmas and Applications

We report the characterization of a soft x-ray plasma source generated by a long-pulse XeCl excimer laser system. The output energy is 4 J at a wavelength of 308 nm in a 100-ns pulse. The intensity of radiation on target is estimated to be 4 × 1012 W cm-2. X-ray emission spectra of the plasma have been recorded using a double focusing spatial resolution spectrometer with a spherical mica crystal. From these measurements, the plasma temperature and electron density have been estimated. Various applications of such a plasma source have been investigated. First images of whole intact living cells from our system, imaged using the technique of soft x-ray contact microscopy, utilizing x rays in the "water window" region (280-530 eV), are shown. The suitability of the source for other applications, for example, x-ray lithography and radiation damage studies, to living cells are discussed. Possible improvements to the x-ray source for the various applications are proposed.     

Time-Resolved, Multi-frame X-Ray Imaging of Laser-Produced Plasmas

A novel x-ray imaging system based on a microchannel-plate combined with a multi-pinhole camera has been employed to study x-ray emission from laser-produced plasmas in the 0.5-3 keV photon energy range. In particular, the interaction of intense laser radiation with such plasmas, under conditions relevant to inertial confinement fusion, was monitored by recording a sequence of consecutive x-ray images with a temporal resolution of 140 ps and a spatial resolution of 10 μm. These images provide valuable information on the main physical mechanisms involved in the interaction process, including collisional absorption of the incident laser energy and electron thermal conduction.     

X-Ray Crystal Spectroscopy of Sub-picosecond Laser-Produced Plasmas beyond 50 keV

The interaction of a sub-picosecond (sub-ps) laser with a high-Z target produces a hard x-ray continuum, but to our knowledge no high-resolution study of the line emission is known. We present here crystal spectroscopy as a tool for the observation of energetic line x-radiation from a sub-ps laser-produced plasma. Reflection properties of flat and bent crystals for x-ray spectroscopy are analyzed theoretically for both the Bragg and the Laue geometries and optimized for a crystal spectroscopy of hard (>50 keV) x-radiation. The crystal setup is optimized for spectroscopic applications with regard to high throughput and spectral resolution. The characteristic tantalum Kα,β- and Lα,β-line emissions from a sub-ps laser-produced plasma is observed for the first time. A resolving power of about 450 is achieved which is much higher than that for comparable absorption filter techniques (E/ΔE ≈ 15).     

Subnanosecond In-Line Soft X-Ray Holography Using Germanium Laser in the 20 nm Wavelength Region

Near- and far-field characteristics of a germanium soft x-ray laser at the wavelengths of 23.2-23.6 nm (J = 2-1 transitions) and 19.6 nm (J = 0-1 transition) are given for quantitative evaluation of the germanium laser for holographic applications. In-line Gabor holography of simple structured objects, such as thin opaque fibers and a standard electron microscope test specimen, is demonstrated. The holograms were recorded on PMMA (polymethyl methacrylate) photoresists and llford Q-plates. The holograms recorded on PMMA were retrieved with an atomic force microscope. The object image was reconstructed by numerical reconstruction with phase retrieval algorithm, resulting in a clear, ghost-free image with sharp edges which infer sub-μm resolution. Future directions for x-ray laser holography are briefly discussed.     

Focusing Properties of X-Ray Spectrometers with 2D-Curved Crystals for Extended X-Ray Sources of Hot Plasmas

The focusing properties of very large (≈33 × 33 cm2) spherically and toroidally curved crystals with a radius of curvature of ≈10 m were determined numerically with an x-ray tracing code and are compared to those of cylindrically bent crystals. Large spherically and toroidally curved crystals are of interest for the diagnostic of future large tokamak fusion experiments and possibly for other extended x-ray sources. Compared with cylindrically bent crystals-which are now widely used for the plasma diagnostic in tokamak experiments, in particular, for Doppler-broadening measurements to determine the central ion temperature-2D-curved crystal spectrometers can provide a significant enhancement of the intensity due to the additional focusing of the sagittal rays.     

Coherent Radiation for X-Ray Imaging-The Soft X-Ray Undulator and the X1A Beamline at the NSLS

An undulator-based beamline was built and commissioned at the National Synchrotron Light Source to provide tunable coherent radiation in the 200-800 eV range. The low emittance of the storage ring means that the undulator source has high brightness so that a large flux of coherent x rays is delivered to experimental stations. The beamline uses a horizontally dispersing bichromator that allows two experiments to run simultaneously, making use of the first and second harmonics of the undulator output. In addition, the use of horizontally deflecting optics enables the beamline alignment to be insensitive to electron beam motion since the horizontal electron beam size is quite large. The beamline and its performance are discussed with emphasis on the optics and on stability, radiation, and vacuum considerations.     

Performance Optimization of a High-Repetition-Rate KrF Laser Plasma X-Ray Source for Microlithography

In order to develop a high-intensity laser plasma x-ray source appropriate for industrial application of x-ray lithography, experiments have been carried out using a high-repetition-rate (up to 40 Hz) excimer laser (249 nm, 300 mJ) with a power density of 2 × 1013 W/ cm2 in the laser focus. In this study emphasis is given to remedying specific problems inherent in operating the laser plasma x-ray source at high repetition rates and in its prolonged operation. Two different methods of minimizing the production of target debris are investigated. First, the use of helium as a quenching gas results in a reduction of the amount of atomic debris particles by more than two orders of magnitude with negligible x-ray absorption. Second, a tape target as opposed to a solid target reduces the production of larger debris particles by a further factor of 100. Remaining debris is stopped by an aluminized plastic or beryllium filter used to avoid exposure of the resist by plasma ultraviolet radiation. The x-ray source has been used to image x-ray transmission mask structures down to 0.3 μm onto general purpose x-ray photo-resist. Results have been analyzed with SEM. The x-ray emission spectrum of the repetitive laser plasmas created from an iron target has been recorded and the conversion efficiency of the laser light into x-rays that contribute to exposure of the resist was measured to be 0.3% over 2π sr.     

20～30岁民航飞行员畸变产物耳声发射特征分析

目的 分析20～30岁民航飞行员畸变产物耳声发射(distortion product otoacoustic emission,DPOAE)特征,探讨DPOAE对于早期发现民航飞行员噪声性听力损失的价值.方法 以39例20～30岁民航飞行员为飞行员组,31例耳科正常人为对照组,分别进行纯音测听和DPOAE测试.依据纯音测听结果,飞行员组分为飞行员A组(各频率纯音听阈均≤20 dB HL),飞行员B组(任何单一频率纯音听阈＞20 dB HL).分析比较飞行员各组与对照组纯音听阈、DPOAE结果.结果 ①飞行员组和飞行员B组纯音听阈较对照组显著升高(P＜0.05或P＜0.01),飞行员A组纯音听阈较对照组无显著差异;②飞行员各组DPOAE幅值较对照组均有明显下降(P＜0.05或P＜0.01);③DPOAE与纯音测听在0.5、6、8 kHz有显著的负相关,其他频率无明显相关性.结论 DPOAE有助于民航飞行员噪声性听力损失的早期发现,可以作为纯音测听的补充,但不能完全替代纯音测听.     

New Concepts for X-Ray, Soft X-Ray, and EUV Optical Instrumentation Including Applications in Spectroscopy, Plasma Diagnostics, and Biomedical Microscopy: A Status Report

In this article, we review current progress in the development of several techniques for extreme ultraviolet, soft x-ray, and x-ray optical instrumentation. Applications of these concepts include diagnostics of hot plasmas, spectroscopic studies of the interaction of multicharged ion beams with matter (atoms, ions, molecules, microstructures, surfaces, solids), and biomedical x-ray microscopy. Novel applications of components include the use of glass capillary converters (GCCs) and multilayer mirrors (MLMs) or crystals. GCC devices provide guiding, focusing, and polarization analysis of short wavelength radiation over a wide bandwidth. The MLM or crystal optical elements can be used for dispersing, focusing, and polarization-sensitive studies of radiation within a narrow bandwidth. In this report we focus on the development and testing of optical diagnostic devices for the short wavelength spectral region 0.1 nm < λ < 100 nm.     

Nd:YAG激光和C02激光治疗重度宫颈糜烂的疗效比较

目的 比较Nd:YAG激光和CO2激光治疗重度宫颈糜烂的疗效.方法 以Nd:YAG激光或CO2激光治疗重度宫颈糜烂各79例,比较其术中和术后出血情况、术后阴道排液时间及治愈率和伤口愈合时间,评价两种方法治疗重度官颈糜烂的疗效.结果 Nd:YAG激光组术中术后出血发生率低于CO2激光组,血术后阴道排液时间、一次件治愈率则高于CO2激光组,愈合时间则短于CO2激光组.其巾术巾术后出血发生率和一次性治愈率、术后阴道排液停止的时间(P<0.001)、愈合时间(P<0.01),两组比较差异均有非常显著意义.结论 Nd:YAG激光治疗重度宫颈糜烂术中术后出血发生率低,治愈率高,愈合时间快,疗效确切.     

A Comparison of DEF X-Ray Film and a Photodiode Array (Reticon) as Detectors for an X-Ray Crystal Spectrometer

A crystal spectrometer with a photodiode array (PDA) detector was tested for a range of x-ray energies between 1 and 2 keV. A laser-produced plasma has been used as an x-ray source and was generated by the high-power (Vulcan) glass laser system at the SERC Rutherford Appleton Laboratory, UK. The performance of the array was directly compared with the response of Kodak DEF x-ray film. In order to compare quantitatively the performances of the PDA and the film, detective quantum efficiency (DQE) considerations are presented for both devices. It is demonstrated that the PDA has a useful dynamic range which is approximately seven times greater than that of film, a peak DQE of approximately six times that of film, and a greatly superior low-signal performance. The operational characteristics of the PDA are discussed.     

A Figure of Merit Comparison between Bremsstrahlung and Monoenergetic X-Ray Sources for Angiography

A figure of merit (FOM) has been developed which embodies parameters related to image quality in the numerator and radiation integral dose to the patient in the denominator. In this manner, maximizing image quality and minimizing radiation dose amounts to maximizing the FOM. Furthermore, the FOM is designed to be independent of x-ray exposure (number of photons used), and this eliminates one important parameter in an optimization scenario. Monoenergetic x-ray beams (0% bandwidth) are compared with conventional Bremsstrahlung x-ray sources from a tungsten target, for angiographic imaging systems using 144 mg/cm2 Csl image intensifiers as the detector. Thus the results are applicable to both digital subtraction angiography (DSA) and digital fluoroscopic procedures involving iodine-based contrast (e.g., roadmapping). The results demonstrate improvement factors (the ratio of the best FOM of the monoenergetic beam over the best FOM of the polyenergetic beam) ranging from 2.3 to 1.4. The improvement factors averaged over four iodine contrast thicknesses (50, 100, 500, and 1000 mg/cm2) were 1.61 (σ = 0.159) for the 10 cm thick patient, 1.68 (σ= 0.172) for the 20 cm thick patient, and 1.82 (σ= 0.186) for the 30 cm thick patient. The conclusions are that monoenergetic x-ray beams are capable of delivering the same image quality at about half the radiation dose to the patient compared to conventional X-ray tubes.     

Soft X-Ray Contact Microscopy of Biological Specimens: Aluminum-Coated Silicon Nitride Windows as XUV Filters

The optimum wavelengths for soft x-ray contact microscopy of biological specimens are between 2.2 and 4.4 nm as, relative to water, this gives maximum contrast between carbon- and oxygen-containing constituents. Irradiation outside of this so-called "water window" interferes with either the resolution and/or the contrast that can be obtained. The previous belief that silicon nitride windows act as an effective filter for the longer wavelength, XUV radiation generated from laser-produced plasmas is shown to be suspect. However, in this study the use of aluminum-coated windows, which effectively exclude these longer wavelengths, still permits successful imaging of biological specimens. The added strength imparted to coated windows also ensures their survival during the imaging process, thereby demonstrating that the tissues can remain hydrated at the time that the image is formed in the photosensitive resist material used in this technique.     

软组织血管瘤的MRI诊断(附30例分析)

目的探讨软组织血管瘤的MR I表现。方法回顾性分析30例经手术病理、血管造影及临床证实的软组织血管瘤。全部病例先行MR I平扫,其中24例平扫后加增强扫描。结果海绵状血管瘤24例,毛细血管瘤4例,蔓状血管瘤2例。26例病变示蜂窝状或海绵状结构,24例在T1W I上呈中等信号(比肌肉信号高而比脂肪信号低),30例在T2W I呈明显高信号(比脂肪信号高),增强扫描后血管成分显著强化,可呈扭曲血管状,而非血管成分不强化。结论MR I对于本病的定位、定性诊断和病变范围估计及术后疗效的评估均有重要的意义。     

An Elliptical Crystal Spectrometer Suitable for EXAFS Studies of Laser Compressed Materials and for High Resolution X-Ray Spectroscopy

Using an x-ray spectrometer with an elliptically curved crystal it is possible to study absorption spectra from a target placed at one focus of the ellipse using a backlighting source placed at the other focus. This principle has been used to develop a spectrometer for EXAFS studies of laser compressed materials. The backlighting source is placed at one focus of the ellipse and the laser compressed EXAFS sample at the other. Using this technique a small area of the EXAFS target can be probed, thereby minimizing any spatial variations in the compressed plasma due to nonuniformities in the laser beams. Also, the dispersive nature of the crystal ensures that it acts as a bandpass filter, so that the EXAFS sample is not probed by other x-ray wavelengths which may cause unwanted heating. Another advantage is that compressed and uncompressed EXAFS spectra can be compared on a single shot. The optical properties of the spectrometer are discussed analytically and using a computer ray-tracing program. The development and alignment of the elliptical spectrometer are discussed, and its performance using both x-ray film and a CCD detector is evaluated. The use of the elliptical spectrometer as a high-resolution x-ray instrument is presented.     

High-Performance Mo/Si and W/B4C Multilayer Mirrors for Soft X-Ray Imaging Optics

Soft x-ray projection lithography and microscopy require a high throughput and diffraction-limited performance of a multielement imaging system. To meet these requirements for a specific design it is necessary to (1) achieve high normal incidence reflectivity on each optical element while optimizing the d-spacing variation across the surface of the optical element and (2) match the rf-spacing on each optical element to that of the others according to the ray-tracing design. A technique used to achieve normal incidence reflectivity greater than 60% at 13 nm for Mo/Si and greater than 2.7% at the "water window" region for W/B4C coatings is discussed. In addition, methods to obtain a rf-spacing uniformity of ±0.4% and to match the d-spacing between imaging mirrors with an accuracy of ±0.5% are considered. A method for characterizing multilayer coatings on curved surfaces, using cylindrical witness optics with precalculated shape and radius of curvature to simulate final optics, and a manufacturing method for witness optics are also presented.     

Evaluation of Cadmium-Zinc-Telluride Detector-based Single-Photon Emission Computed Tomography for Nuclear Cardiology: a Comparison with Conventional Anger Single-Photon Emission Computed Tomography

Purpose

The differences in performance between the cadmium-zinc-telluride (CZT) camera or collimation systems and conventional Anger single-photon emission computed tomography (A-SPECT) remain insufficient from the viewpoint of the user. We evaluated the performance of the D-SPECT (Spectrum Dynamics, Israel) system to provide more information to the cardiologist or radiological technologist about its use in the clinical field.

Materials and Methods

This study evaluated the performance of the D-SPECT system in terms of energy resolution, detector sensitivity, spatial resolution, modulation transfer function (MTF), and collimator resolution in comparison with that of A-SPECT (Bright-View, Philips, Japan). Energy resolution and detector sensitivity were measured for Tc-99m, I-123, and Tl-201. The SPECT images produced by both systems were evaluated visually using the anthropomorphic torso phantom.

Results

The energy resolution of D-SPECT with Tc-99m and I-123 was approximately two times higher than that of A-SPECT. The detector sensitivity of D-SPECT was higher than that of A-SPECT (Tc-99m: 4.2 times, I-123: 2.2 times, and Tl-201: 5.9 times). The mean spatial resolution of D-SPECT was two times higher than that of A-SPECT. The MTF of D-SPECT was superior to that of the A-SPECT system for all frequencies. The collimator resolution of D-SPECT was lower than that of A-SPECT; however, the D-SPECT images clearly indicated better spatial resolution than the A-SPECT images.

Conclusion

The energy resolution, detector sensitivity, spatial resolution, and MTF of D-SPECT were superior to those of A-SPECT. Although the collimator resolution was lower than that of A-SPECT, the D-SPECT images were clearly of better quality.

     

欧美医用激光产品标准对比分析

欧洲采用的国际电工委员会(IEC)标准和美国采用的食品药品监督管理局属下的器械和放射保健中心(CDRH)标准是两大主要的激光标准体系。通过对比分析两大医用激光标准,总结两者的差异和联系,为我国医用激光产品标准的制定和修订提供借鉴。     

CO2激光配合浅部X线治疗瘢痕疙瘩43例

应用CO_2激光、汽化瘢痕疙瘩,此术后14天起,用浅部X线疗程照射,治疗10～20次,放射线总量25～50Sv。本组43例治愈34例(治愈率79.0％)、有效8例、无效1例。本组与单用浅部X线治疗组和单用CO_2激光治疗组分别在治愈率上比较,统计学上差异均有非常显著性(P<0.001),本方法明显优于二种“单用”方法。本法先后发挥CO_2激光和X线两个物理因子的积极作用,效果确切,治愈率高,是治疗瘢痕疙瘩的一种好方法。     

CT 对胃肠道疾病的诊断价值

目的：比较X线、CT、MRI及DSA在胃肠病变检诊中的应用价值。方法2012年1月～2012年12月间在我科进行影像学检查的胃肠病变患者纳入研究对象,共94例,其中男52例,年龄2～81岁,中位年龄52岁;女42例,年龄8～87岁,中位年龄59岁。检查方法包括 X 线消化道气钡双重造影,CT 平扫,CT 增强（CT-CE）,CT 血管造影（CTA）,MRI平扫,MRI增强,数字血管减影血管成像（DSA）。在随访中,以消化内镜检查和（或）手术病理诊断为参考标准,评价影像方法的诊断正确率。结果94例患者中,X线消化道气钡双重造影检查14例,明确诊断12例,另2例通过C T检查明确诊断。C T检查68例,平扫明确诊断7例,进一步增强扫描明确诊断57例,再进一步结合消化道气钡双重造影明确者1例、MRI明确者1例、DSA明确者1例,还有1例通过手术探查明确。CTA检查11例,直接明确诊断者8例,进一步DSA明确者3例。MRI检查1例,未能直接明确诊断,进一步CT检查明确。结论 CT在胃肠病检诊中较X线、M RI和DSA具有更高的诊断价值,但是合理联合多种方法能够弥补单一影像学方法显示病变的局限,可以明显提高对胃肠病变的诊断正确率。