bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray fluorescence tomographic system design and image reconstruction
Authors: Cong Wenxiang , Shen Haiou , Cao Guohua , Liu Hong , Wang Ge
Published: December 2019

In this paper, we presented a new design of x-ray fluorescence CT imaging system. For detecting fuorescence signals of gold nanoparticles in-vivo, multiple spectroscopic detectors are arranged and rotated orthogonal to an excited region of interest so that a localized scan can be acquired with a maximized efficiency. Excitation filtration was employed to minimize the effects of low-energy x-rays and background scattering for lowering radiation dose to the object. Numerical simulations showed that the radiation dose is less than 300 mGy/second for a complete 30 views tomographic scan; and the sensitivity of 3D fluorescence signal detection is up to 0.2% contrast concentrations of nanoparticles. The x-ray fluorescence computed tomography is an important molecular imaging tool. It can be used directly in samall animal research. It has great translational potential for future clinical applications.
Experimental studies on few-view reconstruction for	high-resolution micro-CT
Authors: Sen Sharma Kriti , Jin Xin , Holzner Christian , Narayanan Shree , Liu Baodong , Wang Dong , Agah Masoud , Wang Linbing , Yu Hengyong , Wang Ge
Published: December 2019

High-resolution micro-CT offers 3D non-destructive imaging but scan times are prohibitively large in many cases. Advancements in image reconstruction offer great reduction in number of views while maintaining reconstruction accuracy; yet filtered back projection remains the de facto standard. An extensive study of few-view reconstruction using compressed-sensing based iterative techniques is carried out. Also, a novel 3D micro-CT phantom is proposed, and used for analyzing reconstruction accuracy. Numerical tests, and studies on real micro-CT data show that if measurement noise in projections is not extremely high, the number of views may be reduced to 1/8^{th} of the typically acquired view numbers. The study motivates the adoption of advanced reconstruction techniques to allow faster scanning, lower dosage, and reduced data size in high-resolution micro-CT.
DOT corrected fluorescence molecular tomography using targeted	contrast agents for small animal tumor imaging
Authors: Tan Yiyong , Cao Zehong , Sajja Hari Krishna , Lipowska Malgorzata , Wang Y. Andrew , Yang Lily , Jiang Huabei
Published: December 2019

PURPOSE: To demonstrate diffuse optical tomography (DOT) corrected fluorescence molecular tomography (FMT) for quantitatively imaging tumor-targeted contrast agents in a 4T1 mouse mammary tumor model.

PROCEDURES: In the first set of experiments, we validated our DOT corrected FMT method using subcutaneously injected 4T1 cells pre-labeled with a near-infrared (NIR) Cy 5.5 dye labeled recombinant amino-terminal fragment (ATF) of the receptor binding domain of urokinase plasminogen activator (uPA), which binds to uPA receptor (uPAR) that is highly expressed in breast cancer tissues. Next, we apply the DOT corrected FMT method to quantitatively evaluate the ability of sensitive tumor imaging after systemic delivery of new uPAR-targeted optical imaging probes in the mice bearing 4T1 mammary tumors. These uPAR-targeted optical imaging probes are ATF peptides labeled with a newly developed NIR-830 dye being conjugated to magnetic iron oxide nanoparticles (IONPs).

RESULTS: Our results have shown that DOT corrected FMT can accurately quantify and localize the injected imaging probe labeled 4T1 cells. Following systemic delivery of the targeted imaging nanoprobes into the mice bearing orthotopic mammary tumors, specific accumulation of the imaging probes in the orthotopic mammary tumors was detected in the mice that received uPAR targeted NIR-830-ATF-IONP probes but not in the mice injected with non-targeted NIR-830-mouse serum albumin (MSA)-IONPs. Additionally, DOT corrected FMT also enables the detection of both locally recurrent tumor and lung metastasis in the mammary tumor model 72 hrs after systemic administration of the uPAR-targeted NIR-830-labeled ATF peptide imaging probes.

CONCLUSIONS: DOT corrected FMT and uPAR-targeted optical imaging probes have great potential for detection of breast cancer, recurrent tumor and metastasis in small animals.
GPU based iterative cone-beam CT reconstruction using empty space	skipping technique
Authors: Zhao Xing , Hu Jing-Jing , Yang Tao
Published: December 2019

Iterative reconstruction of high-resolution cone-beam CT data is still a difficult task due to the demand for vast amounts of computer cycles and associated memory. In order to improve the performance of iterative algorithms for cone-beam CT reconstruction, an acceleration approach integrating GPU acceleration, empty space skipping and multi-resolution technique is proposed. The approach divides the reconstructed volume into equally sized blocks, and empty blocks are identified by reconstructing an initial low-resolution volume and segmenting it with threshold method. Then all non-empty blocks are packed into a new volume, which is initialized by interpolating the low resolution volume and reconstructed at full resolution using iterative algorithms. Finally these non-empty blocks are rearranged to get the reconstructed high-resolution volume. The whole process is implemented in parallel based on GPU. Since only the voxels in non-empty blocks are calculated, the number of considered voxels is greatly reduced, which translates directly into substantial computation, memory requirements and data transfer savings. The method is evaluated by reconstructing images from simulated projection data of phantom and CT datasets. The results indicate that our approach significantly improves the performance of iterative reconstruction while maintaining a high image quality, compared to conventional GPU-based approaches.
Adenosine stress thallium-201 myocardial perfusion imaging for	detecting coronary artery disease at an early stage
Authors: Chen Gui-Bing , Wu Hua , He Xiao-Jiang , Huang Jin-Xiong , Yu Dan , Xu Wei-Yi , Yu Hao
Published: December 2019

The aims of this study were to evaluate the diagnostic value of adenosine thallium-201 myocardial perfusion imaging and to compare it with exercise stress thallium-201 myocardial perfusion imaging for detecting coronary artery disease (CAD) at an early stage. Forty-one patients suspected with CAD were randomly divided into two groups. In Group 1 (n=21) adenosine stress was undertaken; the exercise stress myocardial perfusion imaging was performed in Group 2 (n=20). Coronary angiography (CAG) was performed in each patient within 2 weeks before or after single photon emission computed tomography (SPECT). Adenosine stress group vs. exercise stress group, the sensitivity was 92.86% vs. 100.0%, specificity 57.14% vs. 60.0%, positive predictive value 81.25% vs. 71.43%, negative predictive value 80.0% vs. 100.0%, accuracy 80.95% vs. 80.0% respectively. Detection rates of vessels of coronary artery lesions were 66.67% in Group 1 and 72.22% in Group 2 (P> 0.05). The side effects were mild and transient. Our results demonstrated that adenosine stress myocardial perfusion imaging is a safe and reliable diagnostic method for an early stage of CAD. As a comparative sensitivity and accuracy with exercise stress thallium-201 myocardial perfusion imaging, adenosine stress testing may provide a feasible alternative pharmacological stress method in myocardial SPECT for detection of CAD.
X-ray determination of the thickness of thin metal foils
Authors: Block Robert C. , Geuther Jeffrey A. , Methe Brian , Barry Devin P. , Leinweber Gregory
Published: December 2019

The interpretation of neutron cross section experiments depends upon an in-depth knowledge of the physical characteristics of the target sample. An x-ray image of an encapsulated metallic Eu sample used in a neutron cross section measurement showed a very non-uniform thickness as well as holes in the sample. In light of this problem it was found necessary to determine the thickness distribution in four thin metallic Eu samples without disturbing the encapsulation (and exposing the Eu to air). All four Eu samples were subsequently x-rayed along with a Sm step wedge. The gray levels in the Eu images were then compared to the Sm gray levels and, taking into account differences in the x-ray absorption and density of Eu and Sm, the sample thickness distributions were obtained for each Eu sample.

This work demonstrates that a step wedge can be used to calibrate x-ray images to a thickness scale, and allows the thickness variation of the samples to be represented in a simple probability table for incorporation into the analysis of neutron experiments.
Retroperitoneal laparoscopic versus open dismembered pyeloplasty	for ureteropelvic junction obstruction
Authors: Wang Xisheng , Zhang Zejian , Peng Naixiong , Liu Chunxiao
Published: December 2019

OBJECTIVE: To compare classical open pyeloplasty with retroperitoneal laparoscopic pyeloplasty in effectiveness, potential advantages and complications.

MATERIALS AND METHODS: Between March 2006 and April 2010, 113 patients with ureteropelvic junction obstruction underwent retroperitoneal laparoscopic dismembered pyeloplasty were retrospectively compared with those of 59 patients who underwent open dismemberse pyeloplasty through a retroperitoneal flank approach. The Chi-square test was used for statistical analysis of qualitative data and the Student t-test for analysis of quantitative data. P < 0.05 was considered significant.

RESULTS: Operative time was shorter in the retroperitoneal laparoscopic group (mean 125 min) compared to the open pyeloplasty group (mean 142 min, P < 0.05). Mean hospital stay was shorter in the retroperitoneal laparoscopic group (mean 6 days, compared to 9 days, open). Complication rates, including anastomotic urinary leakage, stenosis and infection, were 4.42% in retroperitoneoscopic compared to 6.78% open surgery. Anastomotic leakage was 3 cases in the retroperitoneoscopic group versus 1 case in the open group. Success, defined as improved ultrasonic or renographic parameters, with resolution of symptoms where discernable, was noted in 98.0% of the open group and 98.1% of the retroperitoneoscopic group with a mean follow up of 38.4 and 32.7 months, respectively.

CONCLUSIONS: Retroperitoneal laparoscopic dismembered pyeloplasty in treatment of ureteropelvic junction obstruction is a minimally invasive, safe and effective therapy with short procedure time, less complications, and shorter convalescence.
Interior reconstruction method based on rotation-translation scanning model
Authors: Wang Xianchao , Tang Ziyue , Yan Bin , Li Lei , Bao Shanglian
Published: December 2019

In various applications of computed tomography (CT), it is common that the reconstructed object is over the field of view (FOV) or we may intend to sue a FOV which only covers the region of interest (ROI) for the sake of reducing radiation dose. These kinds of imaging situations often lead to interior reconstruction problems which are difficult cases in the reconstruction field of CT, due to the truncated projection data at every view angle. In this paper, an interior reconstruction method is developed based on a rotation-translation (RT) scanning model. The method is implemented by first scanning the reconstructed region, and then scanning a small region outside the support of the reconstructed object after translating the rotation centre. The differentiated backprojection (DBP) images of the reconstruction region and the small region outside the object can be respectively obtained from the two-time scanning data without data rebinning process. At last, the projection onto convex sets (POCS) algorithm is applied to reconstruct the interior region. Numerical simulations are conducted to validate the proposed reconstruction method.
Flexible methods for segmentation evaluation: Results from	CT-based luggage screening
Authors: Karimi Seemeen , Jiang Xiaoqian , Cosman Pamela , Martz Harry
Published: December 2019

BACKGROUND: Imaging systems used in aviation security include segmentation algorithms in an automatic threat recognition pipeline. The segmentation algorithms evolve in response to emerging threats and changing performance requirements. Analysis of segmentation algorithms' behavior, including the nature of errors and feature recovery, facilitates their development. However, evaluation methods from the literature provide limited characterization of the segmentation algorithms.

OBJECTIVE: To develop segmentation evaluation methods that measure systematic errors such as oversegmentation and undersegmentation, outliers, and overall errors. The methods must measure feature recovery and allow us to prioritize segments.

METHODS: We developed two complementary evaluation methods using statistical techniques and information theory. We also created a semi-automatic method to define ground truth from 3D images. We applied our methods to evaluate five segmentation algorithms developed for CT luggage screening. We validated our methods with synthetic problems and an observer evaluation.

RESULTS: Both methods selected the same best segmentation algorithm. Human evaluation confirmed the findings. The measurement of systematic errors and prioritization helped in understanding the behavior of each segmentation algorithm.

CONCLUSIONS: Our evaluation methods allow us to measure and explain the accuracy of segmentation algorithms.
The convergence of block cyclic projection with underrelaxation	parameters for compressed sensing based tomography
Authors: Arroyo Fangjun , Arroyo Edward , Li Xiezhang , Zhu Jiehua
Published: December 2019

The block cyclic projection method in the compressed sensing framework (BCPCS) was introduced for image reconstruction in computed tomography and its convergence had been proven in the case of unity relaxation (λ=1). In this paper, we prove its convergence with underrelaxation parameters λ∈(0,1). As a result, the convergence of compressed sensing based block component averaging algorithm (BCAVCS) and block diagonally-relaxed orthogonal projection algorithm (BDROPCS) with underrelaxation parameters under a certain condition are derived. Experiments are given to illustrate the convergence behavior of these algorithms with selected parameters.
Study of solid-conversion gaseous detector based on GEM for high	energy X-ray industrial CT
Authors: Zhou Rifeng , Zhou Yaling
Published: December 2019

The general gaseous ionization detectors are not suitable for high energy X-ray industrial computed tomography (HEICT) because of their inherent limitations, especially low detective efficiency and large volume. The goal of this study was to investigate a new type of gaseous detector to solve these problems. The novel detector was made by a metal foil as X-ray convertor to improve the conversion efficiency, and the Gas Electron Multiplier (hereinafter "GEM") was used as electron amplifier to lessen its volume. The detective mechanism and signal formation of the detector was discussed in detail. The conversion efficiency was calculated by using EGSnrc Monte Carlo code, and the transport course of photon and secondary electron avalanche in the detector was simulated with the Maxwell and Garfield codes. The result indicated that this detector has higher conversion efficiency as well as less volume. Theoretically this kind of detector could be a perfect candidate for replacing the conventional detector in HEICT.
Locally optimized non-local means denoising for low-dose X-ray	backscatter imagery
Authors: Tracey Brian H. , Miller Eric L. , Wu Yue , Alvino Christopher , Schiefele Markus , Al-Kofahi Omar
Published: December 2019

While recent years have seen considerable progress in image denoising, the leading techniques have been developed for digital photographs or other images that can have very different characteristics than those encountered in X-ray applications. In particular here we examine X-ray backscatter (XBS) images collected by airport security systems, where images are piecewise smooth and edge information is typically more correlated with objects while texture is dominated by statistical noise in the detected signal. In this paper, we show how multiple estimates for a denoised XBS image can be combined using a variational approach, giving a solution that enhances edge contrast by trading off gradient penalties against data fidelity terms. We demonstrate the approach by combining several estimates made using the non-local means (NLM) algorithm, a widely used patch-based denoising method. The resulting improvements hold the potential for improving automated analysis of low-SNR X-ray imagery and can be applied in other applications where edge information is of interest.
A correlation of breast cancer and calcium levels in hair analyzed	by X-ray fluorescence
Authors: Chikawa Jun-ichi , Mouri Yoshitaka , Shima Hiroki , Yamada Kousaku , Yamamoto Hitoshi , Yamamoto Shingo
Published: December 2019

Time variations of elemental concentrations and their abnormalities due to breast cancer have been observed along single hair strands by X-ray fluorescence excited by synchrotron radiation. The renal-controlled elements Ca, Sr, S, K, Cl, Br and P have upper and lower levels associated with gating and closing of ion channels in the hair-making cells. The Ca lower level is normal. In cases of Ca deficiency, with a decrease from the normal, store-operated Ca channel gating occurs so as to keep the hair Ca at the normal, and paradoxically high Ca levels near or at the upper level are produced by PTH-operated channel gating of the cells. Chronic Ca deficiency shows a temporal pattern along the hair consisting of a long-term duration of the upper [Ca] level, 10-month long decay to the lower level and abrupt increase to the upper level. The observation for hair from breast-cancer patients also shows the upper Ca level for the time period well before detection, and suggests that cancer is always generated at the long-lasting [Ca] upper level and the hair [Ca] decreases gradually toward the lower level with the cancer growth. This decay of [Ca] is accompanied by those of [Sr] and [K]. Their different decay forms can be explained by parathyroid hormone related peptide (PTHrP) in serum secreted from the cancer having 150 times longer dwell time on the PTH receptors than that of PTH. Patient hair has a memory for the entire cancer process from the state before cancer generation, and the pattern can be distinguished from concentration variation due to the chronic Ca deficiency without cancer, leading to a criterion for cancer detection by the ratio of [Sr]/[Ca]. The hair analysis is useful for early detection of cancer.
Value of diffusion-weighted magnetic resonance imaging on the	follow-up of nasopharyngeal carcinoma after radiotherapy
Authors: Xu Ji-Fei , Wu Xing-Wang , Wang Wan-Qin , Kong Ling-Ling , Wu Li-Ming , Wang Fan
Published: December 2019

PURPOSE: To explore the value of diffusion-weighted imaging (DWI) and magnetic resonance imaging (MRI) on the follow-up of nasopharyngeal carcinoma (NPC) after radiotherapy.

MATERIAL AND METHODS: Eighty-three NPC patients after radiotherapy were divided into two groups: 4 cases of residual tumor and 33 cases of non-residual within 6 months, the cases of recurrent and non-recurrent were 5 and 41 over 6 months, respectively. MRI and DWI imaging of these cases were closely analyzed, and the apparent diffusion coefficient (ADC) of the nasopharyngeal residual mass and nasopharyngeal wall thickening, skull base destruction and lateral pterygoid muscle were measured.

RESULTS: The ADC of the lateral pterygoid muscle was (1.501 ± 0.069) × 10 $^{ - 3}$ mm $^{2}$ /s in 83 cases. The ADCs of the non-residual group, residual group, non-recurrent group and recurrent group were (1.843 ± 0.133.4) × 10 $^{ - 3}$ mm $^{2}$ /s, (1.097 ± 0.183) × 10 $^{ - 3}$ mm $^{2}$ /s, (1.884 ± 0.134) × 10 $^{ - 3}$ mm $^{2}$ /s and (0.787 ± 0.067) × 10 $^{ - 3}$ mm $^{2}$ /s respectively.The ADCs of the residual group and recurrent group were lower than that of the lateral pterygoid muscle, while the ADCs of the non-residual group and non-recurrent group were higher than that of the lateral pterygoid muscle.The differences were statistically significant (P < 0.05).

CONCLUSION: DWI can provide qualitative and quantitative information about the tumor cellular level; it can also identify residual, local fibrosis and recurrence after NPC radiotherapy sensitively and accurately by measuring the ADC of the region of interest.
A systematic procedure to optimise dose and image quality for the	measurement of inter-vertebral angles from lateral spinal projections using	Cobb and superimposition methods
Authors: Al Qaroot Bashar , Hogg Peter , Twiste Martin , Howard David
Published: December 2019

BACKGROUND: Patients with vertebral column deformations are exposed to high risks associated with ionising radiation exposure. Risks are further increased due to the serial X-ray images that are needed to measure and asses their spinal deformation using Cobb or superimposition methods. Therefore, optimising such X-ray practice, via reducing dose whilst maintaining image quality, is a necessity.

OBJECTIVES: With a specific focus on lateral thoraco-lumbar images for Cobb and superimposition measurements, this paper outlines a systematic procedure to the optimisation of X-ray practice.

METHODS: Optimisation was conducted based on suitable image quality from minimal dose. Image quality was appraised using a visual-analogue-rating-scale, and Monte-Carlo modelling was used for dose estimation. The optimised X-ray practice was identified by imaging healthy normal-weight male adult living human volunteers.

RESULTS: The optimised practice consisted of: anode towards the head, broad focus, no OID or grid, 80 kVp, 32 mAs and 130 cm SID.

CONCLUSION: Images of suitable quality for laterally assessing spinal conditions using Cobb or superimposition measurements were produced from an effective dose of 0.05 mSv, which is 83% less than the average effective dose used in the UK for lateral thoracic/lumbar exposures. This optimisation procedure can be adopted and use for optimisation of other radiographic techniques.
A scatter correction method for dual-energy digital mammography:	Monte Carlo simulation
Authors: Ai Kai , Gao Yanhua , Yu Gang
Published: December 2019

PURPOSE: To develop a novel scatter correction method without additional patient dose for dual-energy digital mammography (DEDM) to reduce scatter's impacts and enhance microcalcification detectability in dual-energy X-ray subtraction image.

METHODS: Combining scatter radiation is lower spatial frequency component and calcifications are sparsely distributed in digital mammogram, we develop a new scatter correction strategy. First, an adaptive sampling scheme is presented to find possible noncalcification (zero calcification) pixels. Then the maximum likelihood expectation maximization (MLEM) algorithm is applied to evaluate initial scatter surface. The accurate scatter radiation of sampling pixels is obtained by solving dual-energy computational formula with zero calcification constraint and scatter surface constraint.

RESULTS: After scatter correction, the scatter-to-primary ratio (SPR) of wedge phantom is reduced from ∼36.0% to ∼3.1% for low-energy (LE) image and ∼29.6% to ∼0.6% for high-energy (HE) image. For step phantom, the SPR is reduced from ∼42.1% and ∼30.3% to ∼3.9% and ∼0.9% for LE and HE image, respectively. The calcification contrast-to-noise ratio is improved by two orders of magnitudes in calcification images.

CONCLUSIONS: The proposed method shows an excellent performance on scatter reduction and calcification detection. Compared with hardware based scatter correction strategy, our method need no extra exposure and is easy to implementation.
Monochromatic X-ray imaging using a combination of doubly curved	crystal and polycapillary X-ray lens
Authors: Sun Tianxi , MacDonald C.A.
Published: December 2019

A monochromatic X-ray imaging setup based on a combination of a doubly curved crystal and a polycapillary focusing X-ray lens was designed. In this setup, the bent crystal optic was used not only to monochromatize but also to focus the divergent X-ray beam from a conventional X-ray source to form a monochromatic X-ray focal spot with a size of 426 × 467 μm $^{2}$ at 17.5 keV. The beam expanding from this focal point was focused by the polycapillary optic to obtain a focal spot which was then used as the monochromatic X-ray imaging virtual source. The output focal spot size of the focusing polycapillary optic at 17.5 keV was 97 μm. Compared with the beam expansion after the focal spot of the bent crystal optic, the beam expansion after the focal spot of the focusing polycapillary optic was relatively large. This was helpful for magnifying the X-ray image of the sample. The focused beam was helpful to decrease the exposure time for imaging small samples.
Generalized fourier slice theorem for cone-beam image	reconstruction
Authors: Zhao Shuang-Ren , Jiang Dazong , Yang Kevin , Yang Kang
Published: December 2019

The cone-beam reconstruction theory has been proposed by Kirillov in 1961, Tuy in 1983, Feldkamp in 1984, Smith in 1985, Pierre Grangeat in 1990. The Fourier slice theorem is proposed by Bracewell 1956, which leads to the Fourier image reconstruction method for parallel-beam geometry. The Fourier slice theorem is extended to fan-beam geometry by Zhao in 1993 and 1995. By combining the above mentioned cone-beam image reconstruction theory and the above mentioned Fourier slice theory of fan-beam geometry, the Fourier slice theorem in cone-beam geometry is proposed by Zhao 1995 in short conference publication. This article offers the details of the derivation and implementation of this Fourier slice theorem for cone-beam geometry. Especially the problem of the reconstruction from Fourier domain has been overcome, which is that the value of in the origin of Fourier space is 0/0. The 0/0 type of limit is proper handled. As examples, the implementation results for the single circle and two perpendicular circle source orbits are shown. In the cone-beam reconstruction if a interpolation process is considered, the number of the calculations for the generalized Fourier slice theorem algorithm is $O(N^4)$ , which is close to the filtered back-projection method, here N is the image size of 1-dimension. However the interpolation process can be avoid, in that case the number of the calculations is $O(N^5)$ .
A user-friendly LabVIEW software platform for grating based X-ray	phase-contrast imaging
Authors: Wang Shenghao , Han Huajie , Gao Kun , Wang Zhili , Zhang Can , Yang Meng , Wu Zhao , Wu Ziyu
Published: December 2019

X-ray phase-contrast imaging can provide greatly improved contrast over conventional absorption-based imaging for weakly absorbing samples, such as biological soft tissues and fibre composites. In this study, we introduced an easy and fast way to develop a user-friendly software platform dedicated to the new grating-based X-ray phase-contrast imaging setup at the National Synchrotron Radiation Laboratory of the University of Science and Technology of China. The control of 21 motorized stages, of a piezoelectric stage and of an X-ray tube are achieved with this software, it also covers image acquisition with a flat panel detector for automatic phase stepping scan. Moreover, a data post-processing module for signals retrieval and other custom features are in principle available. With a seamless integration of all the necessary functions in one software package, this platform greatly facilitate users' activities during experimental runs with this grating based X-ray phase contrast imaging setup.
Analytic reconstruction approach for parallel translational	computed tomography
Authors: Kong Huihua , Yu Hengyong
Published: December 2019

To develop low-cost and low-dose computed tomography (CT) scanners for developing countries, recently a parallel translational computed tomography (PTCT) is proposed, and the source and detector are translated oppositely with respect to the imaging object without a slip-ring. In this paper, we develop an analytic filtered-backprojection (FBP)-type reconstruction algorithm for two dimensional (2D) fan-beam PTCT and extend it to three dimensional (3D) cone-beam geometry in a Feldkamp-type framework. Particularly, a weighting function is constructed to deal with data redundancy for multiple translations PTCT to eliminate image artifacts. Extensive numerical simulations are performed to validate and evaluate the proposed analytic reconstruction algorithms, and the results confirm their correctness and merits.
An Experimental and Theoretical Study of Pendellösung Fringes in Synchrotron Section Topographs of Silicon Wafers
Authors: Partanen J. , Tuomi T.
Published: December 2019

X-ray section topographs of nearly perfect Czochralski-grown wafers were made with synchrotron radiation having a continuous spectrum. An intensity curve measured from the x-ray film is compared to the calculated curve obtained using the dynamical theory of x-ray diffraction. A computer simulation of the topograph is also presented. A good agreement between theory and experiment is found except in the middle part of the topograph.
Application of X-Ray Microtomography in Materials Science Illustrated by a Study of a Continuous Fiber Metal Matrix Composite
Authors: Elliott J. C. , Anderson P. , Davis G. , Dover S. D. , Stock S. R. , Breunig T. M. , Guvenilir A. , Antolovich S. D.
Published: December 2019

The advantages of the use of x-ray microtomography in materials science are discussed, and illustrated by the nondestructive study of the mechanical damage in a continuous fiber SiC/Al composite at a resolution of about 25 μm. A laboratory x-ray source was used, and it was shown that quantitative measurements of the linear absorption coefficient at this resolution are possible, even though the AgKα radiation used is accompanied by a considerable amount of white radiation, provided that the counter system is properly corrected for pulse pile up and dead-time.
A Scanning Soft X-Ray Microscope with an Ellipsoidal Focusing Mirror
Authors: Voss J. , Dadras H. , Kunz C. , Moewes A. , Roy G. , Sievers H. , Storjohann I. , Wongel H.
Published: December 2019

We have developed and brought into operation a new type of scanning soft x-ray microscope which can operate at any photon energy from 20 to 1300 eV. This microscope demagnifies a diaphragm by means of an annular section of an ellipsoidal mirror to a smallest spot size of, at present, about 0.4 μm (FWHM), certainly containing only a small fraction of the total intensity. The sample is scanned across this spot. Between mirror and focus a free space of 30 mm is available for detectors, and particles emitted from a surface at more than 30° to the normal can be extracted into a mass or energy analyzer. Transmission, photoemission, luminescence, photostimulated desorption, reflectivity, and other signals may serve for imaging. In addition, a static analysis of very small samples or spots on a sample will become feasible.
Investigation of Damage to Multilayer Optics in X-Ray Laser Cavities: W/C, WRe/C, WC/C, Stainless-Steel/C, and Cr3C2/C Mirrors
Authors: MacGowan B. J. , Mrowka S. , Barbee Jr. T. W. , da Silva L. B. , Eder D. C. , Koch J. A. , Pan L. S. , Turner J. A. , Underwood J. H. , Young P. E.
Published: December 2019

In many applications, multilayer mirrors are exposed to damaging fluences of x rays. In x-ray laser cavities intense optical and broad-band x radiation, from the x-ray laser plasma amplifier, can damage multilayer mirrors on time scales of hundreds of picoseconds. We describe experiments using short duration (500 ps) bursts of soft x rays from a laser produced gold plasma to damage multilayer mirrors designed to reflect wavelengths close to 45 Å at normal incidence. The effect of the damaging x-ray flux on normal incidence reflectivity was time resolved for W/C, WRe/C, WC/C, 303-stainless-steel/C, and Cr3C2/C multilayers. The damage thresholds of the different mirrors were compared, and the Cr3C2/C mirrors were found to be the most resilient. The outer layers of the multilayers were observed to expand slowly as x rays were absorbed, and a more rapid expansion then preceded the total loss of reflectivity, at temperatures well below the melting temperature of the mirror components. It is believed that the dominant expansion mechanism is a change in the amorphous carbon layers to a more graphitic structure. The data are fit quite well by a model that assumes expansion of up to 25% in the thickness of the outermost carbon layers, followed by intermixing of the hotter layers. The rapid expansion has been observed to occur in times from 40 to 150 ps and may be the fastest resolution to date of the phenomenon of graphitization. The integrated reflectivity of the mirrors was observed to increase by up to a factor of 2.5 as they damaged; this reflectivity increase may be consistent with a reduction in the layer roughness.
A Soft X-Ray/EUV Reflectometer Based on a Laser Produced Plasma Source
Authors: Gullikson E. M. , Underwood J. H. , Batson P. C. , Nikitin V.
Published: December 2019

A soft x-ray reflectometer is described which is based on a laser-produced plasma source and is continuously tunable over the range 40 Å < λ < 400 Å. The source is produced by focusing 0.532-μm light from a Q-switched Nd:YAG laser on a solid target. The x-ray wavelength is defined using a high throughput spherical grating monochromator with moderate resolving power (λ/Δλ ≈ 100 to 500). A time-averaged monochromatized flux of more than 109 photons/s in a 1% bandwidth at 100 eV is obtained. Photon “shot noise” limited measurements are obtained by the use of an I0 detector to normalize out the shot-to-shot variations in source intensity. Measurements with submillimeter spot sizes are readily obtainable. Various detectors have been used and the advantages and disadvantages of each are discussed. The higher order contamination of the monochromator output has been analyzed using a second grating for the purpose of making measurement corrections. The reflectometer thus provides the capability for precision absolute measurements of the reflectance of gratings and multilayer mirrors, the transmittance of thin film filters, or other properties of x-ray optical elements.
X-Ray Microscopy at Suboptical Resolution: Direct Observation of the 65-nm Periodicity in Collagen Fibrils
Authors: Burge R. E. , Buckley C. J. , Foster G. F. , Miller A. , Wess T.
Published: December 2019

Using a Fresnel zone plate we demonstrate for the first time the direct visualization by x-ray microscopy of suboptical regularity in a biological specimen, namely the 65-nm axial periodicity of tendon collagen. This resolution test demonstrates a resolving power of about 20λ; a resolving power of <10λ is in prospect.
The Anisotropy of X-Ray Reflection and Scattering from Hexagonal BN
Authors: Filatova E. O. , Blagoveshchenskaya T. A.
Published: December 2019

B K-reflection spectra for grazing incidence angles (θ0 = 4°, 8°), calculated absorption spectra, and angle-dependent scattering distributions at different grazing incidence angles and different wavelengths from hexagonal BN have been described. The reflection and scattering from a surface cut parallel and perpendicular to the c-axis of the crystal have been studied. The strong anisotropy of ultrasoft x-ray reflection and scattering has been discovered.
Flux Maximization Techniques for Compton Backscatter Depth Profilometry
Authors: Lawson Larry
Published: December 2019

Resolution in x-ray backscatter imaging has often been hampered by low fluxes. But, for a given set of resolution requirements and geometric constraints, it is possible to define a maximization problem in the geometric parameters for which the solution is the maximum flux possible in those circumstances. In this way, resolution in noncritical directions can be traded for improved resolution in a desired direction. Making this the thickness, or surface normal direction, makes practicable the depth profiling of layered structures. Such techniques were applied to the problem of imaging the layered structure of corroding aircraft sheet metal joints using Compton backscatter.
Comparison of Ultrathin X-Ray Window Designs
Authors: Viitanen Veli-Pekka , Mutikainen Risto , Nenonen Seppo , Partanen Panu
Published: December 2019

In order to fabricate entrance windows for soft x-ray detectors, various technologies have been developed. Depending on the x-ray-detector type and the environment in which the windows are used, entrance windows must meet several, often contradictory, requirements: while good pressure tolerance and durability as well as gas tightness require thicker structures, good x-ray transmission can only be achieved with thin membranes. In this paper, the suitability of different window types for various applications is discussed. The applicability discussion is based on the results of tests performed on prototype windows, as well as on calculated and measured x-ray transmission properties. A comparative study of endurance vs transmission properties of some candidate membrane materials is also presented. Test results include pressure tolerance and leakage rates as well as some measurements of radiation damage to the window materials. The window technologies presented include coated polyimide membranes with two different supporting schemes as well as submicrometer beryllium membranes.
Grazing X-Ray Reflectometry Data Processing by Fourier Transform
Authors: Bridou F. , Pardo B.
Published: December 2019

Grazing x-ray reflectometry allows analysis of thin-layer stacks. The fitting of the reflectivity curve by a trial and error method can determine the parameters of the films. The Fourier analysis of the experimental reflectivity curve can directly give a rough determination of the profile index. Such results can be useful in choosing a starting model. With the choice of an appropriate model a fit to the reflectivity curve can be undertaken to determine the parameters of the stack. The Fourier analysis method can only be used if the reflectivity data undergo a transformation to produce a periodic curve. Associated artifacts are studied and discussed. Each Fourier peak is associated with two interfaces. The interface roughness spreads the Fourier peaks, adding the squared roughness values. The sample’s absorption of the x-rays does not limit the Fourier analysis.
The New NIST/ARPA National Soft X-Ray Reflectometry Facility
Authors: Tarrio C. , Watts R. N. , Lucatorto T. B. , Haass M. , Calcott T. A. , Jia J.
Published: December 2019

We have recently begun a series of upgrades to the NIST/ARPA National Reflectometry Facility at the Synchrotron Ultraviolet Radiation Facility. The facility currently consists of a new monochromator and the original sample manipulator which allows us to measure optical components less than 10 cm in diameter. The monochromator offers high throughput and modest resolution over the wavelength range 3.5-40 nm. In the next year we will be installing a sample manipulator that will be able to accommodate the much larger optics that will be used in future x-ray projection lithography and astronomy instruments. We offer preliminary measurements of the throughput and resolution of the new monochromator.
Digitization and Image Processing Methods for Enhancement and Quantification of Grazing-Incidence X-Ray Topographs
Authors: Rheinländer Jørgen , Abdali Salim , Zielinska-Rohozinska Elzbieta
Published: December 2019

The conventional photographic prints obtained from double crystal x-ray topography are often hard to interprete and reproduce. Photographic enhancement methods require skillful work by an experienced photographer. They are time consuming and the image information is difficult to present quantitatively. Alternatively, image processing methods may be applied by digitization of the original topographic recording. Image processing computer programs may be applied, e.g., for image enhancement and for quantification of image information. This paper’s main interest is related to —obtaining a sufficiently high magnification ratio; —correcting for intensity variations within the image; —applying spatial filtering techniques in order to reduce film grain noise; —improving contrast, and —retrieving quantative information on image details. The application of such image processing routines is exemplified on topographs obtained by a double-crystal diffractometer set to the (+, -) asymmetric-asymmetric setting. A silicon single crystal was used as the monochromator, while the sample was a silicon single crystal which had undergone both surface damage and metallic contamination before the application of Rapid Thermal Annealing (RTA). Hence, well-defined microdefects are found within the sample. These computer-processed images are compared with corresponding images enhanced by conventional techniques. The results provide indications of which enhancement procedures should be applied for qualitative image improvement and for quantification of image details within different types of topographic recordings.
High-Performance Mo/Si and W/B4C Multilayer Mirrors for Soft X-Ray Imaging Optics
Authors: Gutman Georgy
Published: December 2019

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.
Developments in X-Ray Detectors and Associated Electronics: A Review of the Technology and Possible Future Trends
Authors: Sareen R. A.
Published: December 2019

The detection of low-energy x rays in a precise and efficient manner is now routinely performed with a range of solid state detectors. These devices have been developed continuously over the past 30 years to the point where current performance closely matches theoretical predictions for resolution and efficiency. To achieve these goals parallel developments in field effect transistors and amplifiers were also required. To fully understand the problems associated with the development and use of these detectors it is necessary to discuss both the generation of x rays and the way in which x rays interact with the available detector materials. The energy range considered is 0-100 keV and a comparison between the successful lithium drifted silicon detector and the more recently re-developed high-purity germanium detectors for these low energy applications is given.
Current Status of the VU MFEL Compton X-Ray Program
Authors: Dong W. W. , Brau C. A. , Waters J. W. , Tompkins P. A. , Carroll F. C. , Price R. R. , Pickens D. R. , Roos C. F.
Published: December 2019

The Vanderbilt University medical FEL (free electron laser) Compton x-ray program is close to being operational. The FEL modifications necessary for this new capability are near completion. The transport and detection systems for electron and IR beams have been designed, delivered, and tested. We initially expect to produce 108 x-ray photons per second in the 15- to 20-keV region.
Theoretical and Experimental Investigation of X-Ray Diffraction by a Lamellar Multilayer Amplitude Grating
Authors: Bac S. , Troussel P. , Sammar A. , Guerin P. , Ladan F.-R. , Andre J.-M. , Schirmann D. , Barchewitz R.
Published: December 2019

We present experimental and theoretical studies of the diffraction by an x-ray lamellar multilayer amplitude grating. The main diffraction properties of such a device are given. Experimental efficiency curves are obtained at 800 eV photon energy using synchrotron radiation. The features observed in these curves are identified and interpreted by means of two theoretical methods. Particular emphasis is given to structures observed for the first time which had been theoretically predicted.
Ray Tracing for Crystal-Diffraction Spectrometers with Position-Sensitive Detectors
Authors: Lehnert U. , Zschornack G.
Published: December 2019

Ray tracing calculations for crystal-diffraction spectrometers with position-sensitive detectors are done. After describing fundamentals of the ray tracing formalism, the paper presents selected results for a given spectrometer geometry. The developed method allows a three-dimensional representation of diffraction reflections as well as a matrix display of the recorded events in the detector plane. Applying the formalism of Monte Carlo simulation it is possible to calculate other important quantities, such as the resolving power and luminosity of the analyzed spectrometer.
Bragg X-Ray Optics for Imaging Spectroscopy of Plasma Microsources
Authors: Pikuz T.A. , Ya. Faenov A. , Pikuz S. A. , Romanova V. M. , Shelkovenko T. A.
Published: December 2019

Bragg x-ray optics based on crystals with transmission and reflection properties bent on cylindrical or spherical surfaces are discussed. Applications of such optics for obtaining one- and two-dimensional monochromatic images of different plasma sources in the wide spectral range 1–20 Å are described. Samples of spectra obtained with spectral resolution of up to λ/Δλ ~ 10,000 and spatial resolution of up to 18 μm are presented.