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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Combining image-processing and image compression schemes

An investigation into the combining of image-processing schemes, specifically an image enhancement scheme, with existing compression schemes is discussed. Results are presented on the pyramid coding scheme, the subband coding scheme, and progressive transmission. Encouraging results are demonstrated for the combination of image enhancement and pyramid image coding schemes, especially at low bit rates. Adding the enhancement scheme to progressive image transmission allows enhanced visual perception at low resolutions. In addition, further progressing of the transmitted images, such as edge detection schemes, can gain from the added image resolution via the enhancement.

Greenspan, H.↗
NASA NTRS1996

Single Transducer Ultrasonic Imaging Method that Eliminates the Effect of Plate Thickness Variation in the Image

This article describes a single transducer ultrasonic imaging method that eliminates the effect of plate thickness variation in the image. The method thus isolates ultrasonic variations due to material microstructure. The use of this method can result in significant cost savings because the ultrasonic image can be interpreted correctly without the need for machining to achieve precise thickness uniformity during nondestructive evaluations of material development. The method is based on measurement of ultrasonic velocity. Images obtained using the thickness-independent methodology are compared with conventional velocity and c-scan echo peak amplitude images for monolithic ceramic (silicon nitride), metal matrix composite and polymer matrix composite materials. It was found that the thickness-independent ultrasonic images reveal and quantify correctly areas of global microstructural (pore and fiber volume fraction) variation due to the elimination of thickness effects. The thickness-independent ultrasonic imaging method described in this article is currently being commercialized under a cooperative agreement between NASA Lewis Research Center and Sonix, Inc.

Roth, Don J.↗
NASA NTRS2007

Beam Combination for Stellar Imager and its Application to Full-Aperture Imaging

Stellar Imager (SI) will be a Space-Based telescope consisting of 20 to 30 separated apertures. It is designed for UV/Optical imaging of stellar surfaces and asteroseismology. This report describes details of an alternative optical design for the beam combiner, dubbed the Spatial Frequency Remapper (SFR). It sacrifices the large field of view of the Fizeau combiner. In return, spectral resolution is obtained with a diffraction grating rather than an array of energy-resolving detectors. The SFR design works in principle and has been implemented with MIRC at CHARA for a small number of apertures. Here, we show the number of optical surfaces can be reduced and the concept scales gracefully to the large number of apertures needed for Stellar Imager. We also describe a potential application of this spatial frequency remapping to improved imaging with filled aperture systems. For filled-aperture imaging, the SFR becomes the core of an improved aperture masking system. To date, aperture-masking has produced the best images with ground-based telescopes but at the expense of low sensitivity due to short exposures and discarding most of the light collected by the telescope. This design eliminates the light-loss problem previously claimed to be inherent in all aperture-masking designs. We also argue that at least in principle, the short-integration time limit can also be overcome. With these improvements, it becomes an ideal camera for TPF-C; since it can form speckle-free images in the presence of wavefront errors, it should significantly relax the stability requirements of the current designs.

Mozurkewich, D.↗
DOE OSTI2019

Initial assessment of multilayer silicon detectors for hard X-ray imaging

Silicon detectors with lower material budget, ultrafast readout and radiation hardness are under developments. These unique features make pixelized silicon sensors a good option for hard X-ray imaging. To verify the performance of spatial resolution and energy sensitivity of silicon sensors to hard X-rays, a two layer setup of Pixelink PL-D725MU sensors has been tested at the Argonne National Laboratory Advanced Photon Source (APS) ID-10 sector with 29.2 keV high photon flux (4.5 x 10(8) to 4.5 x 10(10) photons per second) X-rays. Better than 3 mu m spatial resolution and clear energy characterization have been achieved by both layers. Commercial CMOS sensors with superior spatial resolution could be used for phase contrast imaging in current synchrotrons. These studies pave the path for future multilayer ultrafast silicon sensor development with ns to sub-ns readout speeds in hard X-ray imaging at synchrotrons and XFEL beamlines.

Hard X-ray imaging↗
DOE OSTI2017

Nanoscale imaging of alteration layers of corroded international simple glass particles using ToF-SIMS

Glass particles with dimensions typically ranging from tens to hundreds of microns are often used in glass corrosion research in order to accelerate testing. Two-dimensional and three-dimensional nanoscale imaging techniques are badly needed to characterize the alteration layers at the surfaces of these corroded glass particles. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) can provide a lateral resolution as low as ~100 nm, and, compared to other imaging techniques, is sensitive to elements lighter than carbon. In this work, we used ToF-SIMS to characterize the alteration layers of corroded international simple glass (ISG) particles. At most particle surfaces, inhomogeneous or no alteration layers were observed, indicating that the thickness of the alterations layers may be too thin to be observable by ToF-SIMS imaging. Relatively thick (e.g., 1-10 microns) alteration layers were inhomogeneously distributed at a small portion of surfaces. More interestingly, some large-size (tens of microns) glass particles were fully altered. Above observations suggest that weak attachment and the defects on ISG particle surfaces play an important role in ISG glass corrosion.

alteration layer↗
DOE OSTI2016

Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera’s capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantify lattice deformation and fracture; diffraction peak broadening is largely caused by fracture-induced strain inhomogeneity. Finally, our results demonstrate the potential of such multiscale measurements for revealing and understanding high strain-rate phenomena at dynamic extremes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

A new streaked soft x-ray imager for the National Ignition Facility

Here, a new streaked soft x-ray imager has been designed for use on high energy-density (HED) physics experiments at the National Ignition Facility based at the Lawrence Livermore National Laboratory. This streaked imager uses a slit aperture, single shallow angle reflection from a nickel mirror, and soft x-ray filtering to, when coupled to one of the NIF’s x-ray streak cameras, record a 4× magnification, one-dimensional image of an x-ray source with a spatial resolution of less than 90 μm. The energy band pass produced depends upon the filter material used; for the first qualification shots, vanadium and silver-on-titanium filters were used to gate on photon energy ranges of approximately 300–510 eV and 200–400 eV, respectively. A two-channel version of the snout is available for x-ray sources up to 1 mm and a single-channel is available for larger sources up to 3 mm. Both the one and two-channel variants have been qualified on quartz wire and HED physics target shots.

42 ENGINEERING↗
DOE OSTI2015

Diffraction imaging for in situ characterization of double-crystal X-ray monochromators

Imaging of the Bragg-reflected X-ray beam is proposed and validated as an in situ method for characterization of the performance of double-crystal monochromators under the heat load of intense synchrotron radiation. A sequence of images is collected at different angular positions on the reflectivity curve of the second crystal and analyzed. The method provides rapid evaluation of the wavefront of the exit beam, which relates to local misorientation of the crystal planes along the beam footprint on the thermally distorted first crystal. The measured misorientation can be directly compared with the results of finite element analysis. The imaging method offers an additional insight into the local intrinsic crystal quality over the footprint of the incident X-ray beam.

cryogenic cooling↗
DOE OSTI2014

Intensity inhomogeneity correction for magnetic resonance imaging of human brain at 7T

Purpose: To evaluate the performance and efficacy for intensity inhomogeneity correction of various sequences of the human brain in 7T MRI using the extended version of the unified segmentation algorithm. Materials: Ten healthy volunteers were scanned with four different sequences (2D spin echo [SE], 3D fast SE, 2D fast spoiled gradient echo, and 3D time-of-flight) by using a 7T MRI system. Intensity inhomogeneity correction was performed using the “New Segment” module in SPM8 with four different values (120, 90, 60, and 30 mm) of full width at half maximum (FWHM) in Gaussian smoothness. The uniformity in signals in the entire white matter was evaluated using the coefficient of variation (CV); mean signal intensities between the subcortical and deep white matter were compared, and contrast between subcortical white matter and gray matter was measured. The length of the lenticulostriate (LSA) was measured on maximum intensity projection (MIP) images in the original and corrected images. Results: In all sequences, the CV decreased as the FWHM value decreased. The differences of mean signal intensities between subcortical and deep white matter also decreased with smaller FWHM values. The contrast between white and gray matter was maintained at all FWHM values. LSA length was significantly greater in corrected MIP than in the original MIP images. Conclusions: Intensity inhomogeneity in 7T MRI can be successfully corrected using SPM8 for various scan sequences.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Field of view extension and truncation correction for MR-based human attenuation correction in simultaneous MR/PET imaging

Purpose: In quantitative PET imaging, it is critical to accurately measure and compensate for the attenuation of the photons absorbed in the tissue. While in PET/CT the linear attenuation coefficients can be easily determined from a low-dose CT-based transmission scan, in whole-body MR/PET the computation of the linear attenuation coefficients is based on the MR data. However, a constraint of the MR-based attenuation correction (AC) is the MR-inherent field-of-view (FoV) limitation due to static magnetic field (B{sub 0}) inhomogeneities and gradient nonlinearities. Therefore, the MR-based human AC map may be truncated or geometrically distorted toward the edges of the FoV and, consequently, the PET reconstruction with MR-based AC may be biased. This is especially of impact laterally where the patient arms rest beside the body and are not fully considered. Methods: A method is proposed to extend the MR FoV by determining an optimal readout gradient field which locally compensates B{sub 0} inhomogeneities and gradient nonlinearities. This technique was used to reduce truncation in AC maps of 12 patients, and the impact on the PET quantification was analyzed and compared to truncated data without applying the FoV extension and additionally to an established approach of PET-based FoV extension. Results: The truncation artifacts in the MR-based AC maps were successfully reduced in all patients, and the mean body volume was thereby increased by 5.4%. In some cases large patient-dependent changes in SUV of up to 30% were observed in individual lesions when compared to the standard truncated attenuation map. Conclusions: The proposed technique successfully extends the MR FoV in MR-based attenuation correction and shows an improvement of PET quantification in whole-body MR/PET hybrid imaging. In comparison to the PET-based completion of the truncated body contour, the proposed method is also applicable to specialized PET tracers with little uptake in the arms and might reduce the computation time by obviating the need for iterative calculations of the PET emission data beyond those required for reconstructing images.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

SU-E-J-38: Improved DRR Image Quality Using Polyetheretherketone (PEEK) Fiducial in Image Guided Radiotherapy (IGRT)

Purpose Fiducial-based imaging is often used in IGRT. Traditional gold fiducial marker often has substantial reconstruction artifacts. These artifacts Result in poor image quality of DRR for online kV-to-DRR matching. This study evaluated the image quality of PEEK in DRR in static and moving phantom. Methods CT scan of the Gold and PEEK fiducial (both 1×3 mm) was acquired in a 22 cm cylindrical phantom filled with water. Image artifacts was evaluated with maximum CT value deviated from water due to artifacts; volume of artifacts in 10×10 cm in the center slice; maximum length of streak artifacts from the fiducial. DRR resolution were measured using FWHM and FWTM. 4DCT of PEEK fiducial was acquired with the phantom moving sinusoidally in superior-inferior direction. Motion artifacts were assessed for various 4D phase angles. Results The maximum CT value deviation was −174 for Gold and −24 for PEEK. The volume of artifacts in a 10x10 cm 3 mm slice was 0.369 for Gold and 0.074 cm3 for PEEK. The maximum length of streak artifact was 80mm for Gold and 7 mm for PEEK. PEEK in DRR, FWHM was close to actual (1.0 mm for Gold and 1.1 mm for PEEK). FWTM was 1.8 mm for Gold and 1.3 mm for PEEK in DRR. Barrel motion artifact of PEEK fiducial was noticeable for free-breathing scan. The apparent PEEK length due to residual motion was in close agreement with the calculated length (13 mm for 30–70 phase, 10 mm in 40–60 phase). Conclusion Streak artifacts on planning CT associated with use of gold fiducial can be significantly reduced by PEEK fiducial, while having adequate kV image contrast. DRR image resolution at FWTM was improved from 1.8 mm to 1.3 mm. Because of this improvement, we have been routinely use PEEK for liver IGRT.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Nanoscale imaging of Li and B in nuclear waste glass, a comparison of ToF-SIMS, NanoSIMS, and APT: Nanoscale imaging of Li and B in nuclear waste glass

It has been very difficult to use popular elemental imaging techniques to image Li and B distribution in glass samples with nanoscale resolution. In this study, atom probe tomography (APT), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and nanoscale secondary ion mass spectrometry (NanoSIMS) were used to image the distribution of Li and B in two representative glass samples. APT can provide three-dimensional Li and B imaging with very high spatial resolution (≤ 2 nm). In addition, absolute quantification of Li and B is possible, though room remains to improve accuracy. However, the major drawbacks of APT include limited field of view (normally ≤ 100 × 100 × 500 nm 3 ) and poor sample compatibility. As a comparison, ToF-SIMS and NanoSIMS are sample-friendly with flexible field of view (up to 500 × 500 μm 2 and image stitching is feasible); however, lateral resolution is limited to only about 100 nm. Therefore, SIMS and APT can be regarded as complementary techniques for nanoscale imaging Li and B in glass and other novel materials.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Hybrid Ultrasonic TOFD Imaging of Weld Flaws Using Wavelet Transforms and Image Registration

Ultrasonic time of flight diffraction (TOFD) is an effective weld crack inspection technique. Due to the intensity of diffraction wave is rather weak compared with the lateral wave and the bottom echo wave, thus the signal-to-ratio (SNR) of TOFD image is low. A new dichotomous method is comprised of two steps that contains wavelet shrinkage and image registration is proposed in this paper to reduce the noise and improve the resolution of TOFD images as well. In order to evaluate the reliability of our proposed method in this paper, we have established the experiment system, and sampled a number of TOFD data with random distribution of noise characteristics. We adopted one-dimension wavelet transform and two-dimension wavelet transform in the very beginning of the first step of the proposed algorithm respectively. The SNR of the result obtained in this step is improved significantly compared with the classic algorithms. Next, the image registration is applied. After the registered images have been added to form a new one, then it comes to the final result that shows not only the SNR but also the definition of the image is enhanced effectively.

42 ENGINEERING↗
DOE OSTI2017

Quantifying the heterogeneity of shale through statistical combination of imaging across scales

Shale is a highly heterogeneous material across multiple scales. A typical shale consists of nanometer-scale pores and minerals mixed with macro-scale fractures and particles of varying size. High-resolution imaging is crucial for characterizing the composition and microstructure of this rock. Yet, it is generally not feasible to image a large sample of shale at a high resolution over a large field of view (FOV), thus limiting a full characterization of the microstructure of this material. We present a stochastic framework based on multiple-point statistics that uses high-resolution training images to enhance low-resolution images obtained over a large FOV. Here, we demonstrate the approach using X-ray micro-tomography images of organic-rich Woodford shale obtained at two different resolutions and FOV. Results show that the proposed technique can generate realistic high-resolution images of the microstructure of shale over a large FOV.

58 GEOSCIENCES↗
DOE OSTI2017

Five Micron High Resolution MALDI Mass Spectrometry Imaging with Simple, Interchangeable, Multi-Resolution Optical System

High-spatial resolution mass spectrometry imaging (MSI) is crucial for the mapping of chemical distributions at the cellular and subcellular level. In this work, we improved our previous laser optical system for matrix-assisted laser desorption ionization (MALDI)-MSI, from ~9 μm practical laser spot size to a practical laser spot size of ~4 μm, thereby allowing for 5 μm resolution imaging without oversampling. This is accomplished through a combination of spatial filtering, beam expansion, and reduction of the final focal length. Most importantly, the new laser optics system allows for simple modification of the spot size solely through the interchanging of the beam expander component. Using 10×, 5×, and no beam expander, we could routinely change between ~4, ~7, and ~45 μm laser spot size, in less than 5 min. We applied this multi-resolution MALDI-MSI system to a single maize root tissue section with three different spatial resolutions of 5, 10, and 50 μm and compared the differences in imaging quality and signal sensitivity. We also demonstrated the difference in depth of focus between the optical systems with 10× and 5× beam expanders. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

MR Imaging of Chondrogenic Tumors: Update on Select Imaging Challenges

Purpose of Review: This review article discusses the updated World Health Classification of chondrogenic skeletal tumors and the role of conventional and advanced magnetic resonance (MR) imaging in the evaluation of chondrogenic skeletal lesions with emphasis on select diagnostic dilemmas. Recent Findings: The majority of benign chondrogenic skeletal lesions have typical radiographic and MR features. Conventional MR imaging sequences can be helpful in the distinction of tumor-like lesions from chondrogenic tumors, and the evaluation of anatomic extent, particularly with regard to the detection of soft tissue masses associated with a chondrosarcoma (CS). Benign, atypical, and malignant chondrogenic lesions can have overlapping features on diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping although dynamic contrast-enhanced (DCE) sequences can be helpful in the characterization of chondrogenic tumors as benign or malignant. Patients with multiple chondrogenic tumor conditions or syndromes are predisposed to developing CS and extra-skeletal malignancies, and as such, a small subset may benefit from imaging surveillance. Summary: The majority of chondrogenic skeletal lesions can be characterized confidently on imaging. In the small subset of intermediate and malignant chondrogenic lesions with overlapping imaging and pathological features, a multidisciplinary approach should be used.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Retrieving images from tarnished daguerreotypes using X-ray fluorescence imaging with an X-ray micro beam with tunable energy

We report recent observations using a synchrotron X-ray micro-beam to retrieve images from tarnished 19th century daguerreotypes. We confirm that high quality image can always be retrieved from tarnished plates using Hg L α XRF as long as the bulk of the image particles and their distribution remains intact. We also report results from using tunable tender X-rays (2 - 7 keV) to conduct imaging in high vacuum at energy above the Ag L-edge and the Hg M-edge, extracting images using Ag L α and Hg M α , respectively among others (e.g., S to track corrosion). Images obtained with the surface sensitive total electron yield (TEY) and the bulk sensitive fluorescence yield (FLY) as well as corresponding micro-XANES are reported. Flux tolerance to high intensity X-beam is also explored. These results and their implications for cultural heritage research are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A single-pixel X-ray imager concept and its application to secure radiographic inspections

Imaging technology is generally considered too invasive for arms control inspections due to the concern that it cannot properly secure sensitive features of the inspected item. However, this same sensitive information, which could include direct information on the form and function of the items under inspection, could be used for robust arms control inspections. The single-pixel X-ray imager (SPXI) is introduced as a method to make such inspections, capturing the salient spatial information of an object in a secure manner while never forming an actual image. The method is built on the theory of compressive sensing and the single pixel optical camera. The performance of the system is quantified here using simulated inspections of simple objects. Measures of the robustness and security of the method are introduced and used to determine how such an inspection would be made which can maintain high robustness and security. In particular, it is found that an inspection with low noise (<1%) and high undersampling (>256×) exhibits high robustness and security.

Arms Control↗