Fred Duewer

X-ray computed tomography in Zernike phase contrast mode at 8 keV with 50-nm resolution using Cu rotating anode X-ray source

High-resolution X-ray computed tomography (XCT) enables nondestructive 3D imaging of complex structures, regardless of their state of crystallinity. This work describes a sub-50 nm resolution XCT system operating at 8 keV in absorption and Zernike phase contrast modes based on a commercially available Cu rotating anode laboratory X-ray source. The system utilizes a high efficiency reflective capillary condenser lens and high-resolution Fresnel zone plates with an outermost zone width of 35 nm and 700 nm structure height resulting in a spatial resolution better than 50 nm currently. Imaging a fragment of the solid oxide fuel cells (SOFC) with 50 nm resolution is presented as an application example of the XCT technique in materials science and nanotechnology.

Ellipsoidal and parabolic glass capillaries as condensers for x-ray microscopes

Single-bounce ellipsoidal and paraboloidal glass capillary focusing optics have been fabricated for use as condenser lenses for both synchrotron and tabletop x-ray microscopes in the x-ray energy range of 2.5-18 keV. The condenser numerical apertures (NAs) of these devices are designed to match the NA of x-ray zone plate objectives, which gives them a great advantage over zone plate condensers in laboratory microscopes. The fabricated condensers have slope errors as low as 20 murad rms. These capillaries provide a uniform hollow-cone illumination with almost full focusing efficiency, which is much higher than what is available with zone plate condensers. Sub-50 nm resolution at 8 keV x-ray energy was achieved by utilizing this high-efficiency condenser in a laboratory microscope based on a rotating anode generator.

High-resolution x-ray tomography using laboratory sources

X-ray computed tomography (XCT) is a powerful nondestructive 3D imaging technique, which enables the visualization of the three dimensional structure of complex, optically opaque samples. High resolution XCT using Fresnel zone plate lenses has been confined in the past to synchrotron radiation centers due to the need for a bright and intense source of x-rays. This confinement severely limits the availability and accessibility of x-ray microscopes and the wide proliferation of this methodology. We are describing a sub-50nm resolution XCT system operating at 8 keV in absorption and Zernike phase contrast mode based on a commercially available laboratory x-ray source. The system utilizes high-efficiency Fresnel zone plates with an outermost zone width of 35 nm and 700 nm structure height resulting in a current spatial resolution better than 50 nm. In addition to the technical description of the system and specifications, we present application examples in the semiconductor field.

A calibration approach for single-energy x-ray absorptiometry method to provide absolute breast tissue composition accuracy for the long term

We report on development of a new calibration approach for the Single-Energy X-ray Absorptiometry method (SXA) to provide absolute breast tissue composition accuracy in clinical conditions for the long term and realize cross-calibration between machines, sites and manufacturers. The proposed method takes into account both geometric and image related factors that impact the calibration of grayscale image into absolute tissue composition. A specially designed phantom (GEN III) is imaged in place of the breast and analyzed as if it were a breast. An automatic algorithm was developed to extract all necessary parameters for recalibration. Subsequently, the thickness correction factors and recalibration procedures were applied during calculations of density. A breakpoint stepwise approach was used to correct the thickness variations. It provides the thickness measurement variations over time with a typical standard deviation of 0.2-0.3 mm. After recalibration, the recalculated %FGV of the GEN III region of interests are consistent over time, with a typical standard deviation around 1%.

Absolute efficiency measurement of high-performance zone plates

An absolute efficiency measurement technique for Fresnel zone plates using an electron impact micro-focus laboratory X-ray source (Lα line of Tungsten at 8.4 KeV) is demonstrated. A quasi-monochromatic x-ray image of a zone plate was obtained employing a pair of copper and cobalt filters. Applying this method to zone plates optimizes the zone plate fabrication process and provides the ability to explore zone geometry to achieve the best possible efficiency. Several zone plate parameters were tested with first order efficiency measuring from 1% to 29%.

Dark field image of full-field transmission hard X-ray microscope in 8-11 keV

We have demonstrated dark-field imaging using a full-field hard x-ray microscope by using a custom capillary-based condenser. The condenser provides illumination with a numeric aperture about 3-mrad with high efficiency. This high illumination angle allows full-resolution imaging using a 50 nm hard x-ray zone plate. The zeroth order beam from the condenser is well out of the zoneplate range - which allows a high signal-to-noise ratio in the image plane. Small particles with high scattering power, such as colloidal gold markers used in biology are well-suited for dark-field imaging. Combining with high brightness source from NSRRC BL01B, the dark field image can be acquired within several minutes with high contrast ratio. In this paper, the dark field image of IC and the zoneplate defect will be demonstrated and studied in different energy under dark field mode.

Compositional Three-Component Breast Imaging of Fibroadenoma and Invasive Cancer Lesions: Pilot Study

Purpose: To investigate the lesion discrimination ability of compositional 3-component breast imaging technique (3CB) of patients with suspicious breast lesions (BIRADS 4 or greater).

Roles of biologic breast tissue composition and quantitative image analysis of mammographic images in breast tumor characterization

Purpose. Investigate whether knowledge of the biologic image composition of mammographic lesions provides imagebased biomarkers above and beyond those obtainable from quantitative image analysis (QIA) of X-ray mammography. Methods. The dataset consisted of 45 in vivo breast lesions imaged with the novel 3-component breast (3CB) imaging technique based on dual-energy mammography (15 malignant, 30 benign diagnoses). The 3CB composition measures of water, lipid, and protein thicknesses were assessed and mathematical descriptors, ‘3CB features’, were obtained for the lesions and their periphery. The raw low-energy mammographic images were analyzed with an established in-house QIA method obtaining ‘QIA features’ describing morphology and texture. We investigated the correlation within the ‘3CB features’, within the ‘QIA features’, and between the two. In addition, the merit of individual features in the distinction between malignant and benign lesions was assessed. Results. Whereas many descriptors within the ‘3CB features’ and ‘QIA features’ were, often by design, highly correlated, correlation between descriptors of the two feature groups was much weaker (maximum absolute correlation coefficient 0.58, p<0.001) indicating that 3CB and QIA-based biomarkers provided potentially complementary information. Single descriptors from 3CB and QIA appeared equally well-suited for the distinction between malignant and benign lesions, with maximum area under the ROC curve 0.71 for a protein feature (3CB) and 0.71 for a texture feature (QIA). Conclusions. In this pilot study analyzing the new 3CB imaging modality, knowledge of breast tissue composition appeared additive in combination with existing mammographic QIA methods for the distinction between benign and malignant lesions.

Improvements and performance of diagnostic compositional imaging using a novel dual-energy x-ray technique

Determine whether or not improvements to the calibration procedure for a novel dual-energy x-ray mammography technique improve the uniformity, accuracy, and/or reproducibility of the measured breast composition. The long-term goal of this project is to develop a technique that will improve the specificity of mammography diagnosis. Energy dependent corrections for light-field, dark-field, and Heel effect were made for each measurement. A total of 20 women who were scheduled for additional imaging prior to biopsy underwent an additional dual-energy/low dose full-field digital mammography scan as part of a pilot study investigating the use of breast composition measures in mammography. The estimated water/lipid/protein content of suspicious lesions were measured. The modified x-ray calibration procedure resulted in over a 3-fold improvement in the uniformity of a flat-field calibration phantom with known breast density. Some preliminary results from women are available and show that different types of breast lesions have different compositions.