Combined X-ray diffraction and absorption tomography using a conical shell beam.

We combine diffraction and absorption tomography by raster scanning samples through a hollow cone of pseudo monochromatic X-rays with a mean energy of 58.4 keV. A single image intensifier takes 90x90 (x,y) snapshots during the scan. We demonstrate a proof-of-principle of our technique using a heterogeneous three-dimensional (x,y,z) phantom (90x90x170 mm3) comprised of different material phases, i.e., copper and sodium chlorate. Each snapshot enables the simultaneous measurement of absorption contrast and diffracted flux. The axial resolution was ~1 mm along the (x,y) orthogonal scan directions and ~7 mm along the z-axis. The tomosynthesis of diffracted flux measurements enable the calculation of d-spacing values with ~0.1 Å full width at half maximum (FWHM) at ~2 Å. Thus the identified materials may be color-coded in the absorption optical sections. Characterization of specific material phases is of particular interest in security screening for the identification of narcotics and a wide range of homemade explosives concealed within complex "everyday objects." Other potential application areas include process control and biological imaging.

Confocal energy-dispersive X-ray diffraction tomography employing a conical shell beam.

We introduce a new high-energy X-ray diffraction tomography technique for volumetric materials characterization. In this method, a conical shell beam is raster scanned through the samples. A central aperture optically couples the diffracted flux from the samples onto a pixelated energy-resolving detector. Snapshot measurements taken during the scan enable the construction of depth-resolved dark-field section images. The calculation of d-spacing values enables the mapping of material phase in a volumetric image. We demonstrate our technique using five ~15 mm thick, axially separated samples placed within a polymer tray of the type used routinely in airport security stations. Our method has broad analytical utility due to scalability in both scan size and X-ray energy. Additional application areas include medical diagnostics, materials science, and process control.

Depth resolved snapshot energy-dispersive X-ray diffraction using a conical shell beam.

We demonstrate a novel imaging architecture to collect range encoded diffraction patterns from overlapping samples in a single conical shell projection. The patterns were measured in the dark area encompassed by the beam via a centrally positioned aperture optically coupled to a pixelated energy-resolving detector. We show that a single exposure measurement of 0.3 mAs enables d-spacing values to be calculated. The axial positions of the samples were not required and the resultant measurements were robust in the presence of crystallographic textures. Our results demonstrate rapid volumetric materials characterization and the potential for a direct imaging method, which is of great relevance to applications in medicine, non-destructive testing and security screening.

X-ray absorption tomography employing a conical shell beam.

We demonstrate depth-resolved absorption imaging by scanning an object through a conical shell of X-rays. We measure ring shaped projections and apply tomosynthesis to extract optical sections at different axial focal plane positions. Three-dimensional objects have been imaged to validate our theoretical treatment. The novel principle of our method is scalable with respect to both scan size and X-ray energy. A driver for this work is to complement previously reported methods concerning the measurement of diffracted X-rays for structural analysis. The prospect of employing conical shell beams to combine both absorption and diffraction modalities would provide enhanced analytical utility and has many potential applications in security screening, process control and diagnostic imaging.

Energy-dispersive X-ray diffraction using an annular beam.

We demonstrate material phase identification by measuring polychromatic diffraction spots from samples at least 20 mm in diameter and up to 10 mm thick with an energy resolving point detector. Within our method an annular X-ray beam in the form of a conical shell is incident with its symmetry axis normal to an extended polycrystalline sample. The detector is configured to receive diffracted flux transmitted through the sample and is positioned on the symmetry axis of the annular beam. We present the experiment data from a range of different materials and demonstrate the acquisition of useful data with sub-second collection times of 0.5 s; equating to 0.15 mAs. Our technique should be highly relevant in fields that demand rapid analytical methods such as medicine, security screening and non-destructive testing.

New relationships between breast microcalcifications and cancer.

BACKGROUND: Breast microcalcifications are key diagnostically significant radiological features for localisation of malignancy. This study explores the hypothesis that breast calcification composition is directly related to the local tissue pathological state. METHODS: A total of 236 human breast calcifications from 110 patients were analysed by mid-Fouries transform infrared (FTIR) spectroscopy from three different pathology types (112 invasive carcinoma (IC), 64 in-situ carcinomas and 60 benign). The biochemical composition and the incorporation of carbonate into the hydroxyapatite lattice of the microcalcifications were studied by infrared microspectroscopy. This allowed the spectrally identified composition to be directly correlated with the histopathology grading of the surrounding tissue. RESULTS: The carbonate content of breast microcalcifications was shown to significantly decrease when progressing from benign to malignant disease. In this study, we report significant correlations (P<0.001) between microcalcification chemical composition (carbonate content and protein matrix : mineral ratios) and distinct pathology grades (benign, in-situ carcinoma and ICs). Furthermore, a significant correlation (P<0.001) was observed between carbonate concentrations and carcinoma in-situ sub-grades. Using the two measures of pathology-specific calcification composition (carbonate content and protein matrix : mineral ratios) as the inputs to a two-metric discriminant model sensitivities of 79, 84 and 90% and specificities of 98, 82 and 96% were achieved for benign, ductal carcinoma in situ and invasive malignancies, respectively. CONCLUSIONS: We present the first demonstration of a direct link between the chemical nature of microcalcifications and the grade of the pathological breast disease. This suggests that microcalcifications have a significant association with cancer progression, and could be used for future objective analytical classification of breast pathology. A simple two-metric model has been demonstrated, more complex spectral analysis may yeild greater discrimination performance. Furthermore there appears to be a sequential progression of calcification composition.

Model fitting in two dimensions to small angle diffraction patterns from soft tissue.

In our research programme small angle x-ray scattering (SAXS) is used to provide information on the axial arrangement of collagen molecules as well as data about the state of other components of the extra cellular matrix (ECM) in human tissues. Derivation of parameters to describe and simplify the data is required for much of the SAXS patterns analysis. A method is presented here to achieve function fitting to collagen diffraction peaks along with a representation of the underlying diffuse scatter. A simple model was used which proved reliable in fitting a variety of 2D diffraction patterns. The logarithm of the scatter intensity over the area of the scatter image was taken to reduce the range and improve fitting accuracy. Our model was then used to fit the log data. The model consisted of a radial exponential diffuse scatter component added to a specified number of Gaussian peaks. In 2D the peak model is toroidal, each component being rotated about a common specified centre. Initial search parameters from a 1D averaged sector were supplied to the iterative 2D fitting routine. With the aid of data weighting and basic wavelet filtering, successful and reliable fitting of a specified 2D model to real data is achievable. The process is easily automated. Multiple SAXS patterns can be fitted without operator intervention. As described the model is simple enough to converge rapidly and yet allows image data to be parameterized to a form suitable for extracting the requisite information. The fitting method is flexible enough to be extended to achieve a more comprehensive and complex pattern fitting in two dimensions if this turns out to be necessary. It is our intention to implement orientation distribution functions in the near future by including an angular scaling factor.

Classification of fracture and non-fracture groups by analysis of coherent X-ray scatter.

Osteoporotic fractures present a significant social and economic burden, which is set to rise commensurately with the aging population. Greater understanding of the physicochemical differences between osteoporotic and normal conditions will facilitate the development of diagnostic technologies with increased performance and treatments with increased efficacy. Using coherent X-ray scattering we have evaluated a population of 108 ex vivo human bone samples comprised of non-fracture and fracture groups. Principal component fed linear discriminant analysis was used to develop a classification model to discern each condition resulting in a sensitivity and specificity of 93% and 91%, respectively. Evaluating the coherent X-ray scatter differences from each condition supports the hypothesis that a causal physicochemical change has occurred in the fracture group. This work is a critical step along the path towards developing an in vivo diagnostic tool for fracture risk prediction.

A preliminary study of breast cancer diagnosis using laboratory based small angle x-ray scattering.

Breast tissue collected from tumour samples and normal tissue from bi-lateral mastectomy procedures were examined using small angle x-ray scattering. Previous work has indicated that breast tissue disease diagnosis could be performed using small angle x-ray scattering (SAXS) from a synchrotron radiation source. The technique would be more useful to health services if it could be made to work using a conventional x-ray source. Consistent and reliable differences in x-ray scatter distributions were observed between samples from normal and tumour tissue samples using the laboratory based 'SAXSess' system. Albeit from a small number of samples, a sensitivity of 100% was obtained. This result encourages us to pursue the implementation of SAXS as a laboratory based diagnosis technique.

Determination of depth-dependent diffraction data: a new approach.

A direct method for determining powder diffraction data at specific depths from angle-dependent diffraction data is described. The method is non-destructive and only traditional data collections, where the angle of incidence is varied, are required. These angle-dependent spectra are transformed to give diffraction data arising from different depths, which may then be exploited using any conventional method. This is a novel approach as traditional methods are forced to tolerate the inherent depth averaging of grazing-angle diffraction, or only examine specific structural characteristics. In order to obtain depth-dependent X-ray diffraction data, a Fredholm integral equation of the first kind is solved using regularization techniques. The method has been validated by the generation of pseudo-experimental data having known depth profiles and solving the Fredholm integral equation to recover the solution. The method has also been applied to experimental data from a number of thin film systems.

The micro-architecture of human cancellous bone from fracture neck of femur patients in relation to the structural integrity and fracture toughness of the tissue.

Osteoporosis is clinically assessed from bone mineral density measurements using dual energy X-ray absorption (DXA). However, these measurements do not always provide an accurate fracture prediction, arguably because DXA does not grapple with 'bone quality', which is a combined result of microarchitecture, texture, bone tissue properties, past loading history, material chemistry and bone physiology in reaction to disease. Studies addressing bone quality are comparatively few if one considers the potential importance of this factor. They suffer due to low number of human osteoporotic specimens, use of animal proxies and/or the lack of differentiation between confounding parameters such as gender and state of diseased bone. The present study considers bone samples donated from patients (n = 37) who suffered a femoral neck fracture and in this very well defined cohort we have produced in previous work fracture toughness measurements (FT) which quantify its ability to resist crack growth which reflects directly the structural integrity of the cancellous bone tissue. We investigated correlations between BV/TV and other microarchitectural parameters; we examined effects that may suggest differences in bone remodelling between males and females and compared the relationships with the FT properties. The data crucially has shown that TbTh, TbSp, SMI and TbN may provide a proxy or surrogate for BV/TV. Correlations between FT critical stress intensity values and microarchitecture parameters (BV/TV, BS/TV, TbN, BS/BV and SMI) for osteoporotic cancellous tissue were observed and are for the first time reported in this study. Overall, this study has not only highlighted that the fracture model based upon BMD could potentially be improved with inclusion of other microarchitecture parameters, but has also given us clear clues as to which of them are more influential in this role.

X-ray diffraction from bone employing annular and semi-annular beams.

There is a compelling need for accurate, low cost diagnostics to identify osteo-tissues that are associated with a high risk of fracture within an individual. To satisfy this requirement the quantification of bone characteristics such as 'bone quality' need to exceed that provided currently by densitometry. Bone mineral chemistry and microstructure can be determined from coherent x-ray scatter signatures of bone specimens. Therefore, if these signatures can be measured, in vivo, to an appropriate accuracy it should be possible by extending terms within a fracture risk model to improve fracture risk prediction.In this preliminary study we present an examination of a new x-ray diffraction technique that employs hollow annular and semi-annular beams to measure aspects of 'bone quality'. We present diffractograms obtained with our approach from ex vivo bone specimens at Mo Kα and W Kα energies. Primary data is parameterized to provide estimates of bone characteristics and to indicate the precision with which these can be determined.

Physical maturity and outcome of pregnancy in primiparas younger than 16 years of age.

The association of complications and adverse outcomes of early teenage pregnancy with physical growth maturation of mothers was studied in subjects identified from review of medical records in a Pittsburgh obstetrical hospital from 1970 through 1977. Five groups were used to categorize the subjects: (1) 449 primiparas younger than 16 years of age, (2) 347 primiparas 20 to 24 years of age, pair-matched with subjects in group 1 by race, hospital service status, sex of infant, trimester of first prenatal visit, and year of delivery within 5 years, (3) 139 group 1 mothers at the time of their second delivery, (4) 104 group 1 primiparas whose postmenarcheal age was less than or equal to 2.6 years at delivery, and (5) 108 group 1 primiparas whose postmenarcheal age was greater than or equal to 4.1 years at delivery. Subjects in groups 1 and 2, first and second pregnancies of subjects in group 3, and subjects in groups 4 and 5 were compared for prepregnancy weight and height, weight gain during pregnancy, complications of pregnancy, birth weight and gestational age of infant, and perinatal morbidity and mortality. Although primiparas younger than 16 years of age had not achieved mature height and weight, no relationship between mother's physical growth maturation and adverse pregnancy course or outcome was demonstrated.

Age, sex, and season of onset of juvenile diabetes in different geographic areas.

Age, sex, and estimated time of onset of insulin-dependent diabetes were determined for children in Pittsburgh (N = 673), Gainesville (N = 976), Galveston (n = 741), and Melbourne (N = 851). The US cities had a decrease in new cases during the summer and peak incidence in January through April. In Melbourne, monthly trends were reversed: there were more cases during May through August. In US cities, but not in Melbourne, children less than 6 years old showed a greater variation by season than children 6 years old and older. Observations of the same fall and winter onset (in different calendar months) of insulin-dependent diabetes in Australia and the United States, and exaggeration of seasonal differences in young US children, suggest that onset of insulin-dependent diabetes is associated with seasonally varying viral diseases. Mumps and rubella infections do not seem to be responsible for much of the seasonal variation. Seasonal peaks of mumps and rubella are later than those observed for insulin-dependent diabetes, and immunization with live mumps and rubella viruses has not been associated with changes in incidence of insulin-dependent diabetes. An increase in disease incidence in boys over girls below age 6 years and in girls over boys at ages 6 through 11 years was consistently observed but not explained.

An X-ray diffraction study of the effects of heat treatment on bone mineral microstructure.

A series of human cortical bone specimens has been heated to temperatures up to 1200 degrees C and the mineral content examined in detail by X-ray diffraction. Line profile analysis of the diffraction data has been undertaken to characterise the microstructural (crystallite size and microstrain) features of the mineral at each temperature. Individual profile fitting of several maxima from each diffractogram has also provided precise lattice parameters of the apatite at each temperature. The apatite did not show any significant decomposition over the temperature range although CaO was increasingly formed at temperatures above 600 degrees C. Both finite crystallite size and microstrain contributed significantly to the diffraction peak broadening below 600 degrees C. When heated to > 800 degrees C, the small, rod-like mineral crystallites changed from a highly anisotropically strained state to one with significantly larger equidimensional crystals possessing little microstrain. The findings are discussed in the context of graft bone substitutes and surgical heating of bone.

Variation in repeat rates between 18 radiology departments.

A comprehensive analysis of repeat rates has been obtained from an observational study of radiological practice in diagnostic X-ray departments throughout Wales. Interdepartmental and intradepartmental repeat rates are investigated for chest, abdomen, pelvis, sinus, lumbar spine, cervical spine and intravenous pyelographic examinations. The confounding effects upon observed repeat rates of trainee practitioners and automatic exposure control devices are also considered. The overall proportions of total film cost and patient exposure attributable to repeat radiographs are estimated to be 10% and 14% respectively.

X-ray refraction effects: application to the imaging of biological tissues.

The purpose of this study was to explore the potential of refraction contrast X-ray imaging of biological tissues. Images of dissected mouse lungs, heart, liver and legs were produced using the medical beamline at the Elettra Synchrotron at Trieste, Italy. The technique used was diffraction enhanced imaging. This utilizes a silicon crystal positioned between the tissue sample and the detector to separate refracted X-rays from transmitted and scattered radiation by Bragg diffraction. The contrast in the images produced is related to changes in the X-ray refractive index of the tissues, resulting in remarkable clarity compared with conventional X-ray images based on absorption effects. These changes were greatest at the boundaries between different tissues, giving a marked edge enhancement effect and three-dimensional appearance to the images. The technique provides a way of imaging a property of biological tissues not yet exploited, and further studies are planned to identify specific applications in medical imaging.

Acute rheumatic fever and rheumatic heart disease on the Navajo reservation, 1962-77.

The occurrence of acute rheumatic fever (ARF) and rheumatic heart disease (RHD) among Navajos was ascertained for the period from 1962 through 1977 by means of hospital discharge diagnoses and patients' charts. The annualized attack rate for ARF was 12.4 per 100,000 population, with no clear evidence of an overall secular trend. The proportion of recurrences (19.6 percent) and clinical features were similar to those reported elsewhere, but no seasonal variation in attack rates was noted. Between 1962-71 and 1972-77, the age of RHD patients increased, suggesting few newly diagnosed cases and the aging of known patients. A streptococcal disease control program was instituted in many Navajo elementary schools before 1975. In the program, throat cultures were performed routinely for some asymptomatic children and for all symptomatic children. During the subsequent 3 years, ARF rates declined from 13.5 to 8.2 per 100,000 in areas covered by the program, while in the noncovered areas the rates showed little change-9.5 to 10.1 per 100,000.

Bacterial meningitis in Navojo Indians.

An analysis of 219 confirmed cases of bacterial meningitis among Navajo Indians during a 5-year period, July 1, 1968, through June 30, 1973, revealed that 56 percent were caused by Haemophilus influenzae, 26 percent by Neisseria meningitidis, 6 percent by Mycobacterium tuberculosis, and 6 percent by other organisms. The annual incidence of H. influenzae meningitis (17.7 per 100,000 persons) and that of pneumococcal meningitis (8.0 per 100,000) were much higher than the rates for these diseases reported from other population groups. The annual incidence of meningococcal meningitis (2.0 per 100,000) was similar to that found elsewhere. There was an ususual concentration of cases during the first year of life; 78 percent of H. influenzae, 64 percent of pneumococcal, and 50 percent of meningococcal meningitis occurred during this time. However, bacterial meningitis during the first month of life was not frequent (0.29 per 1,000 live births). Case fatality rates were similar to those reported for other population groups.

Effect of foot balance on the intra-articular pressure in the distal interphalangeal joint in vitro.

REASONS FOR PERFORMING STUDY: Increased joint pressure has been implicated in the progression of osteoarthritis. HYPOTHESIS: That intra-articular pressure in the distal interphalangeal joint (DIP) is significantly higher in legs loaded with heel up (HU), low heel (TU), lateral side up (LU) and medial side up (MU) imbalance compared to the balanced position. METHODS: Twelve elbow down limbs were compressed in a hydraulic loading jig and DIP pressure measured. RESULTS: Elevating the heels by 5 degrees significantly increased DIP pressure. After 5 ml of contrast was injected into the joint, heel elevation caused a greater increase in DIP pressure and heel lowering decreased DIP pressure. Silicone rubber castings were taken of 20 DIP whilst under load. The articular contact area was localised on the dorsal aspect in the HU position, palmar aspect in the TU position and towards the elevated side with lateromedial imbalance. CONCLUSIONS: Altered foot orientation, which could result from trimming and shoeing, therefore influences intra-articular pressure in the DIP and the articular contact area. POTENTIAL CLINICAL RELEVANCE: The results support the view that a balanced foot is the ideal and that the elevated heels may be detrimental to long term viability of the DIP joint.