In clinically established-absorption-based-biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray ...contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.
The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small‐ and ...wide‐angle X‐ray scattering with full‐field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research.
ForMAX is a new beamline at the MAX IV Laboratory, providing multiscale and multimodal structural characterization by combining small‐ and wide‐angle X‐ray scattering with full‐field tomographic imaging.
Summary
The study investigates an association between phalangeal bone mineral density (BMD) and self-reported passive smoking using data on 15,038 persons (aged 18–95 years), who underwent a BMD scan ...in the Danish KRAM study. BMD was significantly lower in persons exposed to long-term passive smoking in their home during adulthood.
Introduction
Smoking is associated with decreased bone mineral density (BMD) and increased risk of osteoporotic fractures. This study aimed to investigate a possible association between BMD at the phalangeal bones and self-reported passive smoking.
Methods
The study included a cohort of 15,544 men and women aged 18–95 years, who underwent a BMD scan in the Danish KRAM study. BMD scans of the middle phalanges of the second, third and fourth digits of the non-dominant hand were performed with a compact radiographic absorptiometry system (Alara MetriScan®). Also, height, weight and body fat percentage were measured and 96.7% (
n
= 15,038) of the participants answered a self-reported questionnaire with information on passive smoking, other lifestyle factors, education, etc. The association between passive smoking and BMD was examined using multiple linear regression analysis.
Results
A total of 39.1% (
n
= 5,829) of the participants had been exposed to passive smoking in adulthood at home. BMD was significantly lower in subjects exposed to passive smoking, 0.343 vs. 0.331 g/cm
2
;
p
< 0.01 (unadjusted) and 0.339 vs. 0.337 g/cm
2
;
p
< 0.05 (adjusted for age, gender, height and weight, and smoking). Multiple linear regression analysis showed that exposure to passive smoking for more than 20 years in adulthood at home was significantly related to BMD when adjusted for potential confounders (men,
β
= −4.4 × 10
−3
;
r
= −0.05;
p
< 0.01 and women,
β
= −2.3 × 10
−3
;
r
= −0.03;
p
< 0.05). This relationship was also seen in the group of never smokers (
β
= −3.3 × 10
−3
;
r
= −0.03;
p
= 0.01).
Conclusion
Our study supports a potential negative effect of long-term passive smoking in adulthood at home on phalangeal BMD.
X-ray dark-field imaging modeling Cong, W; Pfeiffer, F; Bech, M ...
Journal of the Optical Society of America. A, Optics, image science, and vision,
06/2012, Letnik:
29, Številka:
6
Journal Article
Recenzirano
Dark-field images are formed from x-ray small-angle scattering signals. The small-angle scattering signals are particularly sensitive to structural variation and density fluctuation on a length scale ...of several tens to hundreds of nanometers, offering a unique contrast mechanism to reveal subtle structural features of an object. In this study, based on the principle of energy conservation, we develop a physical model to describe the relationship between x-ray small-angle scattering coefficients of an object and dark-field intensity images. This model can be used to reconstruct volumetric x-ray small-angle scattering images of an object using classical tomographic algorithms. We also establish a relationship between the small-angle scattering intensity and the visibility function measured with x-ray grating imaging. The numerical simulations and phantom experiments have demonstrated the accuracy and practicability of the proposed model.
We report how the three-dimensional structure of subcutaneous injections of soluble insulin can be visualized by x-ray computed tomography using an iodine based contrast agent. The injections ...investigated are performed ex vivo in porcine adipose tissue. Full tomography scans carried out at a laboratory x-ray source with a total acquisition time of about 1 min yield CT-images with an effective pixel size of 109 × 109 μm². The depots are segmented using a modified Chan-Vese algorithm and we are able to observe differences in the shape of the injection depot and the position of the depot in the skin among equally performed injections. To overcome the beam hardening artefacts, which affect the quantitative prediction of the volume injected, we additionally present results concerning the visualization of two injections using synchrotron radiation. The spatial concentration distribution of iodine is calculated to show the dilution of the insulin drug inside the depot. Characterisation of the shape of the depot and the spatial concentration profile of the injected fluid is important knowledge when improving the clinical formulation of an insulin drug, the performance of injection devices and when predicting the effect of the drug through biomedical simulations.
A novel method for accurate calculation of power spectra of the pulsewidth modulation (PWM) voltage-source inverter with randomized switching frequency is presented. The case of a limited pool of ...switching frequencies, convenient and adequate for technical purposes, is considered, and a mathematical background for this type of random PWM (RPWM) is provided. It is shown that the limited-pool RPWM gives rise to not only a continuous spectrum, but, also, under certain circumstances, pure power spectral components (harmonics), typical for the deterministic PWM. Criteria for the existence of harmonics are given, and formulae for both the power and the power spectral density are derived and verified experimentally.
This paper proposes a new family of random modulation techniques for three-phase power converters which operate with a fixed switching frequency. The techniques are based on adjusting the duration of ...the zero-vectors or adjusting the three pulse positions in a switching period. Three methods are selected for experimental tests because they preserve the fixed switching frequency known from standard PWM techniques. The new methods are also compared with random switching frequency modulation and with fixed switching frequency modulation. Voltage, current and acoustic noise spectra are used for comparison and it is concluded that two of the techniques are especially useful at lower fundamental frequencies. The techniques can substitute classic random modulation techniques with variable switching frequency in some applications.
In this work we demonstrate the feasibility of applying small-angle X-ray scattering computed tomography (SAXS-CT) for non-invasive molecular imaging of myelin sheaths in a rat brain. Our results ...show that the approach yields information on several quantities, including the relative myelin concentration, its periodicity, the total thickness of the myelin sheaths, and the relative concentration of cytoskeletal neurofilaments. For example the periodicity of the myelin sheaths varied in the range from 17.0 to 18.2nm around an average of 17.6 (±0.3)nm. We believe that imaging, i.e., spatially resolved measuring these quantities could provide general means for understanding the relation to a number of neurodegenerative diseases.
► Demonstration of small-angle X-ray scattering computed tomography (SAXS-CT). ► SAXS-CT is demonstrated for non-invasive molecular imaging of myelin sheaths. ► Variations in myelin sheath concentration, periodicity and thickness are mapped. ► SAXS-CT provides a new tool for understanding a number of neurodegenerative diseases.
Scanned-energy mode photoelectron diffraction (PhD) and ab initio density functional theory calculations have been employed to investigate the adsorption geometry of benzoate (C6H5COO−) on ...rutile-TiO2(110)(1 × 1). PhD data indicate that the benzoate moiety binds to the surface through both of its oxygen atoms to two adjacent fivefold surface titanium atoms in an essentially upright geometry. Moreover, its phenyl (C6H5−) and carboxylate (−COO−) groups are determined to be coplanar, being aligned along the 001 azimuth. This experimental result is consistent with the benzoate geometry emerging from DFT calculations conducted for laterally rather well-separated adsorbates. At shorter interadsorbate distances, the theoretical modeling predicts a more tilted and twisted adsorption geometry, where the phenyl and carboxylate groups are no longer coplanar; i.e., interadsorbate interactions influence the configuration of adsorbed benzoate.
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