| 1. |
- Andersson, Mariam, et al.
(författare)
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Axon morphology is modulated by the local environment and impacts the noninvasive investigation of its structure-function relationship
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 117:52, s. 33649-33659
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Tidskriftsartikel (refereegranskat)abstract
- Axonal conduction velocity, which ensures efficient function of the brain network, is related to axon diameter. Noninvasive, in vivo axon diameter estimates can be made with diffusion magnetic resonance imaging, but the technique requires three-dimensional (3D) validation. Here, high-resolution, 3D synchrotron X-ray nano-holotomography images of white matter samples from the corpus callosum of a monkey brain reveal that blood vessels, cells, and vacuoles affect axonal diameter and trajectory. Within single axons, we find that the variation in diameter and conduction velocity correlates with the mean diameter, contesting the value of precise diameter determination in larger axons. These complex 3D axon morphologies drive previously reported 2D trends in axon diameter and g-ratio. Furthermore, we find that these morphologies bias the estimates of axon diameter with diffusion magnetic resonance imaging and, ultimately, impact the investigation and formulation of the axon structure-function relationship.
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| 2. |
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| 3. |
- Fu, Jian, et al.
(författare)
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An algebraic iterative reconstruction technique for differential X-ray phase-contrast computed tomography
- 2013
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Ingår i: Zeitschrift für Medizinische Physik. - : Elsevier BV. - 1876-4436 .- 0939-3889. ; 23:3, s. 186-193
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Tidskriftsartikel (refereegranskat)abstract
- Iterative reconstruction has a wide spectrum of proven advantages in the field of conventional X-ray absorption-based computed tomography (CT). In this paper, we report on an algebraic iterative reconstruction technique for grating-based differential phase-contrast CT (DPC-CT). Due to the differential nature of DPC-CT projections, a differential operator and a smoothing operator are added to the iterative reconstruction, compared to the one commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured at a two-grating interferometer setup. Since the algorithm is easy to implement and allows for the extension to various regularization possibilities, we expect a significant impact of the method for improving future medical and industrial DPC-CT applications.
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| 4. |
- Meinel, Felix G., et al.
(författare)
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Diagnosing and Mapping Pulmonary Emphysema on X-Ray Projection Images: Incremental Value of Grating-Based X-Ray Dark-Field Imaging
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To assess whether grating-based X-ray dark-field imaging can increase the sensitivity of X-ray projection images in the diagnosis of pulmonary emphysema and allow for a more accurate assessment of emphysema distribution. Materials and Methods: Lungs from three mice with pulmonary emphysema and three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Median signal intensities of transmission (T), dark-field (V) and a combined parameter (normalized scatter) were compared between emphysema and control group. To determine the diagnostic value of each parameter in differentiating between healthy and emphysematous lung tissue, a receiver-operating-characteristic (ROC) curve analysis was performed both on a per-pixel and a per-individual basis. Parametric maps of emphysema distribution were generated using transmission, dark-field and normalized scatter signal and correlated with histopathology. Results: Transmission values relative to water were higher for emphysematous lungs than for control lungs (1.11 vs. 1.06, p<0.001). There was no difference in median dark-field signal intensities between both groups (0.66 vs. 0.66). Median normalized scatter was significantly lower in the emphysematous lungs compared to controls (4.9 vs. 10.8, p<0.001), and was the best parameter for differentiation of healthy vs. emphysematous lung tissue. In a per-pixel analysis, the area under the ROC curve (AUC) for the normalized scatter value was significantly higher than for transmission (0.86 vs. 0.78, p<0.001) and dark-field value (0.86 vs. 0.52, p<0.001) alone. Normalized scatter showed very high sensitivity for a wide range of specificity values (94% sensitivity at 75% specificity). Using the normalized scatter signal to display the regional distribution of emphysema provides color-coded parametric maps, which show the best correlation with histopathology. Conclusion: In a murine model, the complementary information provided by X-ray transmission and dark-field images adds incremental diagnostic value in detecting pulmonary emphysema and visualizing its regional distribution as compared to conventional X-ray projections.
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| 5. |
- Schleede, Simone, et al.
(författare)
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Emphysema diagnosis using X-ray dark-field imaging at a laser-driven compact synchrotron light source
- 2012
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 109:44, s. 17880-17885
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Tidskriftsartikel (refereegranskat)abstract
- In early stages of various pulmonary diseases, such as emphysema and fibrosis, the change in X-ray attenuation is not detectable with absorption-based radiography. To monitor the morphological changes that the alveoli network undergoes in the progression of these diseases, we propose using the dark-field signal, which is related to small-angle scattering in the sample. Combined with the absorption-based image, the dark-field signal enables better discrimination between healthy and emphysematous lung tissue in a mouse model. All measurements have been performed at 36 keV using a monochromatic laser-driven miniature synchrotron X-ray source (Compact Light Source). In this paper we present grating-based dark-field images of emphysematous vs. healthy lung tissue, where the strong dependence of the dark-field signal on mean alveolar size leads to improved diagnosis of emphysema in lung radiographs.
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| 6. |
- Schleede, Simone, et al.
(författare)
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Multimodal hard X-ray imaging of a mammography phantom at a compact synchrotron light source
- 2012
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 19, s. 525-529
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Tidskriftsartikel (refereegranskat)abstract
- The Compact Light Source is a miniature synchrotron producing X-rays at the interaction point of a counter-propagating laser pulse and electron bunch through the process of inverse Compton scattering. The small transverse size of the luminous region yields a highly coherent beam with an angular divergence of a few milliradians. The intrinsic monochromaticity and coherence of the produced X-rays can be exploited in high-sensitivity differential phase-contrast imaging with a grating-based interferometer. Here, the first multimodal X-ray imaging experiments at the Compact Light Source at a clinically compatible X-ray energy of 21 keV are reported. Dose-compatible measurements of a mammography phantom clearly demonstrate an increase in contrast attainable through differential phase and dark-field imaging over conventional attenuation-based projections.
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| 7. |
- Schwab, Felix, et al.
(författare)
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Comparison of contrast-to-noise ratios of transmission and dark-field signal in grating-based X-ray imaging for healthy murine lung tissue
- 2013
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Ingår i: Zeitschrift für Medizinische Physik. - : Elsevier BV. - 1876-4436 .- 0939-3889. ; 23:3, s. 236-242
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: An experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue. Materials and Methods: Lungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNRDF /CNRT. Results: In all images, there was a trend for contrast-to-noise ratios of dark-field images (CNRDF) to be higher than for transmission images (CNRT) for all ROIs (median 61 vs. 38, p = 0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p = 0.03). Median RCG was >1 for all Rats (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p = 0.03). Conclusion: The contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI.
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| 8. |
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| 9. |
- Bech-Hanssen, Odd, 1956, et al.
(författare)
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A novel echocardiographic right ventricular dysfunction score can identify hemodynamic severity profiles in left ventricular dysfunction
- 2022
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Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Recognition of congestion and hypoperfusion in patients with chronic left ventricular dysfunction (LVD) has therapeutic and prognostic implications. In the present study we hypothesized that a multiparameter echocardiographic grading of right ventricular dysfunction (RVD) can facilitate the characterization of hemodynamic profiles. Methods: Consecutive patients (n = 105, age 53 ± 14years, males 77%, LV ejection fraction 28 ± 11%) referred for heart transplant or heart failure work-up, with catheterization and echocardiography within 48h, were reviewed retrospectively. Three hemodynamic profiles were defined: compensated LVD (cLVD, normal pulmonary capillary wedge pressure (PCWP < 15mmHg) and normal mixed venous saturation (SvO2 ≥ 60%)); decompensated LVD (dLVD, with increased PCWP) and LV failure (LVF, increased PCWP and reduced SvO2). We established a 5-point RVD score including pulmonary hypertension, reduced tricuspid annular plane systolic excursion, RV dilatation, ≥ moderate tricuspid regurgitation and increased right atrial pressure. Results: The RVD score [median (IQR 25%;75%)] showed significant in-between the three groups differences with 1 (0;1), 1 (0.5;2) and 3.0 (2;3.5) in patients with cLVD, dLVD and LVF, respectively. The finding of RVD score ≥ 2 or ≥ 4 increased the likelihood of decompensation or LVF 5.2-fold and 6.7-fold, respectively. On the contrary, RVD score < 1 and < 2 reduced the likelihood 11.1-fold and 25-fold, respectively. The RVD score was more helpful than standard echocardiography regarding identification of hemodynamic profiles. Conclusions: In this proof of concept study an echocardiographic RVD score identified different hemodynamic severity profiles in patients with chronic LVD and reduced ejection fraction. Further studies are needed to validate its general applicability. Graphical abstract: [Figure not available: see fulltext.]
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| 10. |
- Bech-Hanssen, Odd, 1956, et al.
(författare)
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Grading right ventricular dysfunction in left ventricular disease using echocardiography: a proof of concept using a novel multiparameter strategy.
- 2021
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Ingår i: ESC heart failure. - : Wiley. - 2055-5822. ; 8:4, s. 3223-3236
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Tidskriftsartikel (refereegranskat)abstract
- Grading right ventricular dysfunction (RVD) in patients with left ventricular (LV) disease has earned little attention. In the present study, we established an echocardiographic RVD score and investigated how increments of the score correspond to RVD at right heart catheterization.We included 95 patients with LV disease consecutively referred for heart transplant or heart failure work-up with catheterization and echocardiography within 48h. The RVD score (5 points) included well-known characteristics of the development from compensated to decompensated right ventricular (RV) function: pulmonary hypertension, reduced RV strain, RV area dilatation, moderate/severe tricuspid regurgitation, and increased right atrial pressure (RAP) by echocardiography. Comparing three groups with increments of RVD score [1 (mild), 2-3 (moderate), and 4-5 (severe)] showed more advanced RVD with increasing RV end-diastolic pressure (P<0.001) and signs of uncoupling to load (reduced ratio between RV and pulmonary artery elastance, P<0.001) and more spherical RV shape (RV area/length, P<0.001). Receiver operating characteristic curve analysis for detection of severe RV (RAP≥10mmHg) showed for the RVD score an area under the curve of 0.88 compared with 0.69, 0.68, and 0.64 for RV strain, tricuspid annular plane systolic excursion, and fractional area change, respectively. A patient with RVD score≥4 had a 6.7-fold increase in likelihood of severe RVD, and no patient with RVD score≤1 had severe RVD.In this proof of concept study, a novel RVD score outperformed the widely used longitudinal parameters regarding grading of RVD severity, with a potential role for refined diagnosis, follow-up, and prognosis assessment in heart failure patients.
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| 11. |
- Bech, Martin, et al.
(författare)
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Dual-binary phase gratings for x-ray interferometry
- 2022
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510654686
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Konferensbidrag (refereegranskat)abstract
- X-ray phase-contrast imaging by grating interferometry has in the past decades been established both at synchrotron radiation sources and at conventional x-ray tubes. Due to the sensitivity to x-ray phase shifting, contrast in soft tissue has been improved significantly and the possibilities to do virtual histology of tissue biopsies are being pioneered. Constraints in the design of a grating interferometer are dominated by the phase-shifting structures of the gratings. Typically, binary gratings are used, with alternating regions of shift and no shift. However, other structures are also possible, leading to different patterns of intensity modulations. Here we simulate the possibility of using multiple binary structures in the phase grating, to utilize Moiré effects and avoid the use of attenuating grating structures. In particular the parameters for grating-based phase-contrast imaging using a single optical element are discussed, with focus on laboratory-based x-ray imaging using microfocus sources.
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| 12. |
- Bech, Martin, et al.
(författare)
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In-vivo dark-field and phase-contrast x-ray imaging.
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3:Nov 13
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Tidskriftsartikel (refereegranskat)abstract
- Novel radiography approaches based on the wave nature of x-rays when propagating through matter have a great potential for improved future x-ray diagnostics in the clinics. Here, we present a significant milestone in this imaging method: in-vivo multi-contrast x-ray imaging of a mouse using a compact scanner. Of particular interest is the enhanced contrast in regions related to the respiratory system, indicating a possible application in diagnosis of lung diseases (e.g. emphysema).
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| 13. |
- Bech, Morten L, et al.
(författare)
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Mapping change in the overnight money market
- 2015
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 424, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- We use an information-theoretic approach to describe changes in lending relationships between financial institutions around the time of the Lehman Brothers failure. Unlike previous work that conducts maximum likelihood estimation on undirected networks our analysis distinguishes between borrowers and lenders and looks for broader lending relationships (multi-bank lending cycles) that extend beyond the immediate counter-parties. We detect significant changes in lending patterns following implementation of the Interest on Required and Excess Reserves policy by the Federal Reserve in October 2008. Analysis of micro-scale rates of change in the data suggests these changes were triggered by the collapse of Lehman Brothers a few weeks before.
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| 14. |
- Bech, Martin, et al.
(författare)
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Results from the first preclinical CT scanner with grating based phase contrast and a rotating gantry
- 2012
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Ingår i: International Workshop on X-Ray and Neutron Phase Imaging with Gratings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735410725 ; 1466, s. 130-136
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Konferensbidrag (refereegranskat)abstract
- After successful demonstrations of soft-tissue phase-contrast imaging with grating interferometers at synchrotron radiation sources and at laboratory based x-ray tubes, a first preclinical CT scanner with grating based phase contrast imaging modality has been constructed. The rotating gantry is equipped with a three-grating interferometer, a 50 watt tungsten anode source and a Hamamatsu flat panel detector. The total length of the interferometer is 45 cm, and the bed of the scanner is optimized for mice, with a scanning diameter of 35 mm. From one single scan both phase-contrast and standard attenuation based tomography can be attained, providing an overall gain in image contrast.
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| 15. |
- Dahlin, Lars B., et al.
(författare)
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Three-dimensional architecture of human diabetic peripheral nerves revealed by X-ray phase contrast holographic nanotomography
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- A deeper knowledge of the architecture of the peripheral nerve with three-dimensional (3D) imaging of the nerve tissue at the sub-cellular scale may contribute to unravel the pathophysiology of neuropathy. Here we demonstrate the feasibility of X-ray phase contrast holographic nanotomography to enable 3D imaging of nerves at high resolution, while covering a relatively large tissue volume. We show various subcomponents of human peripheral nerves in biopsies from patients with type 1 and 2 diabetes and in a healthy subject. Together with well-organized, parallel myelinated nerve fibres we show regenerative clusters with twisted nerve fibres, a sprouted axon from a node of Ranvier and other specific details. A novel 3D construction (with movie created) of a node of Ranvier with end segment of a degenerated axon and sprout of a regenerated one is captured. Many of these architectural elements are not described in the literature. Thus, X-ray phase contrast holographic nanotomography enables identifying specific morphological structures in 3D in peripheral nerve biopsies from a healthy subject and from patients with type 1 and 2 diabetes.
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| 16. |
- Dierks, Hanna, et al.
(författare)
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Optimization of phase contrast imaging with a nano-focus x-ray tube
- 2023
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Ingår i: Applied Optics. - 1559-128X. ; 62:20, s. 5502-5507
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Tidskriftsartikel (refereegranskat)abstract
- Propagation-based phase contrast imaging with a laboratory x-ray source is a valuable tool for studying samples that show only low absorption contrast, either because of low density, elemental composition, or small feature size. If a propagation distance between sample and detector is introduced and the illumination is sufficiently coherent, the phase shift in the sample will cause additional contrast around interfaces, known as edge enhancement fringes. The strength of this effect depends not only on sample parameters and energy but also on the experimental geometry, which can be optimized accordingly. Recently, x-ray lab sources using transmission targets have become available, which provide very small source sizes in the few hundred nanometer range. This allows the use of a high-magnification geometry with a very short source-sample distance, while still achieving sufficient spatial coherence at the sample position. Moreover, the high geometrical magnification makes it possible to use detectors with a larger pixel size without reducing the image resolution. Here, we explore the influence of magnification on the edge enhancement fringes in such a geometry. We find experimentally and theoretically that the fringes become maximal at a magnification that is independent of the total source-detector distance. This optimal magnification only depends on the source size, the steepness of the sample feature, and the detector resolution. A stronger influence of the sample feature on the optimal magnification compared to low-magnification geometries is observed.
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| 17. |
- Dreier, Till, et al.
(författare)
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Improved resolution in x-ray tomography by super-resolution
- 2021
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Ingår i: Applied Optics. - 2155-3165. ; 60:20, s. 5783-5794
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, super-resolution imaging is described and evaluated for x-ray tomography and is compared with standard tomography and upscaling during reconstruction. Blurring is minimized due to the negligible point spread of photon counting detectors and an electromagnetically movable micro-focus x-ray spot. Scans are acquired in high and lowmagnification geometry, where the latter is used to minimize penumbral blurring fromthe x-ray source. Sharpness and level ofdetail can be significantly increased in reconstructed slices to the point where the source size becomes the limiting factor. The achieved resolution of the different methods is quantified and compared using biological samples via the edge spread function, modulation transfer function, and Fourier ring correlation.
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| 18. |
- Dreier, Till, et al.
(författare)
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Radiopaque dyes allow vessel imaging in lung tissue using laboratory phase contrast micro-CT
- 2022
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. ; 12242
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Konferensbidrag (refereegranskat)abstract
- Phase contrast micro-CT is a powerful technique allowing imaging of soft tissue at synchrotrons or using lab- oratory sources. The use of contrast agents is a useful approach when imaging vascular structures. However, common x-ray contrast agents typically rely on heavy metals to increase absorption, which may affect the phase contrast and cause artifacts in the reconstructed volumes. Thus, utilizing an agent with lower attenuation similar to soft tissue is clearly advantageous. Here, we evaluated different colored radiopaque solutions (tissue marking dyes) which had been injected into the vascular system of bovine lung samples, prior to embedding in paraffin. Scans were performed using a micro-focus x-tube calibrated to 10 µm spot size at 70 kV and a photon counting detector with a silicon sensor and 75 µm pixels. The resulting volumes have a voxel size of (25 µm)3, limited by the size of the samples, but sufficient to resolve the vascular system. Experiments confirmed that sufficient perfusion of the vessels with the dyes could be achieved, and the different dyes could be clearly discerned in the reconstructed volumes without causing artifacts allowing to clearly identify features in the soft tissue. Further, the findings were confirmed by histology.Keywords:
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| 19. |
- Dreier, Till, et al.
(författare)
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Super-resolution X-ray imaging with hybrid pixel detectors using electromagnetic source stepping
- 2020
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- With increasing demand for high-resolution X-ray images, the super-resolution method allows to estimate a single high-resolution image from several low-resolution images. Hybrid pixel detectors provide high-quality and low-resolution images, which makes them particularlywell suited for super-resolution. However, such detectors consist of a limited number of pixels at high cost. Applying super-resolution with hybrid pixel detectors shows that it is a viable method to obtain high-resolution images. The point-spread function of such detectors can be idealised to be 1 pixel, adding no blur into the image making such detectors the ideal choice for the application of super- resolution X-ray imaging. However, there are charge sharing effects between the pixels caused by the energy and impact position of incoming photons. Utilising an X-ray source, which allows magnetic stepping of the X-ray spot, several slightly shifted images can be obtained without requiring mechanical movements. Registering the shifts between individual images with sub-pixel precision allows to estimate a high-resolution image. With repeatable and equally spaced X-ray spot position patterns, sufficient information can be obtained with only a few images. In this paper, we present the application of super-resolution for X-ray imaging using a Pilatus 100K hybrid pixel detector from Dectris Ltd. and a prototype micro-focus X-ray source from Excillum AB. Moreover, we analyse the image quality for applications in X-ray radiography and tomography. Using a sufficient number of low-resolution images allows us to achieve an increase in resolution, without introducing significant blur or artefacts into the image. Here we quantify the effects on the quality of resulting super-resolution images using different methods of image interpolation, interpolation factors, shifts of the sample on the detector, and amount of low-resolution images.
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| 20. |
- Dyrby, Tim B., et al.
(författare)
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Validation strategies for the interpretation of microstructure imaging using diffusion MRI
- 2018
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 182, s. 62-79
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Tidskriftsartikel (refereegranskat)abstract
- Extracting microanatomical information beyond the image resolution of MRI would provide valuable tools for diagnostics and neuroscientific research. A number of mathematical models already suggest microstructural interpretations of diffusion MRI (dMRI) data. Examples of such microstructural features could be cell bodies and neurites, e.g. the axon's diameter or their orientational distribution for global connectivity analysis using tractography, and have previously only been possible to access through conventional histology of post mortem tissue or invasive biopsies. The prospect of gaining the same knowledge non-invasively from the whole living human brain could push the frontiers for the diagnosis of neurological and psychiatric diseases. It could also provide a general understanding of the development and natural variability in the healthy brain across a population. However, due to a limited image resolution, most of the dMRI measures are indirect estimations and may depend on the whole chain from experimental parameter settings to model assumptions and implementation. Here, we review current literature in this field and highlight the integrative work across anatomical length scales that is needed to validate and trust a new dMRI method. We encourage interdisciplinary collaborations and data sharing in regards to applying and developing new validation techniques to improve the specificity of future dMRI methods.
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| 21. |
- Eckermann, Marina, et al.
(författare)
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3d phase-contrast nanotomography of unstained human skin biopsies may identify morphological differences in the dermis and epidermis between subjects
- 2021
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Ingår i: Skin Research and Technology. - : Wiley. - 0909-752X .- 1600-0846. ; 27:3, s. 316-323
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Tidskriftsartikel (refereegranskat)abstract
- Background: Enteric neuropathy is described in most patients with gastrointestinal dysmotility and may be found together with reduced intraepidermal nerve fiber density (IENFD). The aim of this pilot study was to assess whether three-dimensional (3d) imaging of skin biopsies could be used to examine various tissue components in patients with gastrointestinal dysmotility. Material and methods: Four dysmotility patients of different etiology and two healthy volunteers were included. From each subject, two 3-mm punch skin biopsies were stained with antibodies against protein gene product 9.5 or evaluated as a whole with two X-ray phase-contrast computed tomography (CT) setups, a laboratory µCT setup and a dedicated synchrotron radiation nanoCT end-station. Results: Two patients had reduced IENFD, and two normal IENFD, compared with controls. µCT and X-ray phase-contrast holographic nanotomography scanned whole tissue specimens, with optional high-resolution scans revealing delicate structures, without differentiation of various fibers and cells. Irregular architecture of dermal fibers was observed in the patient with Ehlers-Danlos syndrome and the patient with idiopathic dysmotility showed an abundance of mesenchymal ground substance. Conclusions: 3d phase-contrast tomographic imaging may be useful to illustrate traits of connective tissue dysfunction in various organs and to demonstrate whether disorganized dermal fibers could explain organ dysfunction.
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| 22. |
- Eggl, Elena, et al.
(författare)
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X-ray phase-contrast tomography with a compact laser-driven synchrotron source.
- 2015
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 112:18, s. 5567-5572
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Tidskriftsartikel (refereegranskat)abstract
- Between X-ray tubes and large-scale synchrotron sources, a large gap in performance exists with respect to the monochromaticity and brilliance of the X-ray beam. However, due to their size and cost, large-scale synchrotrons are not available for more routine applications in small and medium-sized academic or industrial laboratories. This gap could be closed by laser-driven compact synchrotron light sources (CLS), which use an infrared (IR) laser cavity in combination with a small electron storage ring. Hard X-rays are produced through the process of inverse Compton scattering upon the intersection of the electron bunch with the focused laser beam. The produced X-ray beam is intrinsically monochromatic and highly collimated. This makes a CLS well-suited for applications of more advanced--and more challenging--X-ray imaging approaches, such as X-ray multimodal tomography. Here we present, to our knowledge, the first results of a first successful demonstration experiment in which a monochromatic X-ray beam from a CLS was used for multimodal, i.e., phase-, dark-field, and attenuation-contrast, X-ray tomography. We show results from a fluid phantom with different liquids and a biomedical application example in the form of a multimodal CT scan of a small animal (mouse, ex vivo). The results highlight particularly that quantitative multimodal CT has become feasible with laser-driven CLS, and that the results outperform more conventional approaches.
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| 23. |
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| 24. |
- Einarsdóttir, Hildur, et al.
(författare)
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Computer-aided diagnosis of pulmonary diseases using x-ray darkfield radiography
- 2015
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 60:24, s. 9253-9268
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Tidskriftsartikel (refereegranskat)abstract
- In this work we develop a computer-aided diagnosis (CAD) scheme for classification of pulmonary disease for grating-based x-ray radiography. In addition to conventional transmission radiography, the grating-based technique provides a dark-field imaging modality, which utilizes the scattering properties of the x-rays. This modality has shown great potential for diagnosing early stage emphysema and fibrosis in mouse lungs in vivo. The CAD scheme is developed to assist radiologists and other medical experts to develop new diagnostic methods when evaluating grating-based images. The scheme consists of three stages: (i) automatic lung segmentation; (ii) feature extraction from lung shape and dark-field image intensities; (iii) classification between healthy, emphysema and fibrosis lungs. A study of 102 mice was conducted with 34 healthy, 52 emphysema and 16 fibrosis subjects. Each image was manually annotated to build an experimental dataset. System performance was assessed by: (i) determining the quality of the segmentations; (ii) validating emphysema and fibrosis recognition by a linear support vector machine using leave-one-out cross-validation. In terms of segmentation quality, we obtained an overlap percentage (Ω) 92.63 ± 3.65%, Dice Similarity Coefficient (DSC) 89.74 ± 8.84% and Jaccard Similarity Coefficient 82.39 ± 12.62%. For classification, the accuracy, sensitivity and specificity of diseased lung recognition was 100%. Classification between emphysema and fibrosis resulted in an accuracy of 93%, whilst the sensitivity was 94% and specificity 88%. In addition to the automatic classification of lungs, deviation maps created by the CAD scheme provide a visual aid for medical experts to further assess the severity of pulmonary disease in the lung, and highlights regions affected.
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| 25. |
- Einarsdóttir, Hildur, et al.
(författare)
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Novelty detection of foreign objects in food using multi-modal X-ray imaging
- 2016
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Ingår i: Food Control. - : Elsevier BV. - 0956-7135. ; 67, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate a method for novelty detection of foreign objects in food products using grating-based multimodal X-ray imaging. With this imaging technique three modalities are available with pixel correspondence, enhancing organic materials such as wood chips, insects and soft plastics not detectable by conventional X-ray absorption radiography. We conduct experiments, where several food products are imaged with common foreign objects typically found in the food processing industry. To evaluate the benefit from using this multi-contrast X-ray technique over conventional X-ray absorption imaging, a novelty detection scheme based on well known image- and statistical analysis techniques is proposed. The results show that the presented method gives superior recognition results and highlights the advantage of grating-based imaging.
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| 26. |
- Fagman, Erika, et al.
(författare)
-
18F-FDG PET/CT in the diagnosis of prosthetic valve endocarditis
- 2016
-
Ingår i: The International Journal of Cardiovascular Imaging. - : Springer Science and Business Media LLC. - 1569-5794 .- 1573-0743. ; 32:4, s. 679-686
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown promising results using 18F-fluorodeoxyglucose positron emission tomography/ computed tomography (18F-FDG PET/CT) in the diagnosis of prosthetic valve endocarditis (PVE). However, previous studies did not include negative controls. The aim of this study was to compare 18F-FDG-uptake around prosthetic aortic valves in patients with and without PVE and to determine the diagnostic performance of 18F-FDG PET/CT in the diagnosis of PVE. 18F-FDG PET/CT examinations in patients with a prosthetic aortic valve performed 2008–2014 were retrieved. Eight patients with a final diagnosis of definite PVE were included in the analysis of the diagnostic performance of 18F-FDG PET/CT. Examinations performed on suspicion of malignancy in patients without PVE (n = 19) were used as negative controls. Visual and semi-quantitative analysis was performed. Maximal standardized uptake value (SUVmax) in the valve area was measured and SUVratio was calculated by dividing valve SUVmax by SUVmax in the descending aorta. The sensitivity was 75 %, specificity 84 %, positive likelihood ratio [LR(+)] 4.8 and negative likelihood ratio [LR(-)] 0.3 on visual analysis. Both SUVmax and SUVratio were significantly higher in PVE patients [5.8 (IQR 3.5–6.5) and 2.4 (IQR 1.7–3.0)] compared to non-PVE patients [3.2 (IQR 2.8–3.8) and 1.5 (IQR 1.3–1.6)] (p<0.001). ROC-curve analysis of SUVratio yielded an area under the curve of 0.90 (95 % CI 0.74–1.0). 18F-FDG-uptake around non-infected aortic prosthetic valves was low. The level of 18F-FDG-uptake in the prosthetic valve area showed a good diagnostic performance in the diagnosis of PVE.
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| 27. |
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| 28. |
- Fu, Jian, et al.
(författare)
-
3D Algebraic Iterative Reconstruction for Cone-Beam X-Ray Differential Phase-Contrast Computed Tomography.
- 2015
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications.
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| 29. |
- Fu, Jian, et al.
(författare)
-
A reconstruction method for cone-beam differential x-ray phase-contrast computed tomography
- 2012
-
Ingår i: Optics Express. - 1094-4087. ; 20:19, s. 21512-21519
-
Tidskriftsartikel (refereegranskat)abstract
- Most existing differential phase-contrast computed tomography (DPC-CT) approaches are based on three kinds of scanning geometries, described by parallel-beam, fan-beam and cone-beam. Due to the potential of compact imaging systems with magnified spatial resolution, cone-beam DPC-CT has attracted significant interest. In this paper, we report a reconstruction method based on a back-projection filtration (BPF) algorithm for cone-beam DPC-CT. Due to the differential nature of phase contrast projections, the algorithm restrains from differentiation of the projection data prior to back-projection, unlike BPF algorithms commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a micro-focus x-ray tube source. Moreover, the numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated cone-beam datasets. We believe that this feature is of particular interest for future medical cone-beam phase-contrast CT imaging applications. (C) 2012 Optical Society of America
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| 30. |
- Fu, J., et al.
(författare)
-
Cone-beam differential phase-contrast laminography with x-ray tube source
- 2014
-
Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 106:6
-
Tidskriftsartikel (refereegranskat)abstract
- We report on an x-ray cone-beam differential phase-contrast computed laminography (DPC-CL) method for tomographic reconstruction of thin and lamellar objects. We describe the specific scan geometry of DPC-CL, which consists of a Talbot-Lau grating interferometer and a lab-based x-ray tube source, and derive a filtered back-projection (FBP) reconstruction algorithm. The experimental results of a flat sphere phantom and a piece of ham demonstrate the validity of the proposed technique. The existing DPC-CL methods are based on synchrotron sources and the parallel-beam geometry. In contrast, our approach adopts a more accessible x-ray tube source and a cone-beam geometry. Therefore it significantly widens the application range of phase-contrast laminography, particularly in practical laboratory settings, beyond applications at large-scale synchrotron facilities. Copyright (C) EPLA, 2014
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| 31. |
- Fu, Jian, et al.
(författare)
-
Helical differential X-ray phase-contrast computed tomography.
- 2014
-
Ingår i: Physica Medica. - : Elsevier BV. - 1120-1797. ; 30:3, s. 374-379
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first experimental results of helical differential phase-contrast computed tomography (helical DPC-CT) with a laboratory X-ray tube source and a Talbot-Lau grating interferometer. The results experimentally verify the feasibility of helical data acquisition and reconstruction in phase-contrast imaging, in analogy to its use in clinical CT systems. This allows fast and continuous volumetric scans for long objects with lengths exceeding the dimension of the detector. Since helical CT revolutionized the field of medical CT several years ago, we anticipate that this method will bring the same significant impact on the future medical and industrial applications of X-ray DPC-CT.
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| 32. |
- Hahn, Dieter, et al.
(författare)
-
Statistical iterative reconstruction algorithm for X-ray phase-contrast CT.
- 2015
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Grating-based phase-contrast computed tomography (PCCT) is a promising imaging tool on the horizon for pre-clinical and clinical applications. Until now PCCT has been plagued by strong artifacts when dense materials like bones are present. In this paper, we present a new statistical iterative reconstruction algorithm which overcomes this limitation. It makes use of the fact that an X-ray interferometer provides a conventional absorption as well as a dark-field signal in addition to the phase-contrast signal. The method is based on a statistical iterative reconstruction algorithm utilizing maximum-a-posteriori principles and integrating the statistical properties of the raw data as well as information of dense objects gained from the absorption signal. Reconstruction of a pre-clinical mouse scan illustrates that artifacts caused by bones are significantly reduced and image quality is improved when employing our approach. Especially small structures, which are usually lost because of streaks, are recovered in our results. In comparison with the current state-of-the-art algorithms our approach provides significantly improved image quality with respect to quantitative and qualitative results. In summary, we expect that our new statistical iterative reconstruction method to increase the general usability of PCCT imaging for medical diagnosis apart from applications focused solely on soft tissue visualization.
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| 33. |
- Hellbach, Katharina, et al.
(författare)
-
In Vivo Dark-Field Radiography for Early Diagnosis and Staging of Pulmonary Emphysema.
- 2015
-
Ingår i: Investigative Radiology. - 0020-9996. ; 50:7, s. 430-435
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the suitability of in vivo x-ray dark-field radiography for early-stage diagnosis of pulmonary emphysema in mice. Furthermore, we aimed to analyze how the dark-field signal correlates with morphological changes of lung architecture at distinct stages of emphysema.
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| 34. |
- Holte, Martin Bech, 1979-
(författare)
-
Essays on Incentives and Leadership
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- "Taxation, Career Concerns and CEO Pay". This paper proposes a simple dynamic model of equilibrium CEO compensation. Motivated by the strengthened career incentives stemming from the fall in the top income tax rates over the past decades, I study the implications of a model where the quality of talent identification depends on how hard individuals work in order to be among the winners in the contest for managerial positions. It is shown how the compensation of CEOs can be interpreted in this light, across time, across industries, and across countries, and I provide some evidence showing that the predictions of the model are in line with several empirical developments over the past decades."Incentives under Communism: The Value of Low-Quality Goods". In this paper, I study how efficiently centrally planned regimes can provide incentives across different stages of economic development. In particular, I study the attractiveness of an incentive system based on exclusive provision of high-quality goods to high-ranked members of society. At low levels of economic development, a self-interested regime can exploit such an incentive system to reduce the cost of providing incentives. However, such an incentive system generally loses its attractiveness as the economy grows. The economic performance of the centrally planned economies is then analyzed in light of this result."The Business of Troubled Autocrats". Many autocrats control resource rents. Typically, they rely on these rents in order to buy political support. In this paper, I study how such autocrats behave in product and capital markets, in particular at times of financial distress. The main questions are: How does the asset position of an autocrat affect his behavior as a producer in a market with rents? From whom does the autocrat obtain financing in order to get out of difficulties? I show that when the asset position of the autocrat drops below a certain threshold, output drops below the level of a standard monopolist. Further, the autocrat can obtain less expensive financing domestically by exploiting the presence of vested interests, implying that there is zero foreign debt in equilibrium.
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| 35. |
- Jensen, Torben Haugaard, et al.
(författare)
-
Imaging of Metastatic Lymph Nodes by X-ray Phase-Contrast Micro-Tomography
- 2013
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Invasive cancer causes a change in density in the affected tissue, which can be visualized by x-ray phase-contrast tomography. However, the diagnostic value of this method has so far not been investigated in detail. Therefore, the purpose of this study was, in a blinded manner, to investigate whether malignancy could be revealed by non-invasive x-ray phase-contrast tomography in lymph nodes from breast cancer patients. Seventeen formalin-fixed paraffin-embedded lymph nodes from 10 female patients (age range 37-83 years) diagnosed with invasive ductal carcinomas were analyzed by X-ray phase-contrast tomography. Ten lymph nodes had metastatic deposits and 7 were benign. The phase-contrast images were analyzed according to standards for conventional CT images looking for characteristics usually only visible by pathological examinations. Histopathology was used as reference. The result of this study was that the diagnostic sensitivity of the image analysis for detecting malignancy was 100% and the specificity was 87%. The positive predictive value was 91% for detecting malignancy and the negative predictive value was 100%. We conclude that x-ray phase-contrast imaging can accurately detect density variations to obtain information regarding lymph node involvement previously inaccessible with standard absorption x-ray imaging.
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| 36. |
- Jepsen, Martin Rudbeck, et al.
(författare)
-
What Awaits Myanmar's Uplands Farmers? Lessons Learned from Mainland Southeast Asia
- 2019
-
Ingår i: Land. - : MDPI AG. - 2073-445X. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- Mainland Southeast Asia (MSA) has seen sweeping upland land use changes in the past decades, with transition from primarily subsistence shifting cultivation to annual commodity cropping. This transition holds implications for local upland communities and ecosystems. Due to its particular political regime, Myanmar is at the tail of this development. However, with Myanmar's official strategy of agricultural commercialization and intensification, recent liberalization of the national economy, and influx of multinational agricultural companies, the effects on upland land transitions could come fast. We analyze the current state of upland land use in Myanmar in a socio-economic and political context, identify the dynamics in three indicator commodity crops (maize, cassava, and rubber), and discuss the state driven economic, tenurial and policy reforms that have occurred in upland areas of mainland Southeast Asian countries in past decades. We draw on these insights to contextualize our study and hypothesize about possible transition pathways for Myanmar. The transition to annual commodity cropping is generally driven by a range of socio-economic and technical factors. We find that land use dynamics for the three indicator crops are associated with market demand and thus the opening of national Southeast-Asian economies, research and development of locally suitable high yielding varieties (HYVs), and subsidies for the promotion of seeds and inputs. In contrast, promotion of HYVs in marginal areas and without adequate agricultural extension services may results in agricultural contraction and yield dis-intensification. The environmental impacts of the transition depend on the transition pathway, e.g., through large-scale plantation projects or smallholder initiatives. The agricultural development in upland MSA follows a clear diffusion pattern with transition occurring first in Thailand, spreading to Vietnam, Cambodia and Laos. While these countries point to prospects for Myanmar, we hypothesize that changes will come slow due to Myanmar's sparse rural infrastructure, with uncertainty about tenure, in particular in areas still troubled by armed conflicts, and unwillingness of international investors to approach Myanmar given the recent setbacks to the democratization process.
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| 37. |
- Kalbfleisch, Sebastian, et al.
(författare)
-
X-ray in-line holography and holotomography at the NanoMAX beamline
- 2022
-
Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 224-229
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent X-ray imaging techniques, such as in-line holography, exploit the high brilliance provided by diffraction-limited storage rings to perform imaging sensitive to the electron density through contrast due to the phase shift, rather than conventional attenuation contrast. Thus, coherent X-ray imaging techniques enable high-sensitivity and low-dose imaging, especially for low-atomic-number (Z) chemical elements and materials with similar attenuation contrast. Here, the first implementation of in-line holography at the NanoMAX beamline is presented, which benefits from the exceptional focusing capabilities and the high brilliance provided by MAX IV, the first operational diffractionlimited storage ring up to approximately 300 eV. It is demonstrated that in-line holography at NanoMAX can provide 2D diffraction-limited images, where the achievable resolution is only limited by the 70 nm focal spot at 13 keV X-ray energy. Also, the 3D capabilities of this instrument are demonstrated by performing holotomography on a chalk sample at a mesoscale resolution of around 155 nm. It is foreseen that in-line holography will broaden the spectra of capabilities of MAX IV by providing fast 2D and 3D electron density images from mesoscale down to nanoscale resolution.
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| 38. |
- Krishna Vadivel, Chella, et al.
(författare)
-
Staphylococcus aureus induce drug resistance in cancer T cells in Sézary Syndrome
- 2024
-
Ingår i: Blood. - 0006-4971 .- 1528-0020. ; 143:15, s. 1496-1512
-
Tidskriftsartikel (refereegranskat)abstract
- Key Points Enterotoxins from Staphylococcus aureus bacteria induce drug resistance in primary malignant T cells in Sézary syndrome. Targeting bacteria, their toxins, and downstream signaling pathways in malignant T cells abrogate the induction of drug resistance. Patients with Sézary syndrome (SS), a leukemic variant of cutaneous T cell lymphoma (CTCL), are prone to Staphylococcus aureus (S. aureus) infections and have a poor prognosis due to treatment-resistance. Here, we report that S. aureus and staphylococcal enterotoxins (SE) induce drug resistance in malignant T-cells against therapeutics commonly used in CTCL. Supernatant from patient-derived, SE-producing S. aureus and recombinant SE significantly inhibit cell death induced by HDAC inhibitor romidepsin in primary malignant T-cells from SS patients. Bacterial killing by engineered, bacteriophage-derived, S. aureus-specific endolysin (XZ.700) abrogates the effect of S. aureus supernatant. Likewise, mutations in MHC Class II binding sites of SE type-A (SEA) and anti-SEA antibody block induction of resistance. Importantly, SE also triggers resistance to other HDAC inhibitors (vorinostat and resminostat) and chemotherapeutic drugs (doxorubicin and etoposide). Multimodal single-cell sequencing indicates TCR, NFB, and JAK/STAT signaling pathways (previously associated with drug-resistance) as putative mediators of SE-induced drug resistance. In support, inhibition of TCR-signaling and Protein Kinase C (upstream of NFB) counteracts SE-induced rescue from drug-induced cell death. Inversely, SE cannot rescue from cell death induced by proteasome/NFB inhibitor bortezomib. Inhibition of JAK/STAT only blocks SE-induced rescue of malignant T-cells in some but not all patients, suggesting two distinct ways SE can induce drug resistance. In conclusion, we show that S. aureus enterotoxins induce drug-resistance in primary malignant T-cells. These findings suggest that S. aureus enterotoxins cause clinical treatment-resistance in SS patients and that anti-bacterial measures may improve the outcome of cancer-directed therapy in patients harboring S. aureus
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| 39. |
- Lauridsen, Torsten, et al.
(författare)
-
Detection of sub-pixel fractures in X-ray dark-field tomography
- 2015
-
Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 121:3, s. 1243-1250
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new method for detecting fractures in solid materials below the resolution given by the detector pixel size by using grating-based X-ray interferometry. The technique is particularly useful for detecting sub-pixel cracks in large samples where the size of the sample is preventing high-resolution mu CT studies of the entire sample. The X-ray grating interferometer produces three distinct modality signals: absorption, phase and dark field. The method utilizes the unique scattering features of the dark-field signal. We have used tomograms reconstructed from each of the three signals to detect cracks in a model sample consisting of stearin.
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| 40. |
- Leutscher, Peter Derek Christian, et al.
(författare)
-
Evaluation of depression as a risk factor for treatment failure in chronic hepatitis C.
- 2010
-
Ingår i: Hepatology. - : Ovid Technologies (Wolters Kluwer Health). - 1527-3350 .- 0270-9139. ; 52:2, s. 430-435
-
Tidskriftsartikel (refereegranskat)abstract
- The Major Depression Inventory (MDI) was used to estimate the value of routine medical interviews in diagnosing major depression among patients receiving peginterferon alfa-2a and ribavirin therapy for chronic hepatitis C virus (HCV) infection (n = 325). According to criteria from the MDI and Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), 19 patients (6%) had major depression at baseline. An additional 114 (37%) developed depression while on HCV combination therapy, with baseline MDI score and female sex independently predicting the emergence of major depression during treatment in a multivariate analysis. Only 36 (32%) of the 114 patients developing major depression according to MDI/DSM-IV criteria were correctly diagnosed during routine medical interviews. The emergence of major depression frequently led to premature discontinuation of peginterferon/ribavirin therapy, and an on-treatment MDI score increment exceeding 30 points (i.e., a validated marker of idiopathic DSM-IV major depression) was correlated with impaired outcome of HCV therapy (P = 0.02). This difference was even more pronounced among patients with an on-treatment increase in MDI score greater than 35 points (P = 0.003). Conclusion: We conclude that (1) depressive symptoms among patients undergoing HCV therapy are commonly overlooked by routine clinical interviews, (2) the emergence of depression compromises the outcome of HCV therapy, and (3) the MDI scale may be useful in identifying patients at risk for treatment-induced depression.
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| 41. |
- Magnusson Hanson, Linda, et al.
(författare)
-
Psychosocial working conditions and depressive symptoms among Swedish employees.
- 2009
-
Ingår i: International archives of occupational and environmental health. - : Springer Science and Business Media LLC. - 1432-1246 .- 0340-0131. ; 82:8, s. 951-60
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate prospective associations between working conditions and depressive symptoms in Swedish men and women. METHODS: The study was based on SLOSH (N = 5,985), a follow-up of a representative sample of gainfully employed Swedes 16-64 years of age from the Swedish Work Environment Survey 2003. Work demands, decision authority, support and conflicts at work were measured in 2003. Depressive symptoms were recorded in 2006 by a short version of the depression subscale of the Symptom Checklist 90 (SCL-90). Linear regression analyses were performed. RESULTS: After adjusting for an indicator of previous depressive symptoms and covariates, conflicts with fellow workers in men were associated with depressive symptoms, whereas demands (men), support from fellow workers (women), and decision authority predicted lower scores. CONCLUSION: The study supports the theory that decision authority, support and conflicts at work are predictive of depressive symptoms in the general Swedish working population.
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| 42. |
- Mathavan, Neashan, et al.
(författare)
-
The compositional and nano-structural basis of fracture healing in healthy and osteoporotic bone
- 2018
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Osteoporosis, a prevalent metabolic bone disorder, predisposes individuals to increased susceptibility to fractures. It is also, somewhat controversially, thought to delay or impair the regenerative response. Using high-resolution Fourier-transform infrared spectroscopy and small/wide-angle X-ray scattering we sought to answer the following questions: Does the molecular composition and the nano-structure in the newly regenerated bone differ between healthy and osteoporotic environments? And how do pharmacological treatments, such as bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA), alter callus composition and nano-structure in such environments? Cumulatively, on the basis of compositional and nano-structural characterizations of newly formed bone in an open-osteotomy rat model, the healing response in untreated healthy and ovariectomy-induced osteoporotic environments was fundamentally the same. However, the BMP-7 induced osteogenic response resulted in greater heterogeneity in the nano-structural crystal dimensions and this effect was more pronounced with osteoporosis. ZA mitigated the effects of the upregulated catabolism induced by both BMP-7 and an osteoporotic bone environment. The findings contribute to our understanding of how the repair processes in healthy and osteoporotic bone differ in both untreated and treated contexts and the data presented represents the most comprehensive study of fracture healing at the nanoscale undertaken to date.
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| 43. |
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| 44. |
- Meinel, Felix G., et al.
(författare)
-
Lung tumors on multimodal radiographs derived from grating-based X-ray imaging - A feasibility study
- 2014
-
Ingår i: Physica Medica. - : Elsevier BV. - 1120-1797. ; 30:3, s. 352-357
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this study was to assess whether grating-based X-ray imaging may have a role in imaging of pulmonary nodules on radiographs. Materials and methods: A mouse lung containing multiple lung tumors was imaged using a small-animal scanner with a conventional X-ray source and a grating interferometer for phase-contrast imaging. We qualitatively compared the signal characteristics of lung nodules on transmission, dark-field and phase-contrast images. Furthermore, we quantitatively compared signal characteristics of lung tumors and the adjacent lung tissue and calculated the corresponding contrast-to-noise ratios. Results: Of the 5 tumors visualized on the transmission image, 3/5 tumors were clearly visualized and 1 tumor was faintly visualized in the dark-field image as areas of decreased small angle scattering. In the phase-contrast images, 3/5 tumors were clearly visualized, while the remaining 2 tumors were faintly visualized by the phase-shift occurring at their edges. No additional tumors were visualized in either the dark-field or phase-contrast images. Compared to the adjacent lung tissue, lung tumors were characterized by a significant decrease in transmission signal (median 0.86 vs. 0.91, p = 0.04) and increase in dark-field signal (median 0.71 vs. 0.65, p = 0.04). Median contrast-to-noise ratios for the visualization of lung nodules were 4.4 for transmission images and 1.7 for dark-field images (p = 0.04). Conclusion: Lung nodules can be visualized on all three radiograph modalities derived from grating-based X-ray imaging. However, our initial data suggest that grating-based multimodal X-ray imaging does not increase the sensitivity of chest radiographs for the detection of lung nodules. (C) 2013 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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| 45. |
- Mohajerani, Pouyan, et al.
(författare)
-
FMT-PCCT: Hybrid Fluorescence Molecular Tomography-X-Ray Phase-Contrast CT Imaging of Mouse Models
- 2014
-
Ingår i: IEEE Transactions on Medical Imaging. - 1558-254X. ; 33:7, s. 1434-1446
-
Tidskriftsartikel (refereegranskat)abstract
- The implementation of hybrid fluorescencemolecular tomography (FMT) and X-ray computed tomography (CT) has been shown to be a necessary development, not only for combining anatomical with functional and molecular contrast, but also for generating optical images of high accuracy. FMT affords highly sensitive 3-D imaging of fluorescence bio-distribution, but in stand-alone form it offers images of low resolution. It was shown that FMT accuracy significantly improves by considering anatomical priors from CT. Conversely, CT generally suffers from low soft tissue contrast. Therefore utilization of CT data as prior information in FMT inversion is challenging when different internal organs are not clearly differentiated. Instead, we combined herein FMT with emerging X-ray phase-contrast CT (PCCT). PCCT relies on phase shift differences in tissue to achieve soft tissue contrast superior to conventional CT. We demonstrate for the first time FMT-PCCT imaging of different animal models, where FMT and PCCT scans were performed in vivo and ex vivo, respectively. The results show that FMT-PCCT expands the potential of FMT in imaging lesions with otherwise low or no CT contrast, while retaining the cost benefits of CT and simplicity of hybrid device realizations. The results point to the most accurate FMT performance to date.
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| 46. |
- Moosmann, Julian, et al.
(författare)
-
Biodegradable magnesium-based implants in bone studied by synchrotron radiation microtomography
- 2017
-
Ingår i: Developments in X-Ray Tomography XI. - : SPIE - International Society for Optical Engineering. ; 10391
-
Konferensbidrag (refereegranskat)abstract
- Permanent implants made of titanium or its alloys are the gold standard in many orthopedic and traumatological applications due to their good biocompatibility and mechanical properties. However, a second surgical intervention is required for this kind of implants as they have to be removed in the case of children that are still growing or on patient's demand. Therefore, magnesium-based implants are considered for medical applications as they are degraded under physiological conditions. The major challenge is tailoring the degradation in a manner that is suitable for a biological environment and such that stabilization of the bone is provided for a controlled period. In order to understand failure mechanisms of magnesium-based implants in orthopedic applications and, further, to better understand the osseointegration, screw implants in bone are studied under mechanical load by means of a push-out device installed at the imaging beamline P05 of PETRA III at DESY. Conventional absorption contrast microtomography and phasecontrast techniques are applied in order to monitor the bone-to-implant interface under increasing load conditions. In this proof-of-concept study, first results from an in situ push-out experiment are presented.
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| 47. |
- Müller, Mark, et al.
(författare)
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Contrast-to-noise ratio optimization for a prototype phase-contrast computed tomography scanner.
- 2015
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:12
-
Tidskriftsartikel (refereegranskat)abstract
- In the field of biomedical X-ray imaging, novel techniques, such as phase-contrast and dark-field imaging, have the potential to enhance the contrast and provide complementary structural information about a specimen. In this paper, a first prototype of a preclinical X-ray phase-contrast CT scanner based on a Talbot-Lau interferometer is characterized. We present a study of the contrast-to-noise ratios for attenuation and phase-contrast images acquired with the prototype scanner. The shown results are based on a series of projection images and tomographic data sets of a plastic phantom in phase and attenuation-contrast recorded with varying acquisition settings. Subsequently, the signal and noise distribution of different regions in the phantom were determined. We present a novel method for estimation of contrast-to-noise ratios for projection images based on the cylindrical geometry of the phantom. Analytical functions, representing the expected signal in phase and attenuation-contrast for a circular object, are fitted to individual line profiles of the projection data. The free parameter of the fit function is used to estimate the contrast and the goodness of the fit is determined to assess the noise in the respective signal. The results depict the dependence of the contrast-to-noise ratios on the applied source voltages, the number of steps of the phase stepping routine, and the exposure times for an individual step. Moreover, the influence of the number of projection angles on the image quality of CT slices is investigated. Finally, the implications for future imaging purposes with the scanner are discussed.
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| 48. |
- Murer, Fredrik K., et al.
(författare)
-
3D Maps of Mineral Composition and Hydroxyapatite Orientation in Fossil Bone Samples Obtained by X-ray Diffraction Computed Tomography
- 2018
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Whether hydroxyapatite (HA) orientation in fossilised bone samples can be non-destructively retrieved and used to determine the arrangement of the bone matrix and the location of muscle attachments (entheses), is a question of high relevance to palaeontology, as it facilitates a detailed understanding of the (micro-)anatomy of extinct species with no damage to the precious fossil specimens. Here, we report studies of two fossil bone samples, specifically the tibia of a 300-million-year-old tetrapod, Discosauriscus austriacus, and the humerus of a 370-million-year-old lobe-finned fish, Eusthenopteron foordi, using XRD-CT - a combination of X-ray diffraction (XRD) and computed tomography (CT). Reconstructed 3D images showing the spatial mineral distributions and the local orientation of HA were obtained. For Discosauriscus austriacus, details of the muscle attachments could be discerned. For Eusthenopteron foordi, the gross details of the preferred orientation of HA were deduced using three tomographic datasets obtained with orthogonally oriented rotation axes. For both samples, the HA in the bone matrix exhibited preferred orientation, with the unit cell c-axis of the HA crystallites tending to be parallel with the bone surface. In summary, we have demonstrated that XRD-CT combined with an intuitive reconstruction procedure is becoming a powerful tool for studying palaeontological samples.
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| 49. |
- Månsson, Emeli, 1978-, et al.
(författare)
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Methicillin-Resistant Staphylococcus epidermidis Lineages in the Nasal and Skin Microbiota of Patients Planned for Arthroplasty Surgery
- 2021
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Ingår i: Microorganisms. - : MDPI. - 2076-2607. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Staphylococcus epidermidis, ubiquitous in the human nasal and skin microbiota, is a common causative microorganism in prosthetic joint infections (PJIs). A high proportion of PJI isolates have been shown to harbor genetic traits associated with resistance to/tolerance of agents used for antimicrobial prophylaxis in joint arthroplasties. These traits were found within multidrug-resistant S. epidermidis (MDRSE) lineages of multiple genetic backgrounds. In this study, the aim was to study whether MDRSE lineages previously associated with PJIs are present in the nasal and skin microbiota of patients planned for arthroplasty surgery but before hospitalization. We cultured samples from nares, inguinal creases, and skin over the hip or knee (dependent on the planned procedure) taken two weeks (median) prior to admittance to the hospital for total joint arthroplasty from 66 patients on agar plates selecting for methicillin resistance. S. epidermidis colonies were identified and tested for the presence of mecA. Methicillin-resistant S. epidermidis (MRSE) were characterized by Illumina-based whole-genome sequencing. Using this method, we found that 30/66 (45%) of patients were colonized with MRSE at 1-3 body sites. A subset of patients, 10/66 (15%), were colonized with MDRSE lineages associated with PJIs. The qacA gene was identified in MRSE isolates from 19/30 (63%) of MRSE colonized patients, whereas genes associated with aminoglycoside resistance were less common, found in 11/30 (37%). We found that MDRSE lineages previously associated with PJIs were present in a subset of patients' pre-admission microbiota, plausibly in low relative abundance, and may be selected for by the current prophylaxis regimen comprising whole-body cleansing with chlorhexidine-gluconate containing soap. To further lower the rate of S. epidermidis PJIs, the current prophylaxis may need to be modified, but it is important for possible perioperative MDRSE transmission events and specific risk factors for MDRSE PJIs to be investigated before reevaluating antimicrobial prophylaxis.
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| 50. |
- Norvik, Christian, et al.
(författare)
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Synchrotron-based phase-contrast micro-CT as a tool for understanding pulmonary vascular pathobiology and the 3-D microanatomy of alveolar capillary dysplasia
- 2020
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Ingår i: American Journal of Physiology: Lung Cellular and Molecular Physiology. - : American Physiological Society. - 1522-1504 .- 1040-0605. ; 318:1, s. 65-75
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to explore the value of synchrotron-based phase-contrast microcomputed tomography (micro-CT) in pulmonary vascular pathobiology. The microanatomy of the lung is complex with intricate branching patterns. Tissue sections are therefore difficult to interpret. Recruited intrapulmonary bronchopulmonary anastomoses (IBAs) have been described in several forms of pulmonary hypertension, including alveolar capillary dysplasia with misaligned pulmonary veins (ACD/MPV). Here, we examine paraffin-embedded tissue using this nondestructive method for high-resolution three-dimensional imaging. Blocks of healthy and ACD/MPV lung tissue were used. Pulmonary and bronchial arteries in the ACD/MPV block had been preinjected with dye. One section per block was stained, and areas of interest were marked to allow precise beam-alignment during image acquisition at the X02DA TOMCAT beamline (Swiss Light Source). A ×4 magnifying objective coupled to a 20-µm thick scintillating material and a sCMOS detector yielded the best trade-off between spatial resolution and field-of-view. A phase retrieval algorithm was applied and virtual tomographic slices and video clips of the imaged volumes were produced. Dye injections generated a distinct attenuation difference between vessels and surrounding tissue, facilitating segmentation and three-dimensional rendering. Histology and immunohistochemistry post-imaging offered complementary information. IBAs were confirmed in ACD/MPV, and the MPVs were positioned like bronchial veins/venules. We demonstrate the advantages of using synchrotron-based phase-contrast micro-CT for three-dimensional characterization of pulmonary microvascular anatomy in paraffin-embedded tissue. Vascular dye injections add additional value. We confirm intrapulmonary shunting in ACD/MPV and provide support for the hypothesis that MPVs are dilated bronchial veins/venules.
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