| 1. |
- Fyrdahl, A., et al.
(författare)
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Sector-wise golden-angle phase contrast with high temporal resolution for evaluation of left ventricular diastolic dysfunction
- 2020
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 83:4, s. 1310-1321
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To develop a high temporal resolution phase‐contrast pulse sequence for evaluation of diastolic filling patterns, and to evaluate it in comparison to transthoracic echocardiography. Methods A phase‐contrast velocity‐encoded gradient‐echo pulse sequence was implemented with a sector‐wise golden‐angle radial ordering. Acquisitions were optimized for myocardial tissue (TE/TR: 4.4/6.8 ms, flip angle: 8º, velocity encoding: 30 cm/s) and transmitral flow (TE/TR: 4.0/6.6 ms, flip angle: 20º, velocity encoding: 150 cm/s). Shared velocity encoding was combined with a sliding‐window reconstruction that enabled up to 250 frames per cardiac cycle. Transmitral and myocardial velocities were measured in 35 patients. Echocardiographic velocities were obtained with pulsed‐wave Doppler using standard methods. Results Myocardial velocity showed a low difference and good correlation between MRI and Doppler (mean ± 95% limits of agreement 0.9 ± 3.7 cm/s, R2 = 0.63). Transmitral velocity was underestimated by MRI (P < .05) with a difference of −11 ± 28 cm/s (R2 = 0.45). The early‐to‐late ratio correlated well (R2 = 0.66) with a minimal difference (0.03 ± 0.6). Analysis of interobserver and intra‐observer variability showed excellent agreement for all measurements. Conclusions The proposed method enables the acquisition of phase‐contrast images during a single breath‐hold with a sufficiently high temporal resolution to match transthoracic echocardiography, which opens the possibility for many clinically relevant variables to be assessed by MRI.
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| 2. |
- Lundin, M., et al.
(författare)
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Diffusely Increased Myocardial Extracellular Volume with or without Focal Late Gadolinium Enhancement: Prevalence and Associations with Left Ventricular Size and Function
- 2022
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Ingår i: Journal of Thoracic Imaging. - 0883-5993 .- 1536-0237. ; 37:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Myocardial extracellular volume fraction (ECV) using cardiovascular magnetic resonance (CMR) can identify diffuse lesions not detected by late gadolinium enhancement (LGE). We aimed to determine the prevalence of increased ECV and its relation to other CMR findings. Materials and Methods: Consecutive patients (n=609, age median [interquartile range] 53 [39 to 66] y, 62% male) underwent CMR at 1.5 T. Focal lesions on LGE images were noted. ECV in regions without focal LGE findings defined diffuse changes. Pronounced increases in left ventricular (LV) end-diastolic volume index and LV mass index, and pronounced decreases in LV ejection fraction were defined as >3 SD from the sex-specific mean in healthy volunteers. Results: Of 609 patients without amyloidosis or hypertrophic cardiomyopathy, 8% had diffusely increased ECV and 5% of all patients had diffusely increased ECV without any focal LGE findings. Multivariate analysis showed that a pronounced increase in the LV end-diastolic volume index was associated with increased ECV (P=0.001), but not LGE (P=0.52). A pronounced decrease in LV ejection fraction was associated with the presence of LGE (P<0.001), but not with increased ECV (P=0.41). Conclusions: Eight percent of patients in this clinical cohort with known or suspected heart disease had diffusely increased ECV and 60% of these lacked focal LGE findings. LV size is independently associated with increased ECV, whereas systolic dysfunction is independently associated with LGE. This image-based clinical study demonstrates that ECV-CMR provides additional information negligibly related to the results of LGE imaging, and thereby increases the diagnostic yield of CMR. © 2020 Lippincott Williams and Wilkins. All rights reserved.
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| 3. |
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| 4. |
- Fornell, Anna, et al.
(författare)
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A microfluidic platform for SAXS measurements of liquid samples
- 2022
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Konferensbidrag (refereegranskat)abstract
- Small-angle X-ray scattering (SAXS) is a technique that can measure the size and shape of small particles such as proteins and nanoparticles using X-rays. At MAX IV, we are developing a microfluidic sample delivery platform to measure liquid samples containing proteins under flow using SAXS. One of the main advantages of using microfluidics is that the sample is continuously flowing, thus minimizing the risk of radiation damage as the sample is continuously refreshed. Other advantages include low sample volume and the possibility to study dynamic processes, e.g. mixing. To obtain good SAXS signals, the X-ray properties of the chip material are essential. The microfluidic chip must have low attenuation of X-rays, low background scattering, and high resistance to X-ray-induced damage, and preferably be low cost and easy to fabricate. In this work, we have evaluated the performance of two different polymer microfluidic chips for SAXS measurements.
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| 5. |
- Fornell, Anna, et al.
(författare)
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A Microfluidic Platform for Synchrotron X-ray Studies of Proteins
- 2021
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Konferensbidrag (refereegranskat)abstract
- New tools are needed to allow for complex protein dynamics studies, especially to study proteins in their native states. In the AdaptoCell project a microfluidic platform for academic and industrial users at MAX IV Laboratory is being developed. MAX IV is a Swedish national laboratory providing brilliant synchrotron X-rays for research. Due to the high photon flux, sensitive samples such as proteins are prone to rapid radiation damage; thus, it is advantageous to have the liquid sample underflow to refresh the sample continuously. This, in combination with small volumes, makes microfluidics a highly suitable sample environment for protein studies at MAX IV. The AdaptoCell platform is being integrated at three beamlines:Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and Micromax (serial synchrotron crystallography). Currently, the platform is fully available atBalder, under commissioning at CoSAXS and being developed for MicroMAX.
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| 6. |
- Fornell, Anna, et al.
(författare)
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AdaptoCell : Microfluidics at MAX IV Laboratory
- 2022
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Ingår i: 25th Swedish Conference on Macromolecular Structure and Function.
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Konferensbidrag (refereegranskat)abstract
- The AdaptoCell project at MAX IV has developed a microfluidic sample delivery platform for academic and industrial users to enable studies of protein samples in solution and in microcrystals underflow. The platform is compatible with various X-ray techniques and has so far been integrated onto two beamlines at MAX IV: the CoSAXS beamline for small angle X-ray scattering studies and the Balder beamline for X-ray absorption spectroscopy studies. Initial implementation of the platform for serial crystallography sample delivery is ongoing and will be integrated onto the BioMAX and MicroMAX beamlines once commissioned. With this platform, we aim to meet the demand from our user community for studying proteins at physiologically relevant temperatures and give the ability to follow dynamical processes in situ as well as decreasing sample volumes and radiation damage.To determine the optimized flow rates and components for mixing etc. using different microfluidic chips, a dedicated off(beam)line test station with a microscope has been established at the Biolab. The Biolab also provides a number of characterization techniques, such as Dynamic Light Scattering, UV-Vis spectrophotometry, for quality control of the samples; as well as an anaerobic chamber for preparation and characterization of metalloproteins. The microfluidic flows are controlled via syringe pumps or a pressure-driven system. Channel design varies, depending on the needs of the experiment, from straight channel, cross-junction to herringbone micromixers etc. On-chip mixing of buffers with different viscosity, pH, ion strength and protein concentrations has been demonstrated successful and will be presented.
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| 7. |
- Fornell, Anna, et al.
(författare)
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AdaptoCell – Microfluidic Platforms at MAX IV Laboratory
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the AdaptoCell project, we are developing microfluidic platforms for X-ray studies of liquid samples. Microfluidics is a suitable technology for samples that are prone to radiation damage, such as proteins. By having the sample underflow, the sample is continuously refreshed, and the risk of radiation damage is reduced. The technology is also suitable for investigating dynamic events such as in situ mixing. The microfluidic platforms are being integrated at three beamlines at MAX IV Laboratory: Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and MicroMAX (serial synchrotron crystallography). Currently, the platforms are available for users at Balder and CoSAXS, which is under development at MicroMAX. In addition, we also provide a microfluidic offline test station where users can test their samples and optimise their devices before the beam time. The main components of the microfluidic setup are the pressure-driven flow controller and the microfluidic chip. We mainly use commercially available polymer microfluidic chips made of COC (cyclic olefin copolymer). COC is used as a chip material as it has high X-ray transmission and high resistance to radiation damage. There are several different chip designs available such as straight channel chips, droplet generator chips and mixing chips. We believe the AdaptoCell platforms will be useful and versatile sample environments for academic and industrial users at MAX IV Laboratory who want to perform experiments with liquid samples under flow.
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| 8. |
- Gericke, Sabrina Maria, et al.
(författare)
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In Situ H2 Reduction of Al2O3-Supported Ni- and Mo-Based Catalysts
- 2022
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Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 12:7
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Tidskriftsartikel (refereegranskat)abstract
- Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H2 at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. Here, we report on the first in situ study on the reduction of alumina supported Ni- and Mo-based catalysts in 1 mbar H2 using ambient-pressure X-ray photoelectron spectroscopy (APXPS). The study confirms that mixing Ni and Mo lowers the reduction temperature of both Ni- and Mo-oxide as compared to the monometallic catalysts and shows that the MoO3 reduction starts at a lower temperature than the reduction of NiO in NiMo/Al2O3 catalysts. Additionally, the reduction of Ni and Mo foil was directly compared to the reduction of the Al2O3-supported catalysts and it was observed that the reduction of the supported catalysts is more gradual than the reduction of the foils, indicating a strong interaction between the Ni/Mo and the alumina support. © 2022 by the authors.
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| 9. |
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| 10. |
- Kvitting, J.P., et al.
(författare)
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Analysis of human myocardial dynamics using virtual markers based on magnetic resonance imaging
- 2010
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 30:1, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- Background: Myocardial dynamics are three-dimensional (3D) and time-varying. Cineradiography of surgically implanted makers in animals or patients is accurate for assessing these events, but this invasive method potentially alters myocardial motion. The aim of the study was to quantify myocardial motion using magnetic resonance imaging (MRI) and hence to provide a non-invasive approach to characterize 3D myocardial dynamics. Methods: Myocardial motion was quantified in ten normal volunteers by tracking the Lagrangian motion of individual points (i.e. virtual markers), based on time-resolved 3D phase-contrast MRI data and Fourier tracking. Nine points in the myocardium were tracked over the entire cardiac cycle, allowing a wire frame model to be generated and systolic and diastolic events identified. Results: Radius of curvature of the left ventricular (LV) wall was calculated from the virtual markers; the ratio between the anterior–posterior (AP) and septal–lateral (SL) walls in the LV shows an oval shape of the apical short axis plane at end systole (ES) and more circular at end diastole (ED). The AP/SL ratio for the basal plane shows an oval shape at ES and ED. We found that the rotation of the basal plane in ES was less compared to the apical plane [−2·0 ± 2·2 versus 4·1 ± 2·6 degrees (P<0·005)]. The apical plane rotated counter clock wise as viewed from the apex. Conclusion: This new non-invasive tool, despite current limitations in temporal and spatial resolution, may provide a comprehensive set of virtual myocardial markers throughout the entire LV without the confounding effects introduced by surgical implantation.
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