| 1. |
- Leupold, Jochen, et al.
(författare)
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Fast chemical shift mapping with multiecho balanced SSFP
- 2006
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 19:5, s. 267-273
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Tidskriftsartikel (refereegranskat)abstract
- Object: A method is proposed that provides spectroscopic images with high spatial resolution and moderate spectral resolution at very short total data acquisition times. Materials and methods: Balanced steady-state free precession (bSSFP, TrueFISP, FIESTA, b-FFE) is combined with a multiecho readout gradient and frequency-sensitive reconstruction such as Fourier reconstruction known from echo-planar spectroscopic imaging (EPSI) or matrix inversion. Balanced SSFP imaging requires short repetition times to minimize banding artefacts, thereby restricting the achievable frequency resolution. Results: Two-dimensional (2D) high-resolution spectroscopic images were produced of three H-1 resonances (water, acetone and fat) on phantoms and water/fat separation in vivo within 1-2 s. Additionally, fast P-31 spectroscopic images were acquired from a phantom consisting of two resonances within 195 ms. Conclusion: Frequency-sensitive reconstruction of multiecho bSSFP data can provide spectroscopic images with high spatial and temporal resolution while the frequency resolution is moderate at around 100 Hz. The method can also separate more than three resonances, allowing for hetero-nuclei metabolite mapping, for example C-13 and P-31.
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| 2. |
- Berman, Sara E, et al.
(författare)
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Intracranial Arterial 4D Flow in Individuals with Mild Cognitive Impairment is Associated with Cognitive Performance and Amyloid Positivity.
- 2017
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Ingår i: Journal of Alzheimer's disease : JAD. - 1875-8908. ; 60:1, s. 243-252
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Tidskriftsartikel (refereegranskat)abstract
- It is becoming increasingly recognized that cerebrovascular disease is a contributing factor in the pathogenesis of Alzheimer's disease (AD). A unique 4D-Flow magnetic resonance imaging (MRI) technique, phase contrast vastly undersampled isotropic projection imaging (PC VIPR), enables examination of angiographic and quantitative metrics of blood flow in the arteries of the Circle of Willis within a single MRI acquisition. Thirty-eight participants with mild cognitive impairment (MCI) underwent a comprehensive neuroimaging protocol (including 4D-Flow imaging) and a standard neuropsychological battery. A subset of participants (n=22) also underwent lumbar puncture and had cerebrospinal fluid (CSF) assayed for AD biomarkers. Cut-offs for biomarker positivity in CSF resulting from a receiver operating characteristic curve analysis of AD cases and controls from the larger Wisconsin Alzheimer's Disease Research Center cohort were used to classify MCI participants as biomarker positive or negative on amyloid-β (Aβ42), total-tau and total-tau/Aβ42 ratio. Internal carotid artery (ICA) and middle cerebral artery (MCA) mean flow were associated with executive functioning performance, with lower mean flow corresponding to worse performance. MCI participants who were biomarker positive for Aβ42 had lower ICA mean flow than did those who were Aβ42 negative. In sum, mean ICA and MCA arterial flow was associated with cognitive performance in participants with MCI and lower flow in the ICA was associated with amyloid positivity. This provides further evidence for vascular health as a contributing factor in the etiopathogenesis of AD, and could represent a point to intervene in the disease process.
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| 3. |
- Berman, Sara E, et al.
(författare)
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Intracranial Arterial 4D-Flow is Associated with Metrics of Brain Health and Alzheimer's Disease.
- 2015
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Ingår i: Alzheimer's & dementia (Amsterdam, Netherlands). - : Wiley. - 2352-8729. ; 1:4, s. 420-428
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Tidskriftsartikel (refereegranskat)abstract
- While cerebrovascular disease has long been known to co-occur with Alzheimer's disease (AD), recent studies suggest an etiologic contribution to AD pathogenesis. We used 4D-Flow magnetic resonance imaging (MRI) to evaluate blood flow and pulsatility indices in the Circle of Willis. We hypothesized decreased mean blood flow and increased pulsatility, metrics indicative of poor vascular health, would be associated with cerebral atrophy and an AD cerebrospinal fluid (CSF) profile.
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| 4. |
- Bissell, Malenka M., et al.
(författare)
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4D Flow cardiovascular magnetic resonance consensus statement : 2023 update
- 2023
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - : BMC. - 1097-6647 .- 1532-429X. ; 25:1
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Forskningsöversikt (refereegranskat)abstract
- Hemodynamic assessment is an integral part of the diagnosis and management of cardiovascular disease. Four-dimensional cardiovascular magnetic resonance flow imaging (4D Flow CMR) allows comprehensive and accurate assessment of flow in a single acquisition. This consensus paper is an update from the 2015 ‘4D Flow CMR Consensus Statement’. We elaborate on 4D Flow CMR sequence options and imaging considerations. The document aims to assist centers starting out with 4D Flow CMR of the heart and great vessels with advice on acquisition parameters, post-processing workflows and integration into clinical practice. Furthermore, we define minimum quality assurance and validation standards for clinical centers. We also address the challenges faced in quality assurance and validation in the research setting. We also include a checklist for recommended publication standards, specifically for 4D Flow CMR. Finally, we discuss the current limitations and the future of 4D Flow CMR. This updated consensus paper will further facilitate widespread adoption of 4D Flow CMR in the clinical workflow across the globe and aid consistently high-quality publication standards.
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| 5. |
- Dyverfeldt, Petter, et al.
(författare)
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4D flow cardiovascular magnetic resonance consensus statement
- 2015
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - : BioMed Central / Informa Healthcare. - 1097-6647 .- 1532-429X. ; 17:72
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Forskningsöversikt (refereegranskat)abstract
- Pulsatile blood flow through the cavities of the heart and great vessels is time-varying and multidirectional. Access to all regions, phases and directions of cardiovascular flows has formerly been limited. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has enabled more comprehensive access to such flows, with typical spatial resolution of 1.5x1.5x1.5 - 3x3x3 mm(3), typical temporal resolution of 30-40 ms, and acquisition times in the order of 5 to 25 min. This consensus paper is the work of physicists, physicians and biomedical engineers, active in the development and implementation of 4D Flow CMR, who have repeatedly met to share experience and ideas. The paper aims to assist understanding of acquisition and analysis methods, and their potential clinical applications with a focus on the heart and greater vessels. We describe that 4D Flow CMR can be clinically advantageous because placement of a single acquisition volume is straightforward and enables flow through any plane across it to be calculated retrospectively and with good accuracy. We also specify research and development goals that have yet to be satisfactorily achieved. Derived flow parameters, generally needing further development or validation for clinical use, include measurements of wall shear stress, pressure difference, turbulent kinetic energy, and intracardiac flow components. The dependence of measurement accuracy on acquisition parameters is considered, as are the uses of different visualization strategies for appropriate representation of time-varying multidirectional flow fields. Finally, we offer suggestions for more consistent, user-friendly implementation of 4D Flow CMR acquisition and data handling with a view to multicenter studies and more widespread adoption of the approach in routine clinical investigations.
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| 6. |
- Leupold, Jochen, et al.
(författare)
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Fast multiecho balanced SSFP metabolite mapping of H-1 and hyperpolarized C-13 compounds
- 2009
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 22:4, s. 251-256
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the feasibility of multiecho balanced steady-state free precession (bSSFP)-based fast chemical shift mapping hyperpolarized C-13 metabolites. The overall goal was to reduce total imaging time and to increase spatial resolution compared to common chemical shift imaging (CSI). A multiecho bSSFP sequence in combination with an iterative reconstruction algorithm was implemented. H-1 experiments were performed on phantoms and on a human volunteer in order to investigate the feasibility of the method on a system with metabolite maps that are known beforehand. C-13 experiments were performed in vivo on pigs, where CSI images were acquired also for comparison. Chemical shift images of three and four distinct H-1 resonance frequencies as well as chemical shift images of up to five hyperpolarized C-13 metabolites were successfully obtained. Fast metabolite mapping based on multiecho balanced SSFP in combination with an iterative reconstruction approach could successfully separate several H-1 resonances and hyperpolarized C-13 metabolites.
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| 7. |
- Petersson, Sven, 1983-
(författare)
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Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study of blood flow is essential in understanding the physiology and pathophysiology of the cardiovascular system. Small disturbances of the blood flow may over time evolve and contribute to cardiovascular pathology. While the blood flow in a healthy human appears to be predominately laminar, turbulent or transitional blood flow is thought to be involved in the pathogenesis of several cardiovascular diseases. Wall shear stress is the frictional force of blood on the vessel wall and has been linked to the pathogenesis of atherosclerosis and aneurysms. Despite the importance of hemodynamic factors, cardiovascular diagnostics largely relies on the indirect estimation of function based on morphological data.Time-resolved three-dimensional (3D) phase-contrast magnetic resonance imaging (MRI), often referred to as 4D flow MRI, is a versatile and non-invasive tool for cardiovascular blood flow assessment. The use of 4D flow MRI permits estimation of flow volumes, pressure losses, wall shear stress, turbulence intensity and many other unique hemodynamic parameters. However, 4D flow MRI suffers from long scan times, sometimes over 40 minutes. Furthermore, the accuracy of the many different 4D flow MRI-based applications and estimates have not been thoroughly examined.In this thesis, the accuracy of 4D flow MRI-based turbulence intensity mapping and wall shear stress estimation was investigated by using numerical simulations of MRI flow measurements. While the results from the turbulence intensity mapping agreed well with reference values from computational fluid dynamics data, the accuracy of the MRI-based wall shear stress estimates was found to be very sensitive to different parameters, especially to spatial resolution, and wall shear stress values over 5 N/m2 were not well resolved.To reduce the scan time, a 4D flow MRI sequence using spiral k-space trajectories was implemented and validated in-vivo and in-vitro. The scan time of 4D flow MRI was reduced by more than two-fold compared to a conventional Cartesian acquisition already accelerated using SENSE factor 2, and the data quality was maintained. For a 4D flow scan of the human heart, the use of spiral k-space trajectories resulted in a scan time of around 13 min, compared to 30 min for the Cartesian acquisition. By combining parallel imaging and spiral trajectories, the total scan time of a 4D flow measurement of the entire heart may be further reduced. This scan time reduction may also be traded for higher spatial resolution.Numerical simulation of 4D flow MRI may act as an important tool for future optimization and validation of the spiral 4D flow sequence. The scan-time reductions offered by the spiral k-space trajectories can help to cut costs, save time, reduce discomfort for the patient as well as to decrease the risk for motion artifacts. These benefits may facilitate an expanded clinical and investigative use of 4D flow MRI, including larger patient research studies.
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| 8. |
- Schrauben, Eric, et al.
(författare)
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Fast 4D flow MRI intracranial segmentation and quantification in tortuous arteries
- 2015
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Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 42:5, s. 1458-1464
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Tidskriftsartikel (refereegranskat)abstract
- PurposeTo describe, validate, and implement a centerline processing scheme (CPS) for semiautomated segmentation and quantification in carotid siphons of healthy subjects. 4D flow MRI enables blood flow measurement in all major cerebral arteries with one scan. Clinical translational hurdles are time demanding postprocessing and user-dependence induced variability during analysis. Materials and MethodsA CPS for 4D flow data was developed to automatically separate cerebral artery trees. Flow parameters were quantified at planes along the centerline oriented perpendicular to the vessel path. At 3T, validation against 2D phase-contrast (PC) magnetic resonance imaging (MRI) and 4D flow manual processing was performed on an intracranial flow phantom for constant flow, while pulsatile flow validation was performed in the internal carotid artery (ICA) of 10 healthy volunteers. The CPS and 4D manual processing times were measured and compared. Flow and area measurements were also demonstrated along the length of the ICA siphon. ResultsPhantom measurements for area and flow were highly correlated between the CPS and 2D measurements (area: R=0.95, flow: R=0.94), while in vivo waveforms were highly correlated (R=0.93). Processing time was reduced by a factor of 4.6 compared with manual processing. Whole ICA measurements revealed a significantly decreased area in the most distal segment of the carotid siphon (P=0.0017), with flow unchanged (P=0.84). ConclusionThis study exhibits fast semiautomated analysis of intracranial 4D flow MRI. Internal consistency was shown through flow conservation along the tortuous ICA siphon, which is typically difficult to assess. J. Magn. Reson. Imaging 2015;42:1458-1464.
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