| 1. |
- Good, Elin, 1983-
(författare)
-
Interrogating Atherosclerotic Plaque Biology Through Responses to Cardiovascular Risk Management and Imaging
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atherosclerosis causes more deaths than any other disease worldwide, and the cause of death is most commonly a rupture of a vulnerable atherosclerotic plaque, resulting in a thrombotic event in the heart or brain. The major risk factors for plaque progression are well known, but all the mechanisms that drive atherosclerotic plaques towards catastrophic events are not yet fully elucidated. This thesis revolves around the atherosclerotic plaque; how plaques can be analysed using cardiovascular magnetic resonance imaging and the study of biological responses to cardiovascular risk management. In Study I we interrogated the quality of cardiovascular risk management in patients diagnosed with high-grade carotid stenosis and found that cardiovascular risk management was deficient in all aspects, despite the very high risk for events in these patients. Thus, we designed the next two studies to address the unmet clinical need for improved cardiovascular risk management in patients with carotid atherosclerosis while at the same time asking mechanistic questions about the effect of this approach on lymphocyte phenotypes (Study II) and on plaque composition (Study III). In Study II, the effect of cardiovascular risk management on Natural Killer cell, Natural Killer T cell and T lymphocyte subpopulations were studied in patients with carotid atherosclerosis. Our results show a polarisation away from a senescent phenotype towards more naïve i.e., juvenile cell types suggesting a transition towards a possibly less pro-inflammatory lymphocyte profile. In Study III, we applied a newly developed quantitative Dixon MRI technique to the quantification of lipid rich necrotic core and hemorrhage inside atherosclerotic plaques. Employing this technique, we explored the relationships between these high-risk plaque compositional features and circulating lipoproteins as they changed over time in response to cardiovascular risk management. In the current study there was no evidence for such a linear relationship. To further study the associations between inflammation and quantitative plaque measurements we explored in Study IV the relationship between inflammation in atherosclerotic plaques as measured by 18F-FDG uptake and features of high-risk plaque as measured by quantitative Dixon MRI. To facilitate the use of carotid MRI in larger cohorts we developed in Study V a technique for the segmentation of the carotid artery using supervised machine learning. Taken together these studies describe the importance of cardiovascular risk management, the complexity of atherosclerotic plaque biology and they propose new strategies for quantitative plaque imaging.
|
|
| 2. |
- Ha, Hojin, et al.
(författare)
-
In-vitro and In-Vivo Assessment of 4D Flow MRI Reynolds Stress Mapping for Pulsatile Blood Flow
- 2021
-
Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media S.A.. - 2296-4185. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Imaging hemodynamics play an important role in the diagnosis of abnormal blood flow due to vascular and valvular diseases as well as in monitoring the recovery of normal blood flow after surgical or interventional treatment. Recently, characterization of turbulent blood flow using 4D flow magnetic resonance imaging (MRI) has been demonstrated by utilizing the changes in signal magnitude depending on intravoxel spin distribution. The imaging sequence was extended with a six-directional icosahedral (ICOSA6) flow-encoding to characterize all elements of the Reynolds stress tensor (RST) in turbulent blood flow. In the present study, we aimed to demonstrate the feasibility of full RST analysis using ICOSA6 4D flow MRI under physiological conditions. First, the turbulence analysis was performed through in vitro experiments with a physiological pulsatile flow condition. Second, a total of 12 normal subjects and one patient with severe aortic stenosis were analyzed using the same sequence. The in-vitro study showed that total turbulent kinetic energy (TKE) was less affected by the signal-to-noise ratio (SNR), however, maximum principal turbulence shear stress (MPTSS) and total turbulence production (TP) had a noise-induced bias. Smaller degree of the bias was observed for TP compared to MPTSS. In-vivo study showed that the subject-variability on turbulence quantification was relatively low for the consistent scan protocol. The in vivo demonstration of the stenosis patient showed that the turbulence analysis could clearly distinguish the difference in all turbulence parameters as they were at least an order of magnitude larger than those from the normal subjects.
|
|
| 3. |
- Sundin, Jonathan, et al.
(författare)
-
Turbulent Intensity of Blood Flow in the Healthy Aorta Increases With Dobutamine Stress and is Related to Cardiac Output
- 2022
-
Ingår i: Frontiers in Physiology. - : FRONTIERS MEDIA SA. - 1664-042X. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: The blood flow in the normal cardiovascular system is predominately laminar but operates close to the threshold to turbulence. Morphological distortions such as vascular and valvular stenosis can cause transition into turbulent blood flow, which in turn may cause damage to tissues in the cardiovascular system. A growing number of studies have used magnetic resonance imaging (MRI) to estimate the extent and degree of turbulent flow in different cardiovascular diseases. However, the way in which heart rate and inotropy affect turbulent flow has not been investigated. In this study we hypothesized that dobutamine stress would result in higher turbulence intensity in the healthy thoracic aorta.Method: 4D flow MRI data were acquired in twelve healthy subjects at rest and with dobutamine, which was infused until the heart rate increased by 60% when compared to rest. A semi-automatic segmentation method was used to segment the thoracic aorta in the 4D flow MR images. Subsequently, flow velocity and several turbulent kinetic energy (TKE) parameters were calculated in the ascending aorta, aortic arch, descending aorta and whole thoracic aorta.Results: With dobutamine infusion there was an increase in heart rate (66 +/- 9 vs. 108 +/- 13 bpm, p < 0.001) and stroke volume (88 +/- 13 vs. 102 +/- 25 ml, p < 0.01). Additionally, there was an increase in Peak Average velocity (0.7 +/- 0.1 vs. 1.2 +/- 0.2 m/s, p < 0.001, Peak Max velocity (1.3 +/- 0.1 vs. 2.0 +/- 0.2 m/s, p < 0.001), Peak Total TKE (2.9 +/- 0.7 vs. 8.0 +/- 2.2 mJ, p < 0.001), Peak Median TKE (36 +/- 7 vs. 93 +/- 24 J/m3, p = 0.002) and Peak Max TKE (176 +/- 33 vs. 334 +/- 69 J/m3, p < 0.001). The relation between cardiac output and Peak Total TKE in the whole thoracic aorta was very strong (R-2 = 0.90, p < 0.001).Conclusion: TKE of blood flow in the healthy thoracic aorta increases with dobutamine stress and is strongly related to cardiac output. Quantification of such turbulence intensity parameters with cardiac stress may serve as a risk assessment of aortic disease development.
|
|
| 4. |
- Viola, Federica, et al.
(författare)
-
Data Quality and Optimal Background Correction Order of Respiratory-Gated k-Space Segmented Spoiled Gradient Echo (SGRE) and Echo Planar Imaging (EPI)-Based 4D Flow MRI
- 2020
-
Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY. - 1053-1807 .- 1522-2586. ; 51:3, s. 885-896
-
Tidskriftsartikel (refereegranskat)abstract
- Background A reduction in scan time of 4D Flow MRI would facilitate clinical application. A recent study indicates that echo-planar imaging (EPI) 4D Flow MRI allows for a reduction in scan time and better data quality than the recommended k-space segmented spoiled gradient echo (SGRE) sequence. It was argued that the poor data quality of SGRE was related to the nonrecommended absence of respiratory motion compensation. However, data quality can also be affected by the background offset compensation. Purpose To compare the data quality of respiratory motion-compensated SGRE and EPI 4D Flow MRI and their dependence on background correction (BC) order. Study Type Retrospective. Subjects Eighteen healthy subjects (eight female, mean age 32 +/- 5 years). Field Strength and Sequence 5T. SGRE and EPI-based 4D Flow MRI. Assessment Data quality was investigated visually and by comparing flows through the cardiac valves and aorta. Measurements were obtained from transvalvular flow and pathline analysis. Statistical Tests Linear regression and Bland-Altman analysis were used. Wilcoxon test was used for comparison of visual scoring. Students t-test was used for comparison of flow volumes. Results No significant difference was found by visual inspection (P = 0.08). Left ventricular (LV) flows were strongly and very strongly associated with SGRE and EPI, respectively (R-2 = 0.86-0.94 SGRE; 0.71-0.79 EPI, BC0-4). LV and right ventricular (RV) outflows and LV pathline flows were very strongly associated (R-2 = 0.93-0.95 SGRE; 0.88-0.91 EPI, R-2 = 0.91-0.95 SGRE; 0.91-0.93 EPI, BC1-4). EPI LV outflow was lower than the short-axis-based stroke volume. EPI RV outflow and proximal descending aortic flow were lower than SGREs. Data Conclusion Both sequences yielded good internal data consistency when an adequate background correction was applied. Second and first BC order were considered sufficient for transvalvular flow analysis in SGRE and EPI, respectively. Higher BC orders were preferred for particle tracing. Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2019.
|
|
