Background It has been demonstrated that the rate of aortic dilatation is influenced by alteration of aortic hemodynamics, such as normalized flow displacement (FDN) and wall shear stress (WSS).... Show moreBackground It has been demonstrated that the rate of aortic dilatation is influenced by alteration of aortic hemodynamics, such as normalized flow displacement (FDN) and wall shear stress (WSS). However, the effects of ageing on aortic hemodynamics have not yet been described. Case summary 4D-Flow MRI derived aorta hemodynamics were derived in the ascending aorta of a patient with ascending aortic aneurysm (mean +/- standard deviation: 46 +/- 1 mm) and a healthy volunteer (aortic diameter 30 +/- 1 mm) with long-term follow-up of ten and eight years, respectively. At all timepoints, compared to the healthy volunteer, the patient demonstrated higher magnitudes of FDN (7% +/- 1% vs. 3% +/- 1%) and WSS angle (36 degrees +/- 3 degrees vs. 24 degrees +/- 6 degrees), and lower WSS magnitude (565 +/- 100 mPa vs. 910 +/- 115 mPa), axial WSS (426 +/- 71 mPa vs. 800 +/- 108 mPa) and circumferential WSS (297 +/- 64 mPa vs. 340 +/- 85 mPa). The patient and healthy volunteer demonstrated different aortic dilatation rates (regression slope +/- standard error: 0.2 +/- 0.1 vs. 0.1 +/- 0.2 mm per year) and trends in FDN (0.1% +/- 0.1% vs. 0.1% +/- 0.2% per year), WSS magnitude (22 +/- 9 vs. 35 +/- 13 mPa per year), axial WSS (19 +/- 4 vs. 37 +/- 7 mPa per year), circumferential WSS (9 +/- 8 vs. 5 +/- 15 mPa per year), and WSS angle (-0.5 degrees +/- 0.4 degrees vs. -0.8 degrees +/- 1.0 degrees per year). Discussion Aortic hemodynamic parameters are marginally affected by ageing and the aortic diameter in this case series. Since aortic hemodynamic parameters have been associated with aortic dilation by previous studies, the outcomes of the two subjects suggest that the aortic dilatation rate will remain constant while individuals are ageing and dilating. Show less
Acute aortic dissection is a rare, but potentially life-threatening and time-critical condition that is frequently misdiagnosed. Therefore, its prompt and proper diagnosis is vital to increase a... Show moreAcute aortic dissection is a rare, but potentially life-threatening and time-critical condition that is frequently misdiagnosed. Therefore, its prompt and proper diagnosis is vital to increase a patient's chance of survival and to prevent grievous complications. Raising awareness and educating the general population and healthcare professionals about an aortic dissection is mandatory, for early diagnosis and improving the chances of survival. Show less
In this study, we analyzed turbulent flows through a phantom (a 180 degrees bend with narrowing) at peak systole and a patient-specific coarctation of the aorta (CoA), with a pulsating flow, using... Show moreIn this study, we analyzed turbulent flows through a phantom (a 180 degrees bend with narrowing) at peak systole and a patient-specific coarctation of the aorta (CoA), with a pulsating flow, using magnetic resonance imaging (MRI) and computational fluid dynamics (CFD). For MRI, a 4D-flow MRI is performed using a 3T scanner. For CFD, the standard k - epsilon, shear stress transport k - omega, and Reynolds stress (RSM) models are applied. A good agreement between measured and simulated velocity is obtained for the phantom, especially for CFD with RSM. The wall shear stress (WSS) shows significant differences between CFD and MRI in absolute values, due to the limited near-wall resolution of MRI. However, normalized WSS shows qualitatively very similar distributions of the local values between MRI and CFD. Finally, a direct comparison between in vivo 4D-flow MRI and CFD with the RSM turbulence model is performed in the CoA. MRI can properly identify regions with locally elevated or suppressed WSS. If the exact values of the WSS are necessary, CFD is the preferred method. For future applications, we recommend the use of the combined MRI/CFD method for analysis and evaluation of the local flow patterns and WSS in the aorta. Show less
Background Cardiovascular guidelines recommend (bi-)annual computed tomography (CT) or magnetic resonance imaging (MRI) for surveillance of the diameter of thoracic aortic aneurysms (TAAs). However... Show moreBackground Cardiovascular guidelines recommend (bi-)annual computed tomography (CT) or magnetic resonance imaging (MRI) for surveillance of the diameter of thoracic aortic aneurysms (TAAs). However, no previous study has demonstrated the necessity for this approach. The current study aims to provide patient-specific intervals for imaging follow-up of non-syndromic TAAs. Methods A total of 332 patients with non-syndromic ascending aortic aneurysms were followed over a median period of 6.7 years. Diameters were assessed using all available imaging techniques (echocardiography, CT and MRI). Growth rates were calculated from the differences between the first and last examinations. The diagnostic accuracy of follow-up protocols was calculated as the percentage of subjects requiring pre-emptive surgery in whom timely identification would have occurred. Results The mean growth rate in our population was 0.2 +/- 0.4 mm/year. The highest recorded growth rate was 2.0 mm/year, while 40.6% of patients showed no diameter expansion during follow-up. Females exhibited significantly higher growth rates than men (0.3 +/- 0.5 vs 0.2 +/- 0.4 mm/year, p = 0.007). Conversely, a bicuspid aortic valve was not associated with more rapid aortic growth. The optimal imaging protocol comprises triennial imaging of aneurysms 40-49 mm in diameter and yearly imaging of those measuring 50-54 mm. This strategy is as accurate as annual follow-up, but reduces the number of imaging examinations by 29.9%. Conclusions In our population of patients with non-syndromic TAAs, we found aneurysm growth rates to be lower than those previously reported. Yearly imaging does not lead to changes in the management of small aneurysms. Thus, lower imaging frequencies might be a good alternative approach. Show less
Acute aortic syndromes comprise a group of potentially fatal conditions that result from weakening of the aortic vessel wall. Pre-emptive surgical intervention is currently reserved for patients... Show moreAcute aortic syndromes comprise a group of potentially fatal conditions that result from weakening of the aortic vessel wall. Pre-emptive surgical intervention is currently reserved for patients with severe aortic dilatation, although abundant evidence describes the occurrence of dissection and rupture in aortas with diameters below surgical thresholds. Modern imaging techniques (such as hybrid PET-CT and 4D flow MRI) afford the non-invasive assessment of anatomic, hemodynamic, and molecular features of the aorta, and may provide for a more accurate selection of patients who will benefit from preventative surgical intervention. In the current review, we summarize evidence and considerations regarding predictive aortic imaging and highlight evolving imaging modalities that have shown promise to improve risk assessment for the occurrence of dissection and rupture.Key PointsGuidelines for the preventative management of aortic disease depend on maximal vessel diameters, while these have shown to be poor predictors for the occurrence of catastrophic acute aortic events.Evolving imaging modalities (such as 4D flow MRI and hybrid PET-CT) afford a more comprehensive insight into anatomic, hemodynamic, and molecular features of the aorta and have shown promise to detect vessel wall instability at an early stage. Show less
BackgroundA velocity offset error in phase contrast cardiovascular magnetic resonance (CMR) imaging is a known problem in clinical assessment of flow volumes in vessels around the heart. Earlier... Show moreBackgroundA velocity offset error in phase contrast cardiovascular magnetic resonance (CMR) imaging is a known problem in clinical assessment of flow volumes in vessels around the heart. Earlier studies have shown that this offset error is clinically relevant over different systems, and cannot be removed by protocol optimization. Correction methods using phantom measurements are time consuming, and assume reproducibility of the offsets which is not the case for all systems. An alternative previously published solution is to correct the in-vivo data in post-processing, interpolating the velocity offset from stationary tissue within the field-of-view. This study aims to validate this interpolation-based offset correction in-vivo in a multi-vendor, multi-center setup.MethodsData from six 1.5T CMR systems were evaluated, with two systems from each of the three main vendors. At each system aortic and main pulmonary artery 2D flow studies were acquired during routine clinical or research examinations, with an additional phantom measurement using identical acquisition parameters. To verify the phantom acquisition, a region-of-interest (ROI) at stationary tissue in the thorax wall was placed and compared between in-vivo and phantom measurements. Interpolation-based offset correction was performed on the in-vivo data, after manually excluding regions of spatial wraparound. Correction performance of different spatial orders of interpolation planes was evaluated.ResultsA total of 126 flow measurements in 82 subjects were included. At the thorax wall the agreement between in-vivo and phantom was -0.20.6cm/s. Twenty-eight studies were excluded because of a difference at the thorax wall exceeding 0.6cm/s from the phantom scan, leaving 98. Before correction, the offset at the vessel as assessed in the phantom was -0.41.5cm/s, which resulted in a-5 +/- 16% error in cardiac output. The optimal order of the interpolation correction plane was 1st order, except for one system at which a 2nd order plane was required. Application of the interpolation-based correction revealed a remaining offset velocity of 0.1 +/- 0.5cm/s and 0 +/- 5% error in cardiac output.Conclusions p id=Par4 This study shows that interpolation-based offset correction reduces the offset with comparable efficacy as phantom measurement phase offset correction, without the time penalty imposed by phantom scans.Trial registration p id=Par5 The study was registered in The Netherlands National Trial Register (NTR) under TC 4865. Registered 19 September 2014. Retrospectively registered. Show less
A dedicated software package that could semi-automatically assess differences in aortic maximal cross-sectional diameters from consecutive CT scans would most likely reduce the post-processing time... Show moreA dedicated software package that could semi-automatically assess differences in aortic maximal cross-sectional diameters from consecutive CT scans would most likely reduce the post-processing time and effort by the physicians. The aim of this study was to present and assess the quality of a new tool for the semi-automatic quantification of thoracic aorta dilation dimensions. Twenty-nine patients with two CTA scans of the thoracic aorta for which the official clinical report indicated an increase in aortic diameters were included in the study. Aortic maximal cross-sectional diameters of baseline and follow-up studies generated semi-automatically by the software were compared with corresponding manual measurements. The semi-automatic measurements were performed at seven landmarks defined on the baseline scan by two operators. Bias, Bland-Altman plots and intraclass correlation coefficients were calculated between the two methods and, for the semi-automatic software, also between two observers. The average time difference between the two scans of a single patient was 1188 +/- 622 days. For the semi-automatic software, in 2 out of 29 patients, manual interaction was necessary; in the remaining 27 patients (93.1%), semi-automatic results were generated, demonstrating excellent intraclass correlation coefficients (all values0.91) and small differences, especially for the proximal aortic arch (baseline: 0.19 +/- 1.30mm; follow-up: 0.44 +/- 2.21mm), the mid descending aorta (0.37 +/- 1.64mm; 0.37 +/- 2.06mm), and the diaphragm (0.30 +/- 1.14mm; 0.37 +/- 1.80mm). The inter-observer variability was low with all errors in diameters1mm, and intraclass correlation coefficients all 0.95. The semi-automatic tool decreased the processing time by 40% (13 vs. 22min). In this work, a semi-automatic software package that allows the assessment of thoracic aorta diameters from baseline and follow-up CTs (and their differences), was presented, and demonstrated high accuracy and low inter-observer variability. Show less
Brouwers, J.J.W.M.; Baetens, T.R.; Schaik, J. van 2018
The prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than... Show moreThe prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than half a billion adults worldwide are classed as obese. The fundamental cause of obesity is an imbalance between energy intake (excessive intake of energy-dense foods) and energy expenditure (reduced physical activity). People with obesity are at risk for a range of chronic conditions including cardiovascular disease (CVD) and nonalcoholic fatty liver disease (NAFLD). Furthermore, obesity is a major risk factor for the development of type 2 diabetes, which is one of the most common chronic diseases in nearly all countries. According to the World Health Organization, the global prevalence of diabetes in 2014 was estimated to be 9%, of which 90% was comprised of type 2 diabetes. This thesis focuses on cardiovascular and cerebral dimensions and function in people with obesity and type 2 diabetes. State-of-the-art imaging techniques are used to investigate links between the heart, liver, abdominal fat, and brain to elucidate parts of the complex relationships between these organs. Show less
Halushka, M.K.; Angelini, A.; Bartoloni, G.; Basso, C.; Batoroeva, L.; Bruneval, P.; ... ; Wal, A.C. van der 2016
This thesis evaluates morphological and functional vessel wall properties measured by magnetic resonance imaging techniques in healthy volunteers and patients with various diseases (i.e. Marfan... Show moreThis thesis evaluates morphological and functional vessel wall properties measured by magnetic resonance imaging techniques in healthy volunteers and patients with various diseases (i.e. Marfan syndrome patients (MFS), patients with thoracic aortic aneurysm and patients with a previous myocardial infarction.). This thesis shows that imaging of carotid vessel wall morphology can be reproducible assessed by high-field MRI and that carotid vessel wall imaging benefits from imaging at higher field strengths. For a functional imaging parameter, the aorta pulse wave velocity (PWV), improving spatial sampling density resulted in more accurate PWV-assessment, even when temporal resolution decreased. Moreover, a scan-time reduction was achieved. Aortic PWV showed a high specificity for predicting absence of regional aortic luminal growth for all aortic segments in MFS. In patients with thoracic aortic aneurysm, regional PWV showed high specificity in the descending thoracic to abdominal aorta and moderate results in the ascending aorta and aortic arch. Next, PWV-leveling between aorta and carotid artery at older age was associated with a reduction in blood flow volume towards the brain. Furthermore, vessel wall morphology and function were associated in healthy volunteers and in patients with established atherosclerotic disease. Finally, our findings might indicate a link between atherosclerotic large vessel disease and cerebral small vessel disease in patients with established atherosclerotic disease. Show less
The prevalence of aortic dilation and related complications as rupture and dissection is higher in patients with a bicuspid aortic valve (BAV) as compared to patients with a tricuspid aortic valve ... Show moreThe prevalence of aortic dilation and related complications as rupture and dissection is higher in patients with a bicuspid aortic valve (BAV) as compared to patients with a tricuspid aortic valve (TAV), although not every individual carries this increased risk. It is therefore essential to identify those patients who are less susceptible for aortic wall pathology, as preventive ascending aortic surgery would not be necessary in this group. Since aortic diameter as a criterion for surgery is only decisive at population level, it would be very valuable to have tailored risk stratification at patient level. The purpose of this thesis was therefore to investigate the possibility to identify patients with BAV, without apparent dilation, with an increased susceptibility for future complications as aortic dilation and dissection. Furthermore the biological mechanism underlying aortic wall pathology in BAV was compared to a known genetically determined syndrome with an increased risk of aortopathy being Marfan syndrome. Show less
