Fully automated on-scanner aortic four-dimensional flow magnetic resonance imaging processing and hemodynamic analysis

BackgroundWe hypothesize that dobutamine-induced stress impacts intracardiac hemodynamic parameters and that this may be linked to decreased exercise capacity in Fontan patients. Therefore, the purpose of this study was to assess the effect of pharmacologic stress on intraventricular kinetic energy (KE), viscous energy loss (EL) and vorticity from four-dimensional (4D) Flow cardiovascular magnetic resonance (CMR) imaging in Fontan patients and to study the association between stress response and exercise capacity.MethodsTen Fontan patients underwent whole-heart 4D flow CMR before and during 7.5 μg/kg/min dobutamine infusion and cardiopulmonary exercise testing (CPET) on the same day. Average ventricular KE, EL and vorticity were computed over systole, diastole and the total cardiac cycle (vorticity_volavg cycle, KEavg cycle, ELavg cycle). The relation to maximum oxygen uptake (VO2 max) from CPET was tested by Pearson’s correlation or Spearman’s rank correlation in case of non-normality of the data.ResultsDobutamine stress caused a significant 88 ± 52% increase in KE (KEavg cycle: 1.8 ± 0.5 vs 3.3 ± 0.9 mJ, P < 0.001), a significant 108 ± 49% increase in EL (ELavg cycle: 0.9 ± 0.4 vs 1.9 ± 0.9 mW, P < 0.001) and a significant 27 ± 19% increase in vorticity (vorticity_volavg cycle: 3441 ± 899 vs 4394 ± 1322 mL/s, P = 0.002). All rest-stress differences (%) were negatively correlated to VO2 max (KEavg cycle: r = − 0.83, P = 0.003; ELavg cycle: r = − 0.80, P = 0.006; vorticity_volavg cycle: r = − 0.64, P = 0.047).Conclusions4D flow CMR-derived intraventricular kinetic energy, viscous energy loss and vorticity in Fontan patients increase during pharmacologic stress and show a negative correlation with exercise capacity measured by VO2 max.

Background: The assessment of left ventricular (LV) mechanical synchrony using phase analysis (PA) provides incremental diagnostic value over conventional indicators and is widely used in clinical practice. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has emerged as an imaging technique to visualize blood flow dynamics. Intra-LV kinetic energy (KE) obtained from 4D-CMR is a novel parameter refers to the quantification of the energy associated with the motion of blood within LV. This study aimed to simultaneously investigate the relationship between LV mechanical synchrony and intra-LV blood flow energy in patients with ischemic heart disease (IHD), using hybrid PET/MR system. Methods: Sixty-six patients (mean age 67 years, male 54) who underwent rest-pharmacological stress 13 N ammonia PET and 4D flow CMR at our hospital between January 2022 and February 2024 were included. Left ventricular ejection fraction (LVEF), PA parameters including histogram bandwidth (BW), phase standard deviation (PSD), and entropy were obtained from rest and stress gated PET. Perfusion defect was assessed as summed defect score from rest and stress static PET images. Intra-LV 4D flow MR acquisition was simultaneously performed for rest and stress. Intra-LV blood flow KE indexed with end-diastolic volume (KEi mJ/mL) was obtained from dynamic 4D flow curve. Results: BW[KF1] was 24.6 ± 17.9 and 24.4 ± 15.4%, PSD was 6.2 ± 3.7 and 6.2 ± 3.5, entropy was 61.6 ± 7.9 and 60.3 ± 9.3 for rest and stress, respectively. Summed defect score was 6.1 ± 7.1 and 11.2 ± 9.4 for rest and stress. KEi[KF2] was 0.018 ± 0.01, and 0.019 ± 0.01 (mJ/mL) for rest and stress. A significant positive correlation was observed between LVEF and KEi at both rest (R=0.30, P=0.014) and stress (R=0.42, P&lt;0.001). Summed defect score was not significantly correlated with KEi at either rest or stress. All PA parameters demonstrated a weak inverse correlation with KEi at rest (BW: R= –0.29, P=0.019; PSD R = –0.27, P=0.026; entropy R = –0.27, P=0.031) and stress (BW: R= –0.28, P=0.023; PSD R = –0.36, P=0.003; entropy R = –0.31, P=0.010). Conclusions: PET-derived PA parameters were significantly associated with intra-LV blood flow KE, suggesting impaired LV mechanical synchrony is linked to intra-LV blood flow energy insufficiency.

To evaluate the intra-cavity left ventricular (LV) blood flow kinetic energy (KE) parameters using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) in patients with hypertension (HTN). Forty-two HTN patients and twenty age-/gender-matched healthy controls who underwent CMR including cines, pre-/post-T1 mapping, and whole-heart 4D flow imaging were retrospectively evaluated. HTN patients were further divided into two subgroups: with preserved ejection fraction (HTN-pEF) and with reduced ejection fraction (HTN-rEF). KE parameters were indexed to LV end-diastolic volume (EDV) to obtain averaged LV, minimal, systolic, diastolic, peak E-wave, peak A-wave, E-wave, and A-wave KEiEDV, as well as the proportion of in-plane LV KE (%), the time difference (TD). These parameters were compared between the HTN group and healthy controls, also between two subgroups. The correlation of LV blood flow KE parameters with LV function and extracellular volume fraction (ECV) were analyzed in the HTN group using multivariate regression analysis. Peak E-wave KEiEDV in the HTN group was significantly lower (p = 0.01), while in-plane KE and TD were significantly higher (all p < 0.01) than those in healthy controls. Compared to the HTN-pEF subgroup, the proportion of in-plane KE and TD was significantly increased in the HTN-rEF subgroup (all p < 0.01). Only the proportion of in-plane KE demonstrated an independent correlation with ECV (β* = 0.59, p < 0.01). The decreased peak E-wave KEiEDV and the increased proportion of in-plane KE, TD reflected the alterations of LV blood flow in HTN patients, and the proportion of in-plane KE was independently associated with ECV. • 4D flow CMR demonstrated that the peak E-wave KEiEDV was decreased, while the in-plane KE and time difference (TD) were increased in hypertensive (HTN) patients. • The proportion of in-plane KE and TD was further increased in HTN patients with reduced ejection fraction than in HTN patients with preserved ejection fraction, and the proportion of in-plane KE was independently associated with extracellular volume fraction in HTN patients. • 4D flow CMR intra-cavity blood flow KE parameters might reveal the LV hemodynamic status in preclinical HTN patients.

Pulmonary arterial hypertension is a severe complication of systemic lupus erythematosus (SLE). Current screening methods often miss early vascular changes. This study aimed to characterize subclinical pulmonary hemodynamic alterations in SLE patients without known pulmonary arterial hypertension using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) and to investigate their association with left ventricular diastolic function. Twenty-five SLE patients without known pulmonary arterial hypertension and 25 age-matched healthy controls were enrolled. All participants underwent 3-T 4D flow CMR to quantify hemodynamic parameters, including wall shear stress (WSS), flow volume, and relative pressure in the pulmonary arteries. SLE patients were further stratified based on echocardiographic assessment of diastolic function to analyze hemodynamic coupling. Compared to controls, SLE patients exhibited significantly lower maximum WSS in the main pulmonary artery (0.29 versus 0.33 Pa, p = 0.040) and asymmetric flow redistribution, characterized by higher relative pressure in the left pulmonary artery (0.54 versus 0.30 mmHg, p = 0.008) and increased flow rate in the right pulmonary artery (3.51 versus 2.90 L/min, p = 0.015). Qualitative analysis revealed vortical flow patterns in SLE patients. Subgroup analysis demonstrated that the reduction in WSS was primarily driven by patients with diastolic dysfunction (p = 0.006 versus controls). SLE patients without pulmonary arterial hypertension exhibit distinct subclinical pulmonary hemodynamic alterations, including lower WSS and flow asymmetry. These alterations are intimately coupled with left ventricular diastolic dysfunction, suggesting that 4D flow CMR serves as a sensitive noninvasive tool for early risk stratification in this population. 4D flow CMR identifies subclinical pulmonary hemodynamic alterations coupled with diastolic dysfunction in SLE patients, serving as a sensitive noninvasive tool for early risk stratification before irreversible vascular remodeling occurs. SLE patients without known pulmonary arterial hypertension show early pulmonary blood flow changes. 4D flow CMR detected asymmetric pulmonary flow redistribution in SLE patients. SLE patients exhibited altered left atrial function despite normal ventricles. Pulmonary flow changes correlated with left atrial remodeling in SLE. 4D flow CMR detects subclinical pulmonary hemodynamic differences in SLE.

BackgroundIn the field of cardiovascular imaging, four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) provides non-invasive assessment of blood flow. Dual velocity encoding (dual-VENC) strategies have emerged to obtain quantitative information on both low and high blood flow velocities simultaneously. However, these strategies often encounter difficulties in coping with large velocity ranges. This work presents a dual-VENC 4D flow CMR sequence that utilizes the coprime rule to define the VENC ratio.MethodsA dual-VENC 4D flow CMR sequence and reconstruction algorithm were developed and validated in vitro at two different field strengths, using a flow phantom generating realistic complex flow patterns. A digital twin of the phantom allowed comparison of the MRI measurements with computational fluid dynamics (CFD) simulations. Three patients with different cardiac pathologies were scanned in order to evaluate the in vivo feasibility of the proposed method.ResultsThe results of the in vitro acquisitions demonstrated significant improvement in velocity-to-noise ratio (VNR) with respect to single-VENC acquisitions (110 ± 3%) and conventional dual-VENC de-aliasing approach (75 ± 3%). Furthermore, the effectiveness of aliasing correction was demonstrated even when both sets of images from the dual-VENC acquisition presented velocity aliasing artifacts. We observed a high degree of agreement between the measured and simulated velocity fields.ConclusionThe strength of this approach lies in the fact that, unlike the conventional de-aliasing method, no data is discarded. The final image is obtained by a weighted average of the VENClow and VENChigh datasets. Consequently, setting the value of the VENChigh to prevent aliasing is no longer necessary, and higher VNR gains are possible

The article "Assessment of superior mesenteric vascular flow quantitation in children using four-dimensional flow magnetic resonance imaging" suggests to use of four-dimensional (4D) flow magnetic resonance imaging (MRI) which is also to measure the blood flow in the superior mesenteric vein (SMV) in pediatric patients over the traditional method. The study focuses on assessing the potential of SMV and superior mesenteric artery (SMA) flow quantification in children utilizing 4D flow MRI. It included 9 pediatric patients aged 18 years and below where 5 were male and 4 were female patients, on whom magnetic resonance enterorrhaphy (MRE) with 4D flow MRI protocol was used. Statistical analysis was performed using MedCalc. Measurements of SMV and SMA between two readers were calculated using Bland-Altman analysis. The results stated that six patients showed no MRE evidence of active inflammatory bowel disease, two patients showed unmarkable bowel appearance on MRI and one patient showed normal MRE without endoscopy performed at the same timeframe. The study utilized available 4D flow MRI sequences in this study aiming to show the feasibility of 4D flow quantitation of SMA and SMV flow in pediatric patients. The study also discovered good agreement for both peak velocity and peak speed measurements of SMA and SMV.

Hemodynamic evaluation using four-dimensional flow magnetic resonance imaging for a patient with multichanneled aortic dissection

Foetal circulation undergoes complex changes in congenital heart disease (CHD) that are challenging to assess with foetal echocardiography. This study aimed to assess clinical feasibility and diagnostic value of 4D flow cardiovascular magnetic resonance (CMR) in foetal CHD. Pregnant women in advanced third trimester pregnancy with foetal CHD were prospectively recruited for foetal CMR between August 2021 and November 2024. CMR protocol included cine and 4D time-resolved PC acquisitions. 4D flow data were evaluated for additional diagnostic information beyond cine imaging. Postnatal examination reports were used to confirm CMR findings. Net flow was quantified in the ascending aorta, distal aortic arch, main pulmonary artery, ductus arteriosus, and descending aorta and normalized to combined ventricular output (CVO). Student's t-test and analysis of variance with Tukey post hoc test were applied. Among 77 participants, 4D flow was of diagnostic quality in 62 (81%) foetuses [11/62 (18%) without CHD, 51/62 (82%) with CHD]. Comparison of net flow distributions revealed significant differences between foetuses without CHD and those with hypoplastic left heart complex (HLHC), dextro-transposition of the great arteries, and coarctation of the aorta. CVO was higher in normal foetal circulation compared with CHD (6.4 ± 1.5 mL vs. 5.1 ± 1.9 mL, P = 0.049). 4D flow provided diagnostic findings beyond cine imaging in 26/51 (51%) foetuses with CHD (e.g. retrograde aortic perfusion in HLHC) that were confirmed postnatally. Foetal 4D flow CMR characterizes flow patterns and provides relevant diagnostic information beyond cine imaging for prenatal CHD assessment.

IntroductionAltered haemodynamic flow patterns in the aorta are linked with increased risk of bicuspid aortic valve (BAV)-associated aortopathy.1–3 Using 4D-flow cardiovascular magnetic resonance (4DF-CMR), we assessed whether our novel 3D...

Background: Four-dimensional (4D) flow cardiovascular magnetic resonance imaging (MRI) is an emerging technique used for intra-cardiac blood flow assessment. The role of 4D flow cardiovascular MRI in the assessment of trans-valvular flow in patients with atrial fibrillation (AF) has not previously been assessed. The purpose of this study was to assess the feasibility, image quality, and internal validity of 4D flow cardiovascular MRI in the quantification of trans-valvular flow in patients with AF. Methods: Patients with AF and healthy controls in sinus rhythm underwent cardiovascular MRI, including 4D flow studies. Quality assurance checks were done on the raw data and streamlines. Consistency was investigated by trans-valvular flow assessment between the mitral valve (MV) and the aortic valve (AV). Results: Eight patients with AF (88% male, mean age 62±13 years, mean heart rate (HR) 83±16 beats per minute (bpm)) were included and compared with ten healthy controls (70% male, mean age 41±20 years, mean HR 68.5±9 bpm). All scans were of either good quality with minimal blurring artefacts, or excellent quality with no artefacts. No significant bias was observed between the AV and MV stroke volumes in either healthy controls (-4.8, 95% CI -15.64 to 6.04; P=0.34) or in patients with AF (1.64, 95% CI -4.7 to 7.94; P=0.56). A significant correlation was demonstrated between MV and AV stroke volumes in both healthy controls (r=0.87, 95% CI 0.52 to 0.97; P=0.001) and in AF patients (r=0.82, 95% CI 0.26 to 0.97; P=0.01). Conclusions: In patients with AF, 4D flow cardiovascular MRI is feasible with good image quality, allowing for quantification of trans-valvular flow.

Background: Four-dimensional (4D) flow cardiovascular magnetic resonance imaging (MRI) is an emerging technique used for intra-cardiac blood flow assessment. The role of 4D flow cardiovascular MRI in the assessment of trans-valvular flow in patients with atrial fibrillation (AF) has not previously been assessed. The purpose of this study was to assess the feasibility, image quality, and internal validity of 4D flow cardiovascular MRI in the quantification of trans-valvular flow in patients with AF. Methods: Patients with AF and healthy controls in sinus rhythm underwent cardiovascular MRI, including 4D flow studies. Quality assurance checks were done on the raw data and streamlines. Consistency was investigated by trans-valvular flow assessment between the mitral valve (MV) and the aortic valve (AV). Results: Eight patients with AF (88% male, mean age 62±13 years, mean heart rate (HR) 83±16 beats per minute (bpm)) were included and compared with ten healthy controls (70% male, mean age 41±20 years, mean HR 68.5±9 bpm). All scans were of either good quality with minimal blurring artefacts, or excellent quality with no artefacts. No significant bias was observed between the AV and MV stroke volumes in either healthy controls (–4.8, 95% CI –15.64 to 6.04; P=0.34) or in patients with AF (1.64, 95% CI –4.7 to 7.94; P=0.56). A significant correlation was demonstrated between MV and AV stroke volumes in both healthy controls (r=0.87, 95% CI 0.52 to 0.97; P=0.001) and in AF patients (r=0.82, 95% CI 0.26 to 0.97; P=0.01). Conclusions: In patients with AF, 4D flow cardiovascular MRI is feasible with good image quality, allowing for quantification of trans-valvular flow.

Background: Four-dimensional (4D) flow cardiovascular magnetic resonance imaging (MRI) is an emerging technique used for intra-cardiac blood flow assessment. The role of 4D flow cardiovascular MRI in the assessment of trans-valvular flow in patients with atrial fibrillation (AF) has not previously been assessed. The purpose of this study was to assess the feasibility, image quality, and internal validity of 4D flow cardiovascular MRI in the quantification of trans-valvular flow in patients with AF. Methods: Patients with AF and healthy controls in sinus rhythm underwent cardiovascular MRI, including 4D flow studies. Quality assurance checks were done on the raw data and streamlines. Consistency was investigated by trans-valvular flow assessment between the mitral valve (MV) and the aortic valve (AV). Results: Eight patients with AF (88% male, mean age 62±13 years, mean heart rate (HR) 83±16 beats per minute (bpm)) were included and compared with ten healthy controls (70% male, mean age 41±20 years, mean HR 68.5±9 bpm). All scans were of either good quality with minimal blurring artefacts, or excellent quality with no artefacts. No significant bias was observed between the AV and MV stroke volumes in either healthy controls (–4.8, 95% CI –15.64 to 6.04; P=0.34) or in patients with AF (1.64, 95% CI –4.7 to 7.94; P=0.56). A significant correlation was demonstrated between MV and AV stroke volumes in both healthy controls (r=0.87, 95% CI 0.52 to 0.97; P=0.001) and in AF patients (r=0.82, 95% CI 0.26 to 0.97; P=0.01). Conclusions: In patients with AF, 4D flow cardiovascular MRI is feasible with good image quality, allowing for quantification of trans-valvular flow.

Staged palliation with the creation of a Fontan circulation is the standard surgical approach in patients with a single ventricle. The Fontan circulation is a complex circuit that is associated with various complications that may present early or later in life and can limit life quality and expectancy. In this context, a good understanding of the Fontan physiology is important to improve outcomes for single-ventricle patients. Cardiovascular magnetic resonance (CMR) is recommended for the long-term follow-up of Fontan patients, as it provides functional and haemodynamic information. Four-dimensional (4D) Flow MRI is a time-resolved, three-dimensional, velocity-encoded cardiovascular magnetic resonance technique that is increasingly used in Fontan patients because it not only enables measuring blood flow within a three-dimensional (3D) volume, but also allows for assessing more advanced haemodynamic parameters that may help in understanding the Fontan physiology and pathophysiology. Furthermore, 4D Flow is used for image-based simulations using computational fluid dynamics. In this review, we provide an overview of the use of cardiovascular magnetic resonance flow assessment, with a focus on four-dimensional flow ('4D Flow').

A test–retest multisite reproducibility study of cardiovascular four-dimensional flow MRI without respiratory gating

Objectives: Four-dimensional (4D) flow cardiac magnetic resonance (CMR) represents an emerging technique for non-invasive evaluation of the aortic flow. The aim of this study was to investigate a 4D-flow CMR sequence for the assessment of thoracic aorta comparing different vendors and different magnetic fields of MR scanner in fifteen healthy volunteers. Methods: CMR was performed on three different MRI scanners: one at 1.5 T and two at 3 T. Flow parameters and planar wall shear stress (WSS) were extracted from six transversal planes along the full thoracic aorta by three operators. Inter-vendor comparability as well as scan–rescan, intra- and interobserver reproducibility were examined. Results: A high heterogeneity was found in the comparisons for each operator and for each scanner in the six transversal planes analysis (Friedman rank-sum test; p-value ≤ 0.05). Among all, the most reproducible measures were extracted for the sinotubular junction plane and for the flow parameters. Conclusions: Our results suggest that standardized procedures have to be defined to make more comparable and reproducible 4D-flow parameters and mainly, clinical impactfulness. Further studies on sequences development are needed to validate 4D-flow MRI assessment across vendors and magnetic fields also compared to a missing gold standard.