Phase-contrast Cine Research Articles

Abstract 24: Effects Of Intensive Blood Pressure Lowering on Brain Tissue Pulsatility in Hypertensive Patients

Recent studies have shown an association between blood pressure (BP), particularly pulse pressure (PP), in increasing brain tissue pulsatility. However, these studies were conducted in a phantom model or in healthy normotensive adults. Effects of intensive BP lowering on brain tissue pulsatility in hypertensive patients remain unknown. Accordingly, we performed a randomized clinical trial to compare effects of intensive BP lowering to target 24-h ambulatory BP <120/70 mmHg (n=26) vs. target of <130/80 mmHg in the control arm (n =19) in hypertensive patients aged 55-79 with normal cognitive function. The brain tissue pulsatility was assessed by the total tissue motion over one cardiac cycle, using CINE phase contrast MRI, with the velocity encoded in all three directions. In each cardiac cycle, the velocity of the tissue was measured at 16 time points. Brain tissue pulsatility was assessed at baseline and after 1 year of follow up. We found that 24-h ambulatory systolic BP (SBP) was reduced from 134.3±9.8 to 112.1±7.2 mmHg in the intensive arm and from 138.5±11.3 to 122.4±7.8 mmHg in the control arm (both p<0.01). The magnitude of 24-h SBP reduction from baseline was greater in the intensive arm than control arm (23.6 vs. 13.1 mmHg, p=0.052) while 24-h diastolic BP was reduced similarly in both groups (11.6 vs. 9.6 mmHg, p=0.8). Similarly, PP based on 24-h BP was reduced from 57.5±11.7 to 45.1±12.1 mmHg in the intensive BP arm and from 62.2±10.6 to 55.4±10.5 mmHg in the control arm (both p<0.01). The magnitude of PP reduction appeared greater in the intensive compared to control arm but was not statistically different (12.4 vs. 6.8 mmHg, p=0.08). We found that the overall gray-white matter tissue pulsatility per cardiac cycle remained unchanged after 12 months in the intensive arm (0.98±0.18 mm to 0.95±0.17 mm) while the brain pulsatility tended to increase in the control arm (0.85±0.17 mm to 0.92±0.16 mm, p=0.09 for treatment group, interaction-p=0.04). Similarly, the white matter (WM) tissue motion remained unchanged in the intensive arm (0.91±0.16 mm to 0.88±0.15 mm) while the WM pulsatility tended to increase in the control arm (from 0.77±0.14 mm to 0.84±0.15 mm, p=0.06 for group, interaction p=0.03). In conclusion, our data suggested a novel effect of intensive BP lowering in preventing the rise in brain tissue pulsatility in hypertensive patients, which may have an implication in the prevention of an accelerated brain injury related to hypertension.

Prognostic value of global coronary flow reserve before and after elective percutaneous coronary intervention in patients with chronic coronary syndrome

BackgroundImpaired global coronary flow reserve (G-CFR), evaluated through phase-contrast cine cardiovascular magnetic resonance (PC-CMR), has been linked to worse outcomes in patients with cardiovascular disease. This study aimed to investigate the prognostic value of G-CFR improvement, as evaluated using PC-CMR imaging pre- and post-percutaneous coronary intervention (PCI). MethodsIn this single-center study, 320 patients with chronic coronary syndrome (CCS) who underwent pre- and post-PCI PC-CMR measurements were followed-up to determine major adverse cardiac or cerebrovascular events (MACCE) predictors. MACCE was defined as a composite of cardiac death, nonfatal myocardial infarction, hospitalization due to heart failure, or ischemic stroke. The association between CMR parameters, including baseline data, G-CFR changes post-PCI and MACCE was investigated. ResultsG-CFR improvement was observed in 165 (51.6%) patients, while MACCE occurred in 26 (8.1%) during a median follow-up period of 2.5 years. G-CFR improvement was significantly associated with a lower pre-PCI G-CFR. The log-rank test revealed a significant association between patients without G-CFR improvement post-PCI and a poor prognosis. Patients with lower pre-PCI G-CFR and lack of G-CFR improvement exhibited the highest incidence of MACCE. The multivariable Cox proportional hazard model revealed that lack of G-CFR improvement was an independently significant MACCE predictor from pre-PCI G-CFR and SYNTAX score. ConclusionsBesides the association between pre- and post-PCI lower G-CFR and worse prognosis, the presence or absence of G-CFR improvement post-PCI may provide novel insights into the prognosis following elective PCI in patients with CCS.

CMR provides comparable measurements of diastolic function as echocardiography

Clinical application of cardiac magnetic resonance (CMR) is expanding but CMR assessment of LV diastolic function is still being validated. The purpose of this study was to validate assessments of left ventricular (LV) diastolic dysfunction (DD) using CMR by comparing with transthoracic echocardiography (TTE) performed on the same day. Patients with suspected or diagnosed cardiomyopathy (n = 63) and healthy volunteers (n = 24) were prospectively recruited and included in the study. CMR diastolic parameters were measured on cine images and velocity-encoded phase contrast cine images and compared with corresponding parameters measured on TTE. A contextual correlation feature tracking method was developed to calculate the mitral annular velocity curve. LV DD was classified by CMR and TTE following 2016 guidelines. Overall DD classification was 78.1% concordant between CMR and TTE (p < 0.0001). The trans-mitral inflow parameters correlated well between the two modalities (E, r = 0.78; A, r = 0.90; E/A, r = 0.82; all p < 0.0001) while the remaining diastolic parameters showed moderate correlation (e’, r = 0.64; E/e’, r = 0.54; left atrial volume index (LAVi), r = 0.61; all p < 0.0001). Classification of LV diastolic function by CMR showed good concordance with standardized grades established for TTE. CMR-based LV diastolic function may be integrated in routine clinical practice.Name of the registry: Technical Development of Cardiovascular Magnetic Resonance Imaging. Trial registration number: NCT00027170. Date of registration: November 26, 2001. URL of trial registry record: https://clinicaltrials.gov/ct2/show/NCT00027170

Unwrapping phase contrast MRI by iterative graph cuts.

To develop and evaluate a phase unwrapping method for cine phase contrast MRI based on graph cuts. A proposed Iterative Graph Cuts method was evaluated in 10 cardiac patients with two-dimensional flow quantification which was repeated at low venc settings to provoke wrapping. The images were also unwrapped by a path-following method (ROMEO), and a Laplacian-based method (LP). Net flow was quantified using semi-automatic vessel segmentation. High venc images were also wrapped retrospectively to asses the residual amount of wrapped voxels. The absolute net flow error after unwrapping at venc = 100cm/s was 1.8mL, which was 0.83mL smaller than for LP. The repeatability error at high venc without unwrapping was 2.5mL. The error at venc = 50cm/s was 7.5mL, which was 8.2mL smaller than for ROMEO and 5.7mL smaller than for LP. For retrospectively wrapped images with synthetic venc of 100/50/25cm/s, the residual amount of wrapped voxels was 0.00/0.12/0.79%, which was 0.09/0.26/8.0percentage points smaller than for LP. With synthetic venc of 25cm/s, omitting magnitude information resulted in 3.2 percentage points more wrapped voxels, and only spatial/temporal unwrapping resulted in 4.6/21 percentage points more wrapped voxels compared to spatiotemporal unwrapping. Iterative Graph Cuts enables unwrapping of cine phase contrast MRI with very small errors, except for at extreme blood velocities, with equal or better performance compared to ROMEO and LP. The use of magnitude information and spatiotemporal unwrapping is recommended.

Comparison of Echo-Planar Imaging and Compressed Sensing in the Estimation of Flow Metrics from Aortic 4D Flow MR Imaging: A Healthy Volunteer Study.

Prolonged scanning of time-resolved 3D phase-contrast MRI (4D flow MRI) limits its routine use in clinical practice. An echo-planar imaging (EPI)-based sequence and compressed sensing can reduce the scan duration. We aimed to determine the impact of EPI for 4D flow MRI on the scan duration, image quality, and quantitative flow metrics. This was a prospective study of 15 healthy volunteers (all male, mean age 33 ± 5 years). Conventional sensitivity encoding (SENSE), EPI with SENSE (EPI), and compressed SENSE (CS) (reduction factors: 6 and 12, respectively) were scanned.Scan duration, qualitative indexes of image quality, and quantitative flow parameters of net flow volume, maximum flow velocity, wall shear stress (WSS), and energy loss (EL) in the ascending aorta were assessed. Two-dimensional phase-contrast cine MRI (2D-PC) was considered the gold standard of net flow volume and maximum flow velocity. Compared to SENSE, EPI and CS12 shortened scan durations by 71% and 73% (EPI, 4 min 39 sec; CS6, 7 min 29 sec; CS12, 4 min 14 sec; and SENSE, 15 min 51 sec). Visual image quality was significantly better for EPI than for SENSE and CS (P < 0.001). The net flow volumes obtained with SENSE, EPI, and CS12 and those obtained with 2D-PC were correlated well (r = 0.950, 0.871, and 0.850, respectively). However, the maximum velocity obtained with EPI was significantly underestimated (P < 0.010). The average WSS was significantly higher with EPI than with SENSE, CS6, and CS12 (P < 0.001, P = 0.040, and P = 0.012, respectively). The EL was significantly lower with EPI than with CS6 and CS12 (P = 0.002 and P = 0.007, respectively). EPI reduced the scan duration, improved visual image quality, and was associated with more accurate net flow volume than CS. However, the flow velocity, WSS, and EL values obtained with EPI and other sequences may not be directly comparable.

MRI Quantification of Left Atrial Circumferential Strain in Mitral Regurgitation: A Feasibility and Reproducibility Study.

MRI-derived left atrial (LA) longitudinal strain has been shown to be a marker for mitral regurgitation, but the utility of LA circumferential strain remains unclear. To assess feasibility and reproducibility of LA circumferential strain, identify changes in mitral regurgitation patients compared to healthy volunteers, and determine strain's association with mitral regurgitation severity and cardiac function. Retrospective. 52 mitral regurgitation patients, 12 healthy volunteers. Steady-state free precession cine and 2D phase contrast sequences at 1.5T. Peak LA circumferential strain was computed in each of three short-axis slices (superior, mid, and inferior) and longitudinal strain computed from long-axis slices using MRI feature-tracking software. Strain test-retest reproducibility was determined from two repeat studies in healthy volunteers. LA circumferential strain test-retest reproducibility was assessed by intra-class correlation coefficient (ICC). Strain was compared between cohorts using Student's t-test or Mann-Whitney U. Mitral regurgitation severity association with strain and LV function was assessed using Spearman correlation and multivariable regression. Significance was defined as P < 0.05. LA circumferential strain assessment was feasible in all subjects with moderate reproducibility in the superior (ICC = 0.74), mid LA (ICC = 0.71), and inferior LA (ICC = 0.63). In mitral regurgitation patients, LA circumferential strain was significantly lower in the superior (11.86% [6.5%,19.2%] vs. 18.73% ± 6.7%) and mid LA slices (18.41% ± 9.5% vs. 28.7% ± 10.4%) compared to healthy volunteers. Mitral regurgitation severity significantly associated with mid LA circumferential strain (β = -0.03) and LAV significantly associated with superior LA circumferential strain (β = -2.09), both independent of LA longitudinal strain and CO. LA circumferential strain assessment is feasible with moderate reproducibility. Compared to healthy volunteers, patients had significantly lower LA circumferential strain. Mitral regurgitation severity and LAV were significantly associated with LA circumferential strain independent of LA longitudinal strain. 3 TECHNICAL EFFICACY: Stage 2.

Prognostic value of global coronary flow reserve improvement after percutaneous coronary intervention in patients with chronic coronary syndrome

Abstract Background Impaired global coronary flow reserve (g-CFR) evaluated by phase-contrast cine cardiovascular magnetic resonance (PC-CMR) has been reported to be associated with worse outcomes in patients with cardiovascular disease. Purpose This study aimed to evaluate the prognostic value of g-CFR improvement evaluated by PC-CMR in patients with chronic coronary syndrome (CCS). Methods A total of 320 patients with CCS who underwent pre- and post-PCI PC-CMR measurements and stress perfusion CMR were followed-up to determine the predictors of major adverse cardiovascular events (MACE). The association between CMR variables including changes in G-CFR after PCI and MACE (cardiac death, nonfatal myocardial infarction, hospitalization for heart failure, or ischemic stroke) was investigated. Results G-CFR improvement was observed in 162 (50.6%) and MACE occurred in 26 (8.1%) during follow-up (2.5 year, 1.3-4.0). G-CFR improvement was significantly associated with lower pre-PCI G-CFR (p&amp;lt;0.001). Patients with MACE showed lower pre-PCI G-CFR, a high prevalence of post-PCI positive stress perfusion, non-G-CFR improvement. In Kaplan-Meier analysis, patients without G-CFR improvement were significantly associated with poor prognosis (log-rank χ2=5.8, P=0.018). After adjusting the presence of post-PCI positive stress perfusion, non-G-CFR improvement was an independent predictor of MACE (P=0.007). Conclusion In addition to the association between lower pre-PCI G-CFR and worse prognosis, G-CFR improvement after PCI may provide a novel insight into the prognosis after PCI in patients with CCS.Kaplan-Meier analysis

Abstract 17366: Effects of Acute Maternal Supplemental Oxygen on the Fetal Circulation in Transposition of the Great Arteries

Introduction: The presence of a restrictive atrial septum in the setting of transposition of the great arteries (TGA) is associated with a high risk of hypoxic ischemic injury upon transition to postnatal circulation. Fetal cardiovascular magnetic resonance (CMR) measures of vessel flow and oxygen saturation provide a unique opportunity to study fetal TGA hemodynamics at baseline and during acute maternal hyperoxygenation. Methods: Thirty-one pregnant mothers with fetuses diagnosed with TGA and an intact ventricular septum (n=23) or small ventricular septal defect (n=8) were recruited and underwent fetal CMR in room air and during administration of 10L/min of oxygen by face mask for up to 45 minutes. Blood flow and oxygen saturations were measured in the major fetal vessels using cine phase contrast MRI and MR relaxometry at baseline and during hyperoxygenation. Results: Two patients exhibited severe restriction at the atrial septum, one undergoing fetal atrial septostomy at 37 weeks and one requiring cannulation onto ECMO shortly after birth. Both revealed reversal of the usual relationship of oxygen saturation between the aorta and the main pulmonary artery at baseline and during hyperoxygenation, i.e. in TGA with restrictive atrial septum the saturations are higher in the aorta than pulmonary. Acute maternal supplemental oxygen was associated with increased pulmonary blood flow (p=0.008) and reduced foramen ovale (p=0.01) and ductus arteriosus shunting (p=0.01). There were no significant changes in umbilical vein, descending aorta and superior vena cava flow. Fetal oxygen saturations increased throughout fetal circulation (p&lt;0.0001) with an associated increase in fetal oxygen delivery (p=0.007), but no increase in fetal cerebral oxygen delivery (p=0.58). Conclusions: This study characterized the effects of acute maternal supplemental oxygen on the fetal circulation in patients with TGA and confirmed the redistribution of flow toward the fetal pulmonary circulation. We observed higher oxygen saturations in the aorta than main pulmonary artery in fetuses with TGA with an intact or highly restrictive atrial septal communication. This finding could be helpful in selecting patients for prenatal or emergency neonatal balloon atrial septostomy.

Impact of compressed sensing (CS) acceleration of two-dimensional (2D) flow sequences in clinical paediatric cardiovascular magnetic resonance (CMR)

ObjectivesTwo-dimensional (2D) through-plane phase-contrast (PC) cine flow imaging assesses shunts and valve regurgitations in paediatric CMR and is considered the reference standard for Clinical quantification of blood Flow (COF). However, longer breath-holds (BH) can reduce compliance with possibly large respiratory manoeuvres altering flow. We hypothesize that reduced BH time by application of CS (Short BH quantification of Flow) (SBOF) retains accuracy while enabling faster, potentially more reliable flows. We investigate the variance between COF and SBOF cine flows.MethodsMain pulmonary artery (MPA) and sinotubular junction (STJ) planes were acquired at 1.5 T in paediatric patients by COF and SBOF.Results21 patients (mean age 13.9, 10–17y) were enrolled. The BH times were COF mean 11.7 s (range 8.4–20.9 s) vs SBOF mean 6.5 s (min 3.6–9.1 s). The differences and 95% CI between the COF and SBOF flows were LVSV -1.43 ± 13.6(ml/beat), LVCO 0.16 ± 1.35(l/min) and RVSV 2.95 ± 12.3(ml/beat), RVCO 0.27 ± 0.96(l/min), QP/QS were SV 0.04 ± 0.19, CO 0.02 ± 0.23. Variability between COF and SBOF did not exceed intrasession variation of COF.ConclusionSBOF reduces breath-hold duration to 56% of COF. RV flow by SBOF was biased compared to COF. The variation (95% CI) between COF and SBOF was similar to the COF intrasession test–retest 95% CI.

Building a comprehensive cardiovascular magnetic resonance exam on a commercial 0.55 T system: A pictorial essay on potential applications.

Contemporary advances in low-field magnetic resonance imaging systems can potentially widen access to cardiovascular magnetic resonance (CMR) imaging. We present our initial experience in building a comprehensive CMR protocol on a commercial 0.55 T system with a gradient performance of 26 mT/m amplitude and 45 T/m/s slew rate. To achieve sufficient image quality, we adapted standard imaging techniques when possible, and implemented compressed-sensing (CS) based techniques when needed in an effort to compensate for the inherently low signal-to-noise ratio at lower field strength. A prototype CMR exam was built on an 80 cm, ultra-wide bore commercial 0.55 T MR system. Implementation of all components aimed to overcome the inherently lower signal of low-field and the relatively longer echo and repetition times owing to the slower gradients. CS-based breath-held and real-time cine imaging was built utilizing high acceleration rates to meet nominal spatial and temporal resolution recommendations. Similarly, CS 2D phase-contrast cine was implemented for flow. Dark-blood turbo spin echo sequences with deep learning based denoising were implemented for morphology assessment. Magnetization-prepared single-shot myocardial mapping techniques incorporated additional source images. CS-based dynamic contrast-enhanced imaging was implemented for myocardial perfusion and 3D MR angiography. Non-contrast 3D MR angiography was built with electrocardiogram-triggered, navigator-gated magnetization-prepared methods. Late gadolinium enhanced (LGE) tissue characterization methods included breath-held segmented and free-breathing single-shot imaging with motion correction and averaging using an increased number of source images. Proof-of-concept was demonstrated through porcine infarct model, healthy volunteer, and patient scans. Reasonable image quality was demonstrated for cardiovascular structure, function, flow, and LGE assessment. Low-field afforded utilization of higher flip angles for cine and MR angiography. CS-based techniques were able to overcome gradient speed limitations and meet spatial and temporal resolution recommendations with imaging times comparable to higher performance scanners. Tissue mapping and perfusion imaging require further development. We implemented cardiac applications demonstrating the potential for comprehensive CMR on a novel commercial 0.55 T system. Further development and validation studies are needed before this technology can be applied clinically.

Potential of non-contrast stress T1 mapping for the assessment of myocardial injury in hypertrophic cardiomyopathy

BackgroundIschemia of the hypertrophied myocardium due to microvascular dysfunction is related to a worse prognosis in hypertrophic cardiomyopathy (HCM). Stress and rest T1 mapping without contrast agents can be used to assess myocardial blood flow. Herein, we evaluated the potential of non-contrast stress T1 mapping in assessing myocardial injury in patients with HCM. MethodsForty-five consecutive subjects (31 HCM patients and 14 control subjects) underwent cardiac magnetic resonance (CMR) at 3T, including cine imaging, T1 mapping at rest and during adenosine triphosphate (ATP) stress, late gadolinium enhancement (LGE), and phase-contrast (PC) cine imaging of coronary sinus flow at rest and during stress to assess coronary flow reserve (CFR). PC cine imaging was performed on 25 subjects (17 patients with HCM and 8 control subjects). Native T1 values at rest and during stress were measured using the 16-segment model, and T1 reactivity was defined as the change in T1 values from rest to stress. ResultsATP stress induced a significant increase in native T1 values in both the HCM and control groups (HCM: p < 0.001, control: p = 0.002). T1 reactivity in the HCM group was significantly lower than that in the control group (4.2 ± 0.3% vs. 5.6 ± 0.5%, p = 0.044). On univariate analysis, T1 reactivity correlated with native T1 values at rest, left ventricular mass index, and CFR. Multiple linear regression analysis demonstrated that only CFR was independently correlated with T1 reactivity (β = 0.449; 95% confidence interval, 0.048–0.932; p = 0.032). Furthermore, segmental analysis showed decreased T1 reactivity in the hypertrophied myocardium and the non-hypertrophied myocardium with LGE in the HCM group. ConclusionsT1 reactivity was lower in the hypertrophied myocardium and LGE-positive myocardium compared to non-injured myocardium. Non-contrast stress T1 mapping is a promising CMR method for assessing myocardial injury in patients with HCM.Trial registration Retrospectively registered.

Coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance imaging of coronary sinus: a meta-analysis

BackgroundPhase-contrast cine cardiovascular magnetic resonance (CMR) of the coronary sinus has emerged as a non-invasive method for measuring coronary sinus blood flow and coronary flow reserve (CFR). However, its clinical utility has not yet been established. Here we performed a meta-analysis to clarify the clinical value of CMR-derived CFR in various cardiovascular diseases. MethodsAn electronic database search was performed of PubMed, Web of Science Core Collection, Cochrane Advanced Search, and EMBASE. We compared the CMR-derived CFR of various cardiovascular diseases (stable coronary artery disease [CAD], hypertrophic cardiomyopathy [HCM], dilated cardiomyopathy [DCM]) and control subjects. We assessed the prognostic value of CMR-derived CFR for predicting major adverse cardiac events (MACE) in patients with stable CAD. ResultsA total of 47 eligible studies were identified. The pooled CFR from our meta-analysis was 3.48 (95% confidence interval [CI], 2.98–3.98) in control subjects, 2.50 (95% CI, 2.38–2.61) in stable CAD, 2.01 (95% CI, 1.70–2.32) in cardiomyopathies (HCM and DCM). The meta-analysis showed that CFR was significantly reduced in stable CAD (mean difference [MD] = −1.48; 95% CI, −1.78 to −1.17; p < 0.001; I2 = 0%; p for heterogeneity = 0.33), HCM (MD = −1.20; 95% CI, −1.63 to −0.77; p < 0.001; I2 = 0%; p for heterogeneity = 0.49), and DCM (MD = −1.53; 95% CI, −1.93 to −1.13; p < 0.001; I2 = 0%; p for heterogeneity = 0.45). CMR-derived CFR was an independent predictor of MACE for patients with stable CAD (hazard ratio = 0.52 per unit increase; 95% CI, 0.37–0.73; p < 0.001; I2 = 84%, p for heterogeneity < 0.001). ConclusionsCMR-derived CFR was significantly decreased in cardiovascular diseases, and a decreased CFR was associated with a higher occurrence of MACE in patients with stable CAD. These results suggest that CMR-derived CFR has potential for the pathological evaluation of stable CAD, cardiomyopathy, and risk stratification in CAD.

Microvascular Dysfunction in Patients with Idiopathic Dilated Cardiomyopathy: Quantitative Assessment with Phase Contrast Cine MR Imaging of the Coronary Sinus.

The purposes of this study were to compare global coronary flow reserve (CFR) between patients with idiopathic dilated cardiomyopathy (DCM) and risk-matched controls using cardiac MRI (CMR), and to evaluate the relationship between global CFR and CMR left ventricular (LV) parameters. Twenty-six patients with DCM and 26 risk-matched controls who underwent comprehensive CMR examination, including stress-rest coronary sinus flow measurement by phase contrast (PC) cine CMR were retrospectively studied. LV peak global longitudinal, radial, and circumferential strains (GLS, GRS, and GCS) were determined by feature tracking. Patients with DCM had significantly lower global CFR compared with the risk-matched controls (2.87 ± 0.86 vs. 4.03 ± 1.47, P = 0.001). Among the parameters, univariate linear regression analyses revealed significant correlation of global CFR with LV end-diastolic volume index (r = -0.396, P = 0.045), LV mass index (r = -0.461, P = 0.018), GLS (r = -0.558, P = 0.003), and GRS (r = 0.392, P = 0.047). Multiple linear regression analysis revealed GLS as the only independent predictor of global CFR (standardized β = -0.558, P = 0.003). Global CFR was significantly impaired in patients with idiopathic DCM and independently associated with LV GLS, suggesting that microvascular dysfunction may contribute to deterioration of LV function in patients with idiopathic DCM.

Endoscopic Third Ventriculostomy for the Management of Chiari I and related Hydrocephalus: Evaluation of CSF Flow Dynamics with Fast Phase-Contrast Cine MRI.

Endoscopic Third Ventriculostomy for the Management of Chiari I and related Hydrocephalus: Evaluation of CSF Flow Dynamics with Fast Phase-Contrast Cine MRI.

Right Ventricular Remodeling Assessed by MRI in Duchenne Muscular Dystrophy.

In Duchenne muscular dystrophy (DMD), the right ventricle (RV) tends to be relatively well preserved, but characterization remains difficult due to its complex architecture. Tissue phase mapping (TPM) is a phase contrast cine MRI technique that allows for multidirectional assessment of myocardial velocities. To use TPM to elucidate relationships between myocardial structure, function, and clinical variables in DMD. Retrospective. A total of 20 patients with muscular dystrophy (median age: 16 years); 18 age-matched normal controls (median age: 15 years). Three-directional velocity encoded cine gradient echo sequence (TPM) at 1.5T, balanced steady-state free procession (bSSFP), T1 mapping with extracellular volume (ECV), and late gadolinium enhancement (LGE). TPM in basal, mid, and apical short-axis planes was performed as part of a standard MRI study with collection of clinical data. Radial, circumferential, and longitudinal velocities (Vr, Vφ, and Vz, respectively) and corresponding time to peak (TTP) velocities were quantified from TPM and used to calculate RV twist as well as intraventricular and interventricular dyssynchrony. The correlations between TPM velocities, myocardial structure/function, and clinical variables were assessed. Unpaired t-test, Wilcoxon rank-sum test, Bland-Altman analyses were used for comparisons between DMD patients and controls and between DMD subgroups. Pearson's test was used for correlations (r). Significance level: P< 0.05. Compared to controls, DMD patients had preserved RV ejection fraction (RVEF 53% ± 8%) but significantly increased interventricular dyssynchrony (Vφ: 0.49 ± 0.21 vs. 0.72 ± 0.17). Within the DMD cohort, RV dyssynchrony significantly increased with lower LV ejection fraction (intraventricular Vr and Vz: r=-0.49; interventricular Vz: r=0.48). In addition, RV intraventricular dyssynchrony significantly increased with older age (Vz: r=0.67). RV remodeling in DMD occurs in the context of preserved RVEF. Within DMD, this abnormal RV deformation is associated with older age and decreased LVEF. 4. Stage 2.

Fully-automated deep learning-based flow quantification of 2D CINE phase contrast MRI

ObjectivesTime-resolved, 2D-phase-contrast MRI (2D-CINE-PC-MRI) enables in vivo blood flow analysis. However, accurate vessel contour delineation (VCD) is required to achieve reliable results. We sought to evaluate manual analysis (MA) compared to the performance of a deep learning (DL) application for fully-automated VCD and flow quantification and corrected semi-automated analysis (corSAA).MethodsWe included 97 consecutive patients (age = 52.9 ± 16 years, 41 female) with 2D-CINE-PC-MRI imaging on 1.5T MRI systems at sinotubular junction (STJ), and 28/97 also received 2D-CINE-PC at main pulmonary artery (PA). A cardiovascular radiologist performed MA (reference) and corSAA (built-in tool) in commercial software for all cardiac time frames (median: 20, total contours per analysis: 2358 STJ, 680 PA). DL-analysis automatically performed VCD, followed by net flow (NF) and peak velocity (PV) quantification. Contours were compared using Dice similarity coefficients (DSC). Discrepant cases (> ± 10 mL or > ± 10 cm/s) were reviewed in detail.ResultsDL was successfully applied to 97% (121/125) of the 2D-CINE-PC-MRI series (STJ: 95/97, 98%, PA: 26/28, 93%). Compared to MA, mean DSC were 0.91 ± 0.02 (DL), 0.94 ± 0.02 (corSAA) at STJ, and 0.85 ± 0.08 (DL), 0.93 ± 0.02 (corSAA) at PA; this indicated good to excellent DL-performance. Flow quantification revealed similar NF at STJ (p = 0.48) and PA (p > 0.05) between methods while PV assessment was significantly different (STJ: p < 0.001, PA: p = 0.04). A detailed review showed noisy voxels in MA and corSAA impacted PV results. Overall, DL analysis compared to human assessments was accurate in 113/121 (93.4%) cases.ConclusionsFully-automated DL-analysis of 2D-CINE-PC-MRI provided flow quantification at STJ and PA at expert level in > 93% of cases with results being available instantaneously.Key Points• Deep learning performed flow quantification on clinical 2D-CINE-PC series at the sinotubular junction and pulmonary artery at the expert level in > 93% of cases.• Location detection and contouring of the vessel boundaries were performed fully-automatic with results being available instantaneously compared to human assessments which approximately takes three minutes per location.• The evaluated tool indicates usability in daily practice.

Impact of compressed sensing (CS) acceleration of two-dimensional (2D) flow sequences in clinical paediatric cardiac magnetic resonance (CMR)

Abstract Background Two-dimensional (2D) through-plane phase-contrast (PC) cine flow imaging assesses shunts and valve regurgitations in paediatric CMR, and is considered the reference standard for Clinical quantification Of blood Flow (COF). However, the longer breath-hold (BH) for a flow cine can reduce patient compliance with possibly large respiratory maneuvers altering flow. Compressed sensing (CS) flow has not been widely evaluated in pediatric clinical CMR, although CS flow reduces scan time with persistent accuracy [1–3]. Kocaoglu et al applied CS to ascending and descending aorta and SVC with good results. We used main pulmonary artery (MPA) and sinotubular junction (STJ) planes as usual for clinical CMR. Purpose We hypothesise that reduced BH time by modest application of CS to 2D cine through-plane flows (Short BH quantification of Flow) (SBOF) retains accuracy while enabling faster and potentially more reliable paediatric flows. We therefore investigate the variance between conventional COF and new SBOF cine flows in paediatric CMR. Methods Paediatric patients were enrolled. Aortic (AO) and MPA COFs were planned from cines of the left and right ventricular outflow tracts. For AO flow the plane was placed at the STJ, and MPA flow was acquired above the pulmonary valve. The same planes were used for COF and SBOF flows at nominally similar parameters except the moderate application of CS exploiting redundancy across the cine frames, SBOF being segmented CS cines not real-time. CVI42 (5.10; Circle CVI) was used for flow analysis (single observer, 3 years' experience). Paired t-tests found the overall differences, and variability was defined at ±2SD for STJSV, MPASV, STJCO, MPACO, and Qp/Qs. Results and discussion 20 patients (mean age 13.7, range 10–17y) were enrolled (12 CHDs, 7 cardiomyopathies or other diseases). The BH times were COF mean 11.7s (range 8.4–20.9s) vs SBOF mean 6.5s (min 3.6–9.1s). For STJ flows the differences and variabilities between the COF and SBOF flows were SV 6.95±13.6 (ml/beat), CO 0.16±1.35 (l/min) and for MPA flows SV 2.95±12.3 (ml/beat), CO 0.27±0.96 (l/min) and for Qp/Qs were 0.04±0.19 by ml/beat and 0.02±0.23 by l/min. The mean differences were non significant, and variability between SBOF and COF was similar to intrasession repeatability of COF in a separate paediatric population at our centre (unpublished), that might arise from physiological flow changes, possibly in terms of pre and post load and heart rate. With shorter BHs also assisting patient compliance of the SBOF, physiological flow effects might be reduced, although given the variability in COV this was unconfirmed. Conclusion Moderate CS applied to clinical segmented-cine paediatric phase-contrast flows in the STJ and MPA planes did not degrade flow repeatability or cause bias. SBOF assists clinical flows by shorter BHs and also may aid compliance and reduce physiological variations. Funding Acknowledgement Type of funding sources: None.

Influence of the area of the aqueduct and region of interest on quantification of stroke volume in healthy volunteers using phase-contrast cine magnetic resonance imaging.

Phase-contrast cine magnetic resonance imaging (PC-MRI) has been used to measure cerebrospinal fluid (CSF) flow dynamics, but the influence of the area of the aqueduct and region of interest (ROI) on quantification of stroke volume (SV) has not been assessed. To assess the influence of the area of the ROI in quantifying the aqueductal SV measured with PC-MRI within the cerebral aqueduct. Nine healthy volunteers (mean age = 29.6 years) were enrolled in the study, and brain MRI examinations were performed on a 3.0-T system. Quantitative analysis of the aqueductal CSF flow was performed using manual ROI placement. ROIs were separately drawn for each of the 12 phases of the cardiac cycle, and changes in aqueduct size during the cardiac cycle were determined. The SV was calculated using 12 different aqueductal ROIs and compared with the SV calculated using a fixed ROI size. There was variation in the size of the aqueduct during the cardiac cycle. In addition, the measured SV increased with a greater area of the ROI. A significant difference in the calculated SVs with the 12 variable ROIs was observed compared with that using a fixed ROI throughout the cardiac cycle. To establish reliable reference values for the SV in future studies, a variable ROI should be considered.

Surgical Management of Chiari Malformation Type I Associated with Syringomyelia: Outcome of Surgeries Based on the New Classification and Study of Cerebrospinal Fluid Dynamics.

Introduction: The mainstay of treatment of syringomyelia associated with Chiari malformation type I (CM-I) is the management of CM-I to normalize the cerebrospinal fluid (CSF) flow at the foramen magnum. CM-I is classified into three independent types. Surgical treatment was selected based on the mechanism of hindbrain ptosis in each CM-I type. Materials and Methods: Foramen magnum decompression (FMD: 213 cases), expansive suboccipital cranioplasty (ESCP: 87 cases), and craniocervical fixation (CCF: 30 cases) were performed. CSF flow dynamics were assessed pre- and post-surgery using cine phase contrast magnetic resonance imaging. During surgery, CSF flow dynamics were examined using color Doppler ultrasonography (CDU). Results: ESCP and FMD demonstrated high rates of improvement in neurological symptoms and signs (82.7%), whereas CCF demonstrated a high rate of improvement in neurological symptoms (89%). The pre-operative maximum flow velocity (cm/s) was significantly lower in patients than in controls and increased post-operatively. During surgery, CDU indicated that the volume of the major cistern was 8 mL, and the maximum flow velocity was >3 mL/s. Conclusions: An appropriate surgical treatment should be selected for CM-I to correct hindbrain ptosis. In addition, it is necessary to confirm the normalization of CSF flow at the foramen of Magendie.

Deep Learning-based Automated Aortic Area and Distensibility Assessment: the Multi-Ethnic Study of Atherosclerosis (MESA).

This study details application of deep learning for automatic segmentation of the ascending and descending aorta from 2D phase-contrast cine magnetic resonance imaging for automatic aortic analysis on the large MESA cohort with assessment on an external cohort of thoracic aortic aneurysm (TAA) patients. This study includes images and corresponding analysis of the ascending and descending aorta at the pulmonary artery bifurcation from the MESA study. Train, validation, and internal test sets consisted of 1123 studies (24,282 images), 374 studies (8067 images), and 375 studies (8069 images), respectively. The external test set of TAAs consisted of 37 studies (3224 images). CNN performance was evaluated utilizing a dice coefficient and concordance correlation coefficients (CCC) of geometric parameters. Dice coefficients were as high as 97.55% (CI: 97.47-97.62%) and 93.56% (CI: 84.63-96.68%) on the internal and external test of TAAs, respectively. CCC for maximum and minimum and ascending aortic area were 0.969 and 0.950, respectively, on the internal test set and 0.997 and 0.995, respectively, for the external test. The absolute differences between manual and deep learning segmentations for ascending and descending aortic distensibility were 0.0194 × 10-4 ± 9.67 × 10-4 and 0.002 ± 0.001mmHg-1, respectively, on the internal test set and 0.44 × 10-4 ± 20.4 × 10-4 and 0.002 ± 0.001mmHg-1, respectively, on the external test set. We successfully developed a U-Net-based aortic segmentation and analysis algorithm in both MESA and in external cases of TAA.