lGeneralized super-resolution 4D Flow MRI-using ensemble learning to extend across the cardiovascular system.

4D Flow Magnetic Resonance Imaging (4D Flow MRI) is a non-invasive measurement technique capable of quantifying blood flow across the cardiovascular system. While practical use is limited by spatial resolution and image noise, incorporation of trained super-resolution (SR) networks has potential to enhance image quality post-scan. However, these efforts have predominantly been restricted to narrowly defined cardiovascular domains, with limited exploration of how SR performance extends across the cardiovascular system; a task aggravated by contrasting hemodynamic conditions apparent across the cardiovasculature. The aim of our study was to explore the generalizability of SR 4D Flow MRI using a combination of heterogeneous training sets and dedicated ensemble learning. With synthetic training data generated across three disparate domains (cardiac, aortic, cerebrovascular), varying convolutional base and ensemble learners were evaluated as a function of domain and architecture, quantifying performance on both in-silico and acquired in-vivo data from the same three domains. Results show that both bagging and stacking ensembling enhance SR performance across domains, accurately predicting high-resolution velocities from low-resolution input data in-silico. Likewise, optimized networks successfully recover native resolution velocities from downsampled in-vivo data, as well as show qualitative potential in generating denoised SR-images from clinicallevel input data. In conclusion, our work presents a viable approach for generalized SR 4D Flow MRI, with ensemble learning extending utility across various clinical areas of interest.

Prognostic utility and characterization of left ventricular hypertrophy using global thickness.

Cardiovascular magnetic resonance (CMR) can accurately measure left ventricular (LV) mass, and several measures related to LV wall thickness exist. We hypothesized that prognosis can be used to select an optimal measure of wall thickness for characterizing LV hypertrophy. Subjects having undergone CMR were studied (cardiac patients, n = 2543; healthy volunteers, n = 100). A new measure, global wall thickness (GT, GTI if indexed to body surface area) was accurately calculated from LV mass and end-diastolic volume. Among patients with follow-up (n = 1575, median follow-up 5.4 years), the most predictive measure of death or hospitalization for heart failure was LV mass index (LVMI) (hazard ratio (HR)[95% confidence interval] 1.16[1.12-1.20], p < 0.001), followed by GTI (HR 1.14[1.09-1.19], p < 0.001). Among patients with normal findings (n = 326, median follow-up 5.8 years), the most predictive measure was GT (HR 1.62[1.35-1.94], p < 0.001). GT and LVMI could characterize patients as having a normal LV mass and wall thickness, concentric remodeling, concentric hypertrophy, or eccentric hypertrophy, and the three abnormal groups had worse prognosis than the normal group (p < 0.05 for all). LV mass is highly prognostic when mass is elevated, but GT is easily and accurately calculated, and adds value and discrimination amongst those with normal LV mass (early disease).

Three-dimensional sector-wise golden angle-improved k-space uniformity after electrocardiogram binning.

PURPOSE: To develop and evaluate a 3D sector-wise golden-angle (3D-SWIG) profile ordering scheme for cardiovascular MR cine imaging that maintains high k-space uniformity after electrocardiogram (ECG) binning. METHOD: Cardiovascular MR (CMR) was performed at 1.5 T. A balanced SSFP pulse sequence was implemented with a novel 3D-SWIG radial ordering, where k-space was divided into wedges, and each wedge was acquired in a separate heartbeat. The high uniformity of k-space coverage after physiological binning can be used to perform functional imaging using a very short acquisition. The 3D-SWIG was compared with two commonly used 3D radial trajectories for CMR (i.e., double golden angle and spiral phyllotaxis) in numerical simulations. Free-breathing 3D-SWIG and conventional breath-held 2D cine were compared in patients (n = 17) referred clinically for CMR. Quantitative comparison was performed based on left ventricular segmentation. RESULTS: Numerical simulations showed that 3D-SWIG both required smaller steps between successive readouts and achieved better k-space sampling uniformity after binning than either the double golden angle or spiral phyllotaxis trajectories. In vivo evaluation showed that measurements of left ventricular ejection fraction calculated from a 48 heart-beat free-breathing 3D-SWIG acquisition were highly reproducible and agreed with breath-held 2D-Cartesian cine (mean ± SD difference of -3.1 ± 3.5% points). CONCLUSIONS: The 3D-SWIG acquisition offers a simple solution for highly improved k-space uniformity after physiological binning. The feasibility of the 3D-SWIG method is demonstrated in this study through whole-heart cine imaging during free breathing with an acquisition time of less than 1 min.

Diffusely Increased Myocardial Extracellular Volume With or Without Focal Late Gadolinium Enhancement: Prevalence and Associations With Left Ventricular Size and Function.

PURPOSE: Myocardial extracellular volume fraction (ECV) using cardiovascular magnetic resonance (CMR) can identify diffuse lesions not detected by late gadolinium enhancement (LGE). We aimed to determine the prevalence of increased ECV and its relation to other CMR findings. MATERIALS AND METHODS: Consecutive patients (n=609, age median [interquartile range] 53 [39 to 66] y, 62% male) underwent CMR at 1.5 T. Focal lesions on LGE images were noted. ECV in regions without focal LGE findings defined diffuse changes. Pronounced increases in left ventricular (LV) end-diastolic volume index and LV mass index, and pronounced decreases in LV ejection fraction were defined as >3 SD from the sex-specific mean in healthy volunteers. RESULTS: Of 609 patients without amyloidosis or hypertrophic cardiomyopathy, 8% had diffusely increased ECV and 5% of all patients had diffusely increased ECV without any focal LGE findings. Multivariate analysis showed that a pronounced increase in the LV end-diastolic volume index was associated with increased ECV (P=0.001), but not LGE (P=0.52). A pronounced decrease in LV ejection fraction was associated with the presence of LGE (P<0.001), but not with increased ECV (P=0.41). CONCLUSIONS: Eight percent of patients in this clinical cohort with known or suspected heart disease had diffusely increased ECV and 60% of these lacked focal LGE findings. LV size is independently associated with increased ECV, whereas systolic dysfunction is independently associated with LGE. This image-based clinical study demonstrates that ECV-CMR provides additional information negligibly related to the results of LGE imaging, and thereby increases the diagnostic yield of CMR.

Generalization of three-dimensional golden-angle radial acquisition to reduce eddy current artifacts in bSSFP CMR imaging.

PURPOSE: We propose a novel generalization of the three-dimensional double-golden-angle profile ordering, which allows for whole-heart volumetric imaging with retrospective binning and reduced eddy current artifacts. METHODS: A novel theory bridging the gap between the three-dimensional double golden-angle trajectory, and the two-dimensional tiny-golden-angle trajectory is presented. This enables a class of double golden-angle profile orderings with a smaller angular distance between successive k-space readouts. The novel profile orderings were evaluated through simulations, phantom experiments, and in vivo imaging. Comparisons were made to the original double-golden-angle trajectory. Image uniformity and off-resonance sensitivity were evaluated using phantom measurements, and qualitative image quality was assessed using in vivo images acquired in a healthy volunteer. RESULTS: The proposed theory successfully reduced the angular step while maintaining image uniformity after binning. Simulations revealed a slow degradation with decreasing angular steps and an increasing number of physiological bins. The phantom images showed a definite improvement in image uniformity and increased robustness to off-resonance, and in vivo imaging corroborated those findings. CONCLUSION: Reducing the angular step in cardio-respiratory-binned golden-angle imaging shows potential for overcoming eddy current-induced image artifacts associated with 3D golden-angle radial imaging.

Clinical validation of three cardiovascular magnetic resonance techniques to measure strain and torsion in patients with suspected coronary artery disease.

BACKGROUND: Several cardiovascular magnetic resonance (CMR) techniques can measure myocardial strain and torsion with high accuracy. The purpose of this study was to compare displacement encoding with stimulated echoes (DENSE), tagging and feature tracking (FT) for measuring circumferential and radial myocardial strain and myocardial torsion in order to assess myocardial function and infarct scar burden both at a global and at a segmental level. METHOD: 116 patients with a high likelihood of coronary artery disease (European SCORE > 15%) underwent CMR examination including cine images, tagging, DENSE and late gadolinium enhancement (LGE) in the short axis direction. In total, 97 patients had signs of myocardial disease and 19 had no abnormalities in terms of left ventricular (LV) wall mass index, LV ejection fraction, wall motion, LGE or a history of myocardial infarction. Thirty-four patients had myocardial infarct scar with a transmural LGE extent (transmurality) that exceeded 50% of the wall thickness in at least one segment. Global circumferential strain (GCS) and global radial strain (GRS) was analyzed using FT of cine loops, deformation of tag lines or DENSE displacement. RESULTS: DENSE and tagging both showed high sensitivity (82% and 71%) at a specificity of 80% for the detection of segments with > 50% LGE transmurality, and receiver operating characteristics (ROC) analysis showed significantly higher area under the curve-values (AUC) for DENSE (0.87) than for tagging (0.83, p < 0.001) and FT (0.66, p = 0.003). GCS correlated with global LGE when determined with DENSE (r = 0.41), tagging (r = 0.37) and FT (r = 0.15). GRS had a low but significant negative correlation with LGE; DENSE r = - 0.10, FT r = - 0.07 and tagging r = - 0.16. Torsion from DENSE and tagging had a weak correlation (- 0.20 and - 0.22 respectively) with global LGE. CONCLUSION: Circumferential strain from DENSE detected segments with > 50% scar with a higher AUC than strain determined from tagging and FT at a segmental level. GCS and torsion computed from DENSE and tagging showed similar correlation with global scar size, while when computed from FT, the correlation was lower.

Comprehensive Cardiovascular Magnetic Resonance Diastolic Dysfunction Grading Shows Very Good Agreement Compared With Echocardiography.

OBJECTIVES: The aims of this study were to develop a comprehensive cardiovascular magnetic resonance (CMR) approach to diastolic dysfunction (DD) grading and to evaluate the accuracy of CMR in the diagnosis of DD compared with echocardiography. BACKGROUND: Left ventricular DD is routinely assessed using echocardiography. METHODS: Consecutive clinically referred patients (n = 46; median age 59 years; interquartile range: 46 to 68 years; 33% women) underwent both conventional echocardiography and CMR. CMR diastolic transmitral velocities (E and A) and myocardial tissue velocity (e') were measured during breath-hold using a validated high-temporal resolution radial sector-wise golden-angle velocity-encoded sequence. CMR pulmonary artery pressure was estimated from 4-dimensional flow analysis of blood flow vortex duration in the pulmonary artery. CMR left atrial volume was measured using the biplane long-axis area-length method. Both CMR and echocardiographic data were used to perform blinded grading of DD according to the 2016 joint American and European recommendations. RESULTS: Grading of DD by CMR agreed with that by echocardiography in 43 of 46 cases (93%), of which 9% were normal, 2% indeterminate, 63% grade 1 DD, 4% grade 2 DD, and 15% grade 3 DD. There was a very good categorical agreement, with a weighted Cohen kappa coefficient of 0.857 (95% confidence interval: 0.73 to 1.00; p < 0.001). CONCLUSIONS: A comprehensive CMR protocol for grading DD encompassing diastolic blood and myocardial velocities, estimated pulmonary artery pressure, and left atrial volume showed very good agreement with echocardiography.

Females have higher myocardial perfusion, blood volume and extracellular volume compared to males - an adenosine stress cardiovascular magnetic resonance study.

Knowledge on sex differences in myocardial perfusion, blood volume (MBV), and extracellular volume (ECV) in healthy individuals is scarce and conflicting. Therefore, this was investigated quantitatively by cardiovascular magnetic resonance (CMR). Healthy volunteers (n = 41, 51% female) underwent CMR at 1.5 T. Quantitative MBV [%] and perfusion [ml/min/g] maps were acquired during adenosine stress and at rest following an intravenous contrast bolus (0.05 mmol/kg, gadobutrol). Native T1 maps were acquired before and during adenosine stress, and after contrast (0.2 mmol/kg) at rest and during adenosine stress, rendering rest and stress ECV maps. Compared to males, females had higher perfusion, ECV, and MBV at stress, and perfusion and ECV at rest (p < 0.01 for all). Multivariate linear regression revealed that sex and MBV were associated with perfusion (sex beta -0.31, p = 0.03; MBV beta -0.37, p = 0.01, model R2 = 0.29, p < 0.01) while sex and hematocrit were associated with ECV (sex beta -0.33, p = 0.03; hematocrit beta -0.48, p < 0.01, model R2 = 0.54, p < 0.001). Myocardial perfusion, MBV, and ECV are higher in female healthy volunteers compared to males. Sex is an independent contributor to perfusion and ECV, beyond other physiological factors that differ between the sexes. These findings provide mechanistic insight into sex differences in myocardial physiology.

Stationary tissue background correction increases the precision of clinical evaluation of intra-cardiac shunts by cardiovascular magnetic resonance.

We aimed to evaluate the clinical utility of stationary tissue background phase correction for affecting precision in the measurement of Qp/Qs by cardiovascular magnetic resonance (CMR). We enrolled consecutive patients (n = 91) referred for CMR at 1.5T without suspicion of cardiac shunt, and patients (n = 10) with verified cardiac shunts in this retrospective study. All patients underwent phase contrast flow quantification in the ascending aorta and pulmonary trunk. Flow was quantified using two semi-automatic software platforms (SyngoVia VA30, Vendor 1; Segment 2.0R4534, Vendor 2). Measurements were performed both uncorrected and corrected for linear (Vendor 1 and Vendor 2) or quadratic (Vendor 2) background phase. The proportion of patients outside the normal range of Qp/Qs was compared using the McNemar's test. Compared to uncorrected measurements, there were fewer patients with a Qp/Qs outside the normal range following linear correction using Vendor 1 (10% vs 18%, p < 0.001), and Vendor 2 (10% vs 18%, p < 0.001), and following quadratic correction using Vendor 2 (7% vs 18%, p < 0.001). No patient with known shunt was reclassified as normal following stationary background correction. Therefore, we conclude that stationary tissue background correction reduces the number of patients with a Qp/Qs ratio outside the normal range in a consecutive clinical population, while simultaneously not reclassifying any patient with known cardiac shunts as having a normal Qp/Qs. Stationary tissue background correction may be used in clinical patients to increase diagnostic precision.

Cardiovascular magnetic resonance 4D flow analysis has a higher diagnostic yield than Doppler echocardiography for detecting increased pulmonary artery pressure.

BACKGROUND: Pulmonary hypertension is definitively diagnosed by the measurement of mean pulmonary artery (PA) pressure (mPAP) using right heart catheterization. Cardiovascular magnetic resonance (CMR) four-dimensional (4D) flow analysis can estimate mPAP from blood flow vortex duration in the PA, with excellent results. Moreover, the peak systolic tricuspid regurgitation (TR) pressure gradient (TRPG) measured by Doppler echocardiography is commonly used in clinical routine to estimate systolic PA pressure. This study aimed to compare CMR and echocardiography with regards to quantitative and categorical agreement, and diagnostic yield for detecting increased PA pressure. METHODS: Consecutive clinically referred patients (n = 60, median [interquartile range] age 60 [48-68] years, 33% female) underwent echocardiography and CMR at 1.5 T (n = 43) or 3 T (n = 17). PA vortex duration was used to estimate mPAP using a commercially available time-resolved multiple 2D slice phase contrast three-directional velocity encoded sequence covering the main PA. Transthoracic Doppler echocardiography was performed to measure TR and derive TRPG. Diagnostic yield was defined as the fraction of cases in which CMR or echocardiography detected an increased PA pressure, defined as vortex duration ≥15% of the cardiac cycle (mPAP ≥25 mmHg) or TR velocity > 2.8 m/s (TRPG > 31 mmHg). RESULTS: Both CMR and echocardiography showed normal PA pressure in 39/60 (65%) patients and increased PA pressure in 9/60 (15%) patients, overall agreement in 48/60 (80%) patients, kappa 0.49 (95% confidence interval 0.27-0.71). CMR had a higher diagnostic yield for detecting increased PA pressure compared to echocardiography (21/60 (35%) vs 9/60 (15%), p < 0.001). In cases with both an observable PA vortex and measurable TR velocity (34/60, 56%), TRPG was correlated with mPAP (R2 = 0.65, p < 0.001). CONCLUSIONS: There is good quantitative and fair categorical agreement between estimated mPAP from CMR and TRPG from echocardiography. CMR has higher diagnostic yield for detecting increased PA pressure compared to echocardiography, potentially due to a lower sensitivity of echocardiography in detecting increased PA pressure compared to CMR, related to limitations in the ability to adequately visualize and measure the TR jet by echocardiography. Future comparison between echocardiography, CMR and invasive measurements are justified to definitively confirm these findings.

Sector-wise golden-angle phase contrast with high temporal resolution for evaluation of left ventricular diastolic dysfunction.

PURPOSE: To develop a high temporal resolution phase-contrast pulse sequence for evaluation of diastolic filling patterns, and to evaluate it in comparison to transthoracic echocardiography. METHODS: A phase-contrast velocity-encoded gradient-echo pulse sequence was implemented with a sector-wise golden-angle radial ordering. Acquisitions were optimized for myocardial tissue (TE/TR: 4.4/6.8 ms, flip angle: 8º, velocity encoding: 30 cm/s) and transmitral flow (TE/TR: 4.0/6.6 ms, flip angle: 20º, velocity encoding: 150 cm/s). Shared velocity encoding was combined with a sliding-window reconstruction that enabled up to 250 frames per cardiac cycle. Transmitral and myocardial velocities were measured in 35 patients. Echocardiographic velocities were obtained with pulsed-wave Doppler using standard methods. RESULTS: Myocardial velocity showed a low difference and good correlation between MRI and Doppler (mean ± 95% limits of agreement 0.9 ± 3.7 cm/s, R2 = 0.63). Transmitral velocity was underestimated by MRI (P < .05) with a difference of -11 ± 28 cm/s (R2 = 0.45). The early-to-late ratio correlated well (R2 = 0.66) with a minimal difference (0.03 ± 0.6). Analysis of interobserver and intra-observer variability showed excellent agreement for all measurements. CONCLUSIONS: The proposed method enables the acquisition of phase-contrast images during a single breath-hold with a sufficiently high temporal resolution to match transthoracic echocardiography, which opens the possibility for many clinically relevant variables to be assessed by MRI.

The dynamics of extracellular gadolinium-based contrast agent excretion into pleural and pericardial effusions quantified by T1 mapping cardiovascular magnetic resonance.

INTRODUCTION: Excretion of cardiovascular magnetic resonance (CMR) extracellular gadolinium-based contrast agents (GBCA) into pleural and pericardial effusions, sometimes referred to as vicarious excretion, has been described as a rare occurrence using T1-weighted imaging. However, the T1 mapping characteristics as well as presence, magnitude and dynamics of contrast excretion into these effusions is not known. AIMS: To investigate and compare the differences in T1 mapping characteristics and extracellular GBCA excretion dynamics in pleural and pericardial effusions. METHODS: Clinically referred patients with a pericardial and/or pleural effusion underwent CMR T1 mapping at 1.5 T before, and at 3 (early) and at 27 (late) minutes after administration of an extracellular GBCA (0.2 mmol/kg, gadoteric acid). Analyzed effusion characteristics were native T1, ΔR1 early and late after contrast injection, and the effusion-volume-independent early-to-late contrast concentration ratio ΔR1early/ΔR1late, where ΔR1 = 1/T1post-contrast - 1/T1native. RESULTS: Native T1 was lower in pericardial effusions (n = 69) than in pleural effusions (n = 54) (median [interquartile range], 2912 [2567-3152] vs 3148 [2692-3494] ms, p = 0.005). Pericardial and pleural effusions did not differ with regards to ΔR1early (0.05 [0.03-0.10] vs 0.07 [0.03-0.12] s- 1, p = 0.38). Compared to pleural effusions, pericardial effusions had a higher ΔR1late (0.8 [0.6-1.2] vs 0.4 [0.2-0.6] s- 1, p < 0.001) and ΔR1early/ΔR1late (0.19 [0.08-0.30] vs 0.12 [0.04-0.19], p < 0.001). CONCLUSIONS: T1 mapping shows that extracellular GBCA is excreted into pericardial and pleural effusions. Consequently, the previously used term vicarious excretion is misleading. Compared to pleural effusions, pericardial effusions had both a lower native T1, consistent with lesser relative fluid content in relation to other components such as proteins, and more prominent early excretion dynamics, which could be related to inflammation. The clinical diagnostic utility of T1 mapping to determine quantitative contrast dynamics in pericardial and pleural effusions merits further investigation.

The relative contributions of myocardial perfusion, blood volume and extracellular volume to native T1 and native T2 at rest and during adenosine stress in normal physiology.

BACKGROUND: Both ischemic and non-ischemic heart disease can cause disturbances in the myocardial blood volume (MBV), myocardial perfusion and the myocardial extracellular volume fraction (ECV). Recent studies suggest that native myocardial T1 mapping can detect changes in MBV during adenosine stress without the use of contrast agents. Furthermore, native T2 mapping could also potentially be used to quantify changes in myocardial perfusion and/or MBV. Therefore, the aim of this study was to explore the relative contributions of myocardial perfusion, MBV and ECV to native T1 and native T2 at rest and during adenosine stress in normal physiology. METHODS: Healthy subjects (n = 41, 26 ± 5 years, 51% females) underwent 1.5 T cardiovascular magnetic resonance (CMR) scanning. Quantitative myocardial perfusion [ml/min/g] and MBV [%] maps were computed from first pass perfusion imaging at adenosine stress (140 microg/kg/min infusion) and rest following an intravenous contrast bolus (0.05 mmol/kg, gadobutrol). Native T1 and T2 maps were acquired before and during adenosine stress. T1 maps at rest and stress were also acquired following a 0.2 mmol/kg cumulative intravenous contrast dose, rendering rest and stress ECV maps [%]. Myocardial T1, T2, perfusion, MBV and ECV values were measured by delineating a region of interest in the midmural third of the myocardium. RESULTS: During adenosine stress, there was an increase in myocardial native T1, native T2, perfusion, MBV, and ECV (p ≤ 0.001 for all). Myocardial perfusion, MBV and ECV all correlated with both native T1 and native T2, respectively (R2 = 0.35 to 0.61, p < 0.001 for all). Multivariate linear regression revealed that ECV and perfusion together best explained the change in native T2 (ECV beta 0.21, p = 0.02, perfusion beta 0.66, p < 0.001, model R2 = 0.64, p < 0.001), and native T1 (ECV beta 0.50, p < 0.001, perfusion beta 0.43, p < 0.001, model R2 = 0.69, p < 0.001). CONCLUSIONS: Myocardial native T1, native T2, perfusion, MBV, and ECV all increase during adenosine stress. Changes in myocardial native T1 and T2 during adenosine stress in normal physiology can largely be explained by the combined changes in myocardial perfusion and ECV. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT02723747. Registered March 16, 2016.

Detection of myocarditis using T1 and ECV mapping is not improved by early compared to late post-contrast imaging.

BACKGROUND: Cardiovascular magnetic resonance (CMR) of myocarditis may include early gadolinium enhancement (EGE) and global relative enhancement (GRE) by T1 -weighted images acquired before and early after contrast administration. However, the importance of timing for post-contrast imaging has not been evaluated using T1 mapping. We aimed to improve the understanding of the contrast mechanisms by evaluating whether early or late post-contrast T1 mapping was better at detecting myocarditis. METHODS: Controls and patients referred to evaluate myocarditis underwent 1·5T CMR. T1 mapping was performed before, and 3 min (early) and 21 min (late) after intravenous contrast (0·2 mmol kg-1 ). Extracellular volume fraction (ECV) and the GRE and EGE equivalents by T1 mapping were calculated. Focally affected myocardium in myocarditis was defined as increased native T1 compared to remote myocardium. RESULTS: The GRE equivalent by T1 mapping was higher in myocarditis (n = 19) compared to controls (n = 19) both early (P<0·001) and late (P<0·001). While remote myocardium in myocarditis had higher enhancement relative to skeletal muscle compared to controls early (P = 0·002) and late (P<0·001), ECV of skeletal muscle was lower compared to controls both early (P = 0·03) and late (P = 0·004), and remote myocardial ECV did not differ from controls early (P = 0·37) or late (P = 0·52). The difference in ECV between affected and remote myocardium was higher late compared to early by 5·3 ± 0·7 versus 4·0 ± 0·6%-points (P = 0·002). CONCLUSION: Quantitative evaluation by T1 mapping shows that early post-contrast imaging does not improve the detection of myocarditis compared to late post-contrast imaging. Focal myocardial abnormalities were more conspicuous late post-contrast.

Projection-based respiratory-resolved left ventricular volume measurements in patients using free-breathing double golden-angle 3D radial acquisition.

OBJECTIVE: To refine a new technique to measure respiratory-resolved left ventricular end-diastolic volume (LVEDV) in mid-inspiration and mid-expiration using a respiratory self-gating technique and demonstrate clinical feasibility in patients. MATERIALS AND METHODS: Ten consecutive patients were imaged at 1.5 T during 10 min of free breathing using a 3D golden-angle radial trajectory. Two respiratory self-gating signals were extracted and compared: from the k-space center of all acquired spokes, and from a superior-inferior projection spoke repeated every 64 ms. Data were binned into end-diastole and two respiratory phases of 15% respiratory cycle duration in mid-inspiration and mid-expiration. LVED volume and septal-lateral diameter were measured from manual segmentation of the endocardial border. RESULTS: Respiratory-induced variation in LVED size expressed as mid-inspiration relative to mid-expiration was, for volume, 1 ± 8% with k-space-based self-gating and 8 ± 2% with projection-based self-gating (P = 0.04), and for septal-lateral diameter, 2 ± 2% with k-space-based self-gating and 10 ± 1% with projection-based self-gating (P = 0.002). DISCUSSION: Measuring respiratory variation in LVED size was possible in clinical patients with projection-based respiratory self-gating, and the measured respiratory variation was consistent with previous studies on healthy volunteers. Projection-based self-gating detected a higher variation in LVED volume and diameter during respiration, compared to k-space-based self-gating.

Ejection fraction in left bundle branch block is disproportionately reduced in relation to amount of myocardial scar.

INTRODUCTION: The relationship between left ventricular (LV) ejection fraction (EF) and LV myocardial scar can identify potentially reversible causes of LV dysfunction. Left bundle branch block (LBBB) alters the electrical and mechanical activation of the LV. We hypothesized that the relationship between LVEF and scar extent is different in LBBB compared to controls. METHODS: We compared the relationship between LVEF and scar burden between patients with LBBB and scar (n = 83), and patients with chronic ischemic heart disease and scar but no electrocardiographic conduction abnormality (controls, n = 90), who had undergone cardiovascular magnetic resonance (CMR) imaging at one of three centers. LVEF (%) was measured in CMR cine images. Scar burden was quantified by CMR late gadolinium enhancement (LGE) and expressed as % of LV mass (%LVM). Maximum possible LVEF (LVEFmax) was defined as the function describing the hypotenuse in the LVEF versus myocardial scar extent scatter plot. Dysfunction index was defined as LVEFmax derived from the control cohort minus the measured LVEF. RESULTS: Compared to controls with scar, LBBB with scar had a lower LVEF (median [interquartile range] 27 [19-38] vs 36 [25-50] %, p < 0.001), smaller scar (4 [1-9] vs 11 [6-20] %LVM, p < 0.001), and greater dysfunction index (39 [30-52] vs 21 [12-35] % points, p < 0.001). CONCLUSIONS: Among LBBB patients referred for CMR, LVEF is disproportionately reduced in relation to the amount of scar. Dyssynchrony in LBBB may thus impair compensation for loss of contractile myocardium.

The ability of the electrocardiogram in left bundle branch block to detect myocardial scar determined by cardiovascular magnetic resonance.

AIMS: We aimed to improve the electrocardiographic 2009 left bundle branch block (LBBB) Selvester QRS score (2009 LBSS) for scar assessment. METHODS: We retrospectively identified 325 LBBB patients with available ECG and cardiovascular magnetic resonance imaging (CMR) with late gadolinium enhancement from four centers (142 [44%] with CMR scar). Forty-four semi-automatically measured ECG variables pre-selected based on the 2009 LBSS yielded one multivariable model for scar detection and another for scar quantification. RESULTS: The 2009 LBSS achieved an area under the curve (AUC) of 0.60 (95% confidence interval 0.54-0.66) for scar detection, and R2 = 0.04, p < 0.001, for scar quantification. Multivariable modeling improved scar detection to AUC 0.72 (0.66-0.77) and scar quantification to R2 = 0.21, p < 0.001. CONCLUSIONS: The 2009 LBSS detects and quantifies myocardial scar with poor accuracy. Improved models with extensive comparison of ECG and CMR had modest performance, indicating limited room for improvement of the 2009 LBSS.

Pulmonary artery imaging under free-breathing using golden-angle radial bSSFP MRI: a proof of concept.

PURPOSE: To evaluate the feasibility of an improved motion and flow robust methodology for imaging the pulmonary vasculature using non-contrast-enhanced, free-breathing, golden-angle radial MRI. METHODS: Healthy volunteers (n = 10, age 46 ± 11 years, 50% female) and patients (n = 2, ages 27 and 84, both female) were imaged at 1.5 T using a Cartesian and golden-angle radial 2D balanced SSFP pulse sequence. The acquisitions were made under free breathing without contrast agent enhancement. The radial acquisitions were reconstructed at 3 temporal footprints. All series were scored from 1 to 5 for perceived diagnostic quality, artifact level, and vessel sharpness in multiple anatomical locations. In addition, vessel sharpness and blood-to-blood clot contrast were measured. RESULTS: Quantitative measurements showed higher vessel sharpness for golden-angle radial (n = 76, 0.79 ± 0.11 versus 0.71 ± 0.16, p < .05). Blood-to-blood clot contrast was found to be 23% higher in golden-angle radial in the 2 patients. At comparable temporal footprints, golden-angle radial was scored higher for diagnostic quality (mean ± SD, 2.3 ± 0.7 versus 2.2 ± 0.6, p < .01) and vessel sharpness (2.2 ± 0.8 versus 2.1 ± 0.5, p < .01), whereas the artifact level did not differ (3.0 ± 0.9 versus 3.0 ± 1.0, p = .80). The ability to retrospectively choose a temporal resolution and perform sliding-window reconstructions was demonstrated in patients. CONCLUSION: In pulmonary artery imaging, the motion and flow robustness of a radial trajectory does both improve image quality over Cartesian trajectory in healthy volunteers, and allows for flexible selection of temporal footprints and the ability to perform real-time sliding window reconstructions, which could potentially provide further diagnostic insight.