Cardiothoracic Magnetic Resonance Angiography.

Catheter-based angiography is regarded as the clinical reference imaging technique for vessel imaging; however, it is invasive and is currently used for intervention or physiologic measurements. Contrast enhanced magnetic resonance angiography (MRA) with gadolinium-based contrast agents can be performed as a three-dimensional (3D) MRA or as a time resolved 3D (4D) MRA without physiologic synchronization, in which case cardiac and respiratory motion may blur the edges of the vessels and cardiac chambers. Ferumoxytol has recently been a popular contrast agent for MRA in patients with chronic renal failure. Noncontrast 3D MRA with ECG gating and respiratory navigation are safe and accurate noninvasive cross-sectional imaging techniques for the visualization of great vessels of the heart and coronary arteries in a variety of cardiovascular disorders including complex congenital heart diseases. Noncontrast flow dependent MRA techniques such as time of flight, phase contrast, and black-blood MRA techniques can be used as complementary or primary techniques. Here we review both conventional and relatively new contrast enhanced and non-contrast enhanced MRA techniques including ferumoxytol enhanced MRA, and bright-blood and water-fat separation based noncontrast 3D MRA techniques.

Accelerated Cine Cardiac MRI Using Deep Learning-Based Reconstruction: A Systematic Evaluation.

BACKGROUND: Breath-holding (BH) for cine balanced steady state free precession (bSSFP) imaging is challenging for patients with impaired BH capacity. Deep learning-based reconstruction (DLR) of undersampled k-space promises to shorten BHs while preserving image quality and accuracy of ventricular assessment. PURPOSE: To perform a systematic evaluation of DLR of cine bSSFP images from undersampled k-space over a range of acceleration factors. STUDY TYPE: Retrospective. SUBJECTS: Fifteen pectus excavatum patients (mean age 16.8 ± 5.4 years, 20% female) with normal cardiac anatomy and function and 12-second BH capability. FIELD STRENGTH/SEQUENCE: 1.5-T, cine bSSFP. ASSESSMENT: Retrospective DLR was conducted by applying compressed sensitivity encoding (C-SENSE) acceleration to systematically undersample fully sampled k-space cine bSSFP acquisition data over an acceleration/undersampling factor (R) considering a range of 2 to 8. Quality imperceptibility (QI) measures, including structural similarity index measure, were calculated using images reconstructed from fully sampled k-space as a reference. Image quality, including contrast and edge definition, was evaluated for diagnostic adequacy by three readers with varying levels of experience in cardiac MRI (>4 years, >18 years, and 1 year). Automated DL-based biventricular segmentation was performed commercially available software by cardiac radiologists with more than 4 years of experience. STATISTICAL TESTS: Tukey box plots, linear mixed effects model, analysis of variance (ANOVA), weighted kappa, Kruskal-Wallis test, and Wilcoxon signed-rank test were employed as appropriate. A P-value <0.05 was considered statistically significant. RESULTS: There was a significant decrease in the QI values and edge definition scores as R increased. Diagnostically adequate image quality was observed up to R = 5. The effect of R on all biventricular volumetric indices was non-significant (P = 0.447). DATA CONCLUSION: The biventricular volumetric indices obtained from the reconstruction of fully sampled cine bSSFP acquisitions and DLR of the same k-space data undersampled by C-SENSE up to R = 5 may be comparable. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 1.

Liver T1 Relaxation Quantification Using a 3-Dimensional Interleaved Look-Locker Acquisition With T2 Preparation Pulse Sequence (3D-QALAS): Comparison With Conventional 2-Dimensional MOLLI.

BACKGROUND: Changes in liver magnetic resonance imaging T1 relaxation times are associated with histologic inflammation and fibrosis. OBJECTIVE: To compare liver T1 measurements obtained using a novel single-breath-hold 3-dimensional (3D) whole-liver T1 estimation method (3D-QALAS) to standard-of-care 2-dimensional (2D) modified Look-Locker (2D-MOLLI) measurements. METHODS: With institutional review board approval, research magnetic resonance imaging examinations were performed in 19 participants at 1.5 T. T1 relaxometry of the liver was performed using a novel 3D whole-liver T1 estimation method (3D-QALAS) as well as a 2D modified Look-Locker (2D-MOLLI) method. The 3D method covered the entire liver in a single breath hold, whereas 2D imaging was performed at 4 anatomic levels in 4 consecutive breath holds. T1 measurements from parametric maps were obtained by a single operator, and region-of-interest area-weighted mean T1 values were calculated. Pearson correlation ( r ) was used to assess correlation between T1 estimation methods, and the paired t test and Bland-Altman analysis were used to compare agreement in T1 measurements. RESULTS: In 18 participants (1 participant was excluded from analysis because of respiratory motion artifacts on 3D-QALAS images), 2D-MOLLI and 3D-QALAS mean T1 measurements were strongly correlated ( r = 0.95, [95% CI: 0.87-0.98]; P < 0.0001). 2D-MOLLI T1 values were significantly longer than 3D-QALAS values (647.2 ± 87.3 milliseconds vs. 554.7 ± 75.8 milliseconds; P < 0.0001) with mean bias = 92.5 milliseconds (95% limits of agreement, 36.8, 148.2 milliseconds). CONCLUSION: Whole-liver T1 measurements obtained using a novel single-breath-hold 3D T1 estimation method correlate with a standard-of-care multiple consecutive-breath-hold 2D single-slice method but demonstrate systematic bias that should be considered or corrected when used in a clinical or research setting.

Influence of aortic valve morphology on vortical structures and wall shear stress.

The aim of this paper is to assess the association between valve morphology and vortical structures quantitatively and to highlight the influence of valve morphology/orientation on aorta's susceptibility to shear stress, both proximal and distal. Four-dimensional phase-contrast magnetic resonance imaging (4D PCMRI) data of 6 subjects, 3 with tricuspid aortic valve (TAV) and 3 with functionally bicuspid aortic values (BAV) with right-left coronary leaflet fusion, were processed and analyzed for vorticity and wall shear stress trends. Computational fluid dynamics (CFD) has been used with moving TAV and BAV valve designs in patient-specific aortae to compare with in vivo shear stress data. Vorticity from 4D PCMRI data about the aortic centerline demonstrated that TAVs had a higher number of vortical flow structures than BAVs at peak systole. Coalescing of flow structures was shown to be possible in the arch region of all subjects. Wall shear stress (WSS) distribution from CFD results at the aortic root is predominantly symmetric for TAVs but highly asymmetric for BAVs with the region opposite the raphe (fusion location of underdeveloped leaflets) being subjected to higher WSS. Asymmetry in the size and number of leaflets in BAVs and TAVs significantly influence vortical structures and WSS in the proximal aorta for all valve types and distal aorta for certain valve orientations of BAV. Analysis of vortical structures using 4D PCMRI data (on the left side) and wall shear stress data using CFD (on the right side).

Left ventricular non-compaction in paediatrics: a novel semi-automated imaging technique bridging imaging findings and clinical outcomes.

AIMS: We set out to design a reliable, semi-automated, and quantitative imaging tool using cardiac magnetic resonance (CMR) imaging that captures LV trabeculations in relation to the morphologic endocardial and epicardial surface, or perimeter-derived ratios, and assess its diagnostic and prognostic utility. METHODS AND RESULTS: We queried our institutional database between January 2008 and December 2018. Non-compacted (NC)-to-compacted (C) (NC/C) myocardium ratios were calculated and our tool was used to calculate fractal dimension (FD), total mass ratio (TMR), and composite surface ratios (SRcomp). NC/C, FD, TMR, and SRcomp were assessed in relation to LVNC diagnosis and outcomes. Univariate hazard ratios with cut-offs were performed using clinically significant variables to find 'at-risk' patients and imaging parameters were compared in 'at-risk' patients missed by Petersen Index (PI). Ninety-six patients were included. The average time to complete the semi-automated measurements was 3.90 min (SEM: 0.06). TMR, SRcomp, and NC/C were negatively correlated with LV ejection fraction (LVEF) and positively correlated with indexed LV end-systolic volumes (iLVESVs), with TMR showing the strongest correlation with LVEF (-0.287; P = 0.005) and SRcomp with iLVESV (0.260; P = 0.011). We found 29 'at-risk' patients who were classified as non-LVNC by PI and hence, were missed. When compared with non-LVNC and 'low-risk' patients, only SRcomp differentiated between both groups (1.91 SEM 0.03 vs. 1.80 SEM 0.03; P = 0.019). CONCLUSION: This method of semi-automatic calculation of SRcomp captured changes in at-risk patients missed by standard methods, was strongly correlated with LVEF and LV systolic volumes and may better capture outcome events.

Myocardial Parametric Mapping by Cardiac Magnetic Resonance Imaging in Pediatric Cardiology and Congenital Heart Disease.

Parametric mapping, that is, a pixel-wise map of magnetic relaxation parameters, expands the diagnostic potential of cardiac magnetic resonance by enabling quantification of myocardial tissue-specific magnetic relaxation on an absolute scale. Parametric mapping includes T1 mapping (native and postcontrast), T2 and T2* mapping, and extracellular volume measurements. The myocardial composition is altered in various disease states affecting its inherent magnetic properties and thus the myocardial relaxation times that can be directly quantified using parametric mapping. Parametric mapping helps in the diagnosis of nonfocal disease states and allows for longitudinal disease monitoring, evaluating therapeutic response (as in Thalassemia patients with iron overload undergoing chelation), and risk-stratification of certain diseases. In this review article, we describe various mapping techniques and their clinical utility in congenital heart disease. We will also review the available literature on normative values in children, the strengths, and weaknesses of these techniques. This review provides a starting point for pediatric cardiologists to understand and implement parametric mapping in their practice.

Performance of C-SENSE Accelerated Rapid Liver Shear Stiffness Measurement Using Displacement Wave Polarity-Inversion Motion Encoding: An Evaluation Study.

BACKGROUND: Liver shear stiffness measurement using magnetic resonance elastography (MRE) aids in the noninvasive diagnosis and staging of liver fibrosis. Inadequate breath-holds can lead to inaccurate stiffness estimation and/or failed MRE exams. PURPOSE: To prospectively evaluate the performance of compressed sensitivity encoding (C-SENSE) accelerated rapid MRE measurement of liver shear stiffness using displacement wave polarity-inversion motion encoding. STUDY TYPE: Retrospective. SUBJECTS: Eleven with liver disease and 10 asymptomatic subjects. FIELD STRENGTH/SEQUENCE: 1.5 T; gradient-recalled-echo (GRE) MRE. ASSESSMENT: All participants underwent: 1) two-dimensional (2D) GRE MRE with inflow saturation using SENSE acceleration factor (R) of 2 (standard of care [SC]); 2) 2D rapid MRE with (RwS); and 3) without (RnS) inflow saturation using C-SENSE R = 3; and 4) spatial three-dimensional (3D) rapid MRE with inflow saturation (R3D) using C-SENSE R = 4; with nominally identical spatial resolution and coverage. Image analyst (D.G., 2 years of experience) drew identical and maximal regions of interest (ROIs) in right hepatic lobe. STATISTICAL TESTS: Linear regression, intra-class correlation coefficients (ICC), Bland-Altman analyses, and the Wilcoxon signed-rank test were used to assess consistency and agreement of liver stiffness measurements for manually drawn identical and maximal ROIs. RESULTS: In 21 participants (37 ± 14 years) with liver stiffness (2.3 ± 0.7 kPa), body mass index (BMI 27 ± 7 kg/m2 ), proton density fat fraction (PDFF 9 ± 9%), and T2 * (27 ± 4 msec); rapid MRE sequences showed excellent agreement (ICC > 0.95) with SC MRE and no correlation (r2 < 0.1) of the differences (mean difference <0.2 kPa, <6%; limits of agreement <0.4 kPa, <16%) with BMI, PDFF, and T2 *. Breath-hold times were: 14 seconds (SC), 5 seconds (RnS), 7 seconds (RwS) per slice, and 16 seconds for the R3D acquisition. DATA CONCLUSIONS: C-SENSE accelerated GRE MRE sequences, using displacement wave polarity-inversion motion encoding, produce equivalent measurements of liver stiffness and have potential clinical benefit in patients with limited breath-holding capacity. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 1.

Agreement Between Automated and Clinically Reported Manual ROI-Based MR Elastography Liver Stiffness Measurements in Children and Young Adults.

MR elastography (MRE) typically requires manual ROI placement to generate liver shear stiffness measurements. Among 419 patients (primarily children and young adults), a computer-based automated MRE processing tool and clinically reported manual ROI-based measurements generated similar results (mean bias = 0.13 kPa). The intraclass correlation coefficient was 0.94 and was at least 0.90 across common indications in male and female patients and in patients with and without elevated liver fat fraction. Automated analysis may promote postprocessing standardization and decrease reporting variability.

Autonomic Nervous System Monitoring: Cardiac Magnetic Resonance Imaging Data as a Surrogate for Autonomic Data in Children.

Perioperative autonomic nervous system (ANS) measurements are evolving toward increasing import and utility. We present a three-year-old male with Down Syndrome who underwent ambulatory autonomic monitoring during surgery followed by cardiac magnetic resonance (CMR) imaging. Autonomic data from both environments are compared to age-related norms. We are the first to describe a method for acquiring and trending autonomic data from clinically indicated CMR scans in order to monitor autonomic function. These data are proof of concept for the use of routinely collected CMR data as a surrogate for autonomic data in children, noting differences in the autonomic effects of anesthetic techniques.

Ultrafast Computation of Left Ventricular Ejection Fraction by Using Temporal Intensity Variation in Cine Cardiac Magnetic Resonance.

Cardiac magnetic resonance enables comprehensive cardiac evaluation; however, intense time and labor requirements for data acquisition and processing have discouraged many clinicians from using it. We have developed an alternative image-processing algorithm that requires minimal user interaction: an ultrafast algorithm that computes left ventricular ejection fraction (LVEF) by using temporal intensity variation in cine balanced steady-state free precession (bSSFP) short-axis images, with or without contrast medium. We evaluated the algorithm's performance against an expert observer's analysis for segmenting the LV cavity in 65 study participants (LVEF range, 12%-70%). In 12 instances, contrast medium was administered before cine imaging. Bland-Altman analysis revealed quantitative effects of LV basal, midcavity, and apical morphologic variation on the algorithm's accuracy. Total computation time for the LV stack was <2.5 seconds. The algorithm accurately delineated endocardial boundaries in 1,132 of 1,216 slices (93%). When contours in the extreme basal and apical slices were not adequate, they were replaced with manually drawn contours. The Bland-Altman mean differences were <1.2 mL (0.8%) for end-diastolic volume, <5 mL (6%) for end-systolic volume, and <3% for LVEF. Standard deviation of the difference was ≤4.1% of LV volume for all sections except the midcavity in end-systole (8.3% of end-systolic volume). We conclude that temporal intensity variation-based ultrafast LVEF computation is clinically accurate across a range of LV shapes and wall motions and is suitable for postcontrast cine SSFP imaging. Our algorithm enables real-time processing of cine bSSFP images on a commercial scanner console within 3 seconds in an unobtrusive automated process.

Quantitative assessment of velocity and flow using compressed SENSE in children and young adults with adequate acquired temporal resolution.

BACKGROUND: Phase contrast (PC) cardiovascular magnetic resonance (CMR) imaging with parallel imaging acceleration is established and validated for measuring velocity and flow. However, additional acceleration to further shorten acquisition times would be beneficial in patients with complex vasculature who need multiple PC-CMR measurements, especially pediatric patients with higher heart rates. METHODS: PC-CMR images acquired with compressed sensitivity encoding (C-SENSE) factors of 3 to 6 and standard of care PC-CMR with sensitivity encoding (SENSE) factor of 2 (S2) acquired as part of clinical CMR examinations performed between November 2020 and January 2021 were analyzed retrospectively. The velocity and flow through the ascending aorta (AAo), descending aorta (DAo), and superior vena cava (SVC) in a transverse plane at the level of pulmonary artery bifurcation were compared. Additionally, frequency power distribution and dynamic time warp distance were calculated for these acquisitions. To further validate the adequate temporal resolution requirement, patients with S2 PC-CMR in the same acquisition plane were added in frequency power distribution analysis. RESULTS: Twenty-eight patients (25 males; 15.9 ± 1.9 years; body surface area (BSA) 1.7 ± 0.2 m2; heart rate 81 ± 16 bpm) underwent all five PC-CMR acquisitions during the study period. An additional 22 patients (16 males; 17.5 ± 7.7 years; BSA 1.6 ± 0.5 m2; heart rate 91 ± 16 bpm) were included for frequency power spectrum analysis. As expected, scan time decreased with increasing C-SENSE acceleration factor = 3 (37.5 ± 6.5 s, 26.4 ± 7.6%), 4 (28.1 ± 4.9 s, 44.7 ± 5.6%), 5 (21.6 ± 3.6 s, 57.6 ± 4.4%), and 6 (19.1 ± 3.2 s, 62.3 ± 4.2%) relative to SENSE = 2 (51.3 ± 10.1 s) PC-CMR acquisition. Mean peak velocity, net flow, and cardiac output were comparable (p > 0.87) between the five PC-CMR acquisitions with mean differences less than < 4%, < 2%, and < 3% respectively. All individual blood vessels showed a non-significant dependence of difference in fmax99 (< 4 Hz, p > 0.2), and dynamic time warp distance (p > 0.3) on the C-SENSE acceleration factor used. There was a strongly correlated (r = 0.74) increase in fmax99 (10.5 ± 2.2, range: 7.1-16.4 Hz) with increasing heart rate. The computed minimum required cardiac phase number was 15 ± 2.0 (range: 11-20) over the heart rate of 86 ± 15 bpm (range: 58-113 bpm). CONCLUSIONS: Stroke volume, cardiac output, and mean peak velocity measurements using PC-CMR with C-SENSE of up to 6 agree with measurements by standard of care PC-CMR with SENSE = 2 and resulted in up to a 65% reduction in acquisition time. Adequate temporal sampling can be ensured by acquiring 20 cardiac phases throughout the entire cardiac cycle over a wide range of pediatric and young adult heart rates.

Dobutamine stress cardiac MRI is safe and feasible in pediatric patients with anomalous aortic origin of a coronary artery (AAOCA).

BACKGROUND: Risk stratification in anomalous aortic origin of a coronary artery (AAOCA) is challenged by the lack of a reliable method to detect myocardial ischemia. We prospectively studied the safety and feasibility of Dobutamine stress-cardiac magnetic resonance (DSCMR), a test with excellent performance in adults, in pediatric patients with AAOCA. METHODS: Consecutive DSCMR from 06/2014-12/2019 in patients≤20 years old with AAOCA were included. Hemodynamic response and major/minor events were recorded. Image quality and spatial/temporal resolution were evaluated. Rest and stress first-pass perfusion and wall motion abnormalities (WMA) were assessed. Inter-observer agreement was assessed using kappa coefficient. RESULTS: A total of 224 DSCMR were performed in 182 patients with AAOCA at a median age of 14 years (IQR 12, 16) and median weight of 58.0 kg (IQR 43.3, 73.0). Examinations were completed in 221/224 (98.9%), all studies were diagnostic. Heart rate and blood pressure increased significantly from baseline (p < 0.001). No patient had major events and 28 (12.5%) had minor events. Inducible hypoperfusion was noted in 31/221 (14%), associated with WMA in 13/31 (42%). Inter-observer agreement for inducible hypoperfusion was very good (Κ = 0.87). Asymptomatic patients with inducible hypoperfusion are considered high-risk and those with a negative test are of standard risk. CONCLUSIONS: DSCMR is feasible in pediatric patients with AAOCA to assess for inducible hypoperfusion and WMA. It can be performed safely with low incidence of major/minor events. Thus, DSCMR is potentially a valuable test for detection of myocardial ischemia and helpful in the management of this patient population.

Comparison of compressed SENSE and SENSE for quantitative liver MRI in children and young adults.

OBJECTIVE: Compressed SENSE (C-SENSE) allows more rapid MRI acquisition through incoherent, pseudorandom k-space undersampling. The purpose of our study was to compare conventional sensitivity encoded imaging (SENSE) quantitative MR images to those obtained using C-SENSE for measurement of liver proton density fat fraction (PDFF), T2*, and stiffness. METHODS AND MATERIALS: Clinical liver MRI examinations that included SENSE and C-SENSE quantitative MRI sequences were retrospectively identified. Patient age, gender, liver PDFF (%), T2* (ms), and stiffness (kPa) were recorded. Spearman's rank-order correlation (r) was used to evaluate association between methods, and Bland-Altman analysis was used to determine the mean bias and 95% limits of agreement. RESULTS: Clinical liver MRI examinations that included SENSE and C-SENSE quantitative MRI sequences were retrospectively identified. Patient age, gender, liver PDFF (%), T2* (ms), and stiffness (kPa) were recorded. Spearman's rank-order correlation (r) was used to evaluate association between methods, and Bland-Altman analysis was used to determine the mean bias and 95% limits of agreement. Thirty-six examinations met the inclusion criteria. Mean patient age was 15.7 ± 7.7 years; twelve exams (33%) were in female patients. Liver PDFF showed very strong positive correlation (r = 0.98) between sequences, with a mean bias of 0.28% (95% LOA: -0.85, 1.41%). T2* showed moderate positive correlation (r = 0.53), with a mean bias of - 3.0 ms (95% LOA: - 12.0, 6.0 ms). Stiffness showed very strong positive correlation (r = 0.97), with a mean bias of 0.13 kPa (95% LOA: - 0.37, 0.63 kPa) that increased with increasing liver stiffness. CONCLUSION: There were strong positive correlations between SENSE and C-SENSE MRI measurements of liver PDFF and stiffness, with no to minimal bias. However, there was moderate correlation and greater negative mean bias between T2* measurements. Our results demonstrate the potential of compressed sensing to reliably measure PDFF and stiffness in the clinic.

Assessment of agreement between manual and automated processing of liver MR elastography for shear stiffness estimation in children and young adults with autoimmune liver disease.

PURPOSE: To compare automated versus standard of care manual processing of 2D gradient recalled echo (GRE) liver MR Elastography (MRE) in children and young adults. MATERIALS AND METHODS: 2D GRE liver MRE data from research liver MRI examinations performed as part of an autoimmune liver disease registry between March 2017 and March 2020 were analyzed retrospectively. All liver MRE data were acquired at 1.5 T with 60 Hz mechanical vibration frequency. For manual processing, two independent readers (R1, R2) traced regions of interest on scanner generated shear stiffness maps. Automated processing was performed using MREplus+ (Resoundant Inc.) using 90% (A90) and 95% (A95) confidence masks. Agreement was evaluated using intra-class correlation coefficients (ICC) and Bland-Altman analyses. Classification performance was evaluated using receiver operating characteristic curve (ROC) analyses. RESULTS: In 65 patients with mean age of 15.5 ± 3.8 years (range 8-23 years; 35 males) median liver shear stiffness was 2.99 kPa (mean 3.55 ± 1.69 kPa). Inter-reader agreement for manual processing was very strong (ICC = 0.99, mean bias = 0.01 kPa [95% limits of agreement (LoA): - 0.41 to 0.44 kPa]). Correlation between manual and A95 automated processing was very strong (R1: ICC = 0.988, mean bias = 0.13 kPa [95% LoA: - 0.40 to 0.68 kPa]; R2: ICC = 0.987, mean bias = 0.13 kPa [95% LoA: - 0.44 to 0.69 kPa]). Automated measurements were perfectly replicable (ICC = 1.0; mean bias = 0 kPa). CONCLUSION: Liver shear stiffness values obtained using automated processing showed excellent agreement with manual processing. Automated processing of liver MRE was perfectly replicable.

Fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths MR elastography.

PURPOSE: To design a new 2D gradient recalled echo MR elastography (MRE) pulse sequence with inflow saturation for measuring liver stiffness in half the breath-hold time compared to standard of care (SC) 2D GRE MRE sequences. METHODS: FASTWALTZ (fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths) MRE employs an interleaved dual TR strategy with wave amplitude labeling and compressed SENSE undersampling to reduce breath-hold time while incorporating inflow saturation to suppress flow artifacts. The sequence was implemented and compared with SC MRE both in phantoms and in vivo in 5 asymptomatic volunteers. Stiffness values, region of interest size, and breath-hold times were compared between sequences. RESULTS: Stiffness values were comparable between FASTWALTZ and SC MRE for both phantoms and in-vivo data. In volunteers, the group mean stiffness values at 60 Hz and region of interest size were 1.96 ± 0.30 kilopascals and 2279 ± 516 mm2 for SC MRE, and 1.95 ± 0.29 kilopascals and 2061 ± 464 mm2 for FASTWALTZ. Breath-hold duration for FASTWALTZ was 6.3 s compared to 13.3 s for SC MRE. CONCLUSION: FASTWALTZ provides comparable stiffness values in half the breath-hold time compared to SC MRE and may have clinical benefits in patients with limited breath-holding capacity.

Breath-hold and free-breathing quantitative assessment of biventricular volume and function using compressed SENSE: a clinical validation in children and young adults.

BACKGROUND: Although the breath-hold cine balanced steady state free precession (bSSFP) imaging is well established for assessment of biventricular volumes and function, shorter breath-hold times or no breath-holds are beneficial in children and severely ill or sedated patients. METHODS: Clinical cardiovascular magnetic resonance (CMR) examinations from September 2019 to October 2019 that included breath-hold (BH) and free-breathing (FB) cine bSSFP imaging accelerated using compressed sensitivity encoding (C-SENSE) factor of 3 in addition to the clinical standard BH cine bSSFP imaging using SENSE factor of 2 were analyzed retrospectively. Patients with structurally normal hearts who could perform consistent BHs were included. Aortic flow measured by phase contrast acquisition was used as a reference for the left ventricular (LV) stroke volume. Comparative analysis was performed for evaluation of biventricular volumes and function, imaging times, quantitative image quality, and qualitative image scoring. RESULTS: There were 26 patients who underwent all three cine scans during the study period (16.7 ± 6.4 years, body surface area (BSA) 1.6 ± 0.4 m2, heart rate 83 ± 7 beats/min). BH durations of 8 ± 1 s with C-SENSE = 3 were significantly shorter (p < 0.001) by 33% compared to 12 ± 1 s with SENSE = 2. Actual scan time for BH SENSE (4.9 ± 1.2 min) was comparable to that with FB C-SENSE (5.2 ± 1.5 min; p= NS). Biventricular stroke volume and ejection fraction, and LV mass computed using all three sequences were comparable. There was a small but statistically significant (p < 0.05) difference in LV end-diastolic volume (- 3.0 ± 6.8 ml) between BH SENSE and FB C-SENSE. There was a small but statistically significant (p < 0.005) difference in end-diastolic LV (- 5.0 ± 7.7 ml) and RV (- 6.0 ± 8.5 ml) volume and end-systolic LV (- 3.2 ± 4.3 ml) and RV(- 4.2 ± 6.8 ml) volumes between BH C-SENSE and FB C-SENSE. The LV stroke volumes from all three sequences had excellent correlations (r = 0.96, slope = 0.98-1.02) with aortic flow, with overestimation by 2.7 (5%) to 4.6 (8%) ml/beat. The image quality score was Excellent (16 of 26) to Good (10 of 26) with BH SENSE, Excellent (13 of 26) to Good (13 of 26) with BH C-SENSE, and Excellent (3 of 26) to Good (21 of 26) to Adequate (2 of 26) with FB C-SENSE. CONCLUSIONS: Image quality and ventricular volumetric and functional indices using either BH or FB C-SENSE cine bSSFP imaging were comparable to standard BH SENSE cine bSSFP imaging while maintaining nominally identical spatio-temporal resolution. This accelerated image acquisition provides an alternative to accommodate patients with impaired BH capacity.

Newly Developed Methods for Reducing Motion Artifacts in Pediatric Abdominal MRI: Tips and Pearls.

OBJECTIVE. The purpose of this article is to review established and emerging methods for reducing motion artifacts in pediatric abdominal MRI. CONCLUSION. Clearly understanding the strengths and limitations of motion reduction methods can enable practitioners of pediatric abdominal MRI to select and combine the appropriate techniques and potentially reduce the need for sedation and anesthesia.

Mitral Valve Flow and Myocardial Motion Assessed with Dual-Echo Dual-Velocity Cardiac MRI.

PURPOSE: To develop a dual-echo phase-contrast (DEPC) MRI approach with which each echo is acquired by using a different velocity sensitivity within one repetition time (TR) and demonstrate the feasibility of this approach to measure transmitral blood flow (E) and myocardial tissue (E m) velocities. MATERIALS AND METHODS: The flow across tubes of known diameter was measured by using the proposed DEPC method and compared with flowmeter measurements and theoretic predictions. Then, with both the DEPC MRI sequence and the conventional single-echo phase-contrast (SEPC) MRI sequence, E, E m, and E/E m were measured in six healthy volunteers (mean age, 49 years ± 13 [standard deviation]) and eight patients (mean age, 54 years ± 15) being evaluated for cardiac disease. Differences between the DEPC and conventional SEPC MRI methods were assessed by percent error, Pearson correlation, and Bland-Altman analyses. RESULTS: Velocities measured in vitro and in vivo by using the SEPC and DEPC MRI approaches were well correlated (r 2 > 0.97), with negligible bias (<0.5 cm/sec) and comparable velocity-to-noise ratios. Imaging times were approximately 19% shorter with the DEPC method (TR, 5.7 msec) than with the SEPC method (TR, 2.8 msec ± 4.2) (P < .05). CONCLUSION: The proposed DEPC method was sensitive to two velocity regimes within a single TR, resulting in a shorter imaging time compared with the imaging time in conventional SEPC MRI. Preliminary human study results suggest the feasibility of using this approach to estimate E/E m.Supplemental material is available for this article.© RSNA, 2020.

Regadenoson Stress Perfusion Cardiac Magnetic Resonance Imaging in Children With Kawasaki Disease and Coronary Artery Disease.

Coronary artery (CA) stenosis and occlusion in convalescent Kawasaki disease (KD) is progressive and may result in myocardial infarction. The use of regadenoson, a strong selective CA vasodilator with low side effect profile, for stress cardiac magnetic resonance (CMR) imaging has not been studied in children with KD. The safety, feasibility, and diagnostic utility of regadenoson stress CMR was assessed in children with KD and CA abnormalities. A retrospective review of regadenoson stress CMR in children with convalescent KD was performed. Hemodynamics changes after regadenoson administration and adverse effects were recorded. First-pass perfusion was evaluated at rest and during pharmacologic stress. The results were compared with anatomic CA imaging. Forty-one stress CMR (18 sedated examinations, 44%) were performed successfully in 32 patients. Median age was 11.2 years (range 2.2 to 18.6) and weight 41 kg (range 13 to 93.4). Heart rate increased 66 ± 25% (p <0.005) after regadenoson. Minor adverse events occurred in 6 sedated and 1 unsedated patients. Hypoperfusion during stress occurred in 16 of 41 (39%), including 5 inducible, 9 inducible and fixed, and 2 fixed lesions. Late gadolinium enhancement was present in 10 of 16 with hypoperfusion and in 1 without hypoperfusion. Stress CMR had 100% positive agreement and >90% negative and overall agreement with moderate-to-severe CA stenoses. Four patients with hypoperfusion underwent revascularization for severe CA stenoses. In conclusion, regadenoson stress CMR is hemodynamically safe and feasible in children with KD and CA disease. It has excellent agreement with CA angiography and aided decision-making to proceed with revascularization.

High frame rate cardiac cine MRI for the evaluation of diastolic function and its direct correlation with echocardiography.

BACKGROUND: Breath-hold cine MR is the method of choice for evaluating left ventricular (LV) systolic function; however, the evaluation of diastolic function remains in the domain of high frame rate echocardiography. Thus, a cine MR technique for simultaneously evaluating LV systolic and diastolic function would be clinically valuable. PURPOSE: To test the feasibility of extracting indices that characterize LV diastolic function from high frame rate cine MR. STUDY TYPE: Single center, prospective. POPULATION: Asymptomatic volunteers (N = 24; age 45.8 ± 12.3 years). FIELD STRENGTH/SEQUENCE: High frame rate (70 fps) cine MR and phase-contrast MR during free breathing were acquired at 1.5T. ASSESSMENT: The following MR-based LV filling metrics were extracted from LV volume changes during the cardiac cycle: 1) the volume-rate ratio, REFP /RLFP (ratio of the peak LV filling rate during the early filling period [EFP] to that during the late filling period [LFP]); and 2) the volume ratio, VEFP /VLFP (the ratio of cumulative LV volume change between the EFP and LFP). These metrics were then compared with traditional transmitral blood flow-based MR and echocardiographic indices. The effect of temporal resolution on these metrics was also evaluated. STATISTICAL TESTS: Bland-Altman and linear regression analyses were used to evaluate the performance of the proposed metrics against traditional indices of diastolic function. RESULTS: The REFP /RLFP and VEFP /VLFP correlated well with E/AQ-flow (r 2 = 0.66 and 0.54, respectively) and E/Aecho (r 2 = 0.58 and 0.49, respectively). Systolic indices remained robust (<3% error) for frame rates ≥20 fps. Although the proposed VEFP /VLFP was robust (<5% error) up to 25 fps, the proposed volume-rate diastolic function metrics were less reliable (>8% error) for frame rates below 35 fps. DATA CONCLUSION: In asymptomatic volunteers, cardiac cine MR images acquired at frame rates >35 fps can be used to extract LV diastolic function indices from the temporal changes in LV volume. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1571-1582.