Quantification of systemic-to-pulmonary collateral flow in univentricular physiology with 4D flow MRI.

PURPOSE: Systemic-to-pulmonary collateral flow is a well-recognised phenomenon in patients with single ventricle physiology, but remains difficult to quantify. The aim was to compare the reported formula's that have been used for calculation of systemic-to-pulmonary-collateral flow to assess their consistency and to quantify systemic-to-pulmonary collateral flow in patients with a Glenn and/or Fontan circulation using four-dimensional flow MRI (4D flow MR). METHODS: Retrospective case-control study of Glenn and Fontan patients who had a 4D flow MR study. Flows were measured at the ascending aorta, left and right pulmonary arteries, left and right pulmonary veins, and both caval veins. Systemic-to-pulmonary collateral flow was calculated using two formulas: 1) pulmonary veins - pulmonary arteries and 2) ascending aorta - caval veins. Anatomical identification of collaterals was performed using the 4D MR image set. RESULTS: Fourteen patients (n = 11 Fontan, n = 3 Glenn) were included (age 26 [22-30] years). Systemic-to-pulmonary collateral flow was significantly higher in the patients than the controls (n = 10, age 31.2 [15.1-38.4] years) with both formulas: 0.28 [0.09-0.5] versus 0.04 [-0.66-0.21] l/min/m2 (p = 0.036, formula 1) and 0.67 [0.24-0.88] versus -0.07 [-0.16-0.08] l/min/m2 (p < 0.001, formula 2). In patients, systemic-to-pulmonary collateral flow differed significantly between formulas 1 and 2 (13% versus 26% of aortic flow, p = 0.038). In seven patients, veno-venous collaterals were detected and no aortopulmonary collaterals were visualised. CONCLUSION: 4D flow MR is able to detect increased systemic-to-pulmonary collateral flow and visualise collaterals vessels in Glenn and Fontan patients. However, the amount of systemic-to-pulmonary collateral flow varies with the formula employed. Therefore, further research is necessary before it could be applied in clinical care.

Pediatric cardiothoracic vasculitis: multimodality imaging review.

The pediatric vasculitides are a relatively uncommon and heterogeneous group of disorders characterized by vessel inflammation, often with cardiothoracic involvement. Diagnosis and monitoring are often clinically challenging because of the nonspecific symptoms and laboratory markers. Thus, imaging has assumed increasing importance for early detection of disease activity, extent and complications as well as long-term monitoring pre- and post-treatment. Herein, we review the major pediatric vasculitides with frequent chest manifestations, including Takayasu arteritis, Kawasaki disease, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis, microscopic polyangiitis, Behçet disease and potential mimics. We highlight key clinical features and management considerations, emphasizing the central role of imaging.

Image-based scaling laws for somatic growth and pulmonary artery morphometry from infancy to adulthood.

Pulmonary artery (PA) morphometry has been extensively explored in adults, with particular focus on intra-acinar arteries. However, scaling law relationships for length and diameter of extensive preacinar PAs by age have not been previously reported for in vivo human data. To understand preacinar PA growth spanning children to adults, we performed morphometric analyses of all PAs visible in the computed tomography (CT) and magnetic resonance (MR) images from a healthy subject cohort [n = 16; age: 1-51 yr; body surface area (BSA): 0.49-2.01 m2]. Subject-specific anatomic PA models were constructed from CT and MR images, and morphometric information-diameter, length, tortuosity, bifurcation angle, and connectivity-was extracted and sorted into diameter-defined Strahler orders. Validation of Murray's law, describing optimal scaling exponents of radii for branching vessels, was performed to determine how closely PAs conform to this classical relationship. Using regression analyses of vessel diameters and lengths against orders and patient metrics (BSA, age, height), we found that diameters increased exponentially with order and allometrically with patient metrics. Length increased allometrically with patient metrics, albeit weakly. The average tortuosity index of all vessels was 0.026 ± 0.024, average bifurcation angle was 28.2 ± 15.1°, and average Murray's law exponent was 2.92 ± 1.07. We report a set of scaling laws for vessel diameter and length, along with other morphometric information. These provide an initial understanding of healthy structural preacinar PA development with age, which can be used for computational modeling studies and comparison with diseased PA anatomy.NEW & NOTEWORTHY Pulmonary artery (PA) morphometry studies to date have focused primarily on large arteries and intra-acinar arteries in either adults or children, neglecting preacinar arteries in both populations. Our study is the first to quantify in vivo preacinar PA morphometry changes spanning infants to adults. For preacinar arteries > 1 mm in diameter, we identify scaling laws for vessel diameters and lengths with patient metrics of growth and establish a healthy PA morphometry baseline for most preacinar PAs.

Cost-effectiveness analysis of magnetic resonance-guided focused ultrasound ablation for palliation of refractory painful bone metastases.

OBJECTIVE: The aim of this study was to determine if magnetic resonance-guided focused ultrasound (MRgFUS) is cost-effective compared with medication, for refractory pain from bone metastases in the United States. METHODS: We constructed a Markov state transition model using TreeAge Pro software (TreeAge Software, Inc., Williamstown, MA, USA) to model costs, outcomes, and the cost-effectiveness of a treatment strategy using MRgFUS for palliative treatment of painful bone metastases compared with a Medication Only strategy (Figure 1). Model transition state probabilities, costs (in 2018 US$), and effectiveness data (quality-adjusted life-years [QALYs]) were derived from available literature, local expert opinion, and reimbursement patterns at two U.S. tertiary academic medical centers actively performing MRgFUS. Costs and QALYs, discounted at three percent per year, were accumulated each month over a 24-month time horizon. One-way and probabilistic sensitivity analyses were performed. RESULTS: In the base-case analysis, the MRgFUS treatment strategy costs an additional $11,863 over the 2-year time horizon to accumulate additional 0.22 QALYs, equal to a $54,160/QALY ICER, thus making MRgFUS the preferred strategy. One-way sensitivity analyses demonstrate that for the base-case analysis, the crossover point at which Medication Only would instead become the preferred strategy is $23,341 per treatment. Probabilistic sensitivity analyses demonstrate that 67 percent of model iterations supported the conclusion of the base case. CONCLUSIONS: Our model demonstrates that MRgFUS is cost-effective compared with Medication Only for palliation of painful bone metastases for patients with medically refractory metastatic bone pain across a range of sensitivity analyses.

Assessment of airway abnormalities in patients with tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collaterals.

BACKGROUND: Children with tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collaterals (TOF/MAPCAs) are at risk for post-operative respiratory complications after undergoing unifocalisation surgery. Thus, we assessed and further defined the incidence of airway abnormalities in our series of over 500 children with TOF/MAPCAs as determined by direct laryngoscopy, chest computed tomography (CT), and/or bronchoscopy. METHODS: The medical records of all patients with TOF/MAPCAs who underwent unifocalisation or pulmonary artery reconstruction surgery from March, 2002 to June, 2018 were reviewed. Anaesthesia records, peri-operative bronchoscopy, and/or chest CT reports were reviewed to assess for diagnoses of abnormal or difficult airway. Associations between chromosomal anomalies and airway abnormalities - difficult anaesthetic airway, bronchoscopy, and/or CT findings - were defined. RESULTS: Of the 564 patients with TOF/MAPCAs who underwent unifocalisation or pulmonary artery reconstruction surgery at our institution, 211 (37%) had a documented chromosome 22q11 microdeletion and 28 (5%) had a difficult airway/intubation reported at the time of surgery. Chest CT and/or peri-operative bronchoscopy were performed in 234 (41%) of these patients. Abnormalities related to malacia or compression were common. In total 35 patients had both CT and bronchoscopy within 3 months of each other, with concordant findings in 32 (91%) and partially concordant findings in the other 3. CONCLUSION: This is the largest series of detailed airway findings (direct laryngoscopy, CT, and bronchoscopy) in TOF/MAPCAS patients. Although these findings are specific to an at-risk population for airway abnormalities, they support the utility of CT and /or bronchoscopy in detecting airway abnormalities in patients with TOF/MAPCAs.

Myocardial Bridges on Coronary Computed Tomography Angiography　- Correlation With Intravascular Ultrasound and Fractional Flow Reserve.

BACKGROUND: Myocardial bridges (MB) are commonly seen on coronary CT angiography (CCTA) in asymptomatic individuals, but in patients with recurrent typical angina symptoms, yet no obstructive coronary artery disease (CAD), evaluation of their potential hemodynamic significance is clinically relevant. The aim of this study was to compare CCTA to invasive coronary angiography (ICA), including intravascular ultrasound (IVUS), to confirm MB morphology and estimate their functional significance in symptomatic patients.Methods and Results:We retrospectively identified 59 patients from our clinical databases between 2009 and 2014 in whom the suspicion for MB was raised by symptoms of recurrent typical angina in the absence of significant obstructive CAD on ICA. All patients underwent CCTA, ICA and IVUS. MB length and depth by CCTA agreed well with length (0.6±23.7 mm) and depth (CT coverage) as seen on IVUS. The product of CT length and depth (CT coverage), (MB muscle index (MMI)), ≥31 predicted an abnormal diastolic fractional flow reserve (dFFR) ≤0.76 with a sensitivity and specificity of 74% and 62% respectively (area under the curve=0.722). CONCLUSIONS: In patients with recurrent symptoms of typical angina yet no obstructive CAD, clinicians should consider dynamic ischemia from an MB in the differential diagnosis. The product of length and depth (i.e., MMI) by CCTA may provide some non-invasive insight into the hemodynamic significance of a myocardial bridge, as compared with invasive assessment with dFFR.

Pre- and Postoperative Imaging of the Aortic Root.

Three-dimensional datasets acquired using computed tomography and magnetic resonance imaging are ideally suited for characterization of the aortic root. These modalities offer different advantages and limitations, which must be weighed according to the clinical context. This article provides an overview of current aortic root imaging, highlighting normal anatomy, pathologic conditions, imaging techniques, measurement thresholds, relevant surgical procedures, postoperative complications and potential imaging pitfalls. Patients with a range of clinical conditions are predisposed to aortic root disease, including Marfan syndrome, bicuspid aortic valve, vascular Ehlers-Danlos syndrome, and Loeys-Dietz syndrome. Various surgical techniques may be used to repair the aortic root, including placement of a composite valve graft, such as the Bentall and Cabrol procedures; placement of an aortic root graft with preservation of the native valve, such as the Yacoub and David techniques; and implantation of a biologic graft, such as a homograft, autograft, or xenograft. Potential imaging pitfalls in the postoperative period include mimickers of pathologic processes such as felt pledgets, graft folds, and nonabsorbable hemostatic agents. Postoperative complications that may be encountered include pseudoaneurysms, infection, and dehiscence. Radiologists should be familiar with normal aortic root anatomy, surgical procedures, and postoperative complications, to accurately interpret pre- and postoperative imaging performed for evaluation of the aortic root. Online supplemental material is available for this article.

CT-defined phenotype of pulmonary artery stenoses in Alagille syndrome.

BACKGROUND: Alagille syndrome is a rare disorder commonly associated with pulmonary artery stenosis. Studies exist discussing the cardiovascular sequela but no consistent phenotype, or pattern of pulmonary artery stenosis, has been described. OBJECTIVE: The objective of this study was to characterize the distribution and severity of pulmonary artery stenosis in patients with Alagille syndrome based on computed tomography angiography. MATERIALS AND METHODS: A retrospective chart review identified patients with Alagille syndrome who had undergone CT angiography. Pulmonary trunk (MPA), left main pulmonary artery (LPA) and right main pulmonary artery (RPA) diameters in Alagille patients were compared with those from matched control subjects. Stenoses at lobar and segmental pulmonary arteries were categorized as: Grade 1 (<33% stenosis), Grade 2 (33-66% stenosis) or Grade 3 (>66% stenosis). Involvement among the different lung regions was then compared. RESULTS: Fifteen patients ages 6 months to 17 years were identified; one had surgical augmentation of the central pulmonary arteries and was excluded from the central (main, right and left) pulmonary artery analysis. The proximal LPA and RPA, but not the MPA, were significantly smaller than those of the control subjects (P<0.01). The proximal LPA was significantly smaller than the proximal RPA (P<0.01) in the Alagille group (0.55 LPA:RPA ratio). Within the Alagille group, 75% of the lobar and segmental branches showed mild or no stenoses (Grade 1), 17% showed moderate stenosis (Grade 2) and 8% showed severe stenosis (Grade 3). While not statistically significant, the right lung demonstrated a greater percentage of Grades 2 and 3 stenoses (28%, right vs. 20% left, P=0.1). The right middle and lingula lobes of both lungs showed more Grade 2 and 3 stenoses (33% upper/middle vs. 18% lower, P<0.01). CONCLUSION: We describe a common pattern pulmonary artery stenosis in Alagille patients consisting of severe proximal LPA stenosis, heavy involvement of the lobar and segmental branches (more often right than left), and a greater involvement of the upper lobes. Knowledge of this phenotypic pattern can help in the diagnosis of Alagille syndrome in patients presenting with pulmonary artery stenosis.

Pediatric CT quality management and improvement program.

Modern CT is a powerful yet increasingly complex technology that continues to rapidly evolve; optimal clinical implementation as well as appropriate quality management and improvement in CT are challenging but attainable. This article outlines the organizational structure on which a CT quality management and improvement program can be built, followed by a discussion of common as well as pediatric-specific challenges. Organizational elements of a CT quality management and improvement program include the formulation of clear objectives; definition of the roles and responsibilities of key personnel; implementation of a technologist training, coaching and feedback program; and use of an efficient and accurate monitoring system. Key personnel and roles include a radiologist as the CT director, a qualified CT medical physicist, as well as technologists with specific responsibilities and adequate time dedicated to operation management, CT protocol management and CT technologist education. Common challenges in managing a clinical CT operation are related to the complexity of newly introduced technology, of training and communication and of performance monitoring. Challenges specific to pediatric patients include the importance of including patient size in protocol and dose considerations, a lower tolerance for error in these patients, and a smaller sample size from which to learn and improve.

Physiologic and molecular characterization of a murine model of right ventricular volume overload.

Pulmonary insufficiency (PI) is a common long-term sequel after repair of tetralogy of Fallot, causing progressive right ventricular (RV) dilation and failure. We describe the physiologic and molecular characteristics of the first murine model of RV volume overload. PI was created by entrapping the pulmonary valve leaflets with sutures. Imaging, catheterization, and exercise testing were performed at 1, 3, and 6 mo and compared with sham controls. RNA from the RV free wall was hybridized to Agilent whole genome oligonucleotide microarrays. Volume overload resulted in RV enlargement, decreased RV outflow tract shortening fraction at 1 mo followed by normalization at 3 and 6 mo (39 ± 2, 44 ± 2, and 41 ± 2 vs. 46 ± 3% in sham), early reversal of early and late diastolic filling velocities (E/A ratio) followed by pseudonormalization (0.87 ± 0.08, 0.82 ± 0.08, and 0.96 ± 0.08 vs. 1.04 ± 0.03; P < 0.05), elevated end-diastolic pressure (7.6 ± 0.7, 6.9 ± 0.8, and 7 ± 0.5 vs. 2.7 ± 0.2 mmHg; P < 0.05), and decreased exercise duration (26 ± 0.4, 26 ± 1, and 22 ± 1.3 vs. 30 ± 1.1 min; P < 0.05). Subendocardial RV fibrosis was evident by 1 mo. At 1 mo, 372 genes were significantly downregulated. Mitochondrial pathways and G protein-coupled receptor signaling were the most represented categories. At 3 mo, 434 genes were upregulated and 307 downregulated. While many of the same pathways continued to be downregulated, TNF-α, transforming growth factor-ß(1) (TGF-ß(1)), p53-signaling, and extracellular matrix (ECM) remodeling transitioned from down- to upregulated. We describe a novel murine model of chronic RV volume overload recapitulating aspects of the clinical disease with gene expression changes suggesting early mitochondrial bioenergetic dysfunction, enhanced TGF-ß signaling, ECM remodeling, and apoptosis.

Rapid pediatric cardiac assessment of flow and ventricular volume with compressed sensing parallel imaging volumetric cine phase-contrast MRI.

OBJECTIVE: The quantification of cardiac flow and ventricular volumes is an essential goal of many congenital heart MRI examinations, often requiring acquisition of multiple 2D phase-contrast and bright-blood cine steady-state free precession (SSFP) planes. Scan acquisition, however, is lengthy and highly reliant on an imager who is well-versed in structural heart disease. Although it can also be lengthy, 3D time-resolved (4D) phase-contrast MRI yields global flow patterns and is simpler to perform. We therefore sought to accelerate 4D phase contrast and to determine whether equivalent flow and volume measurements could be extracted. MATERIALS AND METHODS: Four-dimensional phase contrast was modified for higher acceleration with compressed sensing. Custom software was developed to process 4D phase-contrast images. We studied 29 patients referred for congenital cardiac MRI who underwent a routine clinical protocol, including cine short-axis stack SSFP and 2D phase contrast, followed by contrast-enhanced 4D phase contrast. To compare quantitative measurements, Bland-Altman analysis, paired Student t tests, and F tests were used. RESULTS: Ventricular end-diastolic, end-systolic, and stroke volumes obtained from 4D phase contrast and SSFP were well correlated (ρ = 0.91-0.95; r(2) = 0.83-0.90), with no statistically significant difference. Ejection fractions were well correlated in a subpopulation that underwent higher-resolution compressed-sensing 4D phase contrast (ρ = 0.88; r(2) = 0.77). Four-dimensional phase contrast and 2D phase contrast flow rates were also well correlated (ρ = 0.90; r(2) = 0.82). Excluding ventricles with valvular insufficiency, cardiac outputs derived from outlet valve flow and stroke volumes were more consistent by 4D phase contrast than by 2D phase contrast and SSFP. CONCLUSION: Combined parallel imaging and compressed sensing can be applied to 4D phase contrast. With custom software, flow and ventricular volumes may be extracted with comparable accuracy to SSFP and 2D phase contrast. Furthermore, cardiac outputs were more consistent by 4D phase contrast.

Computational simulations for aortic coarctation: representative results from a sampling of patients.

Treatments for coarctation of the aorta (CoA) can alleviate blood pressure (BP) gradients (Δ), but long-term morbidity still exists that can be explained by altered indices of hemodynamics and biomechanics. We introduce a technique to increase our understanding of these indices for CoA under resting and nonresting conditions, quantify their contribution to morbidity, and evaluate treatment options. Patient-specific computational fluid dynamics (CFD) models were created from imaging and BP data for one normal and four CoA patients (moderate native CoA: Δ12 mmHg, severe native CoA: Δ25 mmHg and postoperative end-to-end and end-to-side patients: Δ0 mmHg). Simulations incorporated vessel deformation, downstream vascular resistance and compliance. Indices including cyclic strain, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were quantified. Simulations replicated resting BP and blood flow data. BP during simulated exercise for the normal patient matched reported values. Greatest exercise-induced increases in systolic BP and mean and peak ΔBP occurred for the moderate native CoA patient (SBP: 115 to 154 mmHg; mean and peak ΔBP: 31 and 73 mmHg). Cyclic strain was elevated proximal to the coarctation for native CoA patients, but reduced throughout the aorta after treatment. A greater percentage of vessels was exposed to subnormal TAWSS or elevated OSI for CoA patients. Local patterns of these indices reported to correlate with atherosclerosis in normal patients were accentuated by CoA. These results apply CFD to a range of CoA patients for the first time and provide the foundation for future progress in this area.

Combined respiratory and cardiac triggering improves blood pool contrast-enhanced pediatric cardiovascular MRI.

BACKGROUND: Contrast-enhanced cardiac MRA suffers from cardiac motion artifacts and often requires a breath-hold. OBJECTIVE: This work develops and evaluates a blood pool contrast-enhanced combined respiratory- and ECG-triggered MRA method. MATERIALS AND METHODS: An SPGR sequence was modified to enable combined cardiac and respiratory triggering on a 1.5-T scanner. Twenty-three consecutive children referred for pediatric heart disease receiving gadofosveset were recruited in HIPAA-compliant fashion with IRB approval and informed consent. Children underwent standard non-triggered contrast-enhanced MRA with or without suspended respiration. Additionally, a free-breathing-triggered MRA was acquired. Triggered and non-triggered studies were presented in blinded random order independently to two radiologists twice. Anatomical structure delineation was graded for each triggered and non-triggered acquisition and the visual quality on triggered MRA was compared directly to that on non-triggered MRA. RESULTS: Triggered images received higher scores from each radiologist for all anatomical structures on each of the two reading sessions (Wilcoxon rank sum test, P < 0.05). In direct comparison, triggered images were preferred over non-triggered images for delineating cardiac structures, with most comparisons reaching statistical significance (binomial test, P < 0.05). CONCLUSION: Combined cardiac and respiratory triggering, enabled by a blood pool contrast agent, improves delineation of most anatomical structures in pediatric cardiovascular MRA.

Improved cardiovascular flow quantification with time-resolved volumetric phase-contrast MRI.

BACKGROUND: Cardiovascular flow is commonly assessed with two-dimensional, phase-contrast MRI (2-D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight and has inconsistent results. Time-resolved volumetric PC-MRI (4-D flow) may address these limitations. OBJECTIVE: We assess the degree of agreement and internal consistency between 2-D and 4-D flow quantification in our clinical population. MATERIALS AND METHODS: Software enabling flow calculation from 4-D flow was developed in Java. With IRB approval and HIPAA compliance, 18 consecutive patients without shunts were identified who underwent both (1) conventional 2-D PC-MRI of the aorta and main pulmonary artery and (2) 4-D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques. RESULTS: Both methods showed general agreement in flow rates (ρ: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (ρ: 4-D 0.98-0.99, 2-D 0.93), but more closely matched with 4-D (P < 0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2-D (P < 0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2-D showed improved correlation of flow rates while 4-D phase-contrast remained tightly correlated (ρ: 4-D 0.99-1.00, 2-D 0.99). CONCLUSION: 4-D PC-MRI demonstrates greater consistency than conventional 2-D PC-MRI for flow quantification.

Aorto-iliac/right leg arterial thrombosis necessitating limb amputation, pulmonary arterial, intracardiac, and ilio-caval venous thrombosis in a 40-year-old with COVID-19.

We describe a 40-year-old man with severe COVID-19 requiring mechanical ventilation who developed aorto-bi-iliac arterial, right lower extremity arterial, intracardiac, pulmonary arterial and ilio-caval venous thromboses and required right lower extremity amputation for acute limb ischemia. This unique case illustrates COVID-19-associated thrombotic complications occurring at multiple, different sites in the cardiovascular system of a single infected patient.

Breathheld autocalibrated phase-contrast imaging.

PURPOSE: To compare generalized autocalibrating partially parallel acquisitions (GRAPPA), modified sensitivity encoding (mSENSE), and SENSE in phase-contrast magnetic resonance imaging (PC-MRI) applications. MATERIALS AND METHODS: Aliasing of the torso can occur in PC-MRI applications. If the data are further undersampled for parallel imaging, SENSE can be problematic in correctly unaliasing signals due to coil sensitivity maps that do not match that of the aliased volume. Here, a method for estimating coil sensitivities in flow applications is described. Normal volunteers (n = 5) were scanned on a 1.5 T MRI scanner and underwent PC-MRI scans using GRAPPA, mSENSE, SENSE, and conventional PC-MRI acquisitions. Peak velocity and flow through the aorta and pulmonary artery were evaluated. RESULTS: Bland-Altman statistics for flow in the aorta and pulmonary artery acquired with mSENSE and GRAPPA methods (R = 2 and R = 3 cases) have comparable mean differences to flow acquired with conventional PC-MRI. GRAPPA and mSENSE PC-MRI have more robust measurements than SENSE when there is aliasing artifact caused by insufficient coil sensitivity maps. For peak velocity, there are no considerable differences among the mSENSE, GRAPPA, and SENSE reconstructions and are comparable to conventional PC-MRI. CONCLUSION: Flow measurements of images reconstructed with autocalibration techniques have comparable agreement with conventional PC-MRI and provide robust measurements in the presence of wraparound.

4D flow vs. 2D cardiac MRI for the evaluation of pulmonary regurgitation and ventricular volume in repaired tetralogy of Fallot: a retrospective case control study.

Lengthy exams and breath-holding limit the use of pediatric cardiac MRI (CMR). 3D time-resolved flow MRI (4DF) is a free-breathing, single-sequence exam that obtains magnitude (anatomic) and phase contrast (PC) data. We compare the accuracy of gadobenate dimeglumine-enhanced 4DF on a 1.5 T magnet to 2D CMR in children with repaired tetralogy of Fallot (rTOF) to measure pulmonary net flow (PNF) as a reflection of pulmonary regurgitation, forward flow (FF) and ventricular volumetry. Thirty-four consecutive cases were included. 2D PCs were obtained at the valve level. Using 4DF, we measured PNF at the valve and at the main and branch pulmonary arteries. PNF measured at the valve by 4DF demonstrated the strongest correlation (r = 0.87, p < 0.001) and lowest mean difference (3.5 ± 9.4 mL/beat) to aortic net flow (ANF). Semilunar FF and stroke volume of the respective ventricle demonstrated moderate-strong correlation by 4DF (r = 0.66-0.81, p < 0.001) and strong correlation by 2D (r = 0.81-0.84, p < 0.001) with similar correlations and mean differences between techniques (p > 0.05). Ventricular volumes correlated strongly between 2D and 4DF (r = 0.75-0.96, p < 0.001), though 4DF overestimated right ventricle volumes by 11.8-19.2 mL/beat. Inter-rater reliability was excellent for 2D and 4DF volumetry (ICC = 0.91-0.99). Ejection fraction moderately correlated (r = 0.60-0.75, p < 0.001) with better reliability by 4DF (ICC: 0.80-0.85) than 2D (ICC: 0.69-0.89). 4DF exams were shorter than 2D (9 vs. 71 min, p < 0.001). 4DF provides highly reproducible and accurate measurements of flow with slight overestimation of RV volumes compared to 2D in pediatric rTOF. 4DF offers important advantages in this population with long-term monitoring needs.

Machine learning for endoleak detection after endovascular aortic repair.

Diagnosis of endoleak following endovascular aortic repair (EVAR) relies on manual review of multi-slice CT angiography (CTA) by physicians which is a tedious and time-consuming process that is susceptible to error. We evaluate the use of a deep neural network for the detection of endoleak on CTA for post-EVAR patients using a novel data efficient training approach. 50 CTAs and 20 CTAs with and without endoleak respectively were identified based on gold standard interpretation by a cardiovascular subspecialty radiologist. The Endoleak Augmentor, a custom designed augmentation method, provided robust training for the machine learning (ML) model. Predicted segmentation maps underwent post-processing to determine the presence of endoleak. The model was tested against 3 blinded general radiologists and 1 blinded subspecialist using a held-out subset (10 positive endoleak CTAs, 10 control CTAs). Model accuracy, precision and recall for endoleak diagnosis were 95%, 90% and 100% relative to reference subspecialist interpretation (AUC = 0.99). Accuracy, precision and recall was 70/70/70% for generalist1, 50/50/90% for generalist2, and 90/83/100% for generalist3. The blinded subspecialist had concordant interpretations for all test cases compared with the reference. In conclusion, our ML-based approach has similar performance for endoleak diagnosis relative to subspecialists and superior performance compared with generalists.

Accuracy of a novel stress echocardiography pattern for myocardial bridging in patients with angina and no obstructive coronary artery disease - A retrospective and prospective cohort study.

BACKGROUND: Myocardial bridge (MB) may cause angina in patients with no obstructive coronary artery disease (CAD). We previously reported a novel stress echocardiography (SE) pattern of focal septal buckling with apical sparing in the end-systolic to early-diastolic phase that is associated with the presence of an MB. We evaluated the diagnostic accuracy of this pattern, and prospectively validated our results. METHODS: The retrospective cohort included 158 patients with angina who underwent both SE and coronary CT angiography (CCTA). The validation cohort included 37 patients who underwent CCTA in the emergency department for angina, and prospectively underwent SE. CCTA was used as a reference standard for the presence/absence of an MB, and also confirmed no obstructive CAD. RESULTS: In the retrospective cohort, an MB was present in 107 (67.7%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 91.6%, 70.6%, 86.7% and 80%, respectively. On logistic regression, focal septal buckling and Duke treadmill score were associated with an MB. In the validation cohort, an MB was present in 31 (84%). The sensitivity, specificity PPV and NPV were 90.3%, 83.3%, 96.5% and 62.5%, respectively. On logistic regression, focal septal buckling was associated with an MB. CONCLUSION: Presence of focal septal buckling with apical sparing on SE is an accurate predictor of an MB in patients with angina and no obstructive CAD. This pattern can reliably be used to screen patients who may benefit from advanced non-invasive/invasive testing for an MB as a cause of their angina.

Fluid-structure interaction simulations of patient-specific aortic dissection.

Credible computational fluid dynamic (CFD) simulations of aortic dissection are challenging, because the defining parallel flow channels-the true and the false lumen-are separated from each other by a more or less mobile dissection membrane, which is made up of a delaminated portion of the elastic aortic wall. We present a comprehensive numerical framework for CFD simulations of aortic dissection, which captures the complex interplay between physiologic deformation, flow, pressures, and time-averaged wall shear stress (TAWSS) in a patient-specific model. Our numerical model includes (1) two-way fluid-structure interaction (FSI) to describe the dynamic deformation of the vessel wall and dissection flap; (2) prestress and (3) external tissue support of the structural domain to avoid unphysiologic dilation of the aortic wall and stretching of the dissection flap; (4) tethering of the aorta by intercostal and lumbar arteries to restrict translatory motion of the aorta; and a (5) independently defined elastic modulus for the dissection flap and the outer vessel wall to account for their different material properties. The patient-specific aortic geometry is derived from computed tomography angiography (CTA). Three-dimensional phase contrast magnetic resonance imaging (4D flow MRI) and the patient's blood pressure are used to inform physiologically realistic, patient-specific boundary conditions. Our simulations closely capture the cyclical deformation of the dissection membrane, with flow simulations in good agreement with 4D flow MRI. We demonstrate that decreasing flap stiffness from [Formula: see text] to [Formula: see text] kPa (a) increases the displacement of the dissection flap from 1.4 to 13.4 mm, (b) decreases the surface area of TAWSS by a factor of 2.3, (c) decreases the mean pressure difference between true lumen and false lumen by a factor of 0.63, and (d) decreases the true lumen flow rate by up to 20% in the abdominal aorta. We conclude that the mobility of the dissection flap substantially influences local hemodynamics and therefore needs to be accounted for in patient-specific simulations of aortic dissection. Further research to accurately measure flap stiffness and its local variations could help advance future CFD applications.