Absence of long-term structural and functional cardiac abnormalities on multimodality imaging in a multi-ethnic group of COVID-19 survivors from the early stage of the pandemic.

Aims: Many patients with coronavirus disease-2019 (COVID-19), particularly from the pandemic's early phase, have been reported to have evidence of cardiac injury such as cardiac symptoms, troponinaemia, or imaging or ECG abnormalities during their acute course. Cardiac magnetic resonance (CMR) and transthoracic echocardiography (TTE) have been widely used to assess cardiac function and structure and characterize myocardial tissue during COVID-19 with report of numerous abnormalities. Overall, findings have varied, and long-term impact of COVID-19 on the heart needs further elucidation. Methods and results: We performed TTE and 3 T CMR in survivors of the initial stage of the pandemic without pre-existing cardiac disease and matched controls at long-term follow-up a median of 308 days after initial infection. Study population consisted of 40 COVID-19 survivors (50% female, 28% Black, and 48% Hispanic) and 12 controls of similar age, sex, and race-ethnicity distribution; 35% had been hospitalized with 28% intubated. We found no difference in echocardiographic characteristics including measures of left and right ventricular structure and systolic function, valvular abnormalities, or diastolic function. Using CMR, we also found no differences in measures of left and right ventricular structure and function and additionally found no significant differences in parameters of tissue structure including T1, T2, extracellular volume mapping, and late gadolinium enhancement. With analysis stratified by patient hospitalization status as an indicator of COVID-19 severity, no differences were uncovered. Conclusion: Multimodal imaging of a diverse cohort of COVID-19 survivors indicated no long-lasting damage or inflammation of the myocardium.

Mapping Alveolar Oxygen Partial Pressure in COPD Using Hyperpolarized Helium-3: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study.

Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) 3He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP 3He MRI measuring pAO2, apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm2/s) correlated with emphysema and heterogeneity in pAO2 measurements. Strong correlations were found between the heterogeneity of global pAO2 as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic pAO2 values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between pAO2 SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas pAO2 heterogeneity and the fraction of non-physiological pAO2 results increase in mild to moderate COPD. Measurements of pAO2 are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation.

Quantification of lung ventilation defects on hyperpolarized MRI: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD study.

PURPOSE: To develop an end-to-end deep learning (DL) framework to segment ventilation defects on pulmonary hyperpolarized MRI. MATERIALS AND METHODS: The Multi-Ethnic Study of Atherosclerosis Chronic Obstructive Pulmonary Disease (COPD) study is a nested longitudinal case-control study in older smokers. Between February 2016 and July 2017, 56 participants (age, mean ± SD, 74 ± 8 years; 34 men) underwent same breath-hold proton (1H) and helium (3He) MRI, which were annotated for non-ventilated, hypo-ventilated, and normal-ventilated lungs. In this retrospective DL study, 820 1H and 3He slices from 42/56 (75%) participants were randomly selected for training, with the remaining 14/56 (25%) for test. Full lung masks were segmented using a traditional U-Net on 1H MRI and were imported into a cascaded U-Net, which were used to segment ventilation defects on 3He MRI. Models were trained with conventional data augmentation (DA) and generative adversarial networks (GAN)-DA. RESULTS: Conventional-DA improved 1H and 3He MRI segmentation over the non-DA model (P = 0.007 to 0.03) but GAN-DA did not yield further improvement. The cascaded U-Net improved non-ventilated lung segmentation (P < 0.005). Dice similarity coefficients (DSC) between manually and DL-segmented full lung, non-ventilated, hypo-ventilated, and normal-ventilated regions were 0.965 ± 0.010, 0.840 ± 0.057, 0.715 ± 0.175, and 0.883 ± 0.060, respectively. We observed no statistically significant difference in DCSs between participants with and without COPD (P = 0.41, 0.06, and 0.18 for non-ventilated, hypo-ventilated, and normal-ventilated regions, respectively). CONCLUSION: The proposed cascaded U-Net framework generated fully-automated segmentation of ventilation defects on 3He MRI among older smokers with and without COPD that is consistent with our reference method.

Reproducibility and Changes in Vena Caval Blood Flow by Using 4D Flow MRI in Pulmonary Emphysema and Chronic Obstructive Pulmonary Disease (COPD): The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Substudy.

BackgroundChronic obstructive pulmonary disease (COPD) is associated with hemodynamic changes in the pulmonary vasculature. However, cardiac effects are not fully understood and vary by phenotype of chronic lower respiratory disease.PurposeTo use four-dimensional (4D) flow MRI for comprehensive assessment of the right-sided cardiovascular system, assess its interrater and intraobserver reproducibility, and examine associations with venous return to the right heart in individuals with chronic COPD and emphysema.Materials and MethodsThe Multi-Ethnic Study of Atherosclerosis COPD substudy prospectively recruited participants who smoked and who had COPD and nested control participants from population-based samples. Electrocardiography and respiratory gated 4D flow 1.5-T MRI was performed at three sites with full volumetric coverage of the thoracic vessels in 2014-2017 with postbronchodilator spirometry and inspiratory chest CT to quantify percent emphysema. Net flow, peak velocity, retrograde flow, and retrograde fraction were measured on 14 analysis planes. Interrater reproducibility was assessed by two independent observers, and the principle of conservation of mass was employed to evaluate the internal consistency of flow measures. Partial correlation coefficients were adjusted for age, sex, race/ethnicity, height, weight, and smoking status.ResultsAmong 70 participants (29 participants with COPD [mean age, 73.5 years ± 8.1 {standard deviation}; 20 men] and 41 control participants [mean age, 71.0 years ± 6.1; 22 men]), the interrater reproducibility of the 4D flow MRI measures was good to excellent (intraclass correlation coefficient range, 0.73-0.98), as was the internal consistency. There were no statistically significant differences in venous flow parameters according to COPD severity (P > .05). Greater percent emphysema at CT was associated with greater regurgitant flow in the superior and inferior caval veins and tricuspid valve (adjusted r = 0.28-0.55; all P < .01), particularly in the superior vena cava.ConclusionFour-dimensional flow MRI had good-to-excellent observer variability and flow consistency. Percent emphysema at CT was associated with statistically significant differences in retrograde flow, greatest in the superior vena cava.© RSNA, 2019Online supplemental material is available for this article.See also the editorial by Choe in this issue.

Cerebrovascular Disease and Neurodegeneration in Alzheimer's Disease with and without a Strong Family History: A Pilot Magnetic Resonance Imaging Study in Dominican Republic.

The incidence and prevalence of Alzheimer's disease (AD) dementia are higher among Caribbean Hispanics than among non-Hispanic Whites. The causes of this health disparity remain elusive, partially because of the relative limited capacity for biomedical research in the developing countries that comprise Caribbean Latin America. To begin to address this issue, we were awarded a Development Research Award from the US NIH and Fogarty International Center in order to establish the local capacity to integrate magnetic resonance imaging (MRI) into studies of cognitive aging and dementia in Dominican Republic, establish collaborations with Dominican investigators, and conduct a pilot study on the role of cerebrovascular markers in the clinical expression of AD. Ninety older adult participants with and without AD dementia and with and without a strong family history of AD dementia received MRI scans and clinical evaluation. We quantified markers of cerebrovascular disease (white matter hyperintensities [WMH], presence of infarct, and presence of microbleed) and neurodegeneration (entorhinal cortex volume) and compared them across groups. Patients with AD dementia had smaller entorhinal cortex and greater WMH volumes compared with controls, regardless of family history status. This study provides evidence for the capacity to conduct MRI studies of cognitive aging and dementia in Dominican Republic. The results are consistent with the hypothesis that small vessel cerebrovascular disease represents a core feature of AD dementia, as affected participants had elevated WMH volumes irrespective of family history status.

Human airway branch variation and chronic obstructive pulmonary disease.

Susceptibility to chronic obstructive pulmonary disease (COPD) beyond cigarette smoking is incompletely understood, although several genetic variants associated with COPD are known to regulate airway branch development. We demonstrate that in vivo central airway branch variants are present in 26.5% of the general population, are unchanged over 10 y, and exhibit strong familial aggregation. The most common airway branch variant is associated with COPD in two cohorts (n = 5,054), with greater central airway bifurcation density, and with emphysema throughout the lung. The second most common airway branch variant is associated with COPD among smokers, with narrower airway lumens in all lobes, and with genetic polymorphisms within the FGF10 gene. We conclude that central airway branch variation, readily detected by computed tomography, is a biomarker of widely altered lung structure with a genetic basis and represents a COPD susceptibility factor.

Pulmonary artery stiffness in chronic obstructive pulmonary disease (COPD) and emphysema: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study.

PURPOSE: Chronic obstructive pulmonary disease (COPD) and particularly emphysema are characterized by stiffness of the aorta, due in part to accelerated elastin degradation in the lungs and aorta. Stiffness of the pulmonary arteries (PAs) may also be increased in COPD and emphysema, but data are lacking. We assessed PA stiffness using MRI in patients with COPD and related these measurements to COPD severity and percent emphysema. MATERIALS AND METHODS: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited 290 participants, age 50-79 years with 10 or more packyears and free of clinical cardiovascular disease. COPD severity were defined on postbronchodilator spirometry by ATS/ERS criteria. Percent emphysema was defined as the percentage of regions of the lung < -950 Hounsfield units on full-lung computed tomography (CT). PA stain was defined by the percent change in cross-sectional PA area between systole and diastole on MRI. Blood flow across the tricuspid and mitral valves was assessed by phase-contrast MRI for determination of the ventricular diastolic dysfunction (E/A ratio). RESULTS: PA strain was reduced in COPD compared with controls (P = 0.002) and was inversely correlated with COPD severity (P = 0.004). PA strain was inversely associated to percent emphysema (P = 0.01). PA strain was also markedly correlated with right ventricular diastolic dysfunction measured by E/A ratios in the fully adjusted mix models (P = 0.02). CONCLUSION: PA strain is reduced in COPD, related in part to percent emphysema on CT scan, which may have implications for pulmonary small vessel flow and right ventricular function. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:262-271.

Effect of MRI on breast tissue expanders and recommendations for safe use.

INTRODUCTION: Ferromagnetic port-containing breast tissue expanders are currently labeled MRI-unsafe because of the presumption that magnets should not enter the machine. However, designating these devices as MRI-unsafe can lead to unnecessary procedures or suboptimal imaging choices. This study provides an ex vivo analysis of how breast tissue expanders behave when subjected to strong magnetic fields to determine which variables might affect clinical risk. METHODS: Three different brands of tissue expanders were evaluated in three MRI environments. Translational force was determined using the deflection angle method. Torque on empty, saline-filled, and air-filled expanders was evaluated on a 0-4 scale. Magnetic field was measured using a gaussmeter. The weight required to prevent displacement of the expanders was determined for both air- and saline-filled expanders. Temperature over time was measured using an alcohol thermometer. RESULTS: Magnetic field strength, deflection angle, and torque were the greatest in 3T MRI environments and varied by device manufacturer (Sientra > Mentor > Allergan). Saline-filled expanders required 240 mL and air-filled required 360 mL volume to make the torque undetectable, and the effect of torque could be mitigated with prone positioning. A weight of 120 g was required to prevent displacement of a saline-filled tissue expander and 870 g for an empty expander. There were no appreciable changes in temperature. CONCLUSIONS: Previously described risks may be reduced by using a 1.5T MRI, device selection, filling expanders with saline, and prone positioning. MRI can be considered in patients with breast tissue expanders when appropriate peri-procedural choices have been made so that the benefits of undergoing MRI outweigh the risks.

Quantitative and semiquantitative measures of regional pulmonary microvascular perfusion by magnetic resonance imaging and their relationships to global lung perfusion and lung diffusing capacity: the multiethnic study of atherosclerosis chronic obstructive pulmonary disease study.

OBJECTIVES: The aim of this study was to evaluate the quantitative and semiquantitative measures of regional pulmonary parenchymal perfusion in patients with chronic obstructive pulmonary disease (COPD) in relationship to global lung perfusion (GLP) and lung diffusing capacity (DLCO). MATERIALS AND METHODS: A total of 143 participants in the Multiethnic Study of Atherosclerosis COPD Study were examined by dynamic contrast-enhanced pulmonary perfusion magnetic resonance imaging (MRI) at 1.5 T. Pulmonary microvascular blood flow (PBF) was calculated on a pixel-by-pixel basis by using a dual-bolus technique and the Fermi function model. Semiquantitative parameters for regional pulmonary microvascular perfusion were calculated from signal intensity-time curves in the lung parenchyma. Intraoberserver and interobserver coefficients of variation (CVs) and correlations between quantitative and semiquantitative MRI parameters and with GLP and DLCO were determined. RESULTS: Quantitative and semiquantitative parameters of pulmonary microvascular perfusion were reproducible, with CVs for all parameters of less than 10%. Furthermore, these MRI parameters were correlated with GLP and DLCO, and there was good agreement between PBF and GLP. Quantitative and semiquantitative MRI parameters were closely correlated (eg, r = 0.86 for maximum signal increase with PBF). In participants without COPD, the physiological distribution of pulmonary perfusion could be determined by regional MRI measurements. CONCLUSION: Regional pulmonary microvascular perfusion can reliably be quantified from dynamic contrast-enhanced MRI. Magnetic resonance imaging-derived quantitative and semiquantitative perfusion measures correlate with GLP and DLCO.

A novel adenoviral vector labeled with superparamagnetic iron oxide nanoparticles for real-time tracking of viral delivery.

In vivo tracking of gene therapy vectors challenges the investigation and improvement of biodistribution of these agents in the brain, a key feature for their targeting of infiltrative malignant gliomas. The glioma-targeting Ad5/3-cRGD gene therapy vector was covalently bound to super-paramagnetic iron oxide (Fe(3)O(4)) nanoparticles (SPION) to monitor its distribution by MRI. Transduction of labeled and unlabeled vectors was assessed on the U87 glioma cell line and normal human astrocytes (NHA), and was higher in U87 compared to NHA, but was similar between labeled and unlabeled virus. An in vivo study was performed by intracranial subcortical injection of labeled-Ad5/3-cRGD particles into a pig brain. The labeled vector appeared in vivo as a T2-weighted hyperintensity and a T2-gradient echo signal at the injection site, persisting up to 72 hours post-injection. We describe a glioma-targeting vector that is labeled with SPION, thereby allowing for MRI detection with no change in transduction capability.