bluuebunny/crossref_metadata_2025 huggingface dataset:
An autofocus method to reduce acoustic inhomogeneity in microwave-induced thermo-acoustic tomography based on basis pursuit
Authors: Yu Haoyang , Lv Yiming , Zhao Zhiqin , Nie Zaiping , Liu Qinghuo
Published: July 2021

In microwave-induced thermo-acoustic tomography, the quality of reconstructed images is seriously influenced by the speed of sound distribution, which is usually set according to the speed of sound (SoS) of the background coupling medium or an empirical value. To reduce defocusing and distortions induced by acoustic inhomogeneity in microwave-induced thermo-acoustic tomography, a method is proposed. We classify the initial reconstructed pressure by the difference in dielectrics and update the acoustic property accordingly. A spare spectrum is obtained by the proposed method and partitions the initial pressure into several clusters, and then SoS will be updated based on clinical statistics with which the pressure is reconstructed again. The proposed method is first validated in the anatomically realistic breast phantom; an ex vivo experiment based on a prototype system is carried out for further validation. The results prove that the proposed method has a reliable effect on reducing distortions than the state-of-art methods under the condition of a low signal to noise ratio.
Similarity solutions for strong shock waves in non-ideal magnetogasdynamics under the effect of monochromatic radiation
Authors: Sharma Kajal , Arora Rajan
Published: July 2021

This manuscript aims to deal with the one-dimensional unsteady flow of non-ideal gas with monochromatic radiation under the influence of a magnetic field, where the invariance method of the Lie group of transformations is applied in a cylindrically symmetric motion. The density is assumed to be uniform in the undisturbed medium. The radiation flux is considered to move through the non-ideal gas. The self-similar solutions of the considered model are obtained for the power-law and the exponential-law shock paths. The effects of the adiabatic exponent, radiation parameter, ambient magnetic field, and the parameter of non-idealness on the flow variables are shown graphically. Numerical calculations are performed to obtain the self-similar solutions.
Domain wall dynamics in ferromagnet/Ru/ferromagnet stacks with a wedged spacer
Authors: Zhao Yuelei , Yang Sheng , Xia Jing , Li Xiaoguang , Wu Kai , Zhou Yuqing , Fan Kaiquan , Zhang Xichao , Zhou Yan
Published: July 2021

Synthetic antiferromagnetic spintronics is an important field of study in the area of spintronics. Here, we fabricate a wedged-Ru layer in a ferromagnet/Ru/ferromagnet stack with alternating antiferromagnetic and ferromagnetic exchange-couplings. We systematically investigate the effect of the interlayer exchange coupling J on the chiral domain wall dynamics. The domain wall moves along the wedge unidirectionally driven by an out-of-plane magnetic field in the antiferromagnetically exchange-coupled region. In the ferromagnetically exchange-coupled region, only field-induced maze domain walls can be observed. The boundary between the antiferromagnetically and ferromagnetically exchange-coupled regions can be identified according to the behavior of domain walls. The strongest antiferromagnetic exchange coupling point Jmax in our sample is determined. A simple phenomenological picture is proposed to explain our experimental results. Moreover, we demonstrate that the Néel-type domain wall near the boundary of J = 0 could be driven into motion by an applied electric current. A stripe domain wall can be observed at the boundary of J = 0 only with a negative electric current resulting from the domain wall chirality. Our results may provide a platform to investigate the domain wall chirality and pave a way to spintronic devices based on synthetic antiferromagnets.
Analytical and experimental modeling of the hydrocarbon slick form and its spreading on the water surface
Authors: Kistovich A. V. , Chaplina T. O.
Published: July 2021

This paper is devoted to the effect of different physical and chemical properties of contacting media on the hydrocarbon spreading process on the water surface as well as the comparison of analytically acquired expressions for the form of the hydrocarbon slick observed in experiments. The equations that define the quasi-stationary form of the hydrocarbon slick are presented and numerically solved. Experiments on the compact oil slick field growth under different physical conditions are made. It is shown that the growth of the oil spill slick area with time is greater on fresh water than on saline and also depends on the oil volume and its properties. The dependency of spreading area size on the salinity of water is also revealed.
Mapping of the electrostatic potentials in MOCVD and hybrid GaN tunnel junctions for InGaN/GaN blue emitting light emitting diodes by off-axis electron holography correlated with structural, chemical, and optoelectronic characterization
Authors: Cooper D. , Fan Arcara V. , Damilano B. , Amichi L. , Mavel A. , Rochat N. , Feuillet G. , Courville A. , Vézian S. , Duboz J. Y.
Published: July 2021

Off-axis electron holography has been used to measure the width of the depletion region in a series of tunnel junction GaN light emitting diodes that have been prepared using different growth processes for blue emission. The total measured potentials are combinations of the mean inner potential, dopant potential, and piezoelectric contributions. The dopant potential has been unmixed from the mean inner potential such that the width of the tunnel junctions in the different diodes can be measured. The experimental results are then compared to secondary ion mass spectrometry, simulations, and opto-electronic testing. We find that the measured tunnel junction widths are consistent with simulations as well as the current density and voltage characteristics. As such, off-axis electron holography has been demonstrated as a unique technique that can be used to reproducibly measure the electrostatic potentials in tunnel junctions with nm-scale resolution in real III–V device specimens.
Solution-phase p-type doping of highly enriched semiconducting single-walled carbon nanotubes for thermoelectric thin films
Authors: Stanton Noah J. , Ihly Rachelle , Norton-Baker Brenna , Ferguson Andrew J. , Blackburn Jeffrey L.
Published: July 2021

Single-walled carbon nanotubes (SWCNTs) are attractive materials for next-generation energy-harvesting technologies, including thermoelectric generators, due to their tunable opto-electronic properties and high charge carrier mobilities. Controlling the Fermi level within these unique 1D nanomaterials is often afforded by charge transfer interactions between SWCNTs and electron or hole accepting species. Conventional methods to dope SWCNT networks typically involve the diffusion of molecular redox dopant species into solid-state thin films, but solution-phase doping could potentially provide routes and/or benefits for charge carrier transport, scalability, and stability. Here, we develop a methodology for solution-phase doping of polymer-wrapped, highly enriched semiconducting SWCNTs using a p-type charge transfer dopant, F4TCNQ. This allows doped SWCNT inks to be cast into thin films without the need for additional post-deposition doping treatments. We demonstrate that the introduction of the dopant at varying stages of the SWCNT dispersion process impacts the ultimate thermoelectric performance and observe that the dopant alters the polymer selectivity for semiconducting vs metallic SWCNTs. In contrast to dense semiconducting polymer films, where solution-phase doping typically leads to disrupted morphologies and poorer TE performance than solid-state doping, thin films of solution-doped s-SWCNTs perform similarly to their solid-state doped counterparts. Interestingly, our results also suggest that solution-phase F4TCNQ doping leads to fully ionized and dimerized F4TCNQ anions in solid-state films that are not observed in films doped with F4TCNQ after deposition. Our results provide a framework for the application of solution-phase doping to a broad array of high-performance SWCNT-based thermoelectric materials and devices that may require high-throughput deposition techniques.
Secondary lock-in of vortex-induced vibration and energy transfer characteristics of a vibrating cylinder subject to cross buoyancy
Authors: Liu Bin , Zhu Hongjun
Published: July 2021

The hydrodynamic and thermal characteristics of a freely vibrating circular cylinder subject to cross buoyancy are numerically investigated at low Reynolds numbers. The structural responses and onset of vortex-induced vibration (VIV) are documented over a range of parameter space, 2.0≤ reduced velocity (Ur) ≤10.0, 0.7≤ Prandtl number (Pr) ≤10.0 and 0.5≤ Richardson number (Ri) ≤2.0. The fluid and structural coefficients are chosen as Reynolds number (Re)=100, mass ratio (m*)=10.0, and damping ratio (ζ)=0.01. A phenomenon of secondary VIV lock-in is found in the cases of Ri = 2.0 (the cross buoyancy effect becomes influential), Pr≲2.0 and Ur≳7.0. An extended VIV lock-in region is formed over a wide range of reduced velocity values together with a tremendous kinetic energy transfer between fluid and structure. This finding is significant for the research of hydropower harvesting. On the other hand, the influence of structural dynamics on heat convection over the surface of a heated circular cylinder is recorded and discussed as well. The significance and mutual influence between Prandtl and Richardson numbers on hydrodynamics, structural dynamics, and heat convection are discussed in detail. The temperature contours are found concentrating around the cylinder's surface in the cases of high Prandtl numbers, which are also associated with higher mean Nusselt number (Nu¯) values. The influence on heat convection over a cylinder's surface is quantified via the computation of Nu¯ and its fluctuation for different circumstances. The energy transfer coefficient is employed to quantify the kinetic energy transfer between the fluid and a heated structure in mixed convective flow. The phase angle difference between the transverse displacement and lift force is used to support the discussions of energy transfer in fluid.
Two-dimensional carrier gas at complex oxide interfaces: Control of functionality
Authors: Li Wente , Gao Lingyuan , Guo Wei , Posadas Agham , Demkov Alexander A.
Published: July 2021

New functionalities and unexpected electronic structures can emerge in artificially engineered complex oxide heterointerfaces due to the coupling of multiple physical properties such as ferroelectricity, ferromagnetism, conductivity, charge transfer, etc. Here, we discuss heterointerfaces between perovskite oxides, SrTiO3, LaAlO3, and BaTiO3, as well as the rocksalt ferromagnetic semiconductor EuO. Combining theoretical analysis, experimental growth, and characterization techniques with atomic level resolution, we highlight some of these intriguing emergent interfacial phenomena. We consider several means of creating a two-dimensional carrier gas: through band offset engineering, polarization doping, and oxygen vacancy doping. In addition, we also discuss ways of manipulating these electron/hole gases and their potential applications in new electronic devices.
X-ray photoemission studies of BiInO3: Surface termination and effective Debye temperature
Authors: Dhingra Archit , Sando Daniel , Lu Po-Shen , Marzouk Zoe G. , Nagarajan Valanoor , Dowben Peter A.
Published: July 2021

BiInO3 is a potentially polar oxide with distinct optical properties whose origin could result from a surface that has not been well characterized. The surface properties of BiInO3 thin films have been characterized here by temperature dependent angle-resolved x-ray photoemission spectroscopy. A large surface to bulk core-level binding energy shift for the In 3d5/2 core-level is identified, indicating a surface very different from the bulk. BiInO3 terminates in indium oxide and loses bismuth from the surface of the film at T = 573 K. The Debye–Waller plots suggest effective Debye temperatures of 263 ± 10 and 556 ± 27 K for the surface and bulk components of In 3d core-level, respectively.
Knockout of the family with sequence similarity 181, member A (
Authors: Shah Wasim , Khan Ranjha , Shah Basit , Dil Sobia , Shi Qinghua
Published: July 2021

Family with sequence similarity 181 (Fam181) is a gene family with two paralogues (Fam181a and Fam181b) found among vertebrates. Fam181a exhibits dynamic and stage-specific expression during murine embryo development. Furthermore, searching in the National Center for Biotechnology Information database revealed predominant expression of Fam181a in mouse and human testes, implying that it may have essential roles in spermatogenesis. In this study we investigated the in vivo function of Fam181a in mouse spermatogenesis and fertility by generating Fam181a–/– mice using clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) 9 genome editing technology. The resulting Fam181a–/– mice exhibited normal growth and development. In addition, the mice were completely fertile, with no obvious differences in the testis-to-bodyweight ratio, epididymal sperm count or sperm motility compared with wild-type mice. Further examination of testicular and epididymal histology of Fam181a–/– mice found an intact seminiferous tubule structure and the presence of all types of germ cells, from spermatogonia to mature spermatozoa, similar to wild-type littermates. Similarly, analysis of meiotic prophase I progression revealed normal populations of each substage of prophase I in Fam181a+/+ and Fam181a–/– testes, suggesting that this gene is dispensable for male fertility. These negative findings will help avoid research overlap, save time and resources and allow researchers to concentrate on genes that are critical for male fertility and spermatogenesis.
Estimation of solid-state sintering and material parameters using phase-field modeling and ensemble four-dimensional variational method
Authors: Ishii Akimitsu , Yamanaka Akinori , Miyoshi Eisuke , Okada Yuki , Yamamoto Akiyasu
Published: July 2021

Sintering is a fundamental technology for powder metallurgy, the ceramics industry, and additive manufacturing processes such as three-dimensional printing. Improvement of the properties of sintered materials requires prediction of their microstructure using numerical simulations. However, the physical values and material parameters used for such predictions are generally unknown. Data assimilation (DA) enables the estimation of unobserved states and unknown material parameters by integrating simulation results and observational data. In this paper, we develop a new model that couples an ensemble-based four-dimensional variational (En4DVar) DA with a phase-field model of solid-state sintering (En4DVar-PF model) to estimate the state of the sintered material and multiple unknown material parameters. The developed En4DVar-PF model is validated by numerical experiments called twin experiments, in which a priori assumed-true initial state and multiple material parameters are estimated. The results of the twin experiments demonstrate that, using only three-dimensional morphological data of the sintered microstructure, our developed En4DVar-PF model can simultaneously and accurately estimate the particle shape, distribution of grain boundaries, and material parameters, including diffusion coefficients and mobilities related to grain boundary migration. Furthermore, our work identifies criteria for determining appropriate DA conditions such as the observational time interval required to accurately estimate the material parameters using our developed model. The developed En4DVar-PF model provides a promising framework to obtain unobservable states and difficult-to-measure material parameters in sintering, which is crucial for the accurate prediction of sintering processes and for the development of superior materials.
Day-ahead Low-Carbon Economical Dispatch of Integrated Energy System With CSP and ORC Based on Improved Imperialist Competitive Algorithm
Authors: Zhang Nenghan , Jian Xiyan , Ding Yibo , Wang Yufeng , Chen Lei
Published: July 2021

In this paper an improved imperialist competitive algorithm(ICA) is used for day-ahead low-carbon economic dispatch of the integrated energy system(IES) with CSP and ORC. In order to enhance the utilization efficiency of different types of energy in IES, this paper introduces a concentrating solar power(CSP) plant to act as a power unit and an organic Rankine cycle(ORC) plant to decouple thermoelectric coupling. Combined with the facilities like the gas turbines(GT), power to gas(P2G), photovoltaic power(PV), etc. in IES, a day-ahead low-carbon economical dispatch model of IES is proposed to minimize the system cost. In the paper, the system cost is optimized by using the improved ICA. The analysis of the results of the example verifies that the proposed model is reliable and effective.
Metals and Breast Cancer Risk: A Prospective Study Using Toenail Biomarkers
Authors: Niehoff Nicole M , O’Brien Katie M , Keil Alexander P , Levine Keith E , Liyanapatirana Chamindu , Haines Laura G , Waidyanatha Suramya , Weinberg Clarice R , White Alexandra J
Published: July 2021

The role of metals in breast cancer is of interest because of their carcinogenic and endocrine-disrupting capabilities. Evidence from epidemiologic studies remains elusive, and prior studies have not investigated metal mixtures. In a case cohort nested within the Sister Study (enrolled in 2003–2009; followed through September 2017), we measured concentrations of 15 metals in toenails collected at enrollment in a race/ethnicity-stratified sample of 1,495 cases and a subcohort of 1,605 women. We estimated hazard ratios and 95% confidence intervals for each metal using Cox regression and robust variance. We used quantile g-computation to estimate the joint association between multiple metals and breast cancer risk. The average duration of follow-up was 7.5 years. There was little evidence supporting an association between individual metals and breast cancer. An exception was molybdenum, which was associated with reduced incidence of overall breast cancer risk (third tertile vs. first tertile: hazard ratio = 0.82, 95% confidence interval: 0.67, 1.00). An inverse association for antimony was observed among non-Hispanic Black women. Predefined groups of metals (all metals, nonessential metals, essential metals, and metalloestrogens) were not strongly associated with breast cancer. This study offers little support for metals, individually or as mixtures, as risk factors for breast cancer. Mechanisms for inverse associations with some metals warrant further study.
Phosphate binding sites prediction in phosphorylation-dependent protein–protein interactions
Authors: Lu Zheng-Chang , Jiang Fan , Wu Yun-Dong
Published: July 2021

Motivation

Phosphate binding plays an important role in modulating protein–protein interactions, which are ubiquitous in various biological processes. Accurate prediction of phosphate binding sites is an important but challenging task. Small size and diversity of phosphate binding sites lead to a substantial challenge for developing accurate prediction methods.

Results

Here, we present the phosphate binding site predictor (PBSP), a novel and accurate approach to identifying phosphate binding sites from protein structures. PBSP combines an energy-based ligand-binding sites identification method with reverse focused docking using a phosphate probe. We show that PBSP outperforms not only general ligand binding sites predictors but also other existing phospholigand-specific binding sites predictors. It achieves ∼95% success rate for top 10 predicted sites with an average Matthews correlation coefficient value of 0.84 for successful predictions. PBSP can accurately predict phosphate binding modes, with average position error of 1.4 and 2.4 Å in bound and unbound datasets, respectively. Lastly, visual inspection of the predictions is conducted. Reasons for failed predictions are further analyzed and possible ways to improve the performance are provided. These results demonstrate a novel and accurate approach to phosphate binding sites identification in protein structures.

Availability and implementation

The software and benchmark datasets are freely available at http://web.pkusz.edu.cn/wu/PBSP/.

Supplementary information

Supplementary data are available at Bioinformatics online.
‘Their Mum Messed Up and Gran Can’t Afford to’: Violence towards Grandparent Kinship Carers and the Implications for Social Work
Authors: Holt Amanda , Birchall Jenny
Published: July 2021

Child and adolescent violence towards grandparent kinship carers is a significant and yet under-researched phenomenon. This study draws on data from thirty-six in-depth interviews which include grandparent carers who are experiencing such violence, and professionals from a range of backgrounds whose work intersects with this problem. The study highlights how the kinship care context shapes the violence, its impacts and, in turn, carers’ help-seeking practices. The findings highlight that social workers must better understand the barriers that prevent grandparent kinship carers from asking for help, and improve their responses to such requests. Recommendations for social work practice include asking the right questions, engaging in effective risk assessment, taking a trauma-informed approach, avoiding the language of coercion and improving its response to grandparents’ own articulated support needs.
Patients undergoing invasive coronary angiography after a positive single-photon emission computed tomography or a positive stress cardiac magnetic resonance - What to expect at the cath lab
Authors: Silva C , Goncalves M , Lopes P , Ventosa A , Calqueiro J , Freitas PN , Guerreiro S , Brito J , Abecasis J , Raposo L , Saraiva C , Goncalves PA , Gabriel HM , Almeida M , Ferreira AM
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

Background

 Randomized controlled trials comparing stress cardiac magnetic resonance (CMR) and single-photon emission computed tomography (SPECT) suggest similar diagnostic accuracy for detecting obstructive coronary artery disease (CAD). However, there are few data on whether or not this remains true in routine clinical practice.

The aim of this study was to assess the clinical and angiographic characteristics of patients undergoing invasive coronary angiography (ICA) after a positive stress CMR or positive SPECT, and to compare their positive predictive value with published results from the CE-MARC trial.

Methods

In this retrospective tertiary-center analysis, we included 429 patients (mean age 67 ± 10 years, 28% women, 42% diabetic) undergoing ICA between January 2016 and December 2020, after a positive stress CMR or positive SPECT. Regarding stress test, an adenosine protocol was performed in all stress CMR and in 76.4% (n = 272) of stress SPECT. 

Stress test results, including ischemia location and severity, were classified as reported by their primary readers. Patients with missing data on key variables, and those in whom microvascular disease was considered likely in the original stress test report were excluded. Obstructive CAD was defined as any coronary artery stenosis ≥ 50% in a vessel compatible with the ischemic territory on stress testing.

Results

Out of the total 429 patients, 356 (83%) were referred after a positive SPECT, and 73 (17%) after a positive stress CMR. Patients did not differ regarding age, cardiovascular risk factors, previous revascularization or left ventricular dysfunction, but patients with SPECT were more frequently male (p = 0.046). Overall, 320 patients (75%) had obstructive CAD on ICA. The prevalence of obstructive CAD was similar in patients with positive SPECT vs. positive stress CMR (76.1% vs. 80.8%, respectively, p = 0.385). There were also no significant differences in the prevalence of left main or 3-vessel disease (9.0% vs. 9.6%, p = 0.871, and 19.7% vs. 23.3% p = 0.483, respectively). Revascularization was performed or planned in 59.3% of patients in the SPECT group, and 52.1% of those in the stress CMR group (p = 0.255). The positive predictive values of both techniques were similar to those reported in the CE-MARC trial (Figure), and would increase to 88.1% and 89.4% for SPECT and stress CMR, respectively, if patients reported as having only mild ischemia were excluded.

Conclusion

In this tertiary center analysis, stress CMR and SPECT showed similar positive predictive values, comparable to those reported in the CE-MARC trial.
Prognostic interest of vasodilator stress perfusion cardiovascular magnetic resonance after a first inconclusive stress testing
Authors: Pezel T , Unterseeh T , Garot P , Hovasse T , Kinnel M , Champagne S , Toupin S , Sanguineti F , Garot J
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

While current guidelines recommend to perform a noninvasive test to detect coronary artery disease, stress tests are deemed inconclusive in almost a third of cases. The strategy for risk stratification after inconclusive stress testing is not well standardized.

PURPOSE

To assess the prognostic value of stress cardiovascular magnetic resonance (CMR) parameters and CMR-based coronary revascularization in patients after inconclusive stress testing.

METHODS

Between 2008 and 2020, consecutive patients with a first inconclusive stress test referred for vasodilator stress perfusion CMR were followed for the occurrence of major adverse cardiovascular events (MACE), defined by cardiovascular death or nonfatal myocardial infarction. CMR-related coronary revascularization was defined as any revascularisation occurring within 90 days after CMR. Univariable and multivariable Cox regressions were performed to determine the prognostic value of each parameter.

RESULTS

Of 1,563 patients who completed the CMR protocol, 1,402 patients (66.7% male, mean age 69.5 ± 11.0 years) completed the follow-up (median[interquartile range], 6.5 [5.6-7.5] years); 197 experienced a MACE (14.1%). Stress CMR was well tolerated without severe adverse events. Using Kaplan-Meier analysis, inducible ischemia and late gadolinium enhancement (LGE) were significantly associated with the occurrence of MACE (hazard ratio, HR: 2.88 [95%CI, 2.18-3.81]; and HR: 1.46 [95%CI, 1.16-1.89], both p < 0.001; respectively). In multivariable Cox regression, the presence and extent of inducible ischemia were independent predictors of a higher incidence of MACE (HR: 2.53 [95%CI, 1.89-3.40]; and HR: 1.58 [95%CI, 1.47-1.71]; both p < 0.001; respectively). After adjustment, the extent of inducible ischemia showed the best improvement in model discrimination above traditional risk factors (C-statistic 0.75 [95%CI: 0.69-0.81] with C-statistic improvement: 0.12). The study showed no benefit of CMR-related coronary revascularization in reducing MACE.

CONCLUSION

In patients with a first inconclusive stress test, stress CMR has good prognostic value to predict MACE offering an incremental prognostic value over traditional risk factors.
Automated myocardial segmentation in native t1-mapping cardiovascular magnetic resonance images based on machine learning: a validation study in the UK biobank"s covid-19 subset
Authors: Rauseo E , Lockhart L , Paiva JM , Fung K , Khanji MY , Raisi-Estabragh Z , Amir-Khalili A , Petersen SE
Published: July 2021

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Innovate UK

Background

 Regional assessment of septal native T1 values with cardiovascular magnetic resonance (CMR) is used to characterise diffuse myocardial diseases. Previous studies suggest its potential role in detecting early pathological alterations, which may help identify high-risk subjects at early disease stages. Automated analysis of myocardial native T1 images may enable faster CMR analysis and reduce inter-observer variability of manual analysis. However, the technical performance of such methodologies has not been previously reported.

Purpose

 We tested, in a subset of UK Biobank participants, the degree of agreement between CMR septal myocardial T1 values obtained from our machine learning (ML) algorithm and septal native T1 values computed from manual segmentations.

Methods

 We analysed the first 292 participants who were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and had CMR imaging (1.5 Tesla, Siemens MAGNETOM Aera). T1 mapping was performed in a single mid-ventricular short axis (SAX) slice using ShMOLLI (WIP780B) sequences. Three experienced CMR readers independently measured native T1 values by manually placing a single region of interest (ROI) covering half of the anteroseptal and half of the inferoseptal wall using cvi42 post-processing software (version 5.11). A mean T1 value for each participant was then calculated. A ML algorithm developed by Circle Cardiovascular Imaging Inc. was then applied to the same images to derive the myocardium T1 values automatically. The algorithm was previously trained to segment myocardium from SAX T1 and non-T1 mapping images on two external CMR datasets. We compared the mean septal ROI T1 values to the mean myocardium T1 values predicted by the ML algorithm.

Results

 Two studies were excluded after quality control. The ML-derived and the manually calculated mean T1 values were significantly correlated (r = 0.82, p < 0.001). The Bland-Altman analysis between the two methods showed a mean bias of 3.64 ms, with 95% limits of agreement of −38.88 to 53.46 ms, indicating good agreement (figure 1).

Conclusions

 We demonstrated strong correlation and good agreement between native T1 values obtained from our automated analysis method and manual T1 septal analysis in a subset of UK Biobank participants. This algorithm may represent a valuable tool for clinicians allowing for fast and potentially less operator-dependent myocardial tissue characterisation. However, validation of more extensive datasets and quality control processes are needed.
Myocardial edema, interstitial expansion and clinical correlates in takotsubo syndrome: a cardiac magnetic resonance tissue mapping study
Authors: Arcari L , Camastra G , Ciolina F , Danti M , Semeraro R , Sbarbati S , Ansalone G , Cacciotti L
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

Background

takotsubo syndrome (TTS) is an acute heart failure syndrome characterized by transient systolic dysfunction, widespread myocardial edema and not trivial rate of in-hospital complications. Tissue mapping by cardiac magnetic resonance (CMR) imaging provides measure of myocardial interstitial expansion. Few studies to date comprehensively examined native T1, T2 and extracellular volume (ECV) quantification by CMR in TTS.

Purpose

to describe T1 and T2 mapping findings by cardiac magnetic resonance (CMR) imaging in a cohort of TTS patients and control subjects.

Methods

we performed CMR imaging with native T1 and T2 mapping assessment as well as ECV and late gadolinium enhancement (LGE) imaging in n = 14 TTS patients at a median of 4 (3, 7) days after the acute event. Control group consisted of n = 14 healthy individuals with no known prior acute cardiac events. Extracellular-volume (ECV) fraction estimate was derived from native and post-contrast T1 of myocardium and blood pool corrected for hematocrit as reported in literature. All mapping measurements were performed in the interventricular septum from the mid-short-axis view.

Results

median age of the study population was 72 years, 84% female. Typical apical ballooning was present in 72% of the patients, atypical in 28%, with median left ventricular ejection fraction (LVEF) of 45%; mid interventricular septum was involved in all patients based on the presence of wall motion abnormalities at hospital admission. Median native T1, T2 and ECV were 1078 msec vs 965 msec, 55 msec vs 47 msec and 29% vs 25% in TTS and controls respectively (p < 0.001 for all). A significant direct correlation was found between T2 and both native T1 and ECV in TTS (r = 0.759, p = 0.002 and r = 0.630, p = 0.018 respectively) but not in controls. Moreover, in TTS patients, native T2 inversely correlated with LVEF as assessed at hospital admission (r=-0.563, p = 0.037), whereas non-significant trends were observed between admission LVEF and both native T1 and ECV. No LGE was detected neither in TTS patients nor in controls.

Conclusions

myocardial edema, as signified by increased T2, is a prominent feature of TTS, likely driving interstitial expansion and increase of native T1 and ECV in the acute phase. Correlation of T2 with LVEF on admission suggests that CMR-based parametric assessment of myocardial edema could contribute to better characterize disease severity in TTS.
Changes in CMR parameters and prediction of cardiac complications in thalassemia major: fibrosis tells us more than iron
Authors: Pepe A , Giuliano P , Pistoia L , Giunta N , Renne S , Fina P , Agliata G , Pulini S , Massa A , Benni M , Positano V , Meloni A
Published: July 2021

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): The MIOT project received “no-profit support” from industrial sponsorships (Chiesi Farmaceutici S.p.A. and ApoPharma Inc.).

Background

Cardiovascular magnetic Resonance (CMR) has dramatically changed the clinical practice and improved the prognosis in thalassemia major (TM).

Aim

This is the first study evaluating the predictive value of changes in CMR parameters (myocardial iron, function, and fibrosis) for cardiac complications in TM.

Methods

We followed prospectively 709 TM patients (374 females; 29.77 ± 8.53 years) consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) Network who performed a baseline and a 1st follow up CMR scan after 18 months.  Myocardial iron overload (MIO) was measured by multislice multiecho T2* technique and atrial dimensions and biventricular function by cine images. Macroscopic myocardial fibrosis was detected by late gadolinium enhancement technique.

Risk classes were defined based on  the 4 patterns of MIO from worst to normal. For patients with baseline MIO (at least one segmental T2*<20 ms), improvement was defined as a transition to a better risk class, stabilization as no change in risk class, and worsening as a transition to a worse risk class. For patients without baseline MIO, the worsening was the transition to a worse risk class.

The percentage change was used for continuous variables. For biventricular ejection fractions, improvement was a %change > 10%, stabilization a %change between -10% and 10%, and worsening a %change<-10%. For biventricular volumes, LV mass index, and atrial areas, improvement was a % change<-10%, stabilization a % change between -10% and 10%, and worsening a % change > 10%.

Myocardial fibrosis was considered absent if not detected in any of the two CMRs and present if detected in at least one examination.

Results

During a mean follow-up of 89.4 ± 33.3 months, cardiac events were recorded in 50 (7.1%) patients: 24 (48%) episodes of heart failure, 24 (48%) arrhythmias (23 supraventricular and 1 hypokinetic), and 2 (4.0%) pulmonary hypertension.  Mean time from the 1st follow up CMR to the development of a cardiac complication was 75.31 ± 35.35 months.

In the univariate Cox regression analysis, cardiac iron cleareance and myocardial fibrosis were identified as univariate prognosticators (Table 1). In the multivariate analysis only myocardial fibrosis remained an independent predictor factor.

Conclusion

The presence of myocardial fibrosis at the baseline CMR or developed within 18 months emerges as the strongest long-term predictor for cardiac complications in TM. Our data demonstrate the importance in using the contrast medium for CMR scans in thalassemia patients.
Multiparametric cardiac magnetic resonance assessmenti in sickle-beta-thalassemia
Authors: Pepe A , Meloni A , Peritore G , Zerbini M , Vallone N , Barbuto L , Restaino G , Ermini A , Spadola V , Roccamo G , Positano V , Pistoia L
Published: July 2021

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): The MIOT project receives “no-profit support” from industrial sponsorships (Chiesi Farmaceutici S.p.A., ApoPharma Inc.).

Background. Sickle β-thalassemia (Sβ-thal) is a hereditary hemoglobinopathy resulting from the combined heterozygosity for sickle cell and β-thalassemia genes. Cardiac involvement in Sβ-thal patients has been poorly investigated.

Aim. We aimed to evaluate myocardial iron overload and cardiac function by cardiovascular magnetic resonance (CMR) in patients with Sβ-thal.

Methods. One hundred and eleven Sβ-thal patients consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) network were studied and compared with 46 sickle cell disease (SCD) patients. Biatrial and biventricular function CMR parameters of Sβ-thal patients were compared with those of 111 healthy volunteers, matched by gender and age. Myocardial iron overload (MIO) was assessed by T2* technique. Cine images were acquired to quantify biventricular function. Macroscopic myocardial fibrosis was evaluated by late gadolinium enhancement (LGE) technique.

Results. In Sβ-thal and SCD patients morphological and functional MR parameters were not significantly different, except for left atrial area and SVI (p = 0.023 and p = 0.048, respectively) that were significantly higher in SCD patients. No significant differences between the two groups were found in terms of myocardial iron overload and macroscopic myocardial fibrosis. When compared to healthy subjects, Sβ-thal patients showed significantly higher bi-atrial and biventricular parameters except for LVEF that was significantly lower (Fig.1).

Conclusions. The CMR analysis confirmed that Sβ-thal and SCD patients are phenotypically similar. Since Sβ-thal patients showed markedly different morphological and functional indices from healthy subjects, it would be useful to identify Sβ-thal/SCD-specific bi-atrial and biventricular reference values.
Grading mitral regurgitation using 4D flow CMR: comparison to transthoracic echocardiography
Authors: Ribeyrolles S , Monin JL , Rohnean A , Diakov C , Caussin C , Monnot S , Paul JF
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Mitral Regurgitation (MR) is currently primarily assessed using multiple transthoracic echocardiography (TTE) parameters. Two-dimensional Cardiac Magnetic Resonance (CMR) can be used in difficult cases but has limited agreement with TTE for quantifying MR. We hypothesized that 4D Flow CMR may help to quantify MR.

OBJECTIVES

To determine the 4D Flow CMR thresholds that achieve the best agreement with TTE for grading MR.

METHODS

 We conducted a single-center prospective study of patients evaluated for chronic primary MR in 2016-2020. MR was evaluated blindly by TTE and 4D Flow CMR respectively by two cardiologists and two radiologists with decades of experience. MR was graded with both methods as mild, moderate or severe. 4D Flow CMR measurements included MR regurgitant volume per beat (RV) and mitral anterograde flow per beat (MF). RF was obtained as the ratio RV/MF. Additionally, MF was compared to left ventricular stroke volume (LVSV) by cine-CMR.

RESULTS

 We included 33 patients in the initial cohort and 33 in the validation cohort. Inter-observer agreement was good for TTE and excellent for 4D Flow CMR. Agreement between MF and LVSV was excellent. Using recommended TTE thresholds (30 mL, 60 mL, 30%, 50%), agreement was moderate for RV and RF. The best agreement between 4D Flow CMR and TTE was obtained with CMR thresholds of 20 mL and 40 mL for RV (κ=0.93; 95%CI, 0.8-1) and 20% and 37% for RF (κ=0.90; 95%CI, 0.7-0.9). In the validation cohort, agreement between TTE and 4D Flow CMR was good with the optimal thresholds (κ= 0.78; 95%CI, 0.61-0.94).

CONCLUSION

We propose CMR thresholds that provide a good agreement between TTE and CMR for grading MR. Further studies are needed to fully validate 4D-Flow CMR accuracy for primary MR quantification.
Prognostic assessment following acute myocarditis requires convalescent scanning: neither peak troponin nor index scan T2 signal predicts convalescent late gadolinium enhancement
Authors: Zaman S , Vimalesvaran K , Johns I , Howard JP , Cole GD
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiovascular magnetic resonance (CMR) is a key diagnostic investigation in acute myocarditis (1) and permits quantification of late gadolinium enhancement (LGE) and myocardial oedema.  Follow-up CMR imaging is recommended to check for persistence of scar and oedema (2).  Persistent late gadolinium enhancement is associated with a worse prognosis (3). It is not known whether all patients require follow-up scanning or whether the initial scan can provide useful information to identify which patients need convalescent assessment. 

Purpose

In this study we considered whether extent of troponin elevation, extent of T2 elevation and initial late gadolinium enhancement burden predicted long-term late gadolinium enhancement at follow-up.

Methods

Index and follow-up CMR scans of consecutive patients presenting with a diagnosis of acute myocarditis between 2019 and 2020 across three hospitals were included. Inclusion criteria were: follow-up scan within 9 months of the index scan, CMR with LGE imaging and T2 mapping, and acute myocarditis being the primary diagnosis of the index scan. Myocardial T2 values in the area affected by myocarditis and percentage of LV myocardium showing late enhancement (using a threshold-based full height half width or manual region of interest strategy) were extracted.

Results

20 patients were included in the study (80% male; mean age 37 years). Mean interval between the index and follow-up scan was 4.1 months.  Peak troponin level during the acute illness was not associated with the proportion of LV myocardium affected by LGE in the index scan (R^2 <0.01) (Figure 1A). Myocardial T2 values in the first scan were not associated with the proportional resolution in LGE between the index and follow-up scans (R^2 0.02) (Figure 1B). The mean change in LGE was -61.7% (+/-22.8%) but the initial LGE burden did not predict the proportional degree of improvement in LGE between scans (R^2 <0.01)(Figure 1C).

Conclusions

The extent of troponin elevation and initial CMR phenotype was not a good predictor of the burden of long-term late gadolinium enhancement.  Although most cases showed improvement in LGE scar burden between index and follow-up imaging, neither peak troponin level during the acute episode, nor T2 values at the first CMR scan were predictive of initial or change in scar burden. Serial CMR assessment is required to identify those patients who have residual long-term scarring.
Cardiac magnetic resonance in athletes with ventricular arrhythmias
Authors: Aldrovandi A , Patrizi G , Iadanza M , Tardini L , Lodi E , Sansone R , Savino G , Cappelli S
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

Background

Ventricular arrhythmias in athletes represent an important issue in sport eligibility as they may be a marker of a concealed cardiomyopathy, potentially at risk of sudden cardiac death during sport activity.

Purpose

to assess the utility of cardiac magnetic resonance (CMR) to identify cardiac abnormalities in athletes with documented frequent premature ventricular beats (PVB) or complex ventricular arrhythmias (VA) undergoing competitive sport eligibility screening.

Methods

We enrolled 65 athletes with documented ventricular arrhythmias as follows: 1) frequent PVB at 24-hour ambulatory ECG monitoring (>100 PVB/24h); 2) polymorphic PVB; 3) repetitive PVB (couplets, triplets, or nonsustained ventricular tachicardia). All athletes were studied with rest ECG, exercise stress testing, 24-hour ambulatory ECG monitoring, transthoracic echocardiography and contrast-enhanced CMR.

Results

Sixty-five athletes (56 males, 9 females, age 30 ± 15years) underwent CMR with gadolinium contrast. In 55 patients (84.6%) CMR was normal, in 10 patients (15.4%) the following abnormalities were reported at CMR: four patients with isolated late gadolinium enhancement (LGE) of whom 3 patients with subepicardial LGE in the inferolateral wall and 1 patient with intramyocardial basal inferior LGE; 1 patient with hypertrophic cardiomyopathy with septal LGE; 1 patient with left ventricular non compaction; 3 patients with right ventricular abnormalities (a 13-year-old patient with dilated right ventricle and LGE located at the superior interventricular insertion point, 1 patient with a dilated and hypokinetic right ventricle, 1 patient with a focal right ventricular aneurysm). Transthoracic echocardiography was normal in 7/10 (70%) athletes with CMR abnormalities.

Conclusion

In athletes with frequent or complex ventricular arrhythmias cardiac magnetic resonance identifies cardiac abnormalities in a significant proportion of subjects and it may offer a diagnostic incremental value.
Left atrioventricular coupling index to predict incident heart failure: the multi-ethnic study of atherosclerosis (MESA)
Authors: Pezel T , Ambale Venkatesh B , Kato Y , De Vasconcellos H , Heckbert S , Wu C , Post W , Bluemke D , Cohen Solal A , Henry P , Lima J
Published: July 2021

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Although left atrial (LA) and left ventricular (LV) structural and functional parameters have independent prognostic value as predictors of HF, the close physiological relationship between LA and LV suggest that the assessment of LA/LV coupling could better reflect left atrioventricular dysfunction and be a better predictor of heart failure (HF).

PURPOSE

We investigated the prognostic value of a left atrioventricular coupling index (LACI), measured by cardiovascular magnetic resonance (CMR), as well as change in LACI to predict incident HF in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

In the MESA, 2,250 study participants, free of clinically recognized HF and cardiovascular disease at baseline, had LACI assessed by CMR imaging at baseline (Exam 1, 2000–2002), and ten years later (Exam 5, 2010–2012). LACI was defined as the ratio of LA to LV end-diastolic volumes. Univariable and multivariable Cox proportional hazard models were used to evaluate the associations of LACI and average annualized change in LACI (ΔLACI) with incident HF after adjustment on traditional HF risk factors. The incremental risk prediction was calculated using C-statistic, categorical net reclassification index (NRI) and integrative discrimination index (IDI).

RESULTS

Among the 2,250 participants (mean age 59.3 ± 9.3 years and 47.6% male participants), 50 incident HF events occurred over 6.8 ± 1.3 years after the second CMR exam. After adjustment, greater LACI and ΔLACI were independently associated with HF (adjusted HR 1.44, 95% CI [1.25-1.66] and adjusted HR 1.55, 95% CI [1.30-1.85], respectively; both p < 0.0001). Adjusted models for LACI showed significant improvement in model discrimination and reclassification compared to currently used HF risk score model for predicting HF incidence (C-statistic: 0.81 vs. 0.77; NRI = 0.411; IDI = 0.043). After adjustment, ΔLACI showed also significant improvement in model discrimination compared to the multivariable model with traditional HF risk factors for predicting incident HF (C-statistic: 0.82 vs. 0.77; NRI = 0.491; IDI = 0.058).

CONCLUSIONS

In a multi-ethnic population, atrioventricular coupling (LACI) and coupling change (ΔLACI) are independently associated with incident HF. Both have incremental prognostic value for predicting HF over traditional HF risk factors.