Showing papers by "Steffen E. Petersen published in 2016"

A review of heart chamber segmentation for structural and functional analysis using cardiac magnetic resonance imaging

Abstract: Cardiovascular magnetic resonance (CMR) has become a key imaging modality in clinical cardiology practice due to its unique capabilities for non-invasive imaging of the cardiac chambers and great vessels. A wide range of CMR sequences have been developed to assess various aspects of cardiac structure and function, and significant advances have also been made in terms of imaging quality and acquisition times. A lot of research has been dedicated to the development of global and regional quantitative CMR indices that help the distinction between health and pathology. The goal of this review paper is to discuss the structural and functional CMR indices that have been proposed thus far for clinical assessment of the cardiac chambers. We include indices definitions, the requirements for the calculations, exemplar applications in cardiovascular diseases, and the corresponding normal ranges. Furthermore, we review the most recent state-of-the art techniques for the automatic segmentation of the cardiac boundaries, which are necessary for the calculation of the CMR indices. Finally, we provide a detailed discussion of the existing literature and of the future challenges that need to be addressed to enable a more robust and comprehensive assessment of the cardiac chambers in clinical practice.

Role of multimodality cardiac imaging in the management of patients with hypertrophic cardiomyopathy: an expert consensus of the European Association of Cardiovascular Imaging Endorsed by the Saudi Heart Association

Abstract: Taking into account the complexity and limitations of clinical assessment in hypertrophic cardiomyopathy (HCM), imaging techniques play an essential role in the evaluation of patients with this disease. Thus, in HCM patients, imaging provides solutions for most clinical needs, from diagnosis to prognosis and risk stratification, from anatomical and functional assessment to ischaemia detection, from metabolic evaluation to monitoring of treatment modalities, from staging and clinical profiles to follow-up, and from family screening and preclinical diagnosis to differential diagnosis. Accordingly, a multimodality imaging (MMI) approach (including echocardiography, cardiac magnetic resonance, cardiac computed tomography, and cardiac nuclear imaging) is encouraged in the assessment of these patients. The choice of which technique to use should be based on a broad perspective and expert knowledge of what each technique has to offer, including its specific advantages and disadvantages. Experts in different imaging techniques should collaborate and the different methods should be seen as complementary, not as competitors. Each test must be selected in an integrated and rational way in order to provide clear answers to specific clinical questions and problems, trying to avoid redundant and duplicated information, taking into account its availability, benefits, risks, and cost.

The multi-modality cardiac imaging approach to the Athlete's heart: an expert consensus of the European Association of Cardiovascular Imaging

Abstract: The term 'athlete's heart' refers to a clinical picture characterized by a slow heart rate and enlargement of the heart. A multi-modality imaging approach to the athlete's heart aims to differentiate physiological changes due to intensive training in the athlete's heart from serious cardiac diseases with similar morphological features. Imaging assessment of the athlete's heart should begin with a thorough echocardiographic examination.Left ventricular (LV) wall thickness by echocardiography can contribute to the distinction between athlete's LV hypertrophy and hypertrophic cardiomyopathy (HCM). LV end-diastolic diameter becomes larger (>55 mm) than the normal limits only in end-stage HCM patients when the LV ejection fraction is <50%. Patients with HCM also show early impairment of LV diastolic function, whereas athletes have normal diastolic function.When echocardiography cannot provide a clear differential diagnosis, cardiac magnetic resonance (CMR) imaging should be performed.With CMR, accurate morphological and functional assessment can be made. Tissue characterization by late gadolinium enhancement may show a distinctive, non-ischaemic pattern in HCM and a variety of other myocardial conditions such as idiopathic dilated cardiomyopathy or myocarditis. The work-up of athletes with suspected coronary artery disease should start with an exercise ECG. In athletes with inconclusive exercise ECG results, exercise stress echocardiography should be considered. Nuclear cardiology techniques, coronary cardiac tomography (CCT) and/or CMR may be performed in selected cases. Owing to radiation exposure and the young age of most athletes, the use of CCT and nuclear cardiology techniques should be restricted to athletes with unclear stress echocardiography or CMR.

Lung Deflation and Cardiovascular Structure and Function in Chronic Obstructive Pulmonary Disease. A Randomized Controlled Trial.

Abstract: Rationale: Patients with chronic obstructive pulmonary disease develop increased cardiovascular morbidity with structural alterations.Objectives: To investigate through a double-blind, placebo-controlled, crossover study the effect of lung deflation on cardiovascular structure and function using cardiac magnetic resonance.Methods: Forty-five hyperinflated patients with chronic obstructive pulmonary disease were randomized (1:1) to 7 (maximum 14) days inhaled corticosteroid/long-acting β2-agonist fluticasone furoate/vilanterol 100/25 μg or placebo (7-day minimum washout). Primary outcome was change from baseline in right ventricular end-diastolic volume index versus placebo.Measurements and Main Results: There was a 5.8 ml/m2 (95% confidence interval, 2.74–8.91; P < 0.001) increase in change from baseline right ventricular end-diastolic volume index and a 429 ml (P < 0.001) reduction in residual volume with fluticasone furoate/vilanterol versus placebo. Left ventricular end-diastolic and left atrial end-sy...

Automated Quality Assessment of Cardiac MR Images Using Convolutional Neural Networks

Abstract: Image quality assessment (IQA) is crucial in large-scale population imaging so that high-throughput image analysis can extract meaningful imaging biomarkers at scale. Specifically, in this paper, we address a seemingly basic yet unmet need: the automatic detection of missing (apical and basal) slices in Cardiac Magnetic Resonance Imaging (CMRI) scans, which is currently performed by tedious visual assessment. We cast the problem as classification tasks, where the bottom and top slices are tested for the presence of typical basal and apical patterns. Inspired by the success of deep learning methods, we train Convolutional Neural Networks (CNN) to construct a set of discriminative features. We evaluated our approach on a subset of the UK Biobank datasets. Precision and Recall figures for detecting missing apical slice (MAS) (81.61 % and 88.73 %) and missing basal slice (MBS) (74.10 % and 88.75 %) are superior to other state-of-the-art deep learning architectures. Cross-dataset experiments show the generalization ability of our approach.

Cardiovascular Risk Assessment: A Systematic Review of Guidelines

Abstract: Background Many guidelines exist for screening and risk assessment for the primary prevention of cardiovascular disease in apparently healthy persons. Purpose To systematically review current primary prevention guidelines on adult cardiovascular risk assessment and highlight the similarities and differences to aid clinician decision making. Data sources Publications in MEDLINE and CINAHL between 3 May 2009 and 30 June 2016 were identified. On 30 June 2016, the Guidelines International Network International Guideline Library, National Guideline Clearinghouse, National Library for Health Guidelines Finder, Canadian Medical Association Clinical Practice Guidelines Infobase, and Web sites of organizations responsible for guideline development were searched. Study selection 2 reviewers screened titles and abstracts to identify guidelines from Western countries containing recommendations for cardiovascular risk assessment for healthy adults. Data extraction 2 reviewers independently assessed rigor of guideline development using the Appraisal of Guidelines for Research and Evaluation II instrument, and 1 extracted the recommendations. Data synthesis Of the 21 guidelines, 17 showed considerable rigor of development. These recommendations address assessment of total cardiovascular risk (5 guidelines), dysglycemia (7 guidelines), dyslipidemia (2 guidelines), and hypertension (3 guidelines). All but 1 recommendation advocates for screening, and most include prediction models integrating several relatively simple risk factors for either deciding on further screening or guiding subsequent management. No consensus on the strategy for screening, recommended target population, screening tests, or treatment thresholds exists. Limitation Only guidelines developed by Western national or international medical organizations were included. Conclusion Considerable discrepancies in cardiovascular screening guidelines still exist, with no consensus on optimum screening strategies or treatment threshold. Primary funding source Barts Charity.

Cardiovascular Risk Assessment

Abstract: This review examines the similarities and differences among leading primary prevention guidelines that address cardiovascular screening and risk assessment.

EACVI appropriateness criteria for the use of cardiovascular imaging in heart failure derived from European National Imaging Societies voting

Abstract: This paper presents the first European appropriateness criteria for the use of cardiovascular imaging in heart failure, derived from voting of the European National Imaging Societies representatives. The paper describes the development process and discusses the results.

Comparative cost-effectiveness of non-invasive imaging tests in patients presenting with chronic stable chest pain with suspected coronary artery disease: a systematic review.

Abstract: Coronary artery disease (CAD) remains one of the leading causes of morbidity and mortality globally. The most cost-effective imaging strategy to diagnose CAD in patients with stable chest pain is however uncertain. To review the evidence on comparative cost-effectiveness of different imaging strategies for patients presenting with stable chest pain symptoms suggestive for CAD. Systematic review. Studies performing a formal economic evaluation or decision analysis in the English language published between January 1995 and December 2015 were identified using PubMed, Medline (OvidSP), Embase, Web of Science, Cochrane economic evaluations library, and EconLit. Reviews and meta-analyses were excluded. Two independent reviewers assessed titles and abstracts. Of the 4498 titles identified, 70 met our selection criteria. One reviewer used a modified version of the CHEERS checklist to assess study quality. One reviewer extracted data on study details, which were checked by a second reviewer. There is a major heterogeneity between the available cost-effectiveness studies included in this study. The included studies compared very different testing strategies in very different ways and provided mostly short-term results. Strategies of no-testing and xECG were underrepresented. Nonetheless, the findings from this systematic review suggest that for patients with a low to intermediate prior probability of having obstructive CAD, computed tomography coronary angiography (CTCA) may be cost-effective as an initial diagnostic imaging test in comparison with CAG or other non-invasive diagnostic tests. If functional testing is required, stress echocardiography (SE) or single-photon emission computed tomography (SPECT) are suggested to be cost-effective initial strategies in patients with intermediate prior probability of CAD. Yet, other functional testing strategies such as xECG and positron-emission tomography (PET) scanning have not been studied as intensely. Immediate CAG is suggested to be a cost-effective strategy for patients at a high prior probability of having obstructive CAD whom may benefit from revascularization. The study emphasizes the inextricable link between clinical effectiveness and economic efficiency. Evidence suggests that the optimal diagnostic imaging strategy for individuals suspected of having CAD is CTCA for low and intermediate disease probability, followed by SE or SPECT as necessary, and invasive CAG for high disease probability. Further studies are needed to evaluate the cost-effectiveness of alternative non-invasive tests, including a no-testing strategy.

Towards the Semantic Enrichment of Free-Text Annotation of Image Quality Assessment for UK Biobank Cardiac Cine MRI Scans

Abstract: Image quality assessment is fundamental as it affects the level of confidence in any output obtained from image analysis. Clinical research imaging scans do not often come with an explicit evaluation of their quality, however reports are written associated to the patient/volunteer scans. This rich free-text documentation has the potential to provide automatic image quality assessment if efficiently processed and structured. This paper aims at showing how the use of Semantic Web technology for structuring free-text documentation can provide means for automatic image quality assessment. We aim to design and implement a semantic layer for a special dataset, the annotations made in the context of the UK Biobank Cardiac Cine MRI pilot study. This semantic layer will be a powerful tool to automatically infer or validate quality scores for clinical images and efficiently query image databases based on quality information extracted from the annotations. In this paper we motivate the need for this semantic layer, present an initial version of our ontology as well as preliminary results. The presented approach has the potential to be extended to broader projects and ultimately employed in the clinical setting.

Comparison of Cartesian and Non-Cartesian Real-Time MRI Sequences at 1.5T to Assess Velar Motion and Velopharyngeal Closure during Speech.

Abstract: Dynamic imaging of the vocal tract using real-time MRI has been an active and growing area of research, having demonstrated great potential to become routinely performed in the clinical evaluation of speech and swallowing disorders. Although many technical advances have been made in regards to acquisition and reconstruction methodologies, there is still no consensus in best practice protocols. This study aims to compare Cartesian and non-Cartesian real-time MRI sequences, regarding image quality and temporal resolution trade-off, for dynamic speech imaging. Five subjects were imaged at 1.5T, while performing normal phonation, in order to assess velar motion and velopharyngeal closure. Data was acquired using both Cartesian and non-Cartesian (spiral and radial) real-time sequences at five different spatial-temporal resolution sets, between 10 fps (1.7×1.7×10 mm3) and 25 fps (1.5×1.5×10 mm3). Only standard scanning resources provided by the MRI scanner manufacturer were used to ensure easy applicability to clinical evaluation and reproducibility. Data sets were evaluated by comparing measurements of the velar structure, dynamic contrast-to-noise ratio and image quality visual scoring. Results showed that for all proposed sequences, FLASH spiral acquisitions provided higher contrast-to-noise ratio, up to a 170.34% increase at 20 fps, than equivalent bSSFP Cartesian acquisitions for the same spatial-temporal resolution. At higher frame rates (22 and 25 fps), spiral protocols were optimal and provided higher CNR and visual scoring than equivalent radial protocols. Comparison of dynamic imaging at 10 and 22 fps for radial and spiral acquisitions revealed no significant difference in CNR performance, thus indicating that temporal resolution can be doubled without compromising spatial resolution (1.9×1.9 mm2) or CNR. In summary, this study suggests that the use of FLASH spiral protocols should be preferred over bSSFP Cartesian for the dynamic imaging of velopharyngeal closure, as it allows for an improvement in CNR and overall image quality without compromising spatial-temporal resolution.

The association of left atrial volume with age, ethnicity and cardiovascular risk factors in men and women: the Multi-Ethnic Study of Atherosclerosis (MESA)

Abstract: Methods LA volume indexed to body surface area (LAVi) was measured by CMR using steady-state free precession cine long and short axis images in 2576 participants of the MultiEthnic Study of Atherosclerosis (68.7 years, 53.0% women). We used gender stratified regression models to evaluate the association of LAVi as the dependent variable with demographic and cardiovascular risk factors, left ventricular (LV) parameters and diagnosis of coronary heart disease as independent variables. LAVi between ethnicities were compared using analysis of variance (ANOVA) with Tukey’s post-hoc analysis. To determine normal LA dimensions we also selected a group of participants with normal body mass index (≥18.5 and < 25 kg/m), without hypertension, diabetes, coronary heart disease, congestive heart failure, LV systolic dysfunction (defined as ejection fraction less than 50%), LV hypertrophy or atrial fibrillation (n = 285, 65.6 years, 61.8% women). Results The unadjusted mean LA volume index in the whole cohort was 36.5 ± 11.4 ml/m and was 9% smaller in men (35.9 ± 11.1 vs. 37.0 ± 11.6 ml/m, p < 0.05). LAVi was greater with age in men (b = 0.2 ml/m/yr, p < 0.0001) and women (b = 0.3 ml/m/yr, p < 0.0001). Both Chinese American men and women had significantly (p < 0.05) smaller LAVi compared to other ethnicities (Figure 2). History of coronary disease was associated with 10% larger LAVi in women (b=3.7 ml/m, p < 0.05), but not in men (p = ns). In the normal reference cohort free of cardiovascular disease there were no differences in LAVi by gender (men 34.5 ± 9.9 ml/m, women 36.0 ± 10.2 ml/m, p = 0.30).

A comparison of cardiac motion analysis software packages: application to left ventricular deformation analysis in healthy subjects

Abstract: Background Feature tracking (FT) software packages measure myocardial wall motion deformation parameters through the cardiac cycle. Myocardial tagging technique is currently considered the gold standard for myocardial deformation measurements. This study compares 2 FT-software packages with a tagging software package and investigates the differences in strain deformation parameters measured in healthy subjects.

Clinical Text Prediction with Numerically Grounded Conditional Language Models

Abstract: Assisted text input techniques can save time and effort and improve text quality. In this paper, we investigate how grounded and conditional extensions to standard neural language models can bring improvements in the tasks of word prediction and completion. These extensions incorporate a structured knowledge base and numerical values from the text into the context used to predict the next word. Our automated evaluation on a clinical dataset shows extended models significantly outperform standard models. Our best system uses both conditioning and grounding, because of their orthogonal benefits. For word prediction with a list of 5 suggestions, it improves recall from 25.03% to 71.28% and for word completion it improves keystroke savings from 34.35% to 44.81%, where theoretical bound for this dataset is 58.78%. We also perform a qualitative investigation of how models with lower perplexity occasionally fare better at the tasks. We found that at test time numbers have more influence on the document level than on individual word probabilities.

Automatic left ventricular analysis with Inline VF performs well compared to manual analysis: results from Barts Cardiovascular Registry.

Abstract: Background Manual left ventricular (LV) volumes and function analysis is time consuming and operator dependent. Automated and semi-automated LV analysis tools could be helpful, especially in high volume clinical and research centres. Inline VF (Siemens) is a fully-automated assessment tool performing LV volume analysis during scan acquisition. The aims of this study were: 1) to assess performance of Inline VF against manual analysis of LV volumes and function, 2) to derive conversion formulas from linear regression models and 3) to validate adjusted Inline VF parameters to ascertain whether this improves accuracy of the automated method.

The applicability of current global cardiovascular risk scores and cardiovascular surrogates in chronic obstructive pulmonary disease.

Abstract: Background Chronic obstructive pulmonary disease (COPD) is a complex disorder associated with significant cardiovascular morbidity and mortality. Despite this, current cardiovascular scoring systems do not include COPD in their risk prediction models. The aims of this casecontrol study were to assess whether differences in cardiovascular surrogate markers exist in COPD to further understand the relationship of COPD to cardiovascular structure and function.

Clinical Text Prediction with Numerically Grounded Conditional Language Models

Abstract: Assisted text input techniques can save time and effort and improve text quality. In this paper, we investigate how grounded and conditional extensions to standard neural language models can bring improvements in the tasks of word prediction and completion. These extensions incorporate a structured knowledge base and numerical values from the text into the context used to predict the next word. Our automated evaluation on a clinical dataset shows extended models significantly outperform standard models. Our best system uses both conditioning and grounding, because of their orthogonal benefits. For word prediction with a list of 5 suggestions, it improves recall from 25.03% to 71.28% and for word completion it improves keystroke savings from 34.35% to 44.81%, where theoretical bound for this dataset is 58.78%. We also perform a qualitative investigation of how models with lower perplexity occasionally fare better at the tasks. We found that at test time numbers have more influence on the document level than on individual word probabilities.

An Methodology for Quality Control and Draught Assessment of Room Ventilation Supply Using Laser Light Sheets

Abstract: A common technique to investigate draught problems in a room is to make spot measurements of air velocity. This might identify where the draught problem is located but it does not necessarily identify the distribution and source of the problem. Usually visual inspections of the location of ventilation inlet and smoke experiments are next step to track the draught source. However, these methods do not provide an understanding of the air flow pattern in the room with sufficient resolution to necessarily identify the source of the draught problem. However, laser light sheets together with smoke seeding for on-site visualization of airflow in rooms might be useful for tracking down draught sources in rooms as part of a commissioning process. This paper reports on the first attempts to use this simple method to visualize and characterize air flow patterns in two different classrooms. The visualizations disclosed the air movements, and it was possible to record the movements using a standard smartphone camera. From the movements it was possible to qualitatively assess the overall airflow patterns of the room. The resolution of the video recording was also sufficient to be processed in particle image velocimetry software to gain overall flow pattern visualization, if not accurate readings. The latter result indicates that there could be a potential for real-time velocimetry processing by smartphones but the method in general needs further investigation and documentation.

Towards the creation of the cardiovascular magnetic resonance quality assessment ontology (CMR-QA)

Abstract: 1 Logic and Intelligent Data Group, Department of Informatics, University of Oslo, Norway 2 Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, UK 3 William Harvey Research Institute, NIHR Cardiovascular Biomedical Research Unit at Barts, Queen Mary University of London, UK 4 Information Systems Group, Department of Computer Science, University of Oxford, UK