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Simpson R.,NIHR Royal Brompton Cardiovascular Biomedical Research Unit | Simpson R.,Imperial College London | Simpson R.,Cardiovascular Magnetic Resonance Unit | Keegan J.,NIHR Royal Brompton Cardiovascular Biomedical Research Unit | And 3 more authors.
Journal of Cardiovascular Magnetic Resonance

Background: Three-directional phase velocity mapping (PVM) is capable of measuring longitudinal, radial and circumferential regional myocardial velocities. Current techniques use Cartesian k-space coverage and navigator-gated high spatial and high temporal resolution acquisitions are long. In addition, prospective ECG-gating means that analysis of the full cardiac cycle is not possible. The aim of this study is to develop a high temporal and high spatial resolution PVM technique using efficient spiral k-space coverage and retrospective ECG-gating. Detailed analysis of regional motion over the entire cardiac cycle, including atrial systole for the first time using MR, is presented in 10 healthy volunteers together with a comprehensive assessment of reproducibility. Methods. A navigator-gated high temporal (21 ms) and spatial (1.4 × 1.4 mm) resolution spiral PVM sequence was developed, acquiring three-directional velocities in 53 heartbeats (100% respiratory-gating efficiency). Basal, mid and apical short-axis slices were acquired in 10 healthy volunteers on two occasions. Regional and transmural early systolic, early diastolic and atrial systolic peak longitudinal, radial and circumferential velocities were measured, together with the times to those peaks (TTPs). Reproducibilities were determined as mean ± SD of the signed differences between measurements made from acquisitions performed on the two days. Results: All slices were acquired in all volunteers on both occasions with good image quality. The high temporal resolution allowed consistent detection of fine features of motion, while the high spatial resolution allowed the detection of statistically significant regional and transmural differences in motion. Colour plots showing the regional variations in velocity over the entire cardiac cycle enable rapid interpretation of the regional motion within any given slice. The reproducibility of peak velocities was high with the reproducibility of early systolic, early diastolic and atrial systolic peak radial velocities in the mid slice (for example) being -0.01 ± 0.36, 0.20 ± 0.56 and 0.14 ± 0.42 cm/s respectively. Reproducibility of the corresponding TTP values, when normalised to a fixed systolic and diastolic length, was also high (-13.8 ± 27.4, 1.3 ± 21.3 and 3.0 ± 10.9 ms for early systolic, early diastolic and atrial systolic respectively). Conclusions: Retrospectively gated spiral PVM is an efficient and reproducible method of acquiring 3-directional, high resolution velocity data throughout the entire cardiac cycle, including atrial systole. © 2013 Simpson et al.; licensee BioMed Central Ltd. Source

Kilner P.J.,Cardiovascular Magnetic Resonance Unit
British Journal of Radiology

Transthoracic echocardiography is the first-line modality for cardiovascular imaging in adults with congenital heart disease (ACHD). The windows of access that are possible with transthoracic echocardiography are, however, rarely adequate for all regions of interest. The choice of further imaging depends on the clinical questions that remain to be addressed. The strengths of MRI include comprehensive access and coverage, providing imaging of all parts of the right ventricle, the pulmonary arteries, pulmonary veins and aorta. Cine images and velocity maps are acquired in specifically aligned planes, with stacks of cines or dynamic contrast angiography providing more comprehensive coverage. Tissues can be characterised if necessary, and MRI provides relatively accurate measurements of biventricular function and volume flow. These parameters are important in the assessment and follow-up of adults after repairs for tetralogy of Fallot or transposition of the great arteries and after Fontan operations. The superior spatial resolution and rapid acquisition of CT are invaluable in selected situations, including the visualisation of anomalous coronary or aortopulmonary collateral arteries, the assessment of luminal patency after stenting and imaging in patients with pacemakers. Ionising radiation is, however, a concern in younger patients who may need repeated investigation. Adults with relatively complex conditions should ideally be imaged in a specialist ACHD centre, where dedicated echocardiographic and cardiovascular MRI services are a necessary facility. General radiologists should be aware of the nature and pathophysiology of congenital heart disease, and should be alert for previously undiagnosed cases presenting in adulthood, including cases of atrial septal defect, aortic coarctation, patent ductus arteriosus, double-chambered right ventricle and congenitally corrected transposition. © 2011 The British Institute of Radiology. Source

Baksi A.J.,Cardiovascular Magnetic Resonance Unit | Pennell D.J.,Cardiovascular Magnetic Resonance Unit
Topics in Magnetic Resonance Imaging

This review describes and discusses the rationale, technique, applications, and impact of cardiovascular magnetic resonance (CMR) T2∗ imaging, principally in the assessment of iron loading within the heart, and highlights how this robust imaging strategy has transformed disease outcome. Until recently, no simple noninvasive measurement was available to reliably indicate severe cardiac iron loading before the development of overt cardiac dysfunction or heart failure. Consequently, the majority of patients with transfusion-dependent anemias, such as A-thalassemia major, died prematurely of cardiovascular complications of severe iron overload. The magnetic properties of particulate iron disrupt magnetic field homogeneity in the CMR environment and consequently influence the CMR parameter T2∗, which describes signal decay relating to both field inhomogeneity and loss of spin coherence. There is a direct relationship between T2∗ and myocardial iron concentration, enabling this to be used to identify and quantify myocardial iron load. Single breath-hold gradient-echo sequences in which a single midventricular short-axis myocardial slice is acquired at multiple echo times enables a myocar-dial T2∗ value to be measured from the rate of exponential decay. The application of T2∗ CMR to assessing cardiac iron loading is rapid, reproducible, extensively validated, and now widely performed. Data have highlighted the profound predictive power of this imaging technique and moreover its ability to inform management strategies such that, over a relatively short duration, outcome has been dramatically improved, and the disease course in A-thalassemia major transformed. Copyright © 2014 Lippincott Williams & Wilkins. Source

MacEira A.M.,Cardiac Imaging Unit | Cosin-Sales J.,Hospital Arnau de Vilanova | Roughton M.,Royal Brompton Hospital | Prasad S.K.,Cardiovascular Magnetic Resonance Unit | Pennell D.J.,Cardiovascular Magnetic Resonance Unit
Journal of Cardiovascular Magnetic Resonance

Background: Left atrial (LA) size is related to cardiovascular morbidity and mortality. Cardiovascular magnetic resonance (CMR) provides high quality images of the left atrium with high temporal resolution steady state free precession (SSFP) cine sequences. We used SSFP cines to define normal ranges for LA volumes and dimensions relative to gender, age and body surface area (BSA), and examine the relative value of 2D atrial imaging techniques in patients. For definition of normal ranges of LA volume we studied 120 healthy subjects after careful exclusion of cardiovascular abnormality (60 men, 60 women; 20 subjects per age decile from 20 to 80 years). Data were generated from 3-dimensional modeling, including tracking of the atrioventricular ring motion and time-volume curves analysis. For definition of the best 2D images-derived predictors of LA enlargement, we studied 120 patients (60 men, 60 women; age range 20 to 80 years) with a clinical indication for CMR. Results: In the healthy subjects, age was associated with LA 4-chamber transverse and 3-chamber anteroposterior diameters, but not with LA volume. Gender was an independent predictor of most absolute LA dimensions and volume, but following normalization to BSA, some associations became non-significant. CMR normal ranges were modeled and are tabled for clinical use with normalization, where appropriate, for BSA and gender and display of parameter variation with age. The best 2D predictors of LA volume were the 2-chamber area and 3-chamber area (both r = 0.90, p < 0.001). Conclusions: These CMR data show that LA dimensions and volume in healthy, individuals vary significantly by BSA, with lesser effects of age and gender. © 2010 Maceira et al; licensee BioMed Central Ltd. Source

Grasso A.E.,Cardiovascular Magnetic Resonance Unit | Pennell D.J.,Cardiovascular Magnetic Resonance Unit
International Journal of Cardiology

We present a case of lateral wall infarction in the territory of an anomalous circumflex artery without significant stenosis. The unusual location of the infarction suggests a causal relation with the anomalous artery through minor plaque rupture, which may have resulted from mechanical stress. © 2008 Elsevier Ireland Ltd. All rights reserved. Source

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