Publications
431 results found
Ferreira PF, Kilner PJ, McGill L-A, et al., 2014, In vivo cardiovascular magnetic resonance diffusion tensor imaging shows evidence of abnormal myocardial laminar orientations and mobility in hypertrophic cardiomyopathy, Journal of Cardiovascular Magnetic Resonance, Vol: 16, Pages: 1-16, ISSN: 1097-6647
BackgroundCardiac diffusion tensor imaging (cDTI) measures the magnitudes and directions of intramyocardial water diffusion. Assuming the cross-myocyte components to be constrained by the laminar microstructures of myocardium, we hypothesized that cDTI at two cardiac phases might identify any abnormalities of laminar orientation and mobility in hypertrophic cardiomyopathy (HCM).MethodsWe performed cDTI in vivo at 3 Tesla at end-systole and late diastole in 11 healthy controls and 11 patients with HCM, as well as late gadolinium enhancement (LGE) for detection of regional fibrosis.ResultsVoxel-wise analysis of diffusion tensors relative to left ventricular coordinates showed expected transmural changes of myocardial helix-angle, with no significant differences between phases or between HCM and control groups. In controls, the angle of the second eigenvector of diffusion (E2A) relative to the local wall tangent plane was larger in systole than diastole, in accord with previously reported changes of laminar orientation. HCM hearts showed higher than normal global E2A in systole (63.9° vs 56.4° controls, p =0.026) and markedly raised E2A in diastole (46.8° vs 24.0° controls, p < 0.001). In hypertrophic regions, E2A retained a high, systole-like angulation even in diastole, independent of LGE, while regions of normal wall thickness did not (LGE present 57.8°, p =0.0028, LGE absent 54.8°, p =0.0022 vs normal thickness 38.1°).ConclusionsIn healthy controls, the angles of cross-myocyte components of diffusion were consistent with previously reported transmural orientations of laminar microstructures and their changes with contraction. In HCM, especially in hypertrophic regions, they were consistent with hypercontraction in systole and failure of relaxation in diastole. Further investigation of this finding is required as previously postulated effects of strain might be a confounding factor.
Ambrose N, Pierce IT, Gatehouse PD, et al., 2014, Magnetic resonance imaging of vein wall thickness in patients with Behcet's syndrome, CLINICAL AND EXPERIMENTAL RHEUMATOLOGY, Vol: 32, Pages: S99-S102, ISSN: 0392-856X
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- Citations: 24
Patel HC, Keegan J, Simpson R, et al., 2014, A novel MRI technique to examine renal blood flow: could it be used to evaluate the effects of renal artery interventions?, Annual Meeting of the European-Society-of-Cardiology (ESC), Publisher: OXFORD UNIV PRESS, Pages: 641-641, ISSN: 0195-668X
Keegan J, Drivas P, Firmin DN, 2014, Navigator artifact reduction in three-dimensional late gadolinium enhancement imaging of the atria, Magnetic Resonance in Medicine, Vol: 72, Pages: 779-785, ISSN: 1522-2594
PurposeNavigator-gated three-dimensional (3D) late gadolinium enhancement (LGE) imaging demonstrates scarring following ablation of atrial fibrillation. An artifact originating from the slice-selective navigator-restore pulse is frequently present in the right pulmonary veins (PVs), obscuring the walls and making quantification of enhancement difficult. We describe a simple sequence modification to greatly reduce or remove this artifact.MethodsA navigator-gated inversion-prepared gradient echo sequence was modified so that the slice-selective navigator-restore pulse was delayed in time from the nonselective preparation (NAV-restore-delayed). Both NAV-restore-delayed and conventional 3D LGE acquisitions were performed in 11 patients and the results compared.ResultsOne patient was excluded due to severe respiratory motion artifact in both NAV-restore-delayed and conventional acquisitions. Moderate to severe artifact was present in 9 of the remaining 10 patients using the conventional sequence and was considerably reduced when using the NAV-restore-delayed sequence (ostial PV to blood pool ratio, 1.7 ± 0.5 versus 1.1 ± 0.2, respectively [P < 0.0001]; qualitative artifact scores, 2.8 ± 1.1 versus 1.2 ± 0.4, respectively [P < 0.001]). While navigator signal-to-noise ratio was reduced with the NAV-restore-delayed sequence, respiratory motion compensation was unaffected.ConclusionsShifting the navigator-restore pulse significantly reduces or eliminates navigator artifact. This simple modification improves the quality of 3D LGE imaging and potentially aids late enhancement quantification in the atria
Simpson R, Keegan J, Gatehouse P, et al., 2014, Spiral Tissue Phase Velocity Mapping in a Breath-Hold with Non-Cartesian SENSE, MAGNETIC RESONANCE IN MEDICINE, Vol: 72, Pages: 659-668, ISSN: 0740-3194
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- Citations: 14
Carpenter J-P, He T, Kirk P, et al., 2014, Calibration of myocardial T2 and T1 against iron concentration, JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 16, ISSN: 1097-6647
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- Citations: 28
Nielles-Vallespin S, Mekkaoui C, Gatehouse P, et al., 2014, In Vivo Diffusion Tensor MRI of the Human Heart: Reproducibility of Breath-Hold and Navigator Based Approaches (vol 70, pg 454, 2013), MAGNETIC RESONANCE IN MEDICINE, Vol: 72, Pages: 599-599, ISSN: 0740-3194
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- Citations: 5
Feng Y, He T, Feng M, et al., 2014, Improved Pixel-by-Pixel MRI R2*Relaxometry by Nonlocal Means, MAGNETIC RESONANCE IN MEDICINE, Vol: 72, Pages: 260-268, ISSN: 0740-3194
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- Citations: 14
Keegan J, Jhooti P, Babu-Narayan SV, et al., 2014, Improved Respiratory Efficiency of 3D Late Gadolinium Enhancement Imaging Using the Continuously Adaptive Windowing Strategy (CLAWS), MAGNETIC RESONANCE IN MEDICINE, Vol: 71, Pages: 1064-1074, ISSN: 0740-3194
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- Citations: 25
Tunnicliffe EM, Scott AD, Ferreira P, et al., 2014, Intercentre reproducibility of cardiac apparent diffusion coefficient and fractional anisotropy in healthy volunteers, Journal of Cardiovascular Magnetic Resonance, Vol: 16, Pages: 31-31
Ismail TF, Hsu L-Y, Greve AM, et al., 2014, Coronary microvascular ischemia in hypertrophic cardiomyopathy-a pixel-wise quantitative cardiovascular magnetic resonance perfusion study, Journal of Cardiovascular Magnetic Resonance, Vol: 16, Pages: 49-49
Feng Y, He T, Gatehouse PD, et al., 2013, Improved MRI <i>R</i><sub>2</sub>* Relaxometry of Iron-Loaded Liver with Noise Correction, MAGNETIC RESONANCE IN MEDICINE, Vol: 70, Pages: 1765-1774, ISSN: 0740-3194
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- Citations: 52
Pennell DJ, Baksi AJ, Carpenter JP, et al., 2013, Review of Journal of Cardiovascular Magnetic Resonance 2012, JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 15, ISSN: 1097-6647
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- Citations: 5
Feng Y, He T, Carpenter J-P, et al., 2013, In vivo comparison of myocardial T1 with T2 and T2*in thalassaemia major, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 38, Pages: 588-593, ISSN: 1053-1807
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- Citations: 55
De Luca A, Warboys C, Amini N, et al., 2013, TRANSCRIPTOME PROFILING IN PORCINE ARTERIES TO IDENTIFY NOVEL SHEAR-RESPONSIVE REGULATORS OF ENDOTHELIAL CELL FATE, Annual Conference of the British-Cardiovascular-Society (BCS), Publisher: BMJ PUBLISHING GROUP, ISSN: 1355-6037
Simpson R, Keegan J, Firmin D, 2013, Efficient and reproducible high resolution spiral myocardial phase velocity mapping of the entire cardiac cycle, Journal of Cardiovascular Magnetic Resonance, Vol: 15, ISSN: 1097-6647
BackgroundThree-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.MethodsA 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.ResultsAll 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 reproduc
Wang Y, Downie S, Wood N, et al., 2013, Finite element analysis of the deformation of deep veins in the lower limb under external compression, MEDICAL ENGINEERING & PHYSICS, Vol: 35, Pages: 515-523, ISSN: 1350-4533
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- Citations: 12
Simpson RM, Keegan J, Firmin DN, 2013, MR assessment of regional myocardial mechanics, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 37, Pages: 576-599, ISSN: 1053-1807
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- Citations: 49
McGill L-A, Ismail T, Nielles-Vallespin S, et al., 2013, reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy (vol 14, pg 86, 2012), JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 15, ISSN: 1097-6647
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- Citations: 2
He T, Zhang J, Carpenter J-P, et al., 2013, Automated truncation method for myocardial T2* measurement in thalassemia, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 37, Pages: 479-483, ISSN: 1053-1807
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- Citations: 21
Fair M, Gatehouse PD, Greiser A, et al., 2013, A novel approach to phase-contrast velocity offset correction by in vivo high-SNR acquisitions, Society for Cardiovascular Magnetic Resonance, Publisher: BioMed Central, ISSN: 1532-429X
Baseline offset errors on phase-contrast velocity imagescan be corrected using stationary tissue, for example sub-tracting fitted corrections from the image (1). Althoughcorrections are often curved over the FOV, 1st order(linear) fitting is typical. This may partly be due to lowSNR of static tissue making higher-order fitting unreli-able (2). Aim: To evaluate a new method acquiring addi-tional high SNR velocity images specifically to improveoffset correction.
McGill LA, Ismail T, Nielles-Vallespin S, et al., 2013, Correction: reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy., J Cardiovasc Magn Reson, Vol: 15
Ferreira PF, Gatehouse PD, Mohiaddin RH, et al., 2013, Cardiovascular magnetic resonance artefacts, Journal of Cardiovascular Magnetic Resonance, Vol: 15, Pages: 41-41
Nielles-Vallespin S, Mekkaoui C, Gatehouse P, et al., 2013, In vivo diffusion tensor MRI of the human heart: Reproducibility of breath-hold and navigator-based approaches, Magnetic resonance in medicine, Vol: 70, Pages: 454-465
McGill L-A, Ismail TF, Nielles-Vallespin S, et al., 2012, Reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy, Journal of Cardiovascular Magnetic Resonance, Vol: 14, Pages: 86-86, ISSN: 1097-6647
Background: Myocardial disarray is an important histological feature of hypertrophic cardiomyopathy (HCM) whichhas been studied post-mortem, but its in-vivo prevalence and extent is unknown. Cardiac Diffusion Tensor Imaging(cDTI) provides information on mean intravoxel myocyte orientation and potentially myocardial disarray. Recenttechnical advances have improved in-vivo cDTI, and the aim of this study was to assess the interstudyreproducibility of quantitative in-vivo cDTI in patients with HCM.Methods and results: A stimulated-echo single-shot-EPI sequence with zonal excitation and parallel imaging wasimplemented. Ten patients with HCM were each scanned on 2 different days. For each scan 3 short axismid-ventricular slices were acquired with cDTI at end systole. Fractional anisotropy (FA), mean diffusivity (MD), andhelix angle (HA) maps were created using a cDTI post-processing platform developed in-house. The mean ± SDglobal FA was 0.613 ± 0.044, MD was 0.750 ± 0.154 × 10-3 mm2/s and HA was epicardium −34.3 ± 7.6°,mesocardium 3.5 ± 6.9° and endocardium 38.9 ± 8.1°. Comparison of initial and repeat studies showed globalinterstudy reproducibility for FA (SD = ± 0.045, Coefficient of Variation (CoV) = 7.2%), MD (SD = ± 0.135 × 10-3 mm2/s,CoV = 18.6%) and HA (epicardium SD = ± 4.8°; mesocardium SD = ± 3.4°; endocardium SD = ± 2.9°). Reproducibilityof FA was superior to MD (p = 0.003). Global MD was significantly higher in the septum than the reference lateralwall (0.784 ± 0.188 vs 0.750 ± 0.154 x10-3 mm2/s, p < 0.001). Septal HA was significantly lower than the referencelateral wall in all 3 transmural layers (from −8.3° to −10.4°, all p < 0.001).Conclusions: To the best of our knowledge, this is the first study to assess the interstudy reproducibility of DTI inthe human HCM heart in-vivo and the largest cDTI stu
Ismail TF, Angell P, Jabbour A, et al., 2012, Impact of Anabolic Steroid Use on the Cardiac Interstitium in Recreational Bodybuilders: a T<sub>1</sub>-Mapping Cardiovascular Magnetic Resonance Study, CIRCULATION, Vol: 126, ISSN: 0009-7322
Ismail TF, Hsu L-Y, Greve A, et al., 2012, Novel Evidence of the Coronary Microvascular Steal Phenomenon in Hypertrophic Cardiomyopathy - A Quantitative Stress Perfusion Cardiovascular Magnetic Resonance Study, CIRCULATION, Vol: 126, ISSN: 0009-7322
Pennell DJ, Carpenter JP, Firmin DN, et al., 2012, Review of Journal of Cardiovascular Magnetic Resonance 2011, JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 14, ISSN: 1097-6647
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- Citations: 2
Gatehouse PD, Rolf MP, Bloch KM, et al., 2012, A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors, JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 14, ISSN: 1097-6647
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- Citations: 25
Ferreira PF, Gatehouse PD, Firmin DN, 2012, Myocardial first-pass perfusion imaging with hybrid-EPI: frequency-offsets and potential artefacts, Journal of Cardiovascular Magnetic Resonance, Vol: 14, Pages: 44-44, ISSN: 1097-6647
BackgroundFirst-pass myocardial perfusion is often imaged with a tailored hybrid centric interleaved echo-planar-imaging sequence, providing rapid image acquisition with good contrast enhancement. The centric interleaved phase-encode order minimises the effective time-of-echo but it is sensitive to frequency-offsets. This short article aims to show possible artefacts that might originate with this sequence, in the context of first-pass perfusion imaging, when frequency-offsets are present. Non-uniform magnitude modulation effects were also analysed.MethodsNumerical and phantom simulations were used to illustrate the effects of frequency-offsets and non-uniform magnitude modulation with this sequence in a typical perfusion protocol. In vivo data was post-processed to analyse the h-EPI’s sensitivity to the frequency-offsets.ResultsThe centric phase-order was shown to be highly sensitive to frequency-offsets due to its symmetrical phase slope. Resulting artefacts include blurring, and splitting of the image into two identical copies along the phase-encode direction. It was also shown that frequency-offsets can introduce signal loss and ghosting of the right ventricle signal into the myocardium. The in vivo results were confirmed by numerical and phantom simulations. Magnitude modulation effects were found to be small.ConclusionsImaging first-pass myocardial perfusion with an hybrid centric echo-planar-imaging sequence can be corrupted with ghosting and splitting of the image due to frequency-offsets.
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