Publications
245 results found
Robson MD, Gatehouse PD, 2010, Consequences of <i>T</i><sub>2</sub> Relaxation During Half-Pulse Slice Selection for Ultrashort TE Imaging, MAGNETIC RESONANCE IN MEDICINE, Vol: 64, Pages: 610-615, ISSN: 0740-3194
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- Citations: 16
Keenan NG, Sheppard MN, Grasso A, et al., 2010, Validation of Carotid Arterial Wall Volume Measurement by Cardiovascular Magnetic Resonance, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 31, Pages: 935-941, ISSN: 1053-1807
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- Citations: 5
Chan CF, Keenan NG, Nielles-Vallespin S, et al., 2010, Ultra-short echo time cardiovascular magnetic resonance of atherosclerotic carotid plaque, Journal of Cardiovascular Magnetic Resonance, Vol: 12, ISSN: 1097-6647
BackgroundMulti-contrast weighted cardiovascular magnetic resonance (CMR) allows detailed plaque characterisation and assessment of plaque vulnerability. The aim of this preliminary study was to show the potential of Ultra-short Echo Time (UTE) subtraction MR in detecting calcification.Methods14 ex-vivo human carotid arteries were scanned using CMR and CT, prior to histological slide preparation. Two images were acquired using a double-echo 3D UTE pulse, one with a long TE and the second with an ultra-short TE, with the same TR. An UTE subtraction (ΔUTE) image containing only ultra-short T2 (and T2*) signals was obtained by post-processing subtraction of the 2 UTE images. The ΔUTE image was compared to the conventional 3D T1-weighted sequence and CT scan of the carotid arteries.ResultsIn atheromatous carotid arteries, there was a 71% agreement between the high signal intensity areas on ΔUTE images and CT scan. The same areas were represented as low signal intensity on T1W and areas of void on histology, indicating focal calcification. However, in 15% of all the scans there were some incongruent regions of high intensity on ΔUTE that did not correspond with a high intensity signal on CT, and histology confirmed the absence of calcification.ConclusionsWe have demonstrated that the UTE sequence has potential to identify calcified plaque. Further work is needed to fully understand the UTE findings.
Dahl AL, Gatehouse PD, Kilner PJ, 2010, Background offset error in pulmonary and aortic phase contrast flow imaging of 94 patients, Journal of Cardiovascular Magnetic Resonance, Vol: 12, ISSN: 1097-6647
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- Citations: 1
Gatehouse PD, Rolf MP, Graves MJ, et al., 2010, Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements, Journal of Cardiovascular Magnetic Resonance, Vol: 12, ISSN: 1097-6647
AimsCardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems.Methods and ResultsIn a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement.ConclusionIn the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions.
Pierce I, Kalodiki E, Lattimer C, et al., 2010, Lower limb venous blood flow by magnetic resonance imaging during intermittent pneumatic compression of the calf and foot. EVF Antwerp, 24 Jun 2010, 11th meeting of the European Venous Forum, Publisher: Edizioni Minerva Medica
Pierce I, Kalodiki E, Lattimer CR, et al., 2010, Lower limb venous blood flow by magnetic resonance imaging during intermittent pneumatic compression of the calf and foot. Royal Society of Medicine Venous Forum, London, 28 Apr 2010., Venous Forum
Keenan NG, Mason JC, Maceira A, et al., 2009, Integrated Cardiac and Vascular Assessment in Takayasu Arteritis by Cardiovascular Magnetic Resonance, ARTHRITIS AND RHEUMATISM, Vol: 60, Pages: 3501-3509, ISSN: 0004-3591
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- Citations: 46
Keenan NG, Mason JC, Maceira A, et al., 2009, Integrated cardiac and vascular assessment in takayasu's arteritis by cardiovascular magnetic resonance, EUROPEAN HEART JOURNAL, Vol: 30, Pages: 746-746, ISSN: 0195-668X
Keenan NG, Locca D, Varghese A, et al., 2009, Magnetic resonance of carotid artery ageing in healthy subjects, ATHEROSCLEROSIS, Vol: 205, Pages: 168-173, ISSN: 0021-9150
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- Citations: 10
Keenan NG, Grasso A, Locca D, et al., 2009, Comparison of 2D and multislab 3D magnetic resonance techniques for measuring carotid wall volumes (vol 28, pg 1476, 2008), JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 29, Pages: 1493-1493, ISSN: 1053-1807
He T, Smith GC, Gatehouse PD, et al., 2009, On Using <i>T</i><sub>2</sub> to Assess Extrinsic Magnetic Field Inhomogeneity Effects Myocardial Siderosis on <i>T</i><sub>2</sub>* Measurements in in Thalassemia, MAGNETIC RESONANCE IN MEDICINE, Vol: 61, Pages: 501-506, ISSN: 0740-3194
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- Citations: 19
Bradlow WM, Gatehouse PD, Hughes RL, et al., 2009, Transit-Time Method to Demonstrate Whether or Not an Impedance Matching Occurs at the Pulmonary Junction Response, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 29, Pages: 499-499, ISSN: 1053-1807
Chan CF, Gatehouse PD, Hughes R, et al., 2009, Novel Technique Used to Detect Swallowing in Volume-Selective Turbo Spin-Echo (TSE) for Carotid Artery Wall Imaging, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 29, Pages: 211-216, ISSN: 1053-1807
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- Citations: 9
Ferreira P, Gatehouse P, Kellman P, et al., 2009, Variability of myocardial perfusion dark rim Gibbs artifacts due to sub-pixel shifts, Journal of Cardiovascular Magnetic Resonance, Vol: 11, Pages: 17-17
Keenan NG, Grasso A, Locca D, et al., 2008, Comparison of 2D and Multislab 3D Magnetic Resonance Techniques for Measuring Carotid Wall Volumes, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 28, Pages: 1476-1482, ISSN: 1053-1807
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- Citations: 7
He T, Gatehouse PD, Smith GC, et al., 2008, Myocardial T2* measurements in iron-overloaded thalassemia: An in vivo study to investigate optimal methods of quantification., Magn Reson Med, Vol: 60, Pages: 1082-1089, ISSN: 1522-2594
Reproducible and accurate myocardial T(2) (*) measurements are required for the quantification of iron in heart tissue in transfused thalassemia. The aim of this study was to determine the best method to measure the myocardial T(2) (*) from multi-gradient-echo data acquired both with and without black-blood preparation. Sixteen thalassemia patients from six centers were scanned twice locally, within 1 week, using an optimized bright-blood T(2) (*) sequence and then subsequently scanned at the standardization center in London within 4 weeks, using a T(2) (*) sequence both with and without black-blood preparation. Different curve-fitting models (monoexponential, truncation, and offset) were applied to the data and the results were compared by means of reproducibility. T(2) (*) measurements obtained using the bright- and black-blood techniques. The black-blood data were well fitted by the monoexponential model, which suggests that a more accurate measure of T(2) (*) can be obtained by removing the main source of errors in the bright-blood data. For bright-blood data, the offset model appeared to underestimate T(2) (*) values substantially and was less reproducible. The truncation model gave rise to more reproducible T(2) (*) measurements, which were also closer to the values obtained from the black-blood data. Magn Reson Med 60:1082-1089, 2008. (c) 2008 Wiley-Liss, Inc.
He T, Gatehouse PD, Kirk P, et al., 2008, Myocardial T2* measurement in iron-overloaded thalassemia: An ex vivo study to investigate optimal methods of quantification., Magn Reson Med, Vol: 60, Pages: 350-356, ISSN: 1522-2594
Myocardial T(*) (2) measurement has been increasingly used for iron quantification to assess the risk of cardiac complications in thalassemia patients. In this study the noise effects were evaluated along with different curve-fitting models on an iron overloaded ex vivo heart in order to determine the optimal method of T(*) (2) measurement and to help understand issues affecting reproducibility and accuracy. Gradient multiecho short axis images were acquired with differing numbers of excitations to generate varying signal-to-noise ratio (SNR) images. A noise correction method was implemented; linear and nonlinear curve-fitting algorithms were compared and different curve-fitting models (monoexponential, truncation, baseline subtraction, and offset) were evaluated. This study suggests that the T(*) (2) decay curve in an ex vivo heart can be fitted by a monoexponential model and accurate T(*) (2) measurements can be obtained with proper noise correction. With MRI noise, T(*) (2) is generally overestimated by including late low SNR data points, but underestimated by the offset or baseline subtraction models, which are in fact equivalent. In this situation the truncation model proves to be reproducible and more accurate than the other models. The study also shows that the nonlinear algorithm is preferred in T(*) (2) curve fitting.
Keenan NG, Mason JC, Maceira A, et al., 2008, Integrated cardiac and vascular assessment in Takayasu's arteritis and systemic lupus erythematosus by cardiovascular magnetic resonance, Annual Scientific Conference of the British-Cardiovascular-Society/British-Society-for-Cardiovascular-Research, Publisher: B M J PUBLISHING GROUP, Pages: A78-A79, ISSN: 1355-6037
Keenan NG, Grasso A, Locca D, et al., 2008, Comparison of two-dimensional and multi-slab three-dimensional magnetic resonance techniques for measuring carotid wall volumes, Annual Scientific Conference of the British-Cardiovascular-Society/British-Society-for-Cardiovascular-Research, Publisher: B M J PUBLISHING GROUP, Pages: A78-A78, ISSN: 1355-6037
Ferreira P, Gatehouse P, Bucciarelli-Ducci C, et al., 2008, Measurement of myocardial frequency offsets during first pass of a gadolinium-based contrast agent in perfusion studies, Magnetic resonance in medicine, Vol: 60, Pages: 860-870
Lyne JC, Gatehouse PD, Assomull RG, et al., 2007, Direct comparison of myocardial perfusion cardiovascular magnetic resonance sequences with parallel acquisition, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 26, Pages: 1444-1451, ISSN: 1053-1807
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- Citations: 15
Keegan J, Gatehouse PD, Yang G-Z, et al., 2007, Non-model-based correction of respiratory motion using beat-to-beat 3D spiral fat-selective imaging, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 26, Pages: 624-629, ISSN: 1053-1807
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- Citations: 42
He T, Gatehouse PD, Kirk P, et al., 2007, Black-blood T2*technique for myocardial iron measurement in thalassemia, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 25, Pages: 1205-1209, ISSN: 1053-1807
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- Citations: 74
Bradlow WM, Gatehouse PD, Hughes RL, et al., 2007, Assessing normal pulse wave velocity in the proximal pulmonary arteries using transit time: A feasibility, repeatability, and observer reproducibility study by cardiovascular magnetic resonance, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 25, Pages: 974-981, ISSN: 1053-1807
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- Citations: 30
, 2007, Attenuation resilient AIF estimation based on hierarchical Bayesian modelling for first pass myocardial perfusion MRI., Pages: 393-400
Non-linear attenuation of the Arterial Input Function (AIF) is a major problem in first-pass MR perfusion imaging due to the high concentration of the contrast agent in the blood pool. This paper presents a technique to reconstruct the true AIF using signal intensities in the myocardium and the attenuated AIF based on a Hierarchical Bayesian Model (HBM). With the proposed method, both the AIF and the response function are modeled as smoothed functions by using Bayesian penalty splines (P-Splines). The derived AIF is then used to estimate the impulse response of the myocardium based on deconvolution analysis. The proposed technique is validated both with simulated data using the MMID4 model and ten in vivo data sets for estimating myocardial perfusion reserve rates. The results demonstrate the ability of the proposed technique in accurately reconstructing the desired AIF for myocardial perfusion quantification. The method does not involve any MRI pulse sequence modification, and thus is expected to have wider clinical impact.
Schmid VJ, Gatehouse PD, Yang G-Z, 2007, Attenuation resilient AIF estimation based on hierarchical Bayesian modelling for first pass myocardial perfusion MRI, MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2007, PT 1, PROCEEDINGS, Vol: 4791, Pages: 393-+, ISSN: 0302-9743
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- Citations: 4
Kilner PJ, Gatehouse PD, Firmin DN, 2007, Flow measurement by magnetic resonance: A unique asset worth optimising, JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE, Vol: 9, Pages: 723-728, ISSN: 1097-6647
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- Citations: 140
Gatehouse P, Lyne J, Smith G, et al., 2006, T2* effects in the dual-sequence method for high-dose first-pass myocardial perfusion, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 24, Pages: 1168-1171, ISSN: 1053-1807
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- Citations: 10
He T, Gatehouse PD, Anderson LJ, et al., 2006, Development of a novel optimized breathhold technique for myocardial T2 measurement in thalassemia, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 24, Pages: 580-585, ISSN: 1053-1807
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- Citations: 60
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