Publications
193 results found
O'Regan DP, Harden SP, Cook SA, 2013, RATIONAL IMAGING Investigating stable chest pain of suspected cardiac origin, BMJ-BRITISH MEDICAL JOURNAL, Vol: 347, ISSN: 1756-1833
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- Citations: 3
Bai W, Shi W, O'Regan DP, et al., 2013, A probabilistic patch-based label fusion model for multi-atlas segmentation with registration refinement: application to cardiac MR images, IEEE Transactions on Medical Imaging, Vol: 32, Pages: 1302-1315, ISSN: 0278-0062
The evaluation of ventricular function is important for the diagnosis of cardiovascular diseases. It typically involves measurement of the left ventricular (LV) mass and LV cavity volume. Manual delineation of the myocardial contours is time-consuming and dependent on the subjective experience of the expert observer. In this paper, a multi-atlas method is proposed for cardiac magnetic resonance (MR) image segmentation. The proposed method is novel in two aspects. First, it formulates a patch-based label fusion model in a Bayesian framework. Second, it improves image registration accuracy by utilizing label information, which leads to improvement of segmentation accuracy. The proposed method was evaluated on a cardiac MR image set of 28 subjects. The average Dice overlap metric of our segmentation is 0.92 for the LV cavity, 0.89 for the right ventricular cavity and 0.82 for the myocardium. The results show that the proposed method is able to provide accurate information for clinical diagnosis.
O'Regan DP, Cook SA, 2013, Imaging myocardial edema, Heart and Metabolism, Pages: 15-19, ISSN: 1566-0338
Cardiac magnetic resonance (CMR) imaging offers a powerful noninvasive technique for assessing the effects of ischemia-reperfusion injury in the context of acute coronary syndrome (ACS). T2-weighted CMR sequences performed after coronary occlusion accurately identify regions of myocardial edema downstream of the obstructed vessel that enables retrospective determination of the area at risk. Comparing the area at risk with gadolinium-enhanced infarct sizing provides an important tool for clinical decision making and research as it defines the degree of heart muscle salvage following an ischemic injury. The currently available techniques for assessing myocardial edema in ACS are described in this review with an overview of how these inform our understanding of myocardial salvage following primary coronary intervention.
Corden B, Keenan NG, de Marvao ASM, et al., 2013, Body Fat Is Associated With Reduced Aortic Stiffness Until Middle Age, HYPERTENSION, Vol: 61, Pages: 1322-1327, ISSN: 0194-911X
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- Citations: 68
Shi W, Jantsch M, Aljabar P, et al., 2013, Temporal sparse free-form deformations, Medical Image Analysis
Grapsa J, Cabrita IZ, Durighel G, et al., 2013, Right heart failure and clinical deterioration: the study of idiopathic pulmonary arterial hypertensive patients, EUROPEAN JOURNAL OF HEART FAILURE, Vol: 12, Pages: S280-S280, ISSN: 1388-9842
O'Regan DP, Ariff B, Baksi AJ, et al., 2013, Salvage assessment with cardiac MRI following acute myocardial infarction underestimates potential for recovery of systolic strain, EUROPEAN RADIOLOGY, Vol: 23, Pages: 1210-1217, ISSN: 0938-7994
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- Citations: 11
Durighel G, Dawes T, Ashwin C, et al., 2013, Paradoxical effect of smoking following acute myocardial infarction, Journal of Cardiovascular Magnetic Resonance, Vol: 15, ISSN: 1097-6647
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- Citations: 1
de Marvao A, Dawes T, Keenan NG, et al., 2013, The UK GenScan study - population-based imaging genetics research using 3D Cardiac Magnetic Resonance, Journal of Cardiovascular Magnetic Resonance, Vol: 15, Pages: E2-E2, ISSN: 1097-6647
Kousera CA, Wood NB, Seed WA, et al., 2013, A Numerical Study of Aortic Flow Stability and Comparison With <i>In</i> <i>Vivo</i> Flow Measurements, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 135, ISSN: 0148-0731
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- Citations: 35
Shi W, Caballero J, Ledig C, et al., 2013, Cardiac Image Super-Resolution with Global Correspondence Using Multi-Atlas PatchMatch, 16th International Conference on Medical Image Computing and Computer Assisted Intervention (MICCAI), Publisher: SPRINGER-VERLAG BERLIN, Pages: 9-16, ISSN: 0302-9743
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- Citations: 148
Pszczolkowski S, Pizarro L, O'Regan DP, et al., 2012, Gradient projection learning for parametric nonrigid registration, Pages: 226-233, ISSN: 0302-9743
A potentially large anatomical variability among subjects in a population makes nonrigid image registration techniques prone to inaccuracies and to high computational costs in their optimisation. In this paper, we propose a new learning-based approach to accelerate the convergence rate of any chosen parametric energy-based image registration method. From a set of training images and their corresponding deformations, our method learns offline a projection from the gradient space of the energy functional to the parameter space of the chosen registration method using partial least squares. Combined with a regularisation term, the learnt projection is subsequently used online to approximate the optimisation of the energy functional for unseen images. We employ the B-spline approach as underlying registration method, but other parametric methods can be used as well. We perform experiments on synthetic image data and MR cardiac sequences to show that our approach significantly accelerates the convergence -in number of iterations and total computational cost- of the chosen registration method, while achieving similar results in terms of accuracy. © 2012 Springer-Verlag.
O'Regan DP, Shi W, Ariff B, et al., 2012, Remodeling after acute myocardial infarction: mapping ventricular dilatation using three dimensional CMR image registration, Journal of Cardiovascular Magnetic Resonance, Vol: 14, ISSN: 1532-429X
Background: Progressive heart failure due to remodeling is a major cause of morbidity and mortality followingmyocardial infarction. Conventional clinical imaging measures global volume changes, and currently there is nomeans of assessing regional myocardial dilatation in relation to ischemic burden. Here we use 3D co-registration ofCardiovascular Magnetic Resonance (CMR) images to assess the long-term effects of ischemia-reperfusion injury onleft ventricular structure after acute ST-elevation myocardial infarction (STEMI).Methods: Forty six patients (age range 33–77 years) underwent CMR imaging within 7 days following primarypercutaneous coronary intervention (PPCI) for acute STEMI with follow-up at one year. Functional cine imaging andLate Gadolinium Enhancement (LGE) were segmented and co-registered. Local left ventricular wall dilatation wasassessed by using intensity-based similarities to track the structural changes in the heart between baseline andfollow-up. Results are expressed as means, standard errors and 95% confidence interval (CI) of the difference.Results: Local left ventricular remodeling within infarcted myocardium was greater than in non-infarctedmyocardium (1.6% ± 1.0 vs 0.3% ± 0.9, 95% CI: -2.4% – -0.2%, P = 0.02). One-way ANOVA revealed that transmuralinfarct thickness had a significant effect on the degree of local remodeling at one year (P < 0.0001) with greatestwall dilatation observed when infarct transmurality exceeded 50%. Infarct remodeling was more severe whenmicrovascular obstruction (MVO) was present (3.8% ± 1.3 vs −1.6% ± 1.4, 95% CI: -9.1% – -1.5%, P = 0.007) and whenend-diastolic volume had increased by >20% (4.8% ± 1.4 vs −0.15% ± 1.2, 95% CI: -8.9% – -0.9%, P = 0.017).Conclusions: The severity of ischemic injury has a significant effect on local ventricular wall remodeling with onlymodest dilatation observed within non-ischemic myocardium. Limitatio
O'Regan DP, Ariff B, Neuwirth C, et al., 2011, The ischemic area-at-risk on T2-weighted MRI shows recovery of systolic strain at 1 year, Journal of Cardiovascular Magnetic Resonance, Vol: 13
O'Regan DP, Cook SA, 2011, Myocarditis or myocardial infarction? MRI can help, HEART, Vol: 97, Pages: 1283-1283, ISSN: 1355-6037
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- Citations: 2
Kourliouros A, Soni M, Rasoli S, et al., 2011, Evolution and Current Applications of the Cabrol Procedure and Its Modifications, ANNALS OF THORACIC SURGERY, Vol: 91, Pages: 1636-1641, ISSN: 0003-4975
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- Citations: 32
O'Regan DP, Ariff B, Neuwirth C, et al., 2010, Assessment of severe reperfusion injury with T2*cardiac MRI in patients with acute myocardial infarction, HEART, Vol: 96, Pages: 1885-1891, ISSN: 1355-6037
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- Citations: 58
Malamateniou C, McGuinness AK, Allsop JM, et al., 2010, Snapshot Inversion Recovery: An Optimized Single-Shot T1-weighted Inversion-Recovery Sequence for Improved Fetal Brain Anatomic Delineation., Radiology
Purpose: To prospectively evaluate the clinical effectiveness of snapshot inversion recovery (SNAPIR), which is a dedicated optimized inversion-recovery-prepared single-shot fast spin-echo T1-weighted sequence, in the delineation of normal fetal brain anatomy compared with that of the currently used T1-weighted gradient-echo protocol, which often yields images of poor quality due to motion artifacts and inadequate contrast. Materials and Methods: This study was approved by the hospital research ethics committee, and informed written consent was obtained from all patients. Forty-one fetuses were examined at 19-37 weeks gestation (mean, 29 weeks gestation) by using both the standard T1-weighted protocol and the optimized T1-weighted SNAPIR protocol with a 1.5-T imager. Two independent blinded observers performed qualitative analysis, evaluating overall diagnostic quality, detailed anatomic delineation, and severity of motion artifacts. Quantitative analysis comprised calculation of contrast ratios (CRs) for the cortical gray matter, subplate, white matter, and cerebrospinal fluid. The Wilcoxon signed rank test was used to compare image rating scores, the paired t test was used to compare CRs, and κ statistics were used to test interobserver agreement. Results: Both overall diagnostic quality (P < .001) and detailed anatomic delineation (P < .001) were enhanced with SNAPIR compared with the standard T1-weighted acquisition. Also, motion artifacts were less severe (P = .008) and less extensive (P < .001) with SNAPIR. Corresponding CRs were increased with SNAPIR in seven of eight examined regions. Conclusion: SNAPIR is a promising robust alternative to the current T1-weighted acquisitions; its role in the detection of disease requires further study
Malik SJ, Larkman DJ, O'Regan DP, et al., 2010, Subject-Specific Water-Selective Imaging Using Parallel Transmission, MAGNETIC RESONANCE IN MEDICINE, Vol: 63, Pages: 988-997, ISSN: 0740-3194
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- Citations: 15
Grapsa IA, Dawson D, O'Regan D, et al., 2010, PREDICTION OF CLINICAL DETERIORATION IN IDIOPATHIC PULMONARY ARTERIAL HYPERTENSION: LONGITUDINAL CHANGE IN RIGHT VENTRICULAR REMODELLING WITH REAL TIME 3D ECHOCARDIOGRAPHY AND CARDIAC MAGNETIC RESONANCE, Publisher: ELSEVIER SCIENCE INC, ISSN: 0735-1097
O'Regan D, Ben A, Neuwirth C, et al., 2010, Microvascular obstruction following PCI is associated with reperfusion hemorrhage and chronic left ventricular impairment, Journal of Cardiovascular Magnetic Resonance, Vol: 12, ISSN: 1097-6647
Grapsa J, O'Regan DP, Pavlopoulos H, et al., 2010, Right ventricular remodelling in pulmonary arterial hypertension with three-dimensional echocardiography: comparison with cardiac magnetic resonance imaging, EUROPEAN JOURNAL OF ECHOCARDIOGRAPHY, Vol: 11, Pages: 64-73, ISSN: 1525-2167
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- Citations: 86
O'Regan DP, Ahmed R, Neuwirth C, et al., 2009, Cardiac MRI of myocardial salvage at the peri-infarct border zones after primary coronary intervention, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 297, Pages: H340-H346, ISSN: 0363-6135
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- Citations: 40
Harvey C, O'Regan D, Allen SJ, 2009, Accident and Emergency Radiology, Publisher: Gardners Books, ISBN: 9781856423151
This book is aimed at accident and emergency doctors, surgical, medical and radiology specialist registrars and medical students. This highly illustrated text facilitates instant consultation when faced with an X-ray.
O'Regan DP, Ahmed R, Karunanithy N, et al., 2009, Reperfusion Hemorrhage Following Acute Myocardial Infarction: Assessment with T2*Mapping and Effect on Measuring the Area at Risk, RADIOLOGY, Vol: 250, Pages: 916-922, ISSN: 0033-8419
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- Citations: 77
Schmitz SA, O'Regan DP, Fitzpatrick J, et al., 2008, Quantitative 3T MR imaging of the descending thoracic aorta: Patients with familial hypercholesterolemia have an increased aortic plaque burden despite long-term lipid-lowering therapy, JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY, Vol: 19, Pages: 1403-1408, ISSN: 1051-0443
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- Citations: 11
O'Regan DP, Callaghan MF, Fitzpatrick J, et al., 2008, Cardiac T2* and lipid measurement at 3.0 T-initial experience, EUROPEAN RADIOLOGY, Vol: 18, Pages: 800-805, ISSN: 0938-7994
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- Citations: 17
O'Reagan DP, Callaghan MF, Wylezinska-Arridge M, et al., 2008, Liver Fat Content and T2*: Simultaneous Measurement by Using Breath-hold Multiecho MR Imaging at 3.0 T--Feasibility, Radiology
Schmitz SA, O'Regan DP, Fitzpatrick J, et al., 2008, White matter brain lesions in midlife familial hypercholesterolemic patients at 3-tesla magnetic resonance imaging, ACTA RADIOLOGICA, Vol: 49, Pages: 184-189, ISSN: 0284-1851
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- Citations: 8
Schmitz SA, O'Regan DP, Fitzpatrick J, et al., 2007, MRI at 3 Tesla detects no evidence for ischemic brain damage in intensively treated patients with homozygous familial hypercholesterolemia, NEURORADIOLOGY, Vol: 49, Pages: 927-931, ISSN: 0028-3940
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- Citations: 4
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