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Journal articleFerreira PF, Nielles-Vallespin S, Gatehouse PD, et al., 2013,
Improved navigator based diffusion tensor MRI of the human heart in vivo
, Journal of Cardiovascular Magnetic Resonance, Vol: 15, Pages: W25-W25 -
Journal articleFerreira PF, Nielles-Vallespin S, Gatehouse PD, et al., 2013,
Cardiac diffusion tensor imaging: helix angle (HA) healthy statistical average technique for HA quantification in vivo
, Journal of Cardiovascular Magnetic Resonance, Vol: 15, Pages: W7-W7 -
Journal articleMcGill 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: 1097-6647Background: 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
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Journal articleGulati A, Krishnathasan K, Hsu L-Y, et al., 2012,
Absolute Hyperemic Myocardial Blood Flow is Impaired in Non-Ischemic Dilated Cardiomyopathy and is Related to the Severity of Left Ventricular Systolic Dysfunction
, CIRCULATION, Vol: 126, ISSN: 0009-7322 -
Journal articleGrech-Sollars M, Saunders DE, Phipps KP, et al., 2012,
Survival analysis for apparent diffusion coefficient measures in children with embryonal brain tumours
, NEURO-ONCOLOGY, Vol: 14, Pages: 1285-1293, ISSN: 1522-8517- Cite
- Citations: 6
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Thesis dissertationYang G, 2012,
Numerical Approaches for Solving the Combined Reconstruction and Registration of Digital Breast Tomosynthesis
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Journal articleLaurence I, Ariff B, Quest RA, et al., 2012,
Is there a role for free breathing non-contrast steady-state free precession renal MRA imaging for assessing live donors? A preliminary study
, BRITISH JOURNAL OF RADIOLOGY, Vol: 85, Pages: E448-E454, ISSN: 0007-1285- Author Web Link
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- Citations: 11
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Conference paperYang G, Hipwell J, Hawkes D, et al., 2012,
A nonlinear least squares method for solving the joint reconstruction and registration problem in digital breast tomosynthesis
, Medical Image Understanding and Analysis, Publisher: British Machine Vision Association, Pages: 87-92Digital Breast Tomosynthesis (DBT) offers potential insight into the fine details ofnormal fibroglandular tissues and abnormal lesions, e.g., masses and micro-calcificationsassociated with breast cancer, by the production of a pseudo-3D image. In addition, itavoids the superposition, which is usually found in X-ray mammography, with a compa-rable radiation dose. Algorithms to aid the human observer process DBT data sets involvetwo key tasks: reconstruction and registration. In established medical image modalitiesthese tasks are normally performed sequentially; the images are reconstructed and thenregistered. In this paper, we hypothesise that, for DBT in particular, combining the op-timisation processes of reconstruction and registration into a single algorithm will offersatisfactory for both tasks. Based on this hypothesis, we have devised a mathematicalframework to combine these two tasks, and have implemented both affine and non-linearB-spline registration transformation models as plug-ins. By applying our algorithm tovarious simulated data, we demonstrate the success of our method in terms of both re-construction fidelity and in the registration accuracy of the recovered transformations.
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Conference paperYang G, Hipwell J, Tanner C, et al., 2012,
Joint registration and limited-angle reconstruction of digital breast tomosynthesis
, 11th International Workshop on Breast Imaging, IWDM 2012, Publisher: Springer, Pages: 713-720, ISSN: 0302-9743Digital breast tomosynthesis (DBT), an emerging imaging modality, provides a pseudo-3D image of the breast. Algorithms to aid the human observer process these large datasets involve two key tasks: reconstruction and registration. Previous studies separated these steps, solving each task independently. This can be effective if reconstructing using a complete set of data, e.g., in cone beam CT, assuming that only simple deformations exist. However, for ill-posed limited-angle problems such as DBT, estimating the deformation is complicated by the significant artefacts associated with DBT reconstructions, leading to severe inaccuracies in the registration. In this paper, we present an innovative algorithm, which combines reconstruction of a pair of temporal DBT acquisitions with their simultaneous registration. Using various computational phantoms and in vivo DBT simulations, we show that, compared to the conventional sequential method, jointly estimating image intensities and transformation parameters gives superior results with respect to reconstruction fidelity and registration accuracy.
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Journal articleFerreira 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: 1097-6647BackgroundFirst-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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Mary Finnegan
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Pete Lally
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Jan Sedlacik
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