Publications
9 results found
Lanz H, Ristic M, Chappell K, et al., 2023, Minimum number of scans for collagen fibre direction estimation using Magic Angle Directional Imaging (MADI) with a priori information, Array, Vol: 17, Pages: 1-10, ISSN: 2590-0056
Tissues such as tendons, ligaments, articular cartilage, and menisci contain significant amounts of organised collagen which gives rise to the Magic Angle effect during magnetic resonance imaging (MRI). The MR intensity response of these tissues is dependent on the angle between the main field, B0, and the direction of the collagen fibres. Our previous work showed that by acquiring scans at as few as 7–9 different field orientations, depending on signal to noise ratio (SNR), the tissue microstructure can be deduced from the intensity variations across the set of scans. Previously our Magic Angle Directional Imaging (MADI) technique used rigid registration and manual final alignment, and did not assume any knowledge of the target anatomy being scanned. In the present work, fully automatic soft registration is incorporated into the MADI workflow and a priori knowledge of the target anatomy is used to reduce the required number of scans. Simulation studies were performed to assess how many scans are theoretically necessary. These findings were then applied to MRI data from a caprine knee specimen. Simulations suggested that using 3 scans might be sufficient, but in practice 4 scans were necessary to achieve high accuracy. 5 scans only offered marginal gains over 4 scans. A 15 scan dataset was used as a gold standard for quantitative voxel-to-voxel comparison of computed fibre directions, qualitative comparison of collagen tractography plots are also presented. The results are also encouraging at low SNR values, showing robustness of the method and applicability at low field.
Chappell K, Brujic D, Van Der Straeten C, et al., 2019, Detection of maturity and ligament injury using magic angle directional imaging, Magnetic Resonance in Medicine, Vol: 82, Pages: 1041-1054, ISSN: 0740-3194
Purpose: To investigate whether magnetic field–related anisotropies of collagen may be correlated with postmortem findings in animal models.Methods: Optimized scan planning and new MRI data‐processing methods were proposed and analyzed using Monte Carlo simulations. Six caprine and 10 canine knees were scanned at various orientations to the main magnetic field. Image intensities in segmented voxels were used to compute the orientation vectors of the collagen fibers. Vector field and tractography plots were computed. The Alignment Index was defined as a measure of orientation distribution. The knees were subsequently assessed by a specialist orthopedic veterinarian, who gave a pathological diagnosis after having dissected and photographed the joints.Results: Using 50% less scans than reported previously can lead to robust calculation of fiber orientations in the presence of noise, with much higher accuracy. The 6 caprine knees were found to range from very immature (< 3 months) to very mature (> 3 years). Mature specimens exhibited significantly more aligned collagen fibers in their patella tendons compared with the immature ones. In 2 of the 10 canine knees scanned, partial cranial caudal ligament tears were identified from MRI and subsequently confirmed with encouragingly high consistency of tractography, Alignment Index, and dissection results.Conclusion: This method can be used to detect injury such as partial ligament tears, and to visualize maturity‐related changes in the collagen structure of tendons. It can provide the basis for new, noninvasive diagnostic tools in combination with new scanner configurations that allow less‐restricted field orientations.
Logan K, Emsley RJ, Jeffries S, et al., 2016, Development of Early Adiposity in Infants of Mothers With Gestational Diabetes Mellitus, Diabetes Care, Vol: 39, Pages: 1045-1051, ISSN: 0149-5992
OBJECTIVEInfants born to mothers with gestational diabetes mellitus (GDM) are at greaterrisk of later adverse metabolic health. We examined plausible candidate mediators;adipose tissue (AT) quantity and distribution, and intrahepatocellular lipid(IHCL) content, comparing infants of mothers with GDM and without GDM (controlgroup) over the first 3 postnatal months.RESEARCH DESIGN AND METHODSWe conducted a prospective longitudinal study using MRI and spectroscopy toquantify whole-body and regional AT volumes, and IHCL content, within 2 weeksand 8–12 weeks after birth. We adjusted for infant size and sex, and maternalprepregnancy BMI. Values are reported as the mean difference (95% CI).RESULTSWe recruited 86 infants (GDM group 42 infants; control group 44 infants). Motherswith GDM had good pregnancy glycemic control. Infants were predominantlybreast fed up to the time of the second assessment (GDM group 71%; controlgroup 74%). Total AT volumes were similar in the GDM group compared with thecontrol group at a median age of 11 days (228 cm3 [95% CI 2121, 65], P = 0.55), butwere greater in the GDM group at a median age of 10 weeks (247 cm3 [56, 439], P =0.01). After adjustment for size, the GDM group had significantly greater total ATvolume at 10 weeks than control group infants (16.0% [6.0, 27.1], P = 0.002). ATdistribution and IHCL content were not significantly different at either time point.CONCLUSIONSAdiposity in GDM infants is amplified in early infancy, despite good maternalglycemic control and predominant breast-feeding, suggesting a potential causalpathway to later adverse metabolic health. Reduction in postnatal adiposity maybe a therapeutic target to reduce later health risks.
Gale C, Jeffries S, Logan KM, et al., 2013, Avoiding sedation in research MRI and spectroscopy in infants: our approach, success rate and prevalence of incidental findings, ARCHIVES OF DISEASE IN CHILDHOOD-FETAL AND NEONATAL EDITION, Vol: 98, Pages: F267-F268, ISSN: 1359-2998
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- Citations: 28
Yiannakas MC, Wheeler-Kingshott CAM, Berry AM, et al., 2010, A method for measuring the cross sectional area of the anterior portion of the optic nerve in vivo using a fast 3D MRI sequence., J Magn Reson Imaging, Vol: 31, Pages: 1486-1491
PURPOSE: To investigate the three-dimensional (3D) fast-recovery fast spin-echo accelerated (FRFSE-XL) sequence as a new application for measuring the intraorbital optic nerve (ION) mean cross-sectional area in vivo and to determine its value within a commonly used high resolution imaging protocol. MATERIALS AND METHODS: The entire ION was scanned in nine healthy volunteers (mean age 32 +/- 4 years) using the 3D FRFSE-XL sequence and a commonly used high resolution short-echo fast fluid-attenuated inversion-recovery (sTE fFLAIR) sequence with identical slice locations at 1.5T. The mean cross-sectional area from both sequences was measured on a slice-by-slice basis from 3 mm behind the globe to the orbital apex. The reproducibility of both techniques was assessed from repeated scans (scan-rescan) and repeated image analysis (intraobserver). RESULTS: Measurement of the mean cross-sectional area of the anterior 9 mm segment of the ION was only possible using the 3D FRFSE-XL sequence with a mean area of 11.6 +/- 2.2 mm(2) (scan rescan COV = 3.3 +/- 1.5, intraobserver COV = 2.4 +/- 0.02) whereas the remainder segment of the ION (i.e., 9 mm behind the globe to the orbital apex) could only be measured with the use of the sTE fFLAIR with a mean area of 8.5 +/- 1.7 mm(2) (scan rescan COV = 4.9 +/- 2.5 and intraobserver COV = 3.70 +/- 0.03). CONCLUSION: The 3D FRFSE-XL allows fast and reproducible measurement of the cross-sectional area of the anterior 9 mm segment of the ION, which is not possible using commonly used imaging sequences due to image degradation from motion, and is of complementary value to the existing imaging protocol for ION atrophy quantification.
Reichert ILH, Robson MD, Gatehouse PD, et al., 2005, Magnetic resonance imaging of cortical bone with ultrashort TE pulse sequences, MAGNETIC RESONANCE IMAGING, Vol: 23, Pages: 611-618, ISSN: 0730-725X
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- Citations: 125
Chappell KE, Robson MD, Stonebridge-Foster A, et al., 2004, Magic angle effects in MR neurography, AMERICAN JOURNAL OF NEURORADIOLOGY, Vol: 25, Pages: 431-440, ISSN: 0195-6108
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- Citations: 120
Reichert ILH, Benjamin M, Gatehouse PD, et al., 2004, Magnetic resonance imaging of periosteum with ultrashort TE pulse sequences, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 19, Pages: 99-107, ISSN: 1053-1807
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- Citations: 37
Chappell KE, Patel N, Gatehouse PD, et al., 2003, Magnetic resonance imaging of the liver with ultrashort TE (UTE) pulse sequences, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 18, Pages: 709-713, ISSN: 1053-1807
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- Citations: 38
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