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Hubbard PL, Zhou FL, Eichhorn SJ, Parker GJM. Biomimetic phantom for the validation of diffusion magnetic resonance imaging. Magn Reson Med 2015; 73:299-305. [PMID: 24469863 DOI: 10.1002/mrm.25107] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/29/2013] [Accepted: 12/10/2013] [Indexed: 11/10/2022]
Abstract
PURPOSE A range of advanced diffusion MRI (dMRI) techniques are currently in development which characterize the orientation of white matter fibers using diffusion tensor imaging (DTI). There is a need for a physical phantom with microstructural features of the brain's white matter to help validate these methods. METHODS Hollow, co-electrospun, aligned fibers with a tuneable size distribution have been produced in bulk and with an MR visible solvent infused into the pores. The morphology and size of the phantoms was assessed using scanning electron microscopy (SEM) and compared with DTI results obtained on both a clinical and preclinical scanner. RESULTS By varying inner diameter of the phantom fibers (from SEM: 9.5 μm, 11.9 μm, 13.4 μm) the radial diffusivity and fractional anisotropy, calculated from DTI, vary between 0.38 ± 0.05 × 10(3) and 0.61 ± 0.06 × 10(3) cm s(-1) and between 0.45 ± 0.05 and 0.33 ± 0.04, respectively. CONCLUSION We envisage that these materials will be used for the validation of novel and established methods within the field of diffusion MRI, as well as for routine quality assurance purposes and for establishing scanner performance in multicenter trials.
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Affiliation(s)
- Penny L Hubbard
- Centre for Imaging Sciences, Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, United Kingdom
- Biomedical Imaging Institute, The University of Manchester, Manchester, United Kingdom
| | - Feng-Lei Zhou
- Centre for Imaging Sciences, Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, United Kingdom
- The School of Materials, The University of Manchester, Manchester, United Kingdom
| | - Stephen J Eichhorn
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, United Kingdom
| | - Geoffrey J M Parker
- Centre for Imaging Sciences, Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, United Kingdom
- Biomedical Imaging Institute, The University of Manchester, Manchester, United Kingdom
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Zhou FL, Hubbard PL, Eichhorn SJ, Parker GJM. Coaxially electrospun axon-mimicking fibers for diffusion magnetic resonance imaging. ACS Appl Mater Interfaces 2012; 4:6311-6. [PMID: 23135104 DOI: 10.1021/am301919s] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The study of brain structure and connectivity using diffusion magnetic resonance imaging (dMRI) has recently gained substantial interest. However, the use of dMRI still faces major challenges because of the lack of standard materials for validation. The present work reports on brain tissue-mimetic materials composed of hollow microfibers for application as a standard material in dMRI. These hollow fibers were fabricated via a simple and one-step coaxial electrospining (co-ES) process. Poly(ε-caprolactone) (PCL) and polyethylene oxide (PEO) were employed as shell and core materials, respectively, to achieve the most stable co-ES process. These co-ES hollow PCL fibers have different inner diameters, which mainly depend on the flow rate of the core solution and have the potential to cover the size range of the brain tissue we aimed to mimic. Co-ES aligned hollow PCL fibers were characterized using optical and electron microscopy and tested as brain white matter mimics on a high-field magnetic resonance imaging (MRI) scanner. To the best of our knowledge, this is the first time that co-ES hollow fibers have been successfully used as a tissue mimic or phantom in diffusion MRI. The results of the present study provide evidence that this phantom can mimic the dMRI behavior of cellular barriers imposed by axonal cell membranes and myelin; the measured diffusivity is compatible with that of in vivo biological tissues. Together these results suggest the potential use of co-ES hollow microfibers as tissue-mimicking phantoms in the field of medical imaging.
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Affiliation(s)
- Feng-Lei Zhou
- Centre for Imaging Sciences, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, United Kingdom
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Zhou FL, Hubbard PL, Eichhorn SJ, Parker GJ. Jet deposition in near-field electrospinning of patterned polycaprolactone and sugar-polycaprolactone core–shell fibres. POLYMER 2011. [DOI: 10.1016/j.polymer.2011.06.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Närväinen J, Hubbard PL, Kauppinen RA, Morris GA. Z-spectroscopy with Alternating-Phase Irradiation. J Magn Reson 2010; 207:242-250. [PMID: 20920868 DOI: 10.1016/j.jmr.2010.09.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 09/08/2010] [Accepted: 09/08/2010] [Indexed: 05/29/2023]
Abstract
Magnetization transfer (MT) MRI and Z-spectroscopy are tools to study both water-macromolecule interactions and pH-sensitive exchange dynamics between water and the protons of mobile chemical groups within these macromolecules. Both rely on saturation of frequencies offset from water and observation of the on-resonance water signal. In this work, an RF saturation method called Z-spectroscopy with Alternating-Phase Irradiation (ZAPI) is introduced. Based on the T(2)-selectivity of the irradiation pulse, ZAPI can be used to separate the different contributions to a Z-spectrum, as well as to study the T(2) distribution of the macromolecules contributing to the MT signal. ZAPI can be run at resonance for water and with low power, thus minimizing problems with specific absorption rate (SAR) limits in clinical applications. In this paper, physical and practical aspects of ZAPI are discussed and the sequence is applied in vitro to sample systems and in vivo to rat head to demonstrate the method.
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Affiliation(s)
- Johanna Närväinen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Finland.
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Alexander DC, Hubbard PL, Hall MG, Moore EA, Ptito M, Parker GJM, Dyrby TB. Orientationally invariant indices of axon diameter and density from diffusion MRI. Neuroimage 2010; 52:1374-89. [PMID: 20580932 DOI: 10.1016/j.neuroimage.2010.05.043] [Citation(s) in RCA: 496] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 05/14/2010] [Accepted: 05/16/2010] [Indexed: 11/30/2022] Open
Affiliation(s)
- Daniel C Alexander
- Centre for Medical Image Computing, Department of Computer Science, University College London, London, UK.
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Abstract
Aerosol OT/water exhibits a lamellar phase over a wide range of concentrations. We show, by magnetic resonance (NMR) and scanning electron microscopy (SEM), that the morphology of the lamellar phase varies significantly across that range and that the rate of equilibration depends strongly on concentration (25, 33, and 50 wt %) with, paradoxically, the faster equilibration at higher surfactant concentrations. We find that the 25 wt % sample exhibits a defect-rich local structure, characteristic of a superposed L(3) character. Further into the lamellar region, at 33 wt %, this defect-rich structure persists heterogeneously, while, at 50 wt %, the lamellar phase domains are highly ordered. The NMR methods used here included (2)H spectroscopy and the two-dimensional NMR method, diffusion-diffusion exchange spectroscopy (DEXSY). The latter was used to obtain quantitative information on the domain sizes and defects within the polydomain lamellar mesophase. Comparison of the NMR with the SEM results suggests that, at 25 wt % AOT, bilayer defects play an important role in influencing the (2)H NMR and DEXSY NMR results.
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Affiliation(s)
- Penny L Hubbard
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6001, New Zealand
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Jayasooriya UA, Grinter R, Hubbard PL, Aston GM, Stride JA, Hopkins GA, Camus L, Reid ID, Cottrell SP, Cox SFJ. Muon Implantation of Metallocenes: Ferrocene. Chemistry 2007; 13:2266-76. [PMID: 17163549 DOI: 10.1002/chem.200600853] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Muon Spin Relaxation and Avoided Level Crossing (ALC) measurements of ferrocene are reported. The main features observed are five high field resonances in the ALC spectrum at about 3.26, 2.44, 2.04, 1.19 and 1.17 T, for the low-temperature phase at 18 K. The high-temperature phase at 295 K shows that only the last feature shifted down to about 0.49 T and a muon spin relaxation peak at about 0.106 T which approaches zero field when reaching the phase transition temperature of 164 K. A model involving three muoniated radicals, two with muonium addition to the cyclopentadienyl ring and the other to the metal atom, is postulated to rationalise these observations. A theoretical treatment involving spin-orbit coupling is found to be required to understand the Fe-Mu adduct, where an interesting interplay between the ferrocene ring dynamics and the spin-orbit coupling of the unpaired electron is shown to be important. The limiting temperature above which the full effect of spin-orbit interaction is observable in the muSR spectra of ferrocene was estimated to be 584 K. Correlation time for the ring rotation dynamics of the Fe-Mu radical at this temperature is 3.2 ps. Estimated electron g values and the changes in zero-field splittings for this temperature range are also reported.
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Affiliation(s)
- Upali A Jayasooriya
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, UK.
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Gottwald A, Creamer LK, Hubbard PL, Callaghan PT. Diffusion, relaxation, and chemical exchange in casein gels: a nuclear magnetic resonance study. J Chem Phys 2007; 122:34506. [PMID: 15740208 DOI: 10.1063/1.1825383] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Water in protein/water mixtures can be described in terms of bound water and free water, by exchange between these two states, and by its exchange with appropriate sites on the protein. 1H-NMR diffusion and relaxation measurements provide insights into the mobility of these states. T2 relaxation-time dispersions (i.e., T2 relaxation times at different echo pulse spacings) reveal additional information about exchange. We present a comprehensive set of diffusion and T2 dispersion measurements on casein gels for which the protein/water ratio ranges from 0.25 to 0.5. The combination of these methods, taken in conjunction with concentration dependence, allows a good estimate of the parameters required to fit the data with Luz/Meiboom and Carver/Richards models for relaxation and chemical exchange. We compare the exchange (a) between water and protein and (b) between free water and bound water. Further, we attempt to distinguish chemical site exchange and diffusion/susceptibility exchange.
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Affiliation(s)
- Antje Gottwald
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand.
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Williamson DC, Närväinen J, Hubbard PL, Kauppinen RA, Morris GA. Effects of radiation damping on Z-spectra. J Magn Reson 2006; 183:203-12. [PMID: 16982205 DOI: 10.1016/j.jmr.2006.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 08/11/2006] [Accepted: 08/22/2006] [Indexed: 05/11/2023]
Abstract
Radiation damping induced by the strong water magnetization in Z-spectroscopy experiments can be sufficient to perturb significantly the resultant Z-spectrum. With a probe tuned to exact electrical resonance the effects are relatively straightforward, narrowing the central feature of the Z-spectrum. Where, as is commonly the case, the probe is tuned sufficiently well to give optimum signal-to-noise ratio and radiofrequency field strength but is not at exact resonance, radiation damping introduces an unexpected asymmetry into the Z-spectrum. This has the potential to complicate the use of Z-spectrum asymmetry to study chemical exchange, for example in the estimation of pH in vivo.
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Affiliation(s)
- David C Williamson
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
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Hubbard PL, McGrath KM, Callaghan PT. Orientational anisotropy in the polydomain lamellar phase of a lyotropic liquid crystal. Langmuir 2006; 22:3999-4003. [PMID: 16618138 DOI: 10.1021/la052998n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Diffusion-diffusion correlation measurements by NMR are used to investigate the degree of orientational order in the lamellar phase of Aerosol OT (bis(2-ethylhexyl) sodium sulfosuccinate) and water at a range of surfactant concentrations (25, 33, and 50 wt %). We show that true isotropy of the domains is found at the lowest concentration but that at higher concentrations deviations from isotropy can be found, as evidenced by asymmetry on the 2D correlation distributions. We further discuss the significance of asymmetry in diffusion-diffusion exchange experiments, 2D distributions that should always be symmetric in steady state.
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Affiliation(s)
- Penny L Hubbard
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6001, New Zealand
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Hubbard PL, McGrath KM, Callaghan PT. A study of anisotropic water self-diffusion and defects in the lamellar mesophase. Langmuir 2005; 21:4340-6. [PMID: 16032845 DOI: 10.1021/la0470378] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The correlation of molecular diffusion coefficients obtained via a novel two-dimensional pulsed gradient spin-echo (PGSE) NMR method has been shown to reveal detailed structural information on the mesophases of lyotropic liquid crystals. A four-component system containing both nonionic (pentaethylene glycol monododecyl ether) and ionic (sodium dodecyl sulfate) surfactants, water, and decane was prepared and left to equilibrate. In the temperature region around 309 K, a lamellar mesophase forms. A two-dimensional Laplace inverse transformation was performed on the (gammadeltag)2(delta - delta/3) domain data to separate any multiexponential behavior that resulted from local anisotropy. The results of the double PGSE experiment with contiguous gradient pulse pairs, applied both collinearly and orthogonally, clearly show the presence of local anisotropic self-diffusion of the water molecules and suggest a preferred orientation of the lamellae. Information about defects/domain size was obtained by the insertion of a mixing time (t(m)') between the successive gradient pulse pairs. This work highlights the value of this new NMR correlation method in the study of surfactant systems.
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Affiliation(s)
- Penny L Hubbard
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6001, New Zealand.
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Hubbard PL, Oganesyan VS, Sulaimanov N, Butt JN, Jayasooriya UA. Avoided Level Crossing Muon Spectroscopy of Free Radicals Formed by Muonium Addition to the Constituents of DNA. J Phys Chem A 2004. [DOI: 10.1021/jp0475335] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Penny L. Hubbard
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom, and Paul Scherrer Institute, Villigen, Switzerland
| | - Vasily S. Oganesyan
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom, and Paul Scherrer Institute, Villigen, Switzerland
| | - Nail Sulaimanov
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom, and Paul Scherrer Institute, Villigen, Switzerland
| | - Julea N. Butt
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom, and Paul Scherrer Institute, Villigen, Switzerland
| | - Upali A. Jayasooriya
- School of Chemical Sciences and Pharmacy, Centre for Metalloprotein Spectroscopy and Biology, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom, and Paul Scherrer Institute, Villigen, Switzerland
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Jayasooriya UA, Pratt FL, Aston GM, Hall S, Hubbard PL, McCoustra M. A strategy for the measurement of the vibrations of a muoniated radical centre: experimental evidence. Chemphyschem 2004; 5:257-61. [PMID: 15038291 DOI: 10.1002/cphc.200300832] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Upali A Jayasooriya
- School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
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Raby CT, Hubbard PL, Cobbins RH. Comparison of the California mastitis test, catalase test, and pH readings on quarter milk samples. J Dairy Sci 1967; 50:1234-6. [PMID: 6069503 DOI: 10.3168/jds.s0022-0302(67)87605-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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