1
|
Silva P, Jouda M, Korvink J. Magnetostatic reciprocity for MR magnet design. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:607-617. [PMID: 37905211 PMCID: PMC10539805 DOI: 10.5194/mr-2-607-2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 06/29/2021] [Indexed: 11/02/2023]
Abstract
Electromagnetic reciprocity has long been a staple in magnetic resonance (MR) radio-frequency development, offering geometrical insights and a figure of merit for various resonator designs. In a similar manner, we use magnetostatic reciprocity to compute manufacturable solutions of complex magnet geometries, by establishing a quantitative metric for the placement and subsequent orientation of discrete pieces of permanent magnetic material. Based on magnetostatic theory and non-linear finite element modelling (FEM) simulations, it is shown how assembled permanent magnet setups perform in the embodiment of a variety of designs and how magnetostatic reciprocity is leveraged in the presence of difficulties associated with self-interactions, to fulfil various design objectives, including self-assembled micro-magnets, adjustable magnetic arrays, and an unbounded magnetic field intensity in a small volume, despite realistic saturation field strengths.
Collapse
Affiliation(s)
- Pedro Freire Silva
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
| | - Mazin Jouda
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
| | - Jan G. Korvink
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
| |
Collapse
|
2
|
Mohebbi B, Tavangarrad AH, Claussen J, Blümich B, Hassanizadeh SM, Rosati R. Revealing how interfaces in stacked thin fibrous layers affect liquid ingress and transport properties by single-sided NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 294:16-23. [PMID: 29966854 DOI: 10.1016/j.jmr.2018.06.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 06/22/2018] [Accepted: 06/23/2018] [Indexed: 06/08/2023]
Abstract
Offering multifaceted applications, thin fibrous porous materials are mostly used in stacks of layers, each layer having a defined functionality. Since only a few pores exist across a layer a couple of hundred microns thick, the interface between layers may significantly affect liquid ingress. Thus, the main objective of the study is to substantiate that an interface layer is present during liquid infiltration between stacked thin fibrous layers and that it affects the fluid transport properties. A compact single-sided NMR device with a low static gradient of about 2 T/m perpendicular to the sensor surface and a uniform magnetic field in lateral directions was used to profile a 2-mm thick slice in one shot. The liquid ingress into the thin fibrous layers and their interfaces was visualized by Fourier-transforming the NMR signal and processing the time-dependent 1D profiles with a newly developed mathematical method. The flow characteristics and liquid distribution profiles of a 400-µm thick layer were compared with those of two stacked 200-µm thick layers from the same material but with an interface between them. The results show major differences in distributions and flow dynamics for the single and dual layer cases, which reveal the importance of the interface in fluid flow.
Collapse
Affiliation(s)
- Behzad Mohebbi
- Institute for Technical and Macromolecular Chemistry, Worringerweg 2, RWTH Aachen University, 52056 Aachen, Germany; Procter&Gamble Service GmbH, Sulzbacher Str. 40, 65824 Schwalbach am Taunus, Germany.
| | - Amir Hossein Tavangarrad
- Department of Earth Sciences, Environmental Hydrogeology Group, Utrecht University, Princetonplein 9, 3584CC Utrecht, The Netherlands
| | - Jan Claussen
- Procter&Gamble Service GmbH, Sulzbacher Str. 40, 65824 Schwalbach am Taunus, Germany
| | - Bernhard Blümich
- Institute for Technical and Macromolecular Chemistry, Worringerweg 2, RWTH Aachen University, 52056 Aachen, Germany
| | - S Majid Hassanizadeh
- Department of Earth Sciences, Environmental Hydrogeology Group, Utrecht University, Princetonplein 9, 3584CC Utrecht, The Netherlands
| | - Rodrigo Rosati
- Procter&Gamble Service GmbH, Sulzbacher Str. 40, 65824 Schwalbach am Taunus, Germany
| |
Collapse
|
3
|
Koptyug IV. MRI of mass transport in porous media: drying and sorption processes. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2012; 65:1-65. [PMID: 22781314 DOI: 10.1016/j.pnmrs.2011.12.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 12/05/2011] [Indexed: 06/01/2023]
Affiliation(s)
- Igor V Koptyug
- International Tomography Center, SB RAS, 3A Institutskaya Str., Novosibirsk 630090, Russian Federation.
| |
Collapse
|
4
|
Marble AE. Optimization of echo amplitudes resulting from a series of 90° pulses in an inhomogeneous static field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 216:37-42. [PMID: 22329972 DOI: 10.1016/j.jmr.2011.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 11/22/2011] [Accepted: 12/22/2011] [Indexed: 05/31/2023]
Abstract
In an inhomogeneous static field, the pulse sequence 90°(x)-(τ-90°(y)-τ)(n) results in a train of echoes, the amplitudes of which settle to be proportional to M(0)/2 after a transient period. Analysis of the spin dynamics of the general τ-β°-τ refocusing cycle reveals that for ideal RF pulses, adding a preparation pulse followed by a delay to the above sequence can either eliminate the transient behavior, or increase the asymptotic echo intensity. This is achieved by controlling the alignment between the magnetization m and the rotation axis of the refocusing cycle. The effect of preparations pulses is demonstrated experimentally in the fringe field of a single sided magnet array. It is shown that for this instrument, transient effects in the echo train can be reduced, and asymptotic signal increased. Spin dynamics calculations indicate that the sequences are robust to finite RF pulse widths, but some discrepancy between theory and experiment is observed due to B(1) inhomogeneity. Refocusing sequences of the type studied here are useful in cases where experimental considerations, such as RF power limits, preclude the use of a 180° pulse in the refocusing cycle.
Collapse
Affiliation(s)
- Andrew E Marble
- Department of Systems and Computer Engineering, Carleton University, Mackenzie Building, Room 4462, 1125 Colonel By Dr., Ottawa, Ontario, Canada K1S 5B6.
| |
Collapse
|
5
|
Van Landeghem M, Danieli E, Perlo J, Blümich B, Casanova F. Low-gradient single-sided NMR sensor for one-shot profiling of human skin. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 215:74-84. [PMID: 22244451 DOI: 10.1016/j.jmr.2011.12.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 12/13/2011] [Accepted: 12/14/2011] [Indexed: 05/31/2023]
Abstract
This paper describes a shimming approach useful to reduce the gradient strength of the magnetic field generated by single-sided sensors simultaneously maximizing its uniformity along the lateral directions of the magnet. In this way, the thickness of the excited sensitive volume can be increased without compromising the depth resolution of the sensor. By implementing this method on a standard U-shaped magnet, the gradient strength was reduced one order of magnitude. In the presence of a gradient of about 2 T/m, slices of 2mm could be profiled with a resolution that ranges from 25 μm at the center of the slice to 50 μm at the borders. This sensor is of particular advantage for applications, where the scanning range is of the order of the excited slice. In those cases, the full profile is measured in a single excitation experiment, eliminating the need for repositioning the excited slice across the depth range to complete the profile as occurs with standard high gradient sensors. Besides simplifying the experimental setup, the possibility to move from a point-by-point measurement to the simultaneous acquisition of the full profile led to the shortening of the experimental time. A further advantage of performing the experiment under a smaller static gradient is a reduction of the diffusion attenuation affecting the signal decay measured with a CPMG sequence, making it possible to measure the T(2) of samples with high diffusivity (comparable to the water diffusivity). The performance of the sensor in terms of resolution and sensitivity is first evaluated and compared with conventional singled-sided sensors of higher gradient strength using phantoms of known geometry and relaxation times. Then, the device is used to profile the structure of human skin in vivo. To understand the contrast between the different skin layers, the distribution of relaxation times T(2) and diffusion coefficients is spatially resolved along the depth direction.
Collapse
|
6
|
Hugon C, D'Amico F, Aubert G, Sakellariou D. Design of arbitrarily homogeneous permanent magnet systems for NMR and MRI: theory and experimental developments of a simple portable magnet. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:75-85. [PMID: 20451431 DOI: 10.1016/j.jmr.2010.04.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 02/23/2010] [Accepted: 04/07/2010] [Indexed: 05/29/2023]
Abstract
Starting from general results of magnetostatics, we give fundamental considerations on the design and characterization of permanent magnets for NMR based on harmonic analysis and symmetry. We then propose a simple geometry that takes advantage of some of these considerations and discuss the practical aspects of the assembly of a real magnet based on this geometry, involving the characterization of its elements, the optimization of the layout and the correction of residual inhomogeneities due to material and geometry imperfections. We report with this low-cost, light-weight magnet (100 euros and 1.8 kg including the aluminum frame) a field of 120 mT (5.1 MHz proton) with a 10 ppm natural homogeneity over a sphere of 1.5 mm in diameter.
Collapse
Affiliation(s)
- Cedric Hugon
- CEA, DSM, IRAMIS, SIS2M, LSDRM CEA Saclay F-91191 Gif-sur-Yvette, France.
| | | | | | | |
Collapse
|
7
|
Design, fabrication and evaluation of a low-cost homogeneous portable permanent magnet for NMR and MRI. CR CHIM 2010. [DOI: 10.1016/j.crci.2009.09.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
8
|
Chang WH, Chen JH, Hwang LP. Single-sided mobile NMR apparatus using the transverse flux of a single permanent magnet. Magn Reson Imaging 2010; 28:129-38. [DOI: 10.1016/j.mri.2009.05.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 04/26/2009] [Accepted: 05/10/2009] [Indexed: 10/20/2022]
|
9
|
Coarna C, Newling B. Short, shaped pulses in a large magnetic field gradient. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 196:127-132. [PMID: 19038562 DOI: 10.1016/j.jmr.2008.10.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 10/22/2008] [Accepted: 10/25/2008] [Indexed: 05/27/2023]
Abstract
A number of materials MR developments require that measurements be made in a large magnetic field gradient, including unilateral (single-sided) magnet designs for portability and open access. In such cases, all radiofrequency (RF) pulses are slice selective. Typically, little effort is made to tailor the shape of the selected slice, because shaped RF excitations are viewed as too lengthy in duration to be useful in materials MRI, where signal lifetimes are mostly less than 1 ms. We compare measured magnetization responses to various standard shaped pulses under extreme conditions of application (approximately 30 micros duration, offset frequencies up to 0.3 MHz, and in the presence of a 13 T/m permanent magnetic field gradient). We discuss the feasibility of their implementation for materials MRI in a large gradient, including the difficulty of choosing optimized pulse area, and propose viable solutions.
Collapse
Affiliation(s)
- C Coarna
- UNB MRI Centre, Department of Physics, University of New Brunswick, 8 Bailey Drive, PO Box 4400, Fredericton, NB, Canada E3B 5A3
| | | |
Collapse
|
10
|
Manz B, Benecke M, Volke F. A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 192:131-138. [PMID: 18314366 DOI: 10.1016/j.jmr.2008.02.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 02/07/2008] [Accepted: 02/08/2008] [Indexed: 05/26/2023]
Abstract
A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids.
Collapse
Affiliation(s)
- B Manz
- Arbeitsgruppe Magnetische Resonanz, Fraunhofer-Institut für Biomedizinische Technik, Ensheimer Strasse 48, 66386 St. Ingbert, Germany.
| | | | | |
Collapse
|
11
|
Song YQ, Cho H, Hopper T, Pomerantz AE, Sun PZ. Magnetic resonance in porous media: recent progress. J Chem Phys 2008; 128:052212. [PMID: 18266417 DOI: 10.1063/1.2833581] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Recent years have seen significant progress in the NMR study of porous media from natural and industrial sources and of cultural significance such as paintings. This paper provides a brief outline of the recent technical development of NMR in this area. These advances are relevant for broad NMR applications in material characterization.
Collapse
Affiliation(s)
- Yi-Qiao Song
- Schlumberger-Doll Research, One Hampshire Street, Cambridge, Massaschusetts 02139, USA.
| | | | | | | | | |
Collapse
|
12
|
Bray CL, Hornak JP. Unilateral MRI using a rastered projection. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 188:151-9. [PMID: 17651995 DOI: 10.1016/j.jmr.2007.06.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 06/19/2007] [Accepted: 06/20/2007] [Indexed: 05/16/2023]
Abstract
Unilateral magnetic resonance techniques, where magnet and radio frequency (RF) coil are placed on one side of the sample, can provide valuable information about a sample which otherwise cannot be accommodated in conventional high spectral resolution magnetic resonance systems. A unilateral magnetic resonance imaging approach utilizing the stray field from a disc magnet and a butterfly geometry RF coil is described. The coil excites spins in a volume centered around an arc through the sample. Translating the RF coil relative to the magnet and recording the signal at each translational location creates a projection of the signal in a tomographic slice through the sample. Rotating the RF coil relative to the sample and repeating the translation creates projections through the sample at different angles. Backprojecting this information yields an image. A proof of concept device operating on this principle at 12.4 MHz was constructed and characterized. Projections through three phantoms are presented with a 1.2-4 cm field of view, thickness of 102 microm, and at a distance of 3mm from the RF coil and 14 mm from the magnet. The edge spread function (ESF) was measured resulting in a 4mm full width at half maximum (FWHM) line spread function (LSF) estimation using a Gaussian model. An example of one reconstructed image is presented.
Collapse
Affiliation(s)
- Christina L Bray
- Magnetic Resonance Laboratory, Center for Imaging Science, Rochester Institute of Technology, Rochester, NY 14623-5604, USA
| | | |
Collapse
|
13
|
Marble AE, Mastikhin IV, Colpitts BG, Balcom BJ. A constant gradient unilateral magnet for near-surface MRI profiling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 183:228-34. [PMID: 16996759 DOI: 10.1016/j.jmr.2006.08.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 08/29/2006] [Accepted: 08/30/2006] [Indexed: 05/11/2023]
Abstract
The design and construction of a unilateral NMR (UMR) magnet assembly for near-surface 1D profiling is presented. The arrangement consists of a single permanent magnet topped with a shaped iron pole cap. The analytically determined profile of the pole cap shapes the field over the magnet, giving a constant gradient of 31 G/cm over a 8mm depth at a 1H frequency of 4.26 MHz in a spot approximately 5 mm wide. The moderate gradient allows 1D profiling of planar samples with a frequency encoded spin-echo experiment. The curvature of the magnetic field limits the available resolution to 100's of microm. The device is suitable for profiling planar samples in which a coarse resolution but large spatial extent is desired.
Collapse
Affiliation(s)
- Andrew E Marble
- MRI Centre, Department of Physics, PO Box 4400, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3
| | | | | | | |
Collapse
|
14
|
Cignini R, Melzi R, Tedoldi F, Casieri C, De Luca F. Large surface mapping by a unilateral NMR scanner. Magn Reson Imaging 2006; 24:813-8. [PMID: 16824976 DOI: 10.1016/j.mri.2006.03.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 03/02/2006] [Indexed: 11/17/2022]
Abstract
The nuclear magnetic resonance (NMR) surface scanner, which provides images of sample surfaces larger than the probe dimension, has been realized using a single-sided device. Although conditioned by distortion effects originated by convolution between the sensitive volume of the probe and the space structures to be imaged, the scanner is able to provide images with good spatial resolution. The images obtained by the surface scanner can be made sensitive to relaxation parameters, magnetization or molecular self-diffusion; also, the dimension perpendicular to the sample surface can be scanned by varying the depth from which the probe detects the sample signal. It may scan surfaces arbitrarily large and with some degree of curvature. This aspect, together with the noninvasive characteristic of the apparatus, indicates that the surface scanner could be used profitably in the field of cultural heritage, where it could provide NMR maps of frescos, paintings on wood, marble artifacts, books and others.
Collapse
Affiliation(s)
- Roberto Cignini
- INFM-CRS SOFT and Dipartimento di Fisica, Università degli Studi La Sapienza, Rome, Italy
| | | | | | | | | |
Collapse
|
15
|
Chang WH, Chen JH, Hwang LP. Single-sided mobile NMR with a Halbach magnet. Magn Reson Imaging 2006; 24:1095-102. [PMID: 16997080 DOI: 10.1016/j.mri.2006.04.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Accepted: 04/02/2006] [Indexed: 10/24/2022]
Abstract
A single-sided mobile NMR apparatus with a small Halbach magnet was constructed for the first time. It is lightweight, compact and exhibits good sensitivity. The weight of the device is only 2 kg, and the NMR signal of the pencil eraser block can be detected in one shot using the device. This study describes the characteristics of this instrument, including the profile of static magnetic flux density, B0, the sensitivity in the depth direction and its effectiveness in one-dimensional profiling. Its usefulness in differentiating soft materials and evaluating the extent of damage of a material is demonstrated based on T2 relaxation data. The moisture absorbance also can be observed from the increase of the echo amplitude of the NMR spin echo signal.
Collapse
Affiliation(s)
- Wei-Hao Chang
- Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
| | | | | |
Collapse
|
16
|
Rahmatallah S, Li Y, Seton HC, Gregory JS, Aspden RM. Measurement of relaxation times in foodstuffs using a one-sided portable magnetic resonance probe. Eur Food Res Technol 2005. [DOI: 10.1007/s00217-005-0076-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
17
|
Perlo J, Casanova F, Blümich B. Profiles with microscopic resolution by single-sided NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2005; 176:64-70. [PMID: 15975840 DOI: 10.1016/j.jmr.2005.05.017] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 05/19/2005] [Accepted: 05/19/2005] [Indexed: 05/03/2023]
Abstract
A single-sided NMR sensor to produce depth profiles with microscopic spatial resolution is presented. It uses a novel permanent magnet geometry that generates a highly flat sensitive volume parallel to the scanner surface. By repositioning the sensitive slice across the object one-dimensional profiles of the sample structure can be produced with a space resolution better than 5 microm. The open geometry of the sensor results in a powerful testing tool to characterize arbitrarily sized objects in a non-destructive way.
Collapse
Affiliation(s)
- J Perlo
- Institut für Technische und Makromolekulare Chemie, RWTH, Aachen D-52056, Germany
| | | | | |
Collapse
|