Anisotropy in Tendon Investigated in Vivo by a Portable NMR Scanner, the NMR-MOUSE

Haken, R.A.; Blümich, Bernhard

doi:10.1006/jmre.2000.2040

Cited by 74 publications

(51 citation statements)

References 14 publications

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“…Using the latest very hard permanent magnetic materials, magnetic flux densities exceeding 5 T could be obtained (7). The generated magnetic field in such a Halbach cylinder is transverse to the cylinder axis, which allows the use of simple and efficient solenoidal rf-coils for excitation and also allows new NMR-experiments where the direction of the magnetic field is rotated relative to the sample (8,9). The magnet design does not require the use of yokes.…”

Section: Introductionmentioning

confidence: 98%

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Soltner¹,

Blümler²

2010

Concepts Magnetic Resonance

114

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NMR Mandhalas (Magnetic Arrangement for Novel Discrete Halbach LAyout) are arrays of identically shaped magnets in a Halbach-type arrangement. They provide a simple and cost-effective way to generate high magnetic fields for mobile applications, for example, in magnetic resonance. Based on the introductory publication by Raich and Blü mler (Concepts Magn Reson 2004;23B:16-25), we extend the notion of Mandhalas from cube-shaped magnets to polygonal and cylindrical ones and present construction guidelines for the stacking of such rings to generate homogeneous magnetic fields over larger volumes. For this purpose, we present formulas and numerical values based on a dipole approach to calculate the flux density of single rings and composed 3D systems and compare to corresponding results obtained by 3D boundary element method calculations. As an application of the approach presented here, we constructed prototypes.

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Section: Introductionmentioning

confidence: 98%

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Soltner¹,

Blümler²

2010

Concepts Magnetic Resonance

114

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“…But the self-diffusion coefficient D and multiquantum signals (10) also can be acquired. In macroscopically ordered materials like tendon and strained rubber, the angle dependence of these signals provides information on the orientational distribution function (11). Moreover, fluid and granular flow can be characterized noninvasively although the determination of velocity distributions remains a challenge in the time-invariant inhomogeneous fields of the NMR-MOUSE (12).…”

Section: Introductionmentioning

confidence: 99%

Construction of a NMR‐MOUSE with short dead time

Anferova

Anferov

Adams

et al. 2002

Concepts Magn. Reson.

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ABSTRACT:The NMR-MOUSE is a nuclear magnetic resonance (NMR) sensor for unilateral NMR of materials suitable for process and quality control. Practical aspects of the sensor construction are described, in particular radiofrequency coil design and shielding procedures to reduce probe ringing. Dead times of less than 20 s can be achieved at frequencies in the vicinity of 20 MHz with permanent magnets within sensitive volumes up to 4 mm deep. First applications of the NMR-MOUSE to the analysis of historical books are reported.

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“…(7) The odd-parity image is reflected along the phase-encoding direction and added to the even image (this improves the SNR by a factor of ͱ2). (8) For the case of two orthogonal phase-encoding directions as shown in Fig. 8, the oddparity image is reflected along both phase-encoding directions and then added to the even-parity image.…”

Section: Imaging Sequencementioning

confidence: 99%

“…In the "inside-out" setup it is very difficult to create highly homogeneous fields without making significant compromises regarding field magnitude. Several types of systems that operate in an "inside-out" geometry have been designed and built, demonstrating measurement capabilities of relaxation parameters (7,8), diffusion coefficients (9), spectroscopic data (10), and three-dimensional (3D) imaging (11). In the case of microscopic MRI, where very high field gradients are required to obtain a high resolution, "inside-out" systems were found to be very useful and enabled the acquisition of images with a resolution of 1 m or better, outside a superconducting magnet (4,12), or near a microscopic magnetic tip (13,14).…”

mentioning

confidence: 99%

Ex situ endorectal MRI probe for prostate imaging

Blank

Ish-Shalom

Shtirberg

et al. 2009

Magnetic Resonance in Med

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A unique ex situ MRI probe, which examines samples external to its geometry, is presented. The probe is intended to be used for imaging the prostate gland via an endorectal pathway. It has a semicylindrical shape with a length of 6 cm and typical diameter of ϳ3 cm. The probe's imaging field of view spans almost along its entire length and up to a distance of 2 cm away from its surface, with an angular sector of ϳ90°. The detailed design of the probe is presented, followed by a set of representative results obtained by the current bench prototype of this system. NMR and its descendant MRI are usually pursued in a setup based on a highly homogenous static magnetic field, B 0 , with variance Ͻ1 ppm, creating nuclear spin precession at a corresponding narrow band of frequencies (1). The homogeneous static field setup has several advantages, such as the ability to obtain chemical shifts while ensuring good signal-to-noise ratio (SNR) due to the small bandwidth involved. However, this setup suffers from the need to employ large magnets that usually surround the examined sample/object. In specific cases, such as clinical MRI systems, the large magnet, and the corresponding large radiofrequency (RF) and gradient coils, are a major factor in the relative complexity and the high cost of such systems. If one is interested only in a specific small region within the body, it could be highly advantageous to obtain NMR information by using either a noninvasive handheld probe or an intracavity self-contained (magnet ϩ RF and gradient coils) NMR probe, thus avoiding the requirement for a large external magnet. Such an approach to NMR measurement or NMR imaging without a sample-surrounding magnet is termed "inside-out," or ex situ (2-6). In the "inside-out" setup it is very difficult to create highly homogeneous fields without making significant compromises regarding field magnitude. Several types of systems that operate in an "inside-out" geometry have been designed and built, demonstrating measurement capabilities of relaxation parameters (7,8), diffusion coefficients (9), spectroscopic data (10), and three-dimensional (3D) imaging (11). In the case of microscopic MRI, where very high field gradients are required to obtain a high resolution, "inside-out" systems were found to be very useful and enabled the acquisition of images with a resolution of 1 m or better, outside a superconducting magnet (4,12), or near a microscopic magnetic tip (13,14).The efforts described above were mainly directed toward materials science applications or related subjects, with appreciable achievements. In the field of medicine, recent work has demonstrated the use of a miniature intravascular ex situ NMR probe with one-dimensional imaging capability for the detection of vulnerable plaque in the coronary arteries (15-17). Larger nonimaging and/or one-dimensional imaging probes have been shown to be useful in obtaining interesting clinical results regarding the examination of tendon anisotropy, skin conditions, and breast implants (18). Despite this ...

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Anisotropy in Tendon Investigated in Vivo by a Portable NMR Scanner, the NMR-MOUSE

Cited by 74 publications

References 14 publications

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Construction of a NMR‐MOUSE with short dead time

Ex situ endorectal MRI probe for prostate imaging

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