Implantable planar rf microcoils for NMR microspectroscopy

Renaud, Louis; Armenean, M.; Berry, L.A.; Kleimann, P.; Morin, Pierre; Pitaval, M.; O’Brien, Jonathan M.; Brunet, Max; Saint‐Jalmes, Hervé

doi:10.1016/s0924-4247(01)00914-1

Cited by 37 publications

(27 citation statements)

References 8 publications

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“…13 Among the planar microcoils used for NMR experiments, [8][9][10][11]19,20 the highest average SNR per acquisition of 60 was achieved with a circular spiral microcoil made of Cu, having an outer radius of 1000 µm, 4 turns and a sample volume of 470 nL located 50 µm above the coil center. Other reported planar architectures include stacked multiple planar microcoils.…”

Section: Appendixmentioning

confidence: 99%

“…Micro-NMR systems reported previously have been realized with several types of coils, such as Helmholtz, [1][2][3] solenoidal, 4-6 planar [7][8][9][10][11][12] or even micro-strip lines. 13 These systems operate at different Larmor frequencies with values varying in a wide range, from 63.88 MHz when the externally applied DC magnetic field (MF) has the magnetic field strength (MFS, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Design of planar microcoil-based NMR probe ensuring high SNR

2017

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A microNMR probe for ex vivo applications may consist of at least one microcoil, which can be used as the oscillating magnetic field (MF) generator as well as receiver coil, and a sample holder, with a volume in the range of nanoliters to micro-liters, placed near the microcoil. The Signal-to-Noise ratio (SNR) of such a probe is, however, dependent not only on its design but also on the measurement setup, and the measured sample. This paper introduces a performance factor P independent of both the proton spin density in the sample and the external DC magnetic field, and which can thus assess the performance of the probe alone. First, two of the components of the P factor (inhomogeneity factor K and filling factor η) are defined and an approach to calculate their values for different probe variants from electromagnetic simulations is devised. A criterion based on dominant component of the magnetic field is then formulated to help designers optimize the sample volume which also affects the performance of the probe, in order to obtain the best SNR for a given planar microcoil. Finally, the P factor values are compared between different planar microcoils with different number of turns and conductor aspect ratios, and planar microcoils are also compared with conventional solenoids. These comparisons highlight which microcoil geometry-sample volume combination will ensure a high SNR under any external setup.

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Section: Appendixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design of planar microcoil-based NMR probe ensuring high SNR

2017

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“…More recently, coils have been combined with sample volumes on glass [7] and deposited on plastic [8], and implantable devices have been developed [9]. The best performance is obtained on insulating substrates [10].…”

Section: Related Contentmentioning

confidence: 99%

Micro-coils for MR spectroscopy by deep silicon etching

Syms¹,

Ahmad²,

Young³

et al. 2005

J. Phys.: Conf. Ser.

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A process for batch fabrication of low-cost microcoils for magnetic resonance spectroscopy is demonstrated. Conductors are fabricated on oxidised silicon substrates by electroplating metals inside a deep photoresist mould, and passivated using an epoxy-based resist. Through-wafer deep reactive ion etching is used to define sample volumes and stencil cuts around each die, and dies are separated by snap-out. Single-coil and multiple-coil sensors are constructed by stacking parts on baseplates fabricated on the same wafer. Single-turn coils have a Q-factor of ≈ 15 at 63.6 MHz, and Helmholtz coils a Q-factor of ≈ 13. Magnetic resonance imaging and spectroscopy are performed, and a SNR of 900 is achieved.

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“…We have developed a monolithic design based on the transmission lines between conductor windings on both sides of a dielectric substrate, called Multi-turn Transmission Lines Resonator (MTLR) [5]. Coils with similar designs (also based on transmission lines) have been fabricated on various rigid substrates such as silicon dioxide [6] and glass [7], then on flexible polymeric substrates such as polyimide [7][8][9] and Teflon [10,11]. This last substrate has a low loss tangent (less than 0.0003 at 1 MHz) which allows to reduce the parasitic capacitance and maximize the quality factor Q of the antennas [11].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Packaging of Flexible Polymeric Microantennae for in Vivo Magnetic Resonance Imaging

et al. 2012

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Abstract:In this paper, we detail how microantennae dedicated to Magnetic Resonance Imaging (MRI) can benefit from the advantages offered by polymer substrates, especially flexibility and dielectric properties. We present a monolithic and wireless design based on the transmission lines between conductor windings on both sides of a dielectric substrate and its fabrication process. This last one requires specific plasma treatments to improve polymer/metal adhesion. We have led a comparative study on the effects of the ageing time on the wettability and the metal adhesion to Kapton and Teflon surfaces. Correlation OPEN ACCESSPolymers 2012, 4 657 between wettability (water contact angle) and adhesion (tensile strength) has been established. Then, the use of PolyDiMethylSiloxane (PDMS) as biocompatible packaging material and the optimization of its thickness allows us to conserve suitable f 0 and Q values in a conducting environment such as the biological tissues. These studies allow us to perform 7 Tesla in vivo MRI of the rat brain with a high spatial resolution of 100 x 100 x 200 µm 3 and a Signal to Noise Ratio of 80.

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Implantable planar rf microcoils for NMR microspectroscopy

Cited by 37 publications

References 8 publications

Design of planar microcoil-based NMR probe ensuring high SNR

Design of planar microcoil-based NMR probe ensuring high SNR

Micro-coils for MR spectroscopy by deep silicon etching

Fabrication and Packaging of Flexible Polymeric Microantennae for in Vivo Magnetic Resonance Imaging

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