Design and comparison of two eight‐channel transmit/receive radiofrequency arrays for <i>in vivo</i> rodent imaging on a 7 T human whole‐body MRI system

Orzada, Stephan; Maderwald, Stefan; Göricke, Sophia; Parohl, Nina; Ladd, Susanne C.; Ladd, Mark E.; Quick, Harald H.

doi:10.1118/1.3378478

Cited by 12 publications

(10 citation statements)

References 24 publications

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“…Recently, an eight‐channel body array for a 9.4 T animal scanner has been described (16). Similar increase in number of coil elements can be observed in rat MRI applications using 8‐ and 16‐channel body arrays (17–19). Extending the capabilities of parallel imaging to higher accelerations requires the implementation of a miniature design and solving the challenges of a high density coil with on‐coil preamplifiers.…”

supporting

confidence: 68%

A 20‐channel receive‐only mouse array coil for a 3 T clinical MRI system

Keil

Wiggins

Triantafyllou

et al. 2011

Magnetic Resonance in Med

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A 20-channel phased-array coil for MRI of mice has been designed, constructed, and validated with bench measurements and high-resolution accelerated imaging. The technical challenges of designing a small, high density array have been overcome using individual small-diameter coil elements arranged on a cylinder in a hexagonal overlapping design with adjacent low impedance preamplifiers to further decouple the array elements. Signal-to-noise ratio (SNR) and noise amplification in accelerated imaging were simulated and quantitatively evaluated in phantoms and in vivo mouse images. Comparison between the 20-channel mouse array and a length-matched quadrature driven small animal birdcage coil showed an SNR increase at the periphery and in the center of the phantom of 3-and 1.3-fold, respectively. Comparison with a shorter but SNR-optimized birdcage coil (aspect ratio 1:1 and only half mouse coverage) showed an SNR gain of twofold at the edge of the phantom and similar SNR in the center. G-factor measurements indicate that the coil is well suited to acquire highly accelerated images. Magn Reson Med 66:584-595,

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supporting

confidence: 68%

A 20‐channel receive‐only mouse array coil for a 3 T clinical MRI system

Keil

Wiggins

Triantafyllou

et al. 2011

Magnetic Resonance in Med

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“…10 The preamplifier decoupling method can alleviate the mutual coupling in receiver arrays, 9 however, it is not readily feasible in transceiver arrays. 11 Capacitive and inductive decoupling networks introduced between two adjacent coil elements are often employed to compensate for the mutual coupling. [12][13][14][15][16][17] This method requires a dedicated circuit connecting adjacent coil with lumped L=C elements whose values can become impractically small especially at ultrahigh magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

ICE decoupling technique for RF coil array designs

Xie

Pang

et al. 2011

Medical Physics

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The theoretical analysis and experiments demonstrated the feasibility of the decoupling method for high field RF coil array designs without overlapping or direct physical connections between coil elements, which provide more flexibility for coil array design and optimization. The method offers a new approach to address the RF array decoupling issue, which is a major challenge in implementing parallel imaging.

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“…The lowimpedance preamplifier decoupling approach 19 and digital post-processing techniques 20 can reduce mutual coupling in receiver arrays, but not applicable to transmit arrays. 21,22 Shielded array designs 23 and capacitive or inductive networks [24][25][26][27][28] are also available, but typically require additional space or physical connections between coils, precluding independent functioning of each coil and for cylindrical array coils, critically decreasing the usable imaging volume. 23 Although some recent work has demonstrated effective decoupling techniques without physical connection between RF array elements, using induced current compensation or elimination, [29][30][31] or even self-decoupled RF coils, 32 these methodologies are more applicable to surface coils rather than volume coils.…”

Section: Decoupling Approaches For Concentric Solenoidsmentioning

confidence: 99%

A geometrically decoupled, twisted solenoid single‐axis gradient coil set for TRASE

Sun

AlZubaidi

Purchase³

et al. 2019

Magnetic Resonance in Med

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A highly efficient twisted solenoid coil was proposed recently for TRASE imaging for transverse B 0 geometries. This novel coil can be rotated to generate a phase gradient in any transverse direction, therefore, combining two such coils would double k-space coverage for single-axis encoding, resulting in higher spatial resolution. However, the strong inductive coupling between a pair of coaxial twisted solenoids must be overcome. Methods: Here, we demonstrate that two concentric twisted solenoids, designed using previously described Biot-Savart calculations, can be geometrically decoupled by attaching to each a regular solenoid in series. The regular solenoid geometry resulting in minimization of mutual inductance was determined from simulations using the FastHenry2 tool. The effects on TRASE encoding performance due to the regular solenoids were assessed from simulations and experiments. Results: The maximum resulting B 1 magnitude and phase distortions were 3.7% and 4.6 • , while a good isolation S 12 = −17.5 dB between the coil pair was obtained. TRASE experiments confirmed the double k-space coverage, and achieved a rapid spin echo train with 128 k-space points collected within 80 ms, allowing short T 2 samples to be accurately imaged. Conclusions: This study demonstrates that a pair of twisted solenoid phase gradient RF coils can be geometrically decoupled. Advantages over active PIN diode decoupling include faster switching, lower hardware complexity, and scalability. K E Y W O R D S geometric decoupling, RF coil, TRASE MRI, twisted solenoid 1 | INTRODUCTION 1.1 | TRASE overview and encoding principle Transmit Array Spatial Encoding (TRASE) is an MRI encoding approach that enables k-space data to be acquired using phase gradients in the radio frequency (RF) transmit fields (B 1). 1 Unlike conventional MRI encoding methods which rely on the use of main field (B 0) gradients, the substitution of B 0 gradients by B 1 phase gradients using simple RF technologies allows compact MRI systems to be made, particularly suitable for low-field, low-cost scenarios. 2 Recent work suggest that clinical-level millimeter spatial resolution is practically achievable, under both in vivo 3 and phantom situations. 1,2,4-6 | 1485 SUN et al. The fundamental concept of TRASE is that the pulse sequence consists of an echo train of 180 • refocusing pulses that are transmitted in an alternating pattern by switching the phase gradient B 1 field for each RF pulse. For onedimensional TRASE encoding, two different B 1 fields A and B with different phase gradients k A and k B are needed. These two phase gradients are transmitted alternatively down the spin echo train to impart a progressively increasing spatial phase modulation, with each k-space point collected by averaging the center points of each acquired echo. For higher dimensional TRASE encoding, more such B 1 phase gradient fields are needed, so for instance, three B 1 fields are sufficient for 2D TRASE encoding. Other reported phase gradient coil designs have included Helmholtz-M...

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Design and comparison of two eight‐channel transmit/receive radiofrequency arrays for in vivo rodent imaging on a 7 T human whole‐body MRI system

Abstract: The results show that both coil designs are suitable for small animal imaging on 7 T whole-body systems; the preferred coil depends on the demands of the application.

Cited by 12 publications

References 24 publications

A 20‐channel receive‐only mouse array coil for a 3 T clinical MRI system

A 20‐channel receive‐only mouse array coil for a 3 T clinical MRI system

ICE decoupling technique for RF coil array designs

A geometrically decoupled, twisted solenoid single‐axis gradient coil set for TRASE

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