Comparison of high-density composite and surface coil arrays for MRI of spherical imaging volumes

Maunder, Adam; Daneshmand, Mojgan; Mousavi, Pedram; Fallone, B. G.; Zanche, Nicola De

doi:10.1109/mwsym.2014.6848554

Cited by 4 publications

(6 citation statements)

References 13 publications

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“…We believe that, by combining an array of 16 surface TxRx loops placed in two rows with 16 additional vertical Rx‐only loops, full brain coverage, Tx efficiency and Rx performance can be further optimized. We also believe that the combination of surface and vertical loops can provide for higher SNR not only in the peripheral area, but also near the center of the brain …”

Section: Discussionmentioning

confidence: 93%

“…The idea of simultaneously using a geometrically decoupled combination of perpendicular loops has been explored previously by multiple research groups. For example, a pair of such loops can be used as a quadrature Tx coil or as an Rx‐only coil for SNR improvement . Work by Maunder et al proposed the use of a combination of a surface loop and two perpendicular orthogonal vertical loops as an element of an Rx‐only, so‐called composite, array.…”

Section: Introductionmentioning

confidence: 99%

“…For example, a pair of such loops can be used as a quadrature Tx coil or as an Rx‐only coil for SNR improvement . Work by Maunder et al proposed the use of a combination of a surface loop and two perpendicular orthogonal vertical loops as an element of an Rx‐only, so‐called composite, array. However, to the best of our knowledge, using one half of the composite array (the surface loop) as a TxRx, and the other half (the vertical loop) as an additional Rx‐only element, has not been explored previously.…”

Section: Introductionmentioning

confidence: 99%

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Combination of surface and ‘vertical’ loop elements improves receive performance of a human head transceiver array at 9.4 T

et al. 2017

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Ultra-high-field (UHF, ≥7 T) human magnetic resonance imaging (MRI) provides undisputed advantages over low-field MRI (≤3 T), but its development remains challenging because of numerous technical issues, including the low efficiency of transmit (Tx) radiofrequency (RF) coils caused by the increase in tissue power deposition with frequency. Tight-fit human head transceiver (TxRx) arrays improve Tx efficiency in comparison with Tx-only arrays, which are larger in order to fit multi-channel receive (Rx)-only arrays inside. A drawback of the TxRx design is that the number of elements in an array is limited by the number of available high-power RF Tx channels (commonly 8 or 16), which is not sufficient for optimal Rx performance. In this work, as a proof of concept, we developed a method for increasing the number of Rx elements in a human head TxRx surface loop array without the need to move the loops away from a sample, which compromises the array Tx performance. We designed and constructed a prototype 16-channel tight-fit array, which consists of eight TxRx surface loops placed on a cylindrical holder circumscribing a head, and eight Rx-only vertical loops positioned along the central axis (parallel to the magnetic field B ) of each TxRx loop, perpendicular to its surface. We demonstrated both experimentally and numerically that the addition of the vertical loops has no measurable effect on the Tx efficiency of the array. An increase in the maximum local specific absorption rate (SAR), evaluated using two human head voxel models (Duke and Ella), measured 3.4% or less. At the same time, the 16-element array provided 30% improvement of central signal-to-noise ratio (SNR) in vivo relative to a surface loop eight-element array. The novel array design also demonstrated an improvement in the parallel Rx performance in the transversal plane. Thus, using this method, both the Rx and Tx performance of the human head array can be optimized simultaneously.

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Combination of surface and ‘vertical’ loop elements improves receive performance of a human head transceiver array at 9.4 T

et al. 2017

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“…Another study, which may shed light on the problem of central SNR improvement, also deals with a spherical phantom and arrays, which consist of circular surface loops and so‐called composite elements . Each composite element contains a surface loop and 2 orthogonal “vertical” loops, positioned perpendicularly to both the surface loop and each other.…”

Section: Discussionmentioning

confidence: 99%

“…Another study, which may shed light on the problem of central SNR improvement, also deals with a spherical phantom and arrays, which consist of circular surface loops and so-called composite elements. 42,43 Each composite element contains a surface loop and 2 orthogonal "vertical" loops, positioned perpendicularly to both the surface loop and each other. In this work, the authors demonstrated that the composite array slightly improves SNR near the center of the spherical phantom compared to an array of surface coils with the same total number of loops (both surface and vertical).…”

Section: Discussionmentioning

confidence: 99%

Double‐row 18‐loop transceive–32‐loop receive tight‐fit array provides for whole‐brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T

Avdievich

Giapitzakis

Bause

et al. 2018

Magnetic Resonance in Med

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Purpose To improve the transmit (Tx) and receive (Rx) performance of a human head array and provide whole‐brain coverage at 9.4T, a novel 32‐element array design was developed, constructed, and tested. Methods The array consists of 18 transceiver (TxRx) surface loops and 14 Rx‐only vertical loops all placed in a single layer. The new design combines benefits of both TxRx and transmit‐only–receive‐only (ToRo) designs. The general idea of the design is that the total number of array elements (both TxRx and Rx) should not exceed the number of required Rx elements. First, the necessary number of TxRx loops is placed around the object tightly to optimize the Tx performance. The rest of the elements are loops, which are used only for reception. We also compared the performance of the new array with that of a state‐of‐the‐art ToRo array consisting of 16 Tx‐only loops and 31 Rx‐only loops. Results The new array provides whole‐brain coverage, ~1.5 times greater Tx efficiency and 1.3 times higher SNR near the brain center as compared to the ToRo array, while the latter delivers higher (up to 1.5 times) peripheral SNR. Conclusion In general, the new approach of constructing a single‐layer array consisting of both TxRx‐ and Rx‐only elements simplifies the array construction by minimizing the total number of elements and makes the entire design more robust and, therefore, safe. Overall, our work provides a recipe for a Tx‐ and Rx‐efficient head array coil suitable for parallel transmission and reception as well as whole‐brain imaging at UHF.

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Analysis of a Flexible Dual-Channel Octagonal Coil System for UHF MRI

et al. 2022

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Nowadays, MRI is focused on using ultra-high static magnetic fields (> 7 T) to increase the signal-to-noise ratio. The use of high fields, on the other hand, requires novel technical solutions as well as more stringent design criteria for specific absorption rate levels, reducing radiative effect and coil resistance. In this paper, two flexible RF coils for 7 T human magnetic resonance, and 298 MHz ultrahigh frequency operations were analyzed and characterized. Imaging of lower human limbs is regarded as a case study. The lumped element theory and subsequent numerical simulations were used to finetune the single-coil element and the dual-coil array design, respectively. Here, we demonstrate how the shape, size, configuration, and presence of the sample influence the coil performance. The penetration depth of the B 1 -field and the specific absorption rate values have been determined numerically using two numerical surface phantoms: saline and a multilayer human tissue. A preliminary study in the presence of a saline solution phantom has been carried out to develop and validate the dual-coil system. The frequency response of the dual-coil array was measured to assess its robustness when coupled to twelve human volunteers. We found that our design is robust to variations in the anatomical properties of the human thighs, and hence to coil bending. The presented approach can be useful for the implementation of flexible devices with high sensitivity levels and low specific absorption rate.

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Comparison of high-density composite and surface coil arrays for MRI of spherical imaging volumes

Cited by 4 publications

References 13 publications

Combination of surface and ‘vertical’ loop elements improves receive performance of a human head transceiver array at 9.4 T

Combination of surface and ‘vertical’ loop elements improves receive performance of a human head transceiver array at 9.4 T

Double‐row 18‐loop transceive–32‐loop receive tight‐fit array provides for whole‐brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T

Analysis of a Flexible Dual-Channel Octagonal Coil System for UHF MRI

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