A 128-channel receive-only cardiac coil for highly accelerated cardiac MRI at 3 Tesla

Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Magnetic Resonance in Medicine (Impact Factor: 3.57). 06/2008; 59(6):1431-9. DOI: 10.1002/mrm.21598
Source: PubMed


A 128-channel receive-only array coil is described and tested for cardiac imaging at 3T. The coil is closely contoured to the body with a "clam-shell" geometry with 68 posterior and 60 anterior elements, each 75 mm in diameter, and arranged in a continuous overlapped array of hexagonal symmetry to minimize nearest neighbor coupling. Signal-to-noise ratio (SNR) and noise amplification for parallel imaging (G-factor) were evaluated in phantom and volunteer experiments. These results were compared to those of commercially available 24-channel and 32-channel coils in routine use for cardiac imaging. The in vivo measurements with the 128-channel coil resulted in SNR gains compared to the 24-channel coil (up to 2.2-fold in the apex). The 128- and 32-channel coils showed similar SNR in the heart, likely dominated by the similar element diameters of these coils. The maximum G-factor values were up to seven times better for a seven-fold acceleration factor (R=7) compared to the 24-channel coil and up to two-fold improved compared to the 32-channel coil. The ability of the 128-channel coil to facilitate highly accelerated cardiac imaging was demonstrated in four volunteers using acceleration factors up to seven-fold (R=7) in a single spatial dimension.

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Available from: Lawrence L Wald, Dec 18, 2013
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    • "With the rapid increase in the number of RF coils in multi-channel MRI receiver arrays [1] [2] [3] [4], RF cables and connectors have grown proportionately, contributing to coil bulk and weight, increasing patient discomfort and lengthening setup times. The connecting cables also require the use of cable traps to block common-mode currents and are subject to RF heating in extreme cases. "
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    ABSTRACT: As the number of coils increases in multi-channel MRI receiver-coil arrays, RF cables and connectors become increasingly bulky and heavy, degrading patient comfort and slowing workflow. Inductive coupling of signals provides an attractive “wireless” approach, with the potential to reduce coil weight and cost while simplifying patient setup. In this work, multi-channel inductively coupled anterior arrays were developed and characterized for 1.5 T imaging. These comprised MR receiver coils inductively (or “wirelessly”) linked to secondary or “sniffer” coils whose outputs were transmitted via preamps to the MR system cabinet. The induced currents in the imaging coils were blocked by passive diode circuits during RF transmit. The imaging arrays were totally passive, obviating the need to deliver power to the coils, and providing lightweight, untethered signal reception with easily positioned coils. Single-shot fast spin echo images were acquired from 5 volunteers using a 7-element inductively coupled coil array and a conventionally cabled 7-element coil array of identical geometry, with the inductively-coupled array showing a relative signal-to-noise ratio of 0.86 +/− 0.07. The concept was extended to a larger 9-element coil array to demonstrate the effect of coil element size on signal transfer and RF-transmit blocking.
    Magnetic Resonance Imaging 12/2014; 33(3). DOI:10.1016/j.mri.2014.12.004 · 2.09 Impact Factor
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    • "Modern research MR systems are nowadays also fitted with more than one Rx channel in order to profit from the gain in signal-to-noise ratio (SNR) and/or from accelerated imaging, both of which are offered by coil arrays. Recent developments increased the number of receivers (and elements in the coil array) on clinical scanners up to 128 (2). This significant difference in the available number of channels between clinical and research instruments is caused by the fact that the multichannel technology at higher frequencies and smaller array geometries is technically more challenging while at the same time the market for research systems is much smaller than the clinical MR market. "
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    ABSTRACT: Murine MRI studies are conducted on dedicated MR systems, typically equipped with ultra-high-field magnets (>or=4.7 T; bore size: approximately 12-25 cm), using a single transmit-receive coil (volume or surface coil in linear or quadrature mode) or a transmit-receive coil combination. Here, we report on the design and characterization of an eight-channel volume receive-coil array for murine MRI at 400 MHz. The array was combined with a volume-transmit coil and integrated into one probe head. Therefore, the animal handling is fully decoupled from the radiofrequency setup. Furthermore, fixed tune and match of the coils and a reduced number of connectors minimized the setup time. Optimized preamplifier design was essential for minimizing the noise coupling between the elements. A comprehensive characterization of transmit volume resonator and receive coil array is provided. The performance of the coil array is compared to a quadrature-driven birdcage coil with identical sensitive volume. It is shown that the miniature size of the elements resulted in coil noise domination and therefore reduced signal-to-noise-ratio performance in the center compared to the quadrature birdcage. However, it allowed for 3-fold accelerated imaging of mice in vivo, reducing scan time requirements and thus increasing the number of mice that can be scanned per unit of time.
    Magnetic Resonance in Medicine 07/2010; 64(1):80-7. DOI:10.1002/mrm.22414 · 3.57 Impact Factor
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    • "Standard nuclear magnetic resonance (NMR) systems use highquality factor reception coils and low-noise Gallium-Arsenide electronics in their radio-frequency (RF) frontend. Recently, there has been considerable effort to combine up to 128 of these discretecomponent receivers into large arrays [1] [2] [3] [4] [5] [6]. For imaging, an array of receivers can be used to increase the field-of-view while maintaining the spatial resolution of the component receivers. "
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    ABSTRACT: We present the first single-chip array of integrated NMR receivers for parallel spectroscopy and imaging. The array, optimized for operation at 300 MHz, is composed of eight separate channels, with each channel consisting of a detection coil, a tuning capacitor, a low noise amplifier and a 50 ohm buffer. As all the integrated electronics are placed underneath the reception coils, the array is densely packed. Each single-channel reception coil has a diameter of 500 microm, resulting in a total active area of 1 mm by 2 mm for the array. The (1)H time-domain spin sensitivity of a single channel is approximately 1x10(15) spins/square root(Hz).
    Journal of Magnetic Resonance 12/2009; 201(2):239-49. DOI:10.1016/j.jmr.2009.09.019 · 2.51 Impact Factor
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