Arrays of mutually coupled receiver coils: Theory and application

Abstract

Specialized receiver coils having a small sensitive region can provide an improvement in SNR for MR imaging and spectroscopy, at the expense of limiting the usable field of view. This work presents a technique for designing coil arrays that allows the size and location of the sensitive region to be selected remotely. Only one element of the coil array is directly connected to the receiver, allowing flexibility in system design and implementation. A method is presented for the analysis and design of mutually coupled coil arrays of any number of elements of arbitrary shape. The analysis includes mutual coupling effects between primary coils, to allow multiple primary coils to be used simultaneously. A controller system allows remote selection of the sensitive region and automatically matches the impedance of the array to the preamplifier. Results obtained using a mutually coupled coil array designed for spine imaging are shown.

Evaluation of Image Quality of a 32-Channel versus a 12-Channel Head Coil at 1.5T for MR Imaging of the Brain

“…Significant gains in sensitivity are realized at small distances from the coils, and the addition of more coil elements reduces the sensitivity loss at farther distances. 1,14,22 An initial study with a 32-channel receive-only phased-array head coil showed gains in SNR throughout the field compared with a similar 8-channel head coil.…”

“…1,3,4 When coupled with multichannel receiver MR imaging scanners and PI acquisition and processing techniques, additional data from these coils can be used to fill undersampled k-space. Thus, scanning times may be accelerated without expected changes in contrast or spatial resolution.…”

“…[8][9][10][11] While PI is the most common use of multichannel coils, the additional data acquired by the coil elements can be processed by standard techniques to maximize spatial resolution and SNR. 1,2,[12][13][14] Recent studies with site-specific multichannel receiver coils and more conservative acceleration of scanning times have reported improvements in diagnostic quality in nondynamic organs, such as the breast and musculoskeletal system. [15][16][17] Consequently, there is evidence that a multichannel coil and standard processing techniques can confer some of the advantages to image quality that are characteristic of increasing field strengths.…”

Stretchable coil arrays: Application to knee imaging under varying flexion angles

“…Present-day MRI relies strongly on signal detection with receiver arrays, which were first described in the late 1980s (1)(2)(3)(4) and analyzed in detail by Roemer et al (4). Initially, receiver arrays were devised and used to enhance the net signal-to-noise ratio (SNR) compared with single-coil acquisitions.…”

An MRI study of the differences in the rate of thrombolysis between red blood cell‐rich and platelet‐rich components of venous thrombi ex vivo

“…A shorter repetition time would introduce heavier T 1 -weighing but also more image noise, whereas a longer repetition time would result in less image contrast but better signal-to-noise ratio (SNR) and also prolong the scanning time. On modern clinical scanners parallel imaging is available that allows a substantial scan time reduction at unchanged image contrast (32,33). For example, use of parallel imaging with sensitivity encoding (SENSE) with the parallelization factor of 4 would reduce image scan time from the present 30 min to only 7 min, which is already clinically acceptable.…”