Development and evaluation of a 16‐channel receive‐only RF coil to improve 7T ultra‐high field body MRI with focus on the spine

Abstract

Purpose A 16‐channel receive (16Rx) radiofrequency (RF) array for 7T ultra‐high field body MR imaging is presented. The coil is evaluated in conjunction with a 16‐channel transmit/receive (16TxRx) coil and additionally with a 32‐channel transmit/receive (32TxRx) remote body coil for RF transmit and serving as receive references. Methods The 16Rx array consists of 16 octagonal overlapping loops connected to custom‐built detuning boards with preamplifiers. Performance metrics like noise correlation, g‐factors, and signal‐to‐noise ratio gain were compared between 4 different RF coil configurations. In vivo body imaging was performed in volunteers using radiofrequency shimming, time interleaved acquisition of modes (TIAMO), and 2D spatially selective excitation using parallel transmit (pTx) in the spine. Results Lower g‐factors were obtained when using the 16Rx coil in addition to the 16TxRx array coil configuration versus the 16TxRx array alone. Distinct signal‐to‐noise ratio gain using the 16Rx coil could be demonstrated in the spine region both for a comparison with the 16TxRx coil (>50% gain) in vivo and the 32TxRx coil (>240% gain) in a phantom. The 16Rx coil was successfully applied to improve anatomical imaging in the abdomen and 2D spatially selective excitation in the spine of volunteers. Conclusion The novel 16‐channel Rx‐array as an add‐on to multichannel TxRx RF coil configurations provides increased signal‐to‐noise ratio, lower g‐factors, and thus improves 7T ultra‐high field body MR imaging.

Evolution of UHF Body Imaging in the Human Torso at 7T

“…Another advantage of exciting spins within a limited target anatomy is that artifacts resulting from motion of tissue beyond the region of interest can be reduced. An example of reduced FOV imaging has been demonstrated in the spine 176 and kidney at 7T. 177…”

Ultra-high-field MR in Prostate cancer: Feasibility and Potential

“…To fully resemble a clinical system with an integrated RF coil, a complete 32-channel parallel transmit system was designed of which the coil elements were placed in the gap between the gradient coil and liner of the patient tunnel [ 13 ]. This transmit array had a wide B 1 transmit field of 50 cm, and could be combined with receive-only loops [ 29 ]. Although this setup provides more freedom and comfort to the patient, as only a thin layer of loop coils is needed on top of and below the body, it remains challenging to transmit at high power with well-decoupled distant coil elements.…”

7 Tesla and Beyond

“… 109 Comparisons of the diagnostic performance in lumbar spine MRI at 7 T versus 1.5/3 T could not prove superior imaging quality, so far precluding routine clinical use. 111 However, recent developments of novel coil technology (ie, 16-channel receive array as an add-on to multichannel transmit/receive RF coil configurations) have been demonstrated to increase SNR, lower g-factors, and thus improve 7 T spine MRI at 7 T. 112 …”