Design and application of a four‐channel transmit/receive surface coil for functional cardiac imaging at 7T

Abstract

Purpose: To design and evaluate a four-channel cardiac transceiver coil array for functional cardiac imaging at 7T. Materials and Methods:A four-element cardiac transceiver surface coil array was developed with two rectangular loops mounted on an anterior former and two rectangular loops on a posterior former. specific absorption rate (SAR) simulations were performed and a B þ 1 calibration method was applied prior to obtain 2D FLASH CINE (mSENSE, R ¼ 2) images from nine healthy volunteers with a spatial resolution of up to 1 Â 1 Â 2.5 mm 3 .Results: Tuning and matching was found to be better than 10 dB for all subjects. The decoupling (S 21 ) was measured to be >18 dB between neighboring loops, >20 dB for opposite loops, and >30 dB for other loop combinations. SAR values were well within the limits provided by the IEC. Imaging provided clinically acceptable signal homogeneity with an excellent blood-myocardium contrast applying the B þ 1 calibration approach. Conclusion: A four-channel cardiac transceiver coil array for 7T was built, allowing for cardiac imaging with clinically acceptable signal homogeneity and an excellent blood-myocardium contrast. Minor anatomic structures, such as pericardium, mitral, and tricuspid valves and their apparatus, as well as trabeculae, were accurately delineated.

Skin sodium measured with 23Na MRI at 7.0 T

“…This finding is in alignment with a recent in vivo study performed at The results reported for this feasibility study are likely to pave the way for further advances in RF coil technology tailored for assessment of skin sodium content. These efforts will help to further gain sensitivity by reducing loop element size and by including more loop elements as recently demonstrated for transceiver arrays customized for proton MRI at 7.0 T (41)(42)(43)(44)(45)(46), and hence will contribute to further improvements of in-plane resolution. The use of a large slice thickness for transversal slices of skin in the lower leg implies perfect orientation of the calf-skin and agarose standards parallel to the main axis of the MR scanner to reduce partial volume effects of skin Na + signal, Na + free environment and low Na + subcutaneous fat tissue.…”

Myocardial T2* Mapping with Ultrahigh Field Magnetic Resonance: Physics and Frontier Applications

“…Local transceiver (TX/RX) and multi-channel transmission arrays in conjunction with multi-channel local receive arrays have been suggested as possible solutions. Eminent developments put building blocks to use consisting of stripline elements [41][42][43][44][45], electrical dipoles [45][46][47][48][49][50][51], dielectric resonant antennas [52], slot antennas [53], and loop elements [54][55][56][57][58][59]. Rigid, flexible and modular configurations have been exploited.…”

“…Irrespective of the building block technology, a trend toward higher numbers of transmit and receive elements can be observed with the purpose to advance anatomic coverage [47,[54][55][56][57][58][59] and to add degrees of freedom for transmission field shaping [60]. Figure 3 compiles developments of loop element based transceiver configurations optimized for CMR at 7.0 T. A 4-channel TX/RX [55] (Figure 3A) and an 8-channel TX/RX [58] ( Figure 3B) one-dimensional array were reported and extended to a 16-channel two-dimensional design [56] (Figure 3C). A modular 32-channel TX/RX [59] (Figure 3D) array further exploited the two-dimensional building block layout.…”

ultraMEDIS – Ultra-Wideband Sensing in Medicine

“…However, there are unmet needs of clinical CMR, particularly for high (≥ 3 T) and ultra-high (≥ 7 T) field MRI. Higher magnetic fields offer the chance to acquire images of better spatial resolution [63], but on the downside the ECG signal is increasingly perturbed by the magneto-hydrodynamic effect [64] until it becomes effectively useless for cardiac gating at ultraMEDIS -Ultra-Wideband Sensing in Medicine 285 7 T. Furthermore, ECG electrodes are directly attached to the patient's skin, which may result in local RF burns. In addition, ECG and alternative approaches like pulse oximetric or acoustic cardiac triggering [65] do not provide any information about the respiratory state.…”