A flexible five‐channel shielded‐coaxial‐cable (SCC) transceive neck coil for high‐resolution carotid imaging at 7T

Abstract

Purpose: Imaging the carotid arteries at 7T ideally requires a flexible multichannel array that allows B1-shimming and conforms to different neck sizes. The major challenge is to minimize coupling between closely spaced coils and to make the coupling relatively insensitive to loading conditions. Methods: We have designed a five-channel flexible transceive array composed of shielded-coaxial-cable coils placed on the anterior part of the neck and conforming to the anatomy. In vivo imaging of the carotid arteries in three subjects has been performed. Results: The measured noise correlation matrices show the decoupling level between the individual elements to be −12.5 dB and better. Anatomical localizer imaging of the carotids shows both carotids in every subject well visualized after B1-shimming.In vivo black-blood, carotid images were acquired with very high in-plane spatial resolution (0.25 × 0.25 mm 2 ) with clear depiction of the vessel walls. Conclusions: The flexibility of the proposed coil has been demonstrated by imaging subjects with different neck circumferences. To the best of our knowledge, the inplane resolution of 0.25 × 0.25 mm 2 is the highest reported at 7T. K E Y W O R D S7T MRI, carotid imaging, neck coil, ultra-high field

Flexible Multi-Turn Multi-Gap Coaxial RF Coils: Design Concept and Implementation for Magnetic Resonance Imaging at 3 and 7 Tesla

“…A tuning capacitor C T instead of L T would add to the coaxial stub capacitance (X TL ) and could therefore be used to lower the frequency if the self-resonance was higher than the target f Larmor . Note that in work of Ruytenberg et al [28], [38], purely capacitive tuning and matching is used for 10 cm Tx/Rx CCs with a first self-resonance of ≈ 110 MHz (see simulated and calculated values shown in Table II for a 10 cm 1T1G, cable A). For this coil example, with a tuning capacitor across the coil port (Fig.…”

“…around 300 MHz. Therefore, due to the multiple resonances of a CC originating from the coaxial stub impedance behavior, the 1T1G-CC with a self-resonance f 0 < f Larmor used in [28], [38] can still be tuned and matched to 297.2 MHz with only capacitive components. To compare coil designs and motivate the use of a coil with an f 0 as close as possible to f Larmor , the current distribution and amplitude along the oCo, depending on the coil geometry and operation frequency, was analyzed using electromagnetic simulation of the abovementioned example of a 10 cm 1T1G-CC ( f 0 < f Larmor ) compared to a 1T2G-CC used in this study ( f 0 ≈ f Larmor ), for f Larmor = 297.2 MHz.…”

Elastomer coils for wearable MR detection

“…This expands design options by eliminating the need for substrates that provide all restoring force as needed for braided 21 or meandering 22 copper or conductive thread. 23 Compared with screen-printed coils 12 and coils based on coaxial cable, [16][17][18][19][20] elastomer coils offer stretchability and elasticity in addition to flexibility. In addition, a conductive elastomer can readily be subject to washing and should lend itself to sanitization, which is an attractive feature with a view to clinical use of wearable arrays.…”

“…Geometric adaptiveness in MR detection was first pursued with rigid-adjustable [1][2][3][4][5] and flexible [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] coil designs. Stretchable coils have been made based on braided 21 and meandering 22 copper wires or conductive thread.…”

Interelement Decoupling Strategies at UHF MRI

“…The shielded-coaxial-cable (SCC) coil has recently been proposed for use at UHF [19,20]. The SCC coil is made of a coaxial cable with the shield interrupted at one point and with the central conductor interrupted at the opposite point of the shield interruption.…”