A purpose-built neck coil for black-blood DANTE-prepared carotid artery imaging at 7 T

Abstract

Atherosclerotic plaques in the bifurcation of the carotid arteries can pose a significant health risk due to possible plaque rupture and subsequent stroke. The assessment of plaques, and evaluation of the risk they pose, can be performed with Black-Blood (BB) vessel wall magnetic resonance imaging. However, resolution at standard clinical field strengths (up to 3T) is limited, hampering reliable assessment and diagnosis. The aim of this study was to investigate the benefits of 7T MRI using a BB application that has been successful at clinical field strengths. Therefore, for BB imaging, each sequence was preceded with ‘Delay Alternating with Nutation for Tailored Excitation’ (DANTE) preparation pulses for blood signal suppression. A coil comprising a 4-channel Tx array was designed and built to provide the required excitation coverage for the DANTE train; and a 4-channel Rx array was constructed to target the carotid bifurcation. Human and phantom results showed satisfactory blood suppression and comparable SNR and CNR to 3T, therefore demonstrating the feasibility of the application at 7T. However, the imposed SAR restrictions led to long scan times and subsequent motion artifacts. Thus, more accurate local SAR supervision schemes are required which could lead to a further improvement of BB DANTE vessel wall imaging at 7T.