Imaging the Internal Auditory Canal with an 8 × 2 Transceiver Array Head Coil at 7T

SUMMARY:

7T neuroimaging has known problems with B₁⁺ strength, homogeneity and B₀ susceptibility that make imaging in the inferior brain regions difficult. We investigated the utility of a decoupled 8 × 2 transceiver coil and shim insert to image the internal auditory canal (IAC) and inferior brain in comparison to the standard Nova 8/32 coil. B₁⁺, B₀, and the T2 sampling perfection with application-optimized contrasts by using flip angle evolution sequence (SPACE) were compared by using research and standard methods in n = 8 healthy adults by using a Terra system. A T2 TSE was also acquired, and 2 neuroradiologists evaluated structures in and around the IAC, blinded to the acquisition, by using a 5-point Likert scale. The Nova 8/32 coil gave lower B₁⁺ inferiorly compared with the whole brain while the transceiver maintained similar B₁⁺ throughout. SPACE images showed that the transceiver performed significantly better, e.g., the transceiver scored 4.0 ± 0.8 in the left IAC, compared with 2.5 ± 0.8 with the Nova 8/32. With T2-weighted imaging that places a premium on refocusing pulses, these results show that with improved B₁⁺ performance inferiorly, good visualization of the structure of the IAC and inferior brain regions is possible at 7T.