Combined 23Na and 13C imaging at 3.0 Tesla using a single‐tuned large FOV birdcage coil. Issue 3 (2nd May 2021) - Kaggie, Joshua D.
Abstract : Purpose: An unmet need in carbon‐13 ( 13 C)‐MRI is a transmit system that provides uniform excitation across a large FOV and can accommodate patients of wide‐ranging body habitus. Due to the small difference between the resonant frequencies, sodium‐23 ( 23 Na) coil developments can inform 13 C coil design while being simpler to assess due to the higher naturally abundant 23 Na signal. Here we present a removable 23 Na birdcage, which also allows operation as a 13 C abdominal coil. Methods: We demonstrate a quadrature‐driven 4‐rung 23 Na birdcage coil of 50 cm in length for both 23 Na and 13 C abdominal imaging. The coil transmit efficiencies and B 1 + maps were compared to a linearly driven 13 C Helmholtz‐based (clamshell) coil. SNR was investigated with 23 Na and 13 C data using an 8‐channel 13 C receive array within the 23 Na birdcage. Results: The 23 Na birdcage longitudinal FOV was > 40 cm, whereas the 13 C clamshell was < 32 cm. The transmit efficiency of the birdcage at the 23 Na frequency was 0.65 µT/sqrt(W), similar to the clamshell for 13 C. However, the coefficient of variation of 23 Na‐ B 1 + was 16%, nearly half that with the 13 C clamshell. The 8‐channel 13 C receive array combined with the 23 Na birdcage coil generated a greater than twofold increase in 23 Na‐SNR from the central abdomen compared with the birdcage alone. Discussion: This 23 Na birdcage coil has a larger FOV and improved B 1 + uniformity when compared to the widely used clamshell coil design while also providing similar transmit efficiency. The coil has the potential to be used for both 23 Na and 13 C imaging.