Fig. 8.

FDTD simulation results of the B₁ distribution of the double-tuned CMDM volume coil at 7T in the loaded case. The black circles in (a) and (b) and black rectangles in (d) and (e) denote the phantom position. (a) Axial plane B₁ distribution of the common mode channel for ¹H. (b) Axial plane B₁ distribution of the differential mode channel for ¹³C. (c) 1-D plot of the axial plane B₁ distribution, blue line and red line denote the ¹H and ¹³C, respectively. (d), (e) Sagittal plane B₁ distributions of the common mode channel for ¹H and the differential mode channel for ¹³C. (f) 1-D profile of the sagittal plane B₁ distribution, blue line and red line denote the ¹H and ¹³C respectively. It is shown that for ¹³C channel with the differential mode operating at 75 MHz, homogeneous B₁ field distribution was obtained in both axial and sagittal directions, while for ¹H channel with the common mode operating at 300 MHz, although “dielectric resonance” effects at ultrahigh fields distort the B₁ field, a fairly homogeneous B₁ distribution was still obtained in this case.