Figure 2

(a) Picture of the phantom made of a PCTFE (Kel-F) insert with two boreholes parallel and one perpendicular to the spinning axis (1 mm in diameter) filled with the CDA powder. (b) Isosurface representation of the ³¹P 3D MAS image of the phantom recorded at 17.6 T with a spinning frequency of 10 kHz using the spin echo sequence shown in Fig. 3a. The isosurface value is 40% of the maximum signal intensity. ¹H-³¹P cross polarization with a contact time of 3 ms was used and 80 transients were co-added with a recycle delay of 0.5 s corresponding to an experimental duration of 11 h 32 min. The nominal resolution is 132 µm in the read dimension (corresponding to a gradient of 15.47 G/cm) and 155 µm in the phase dimensions with a field of view of 7.5*7.5*15 mm. SNR = 103. The dataset was zero-filled three times leading to voxel size of 30 × 30 × 30 µm³. (c,d) ³¹P 2D slice-selected MAS images of the CDA phantom taken at (c) the top and d) the middle part of the sample. A refocusing-SNOB pulse of 900 µs duration (excitation bandwidth of 2.6 kHz) was used to select a slice of 710 µm thickness. The spatial resolution is 117 µm in read dimension (gradient of 17.44 G/cm) and 155 µm in phase dimension, corresponding to an experimental time of 17 min. SNR = 60 and pixel size of 30 × 30 µm² after zero-filling of the dataset. The color bar scales from zero up to the maximum signal intensity.