Magnetic Resonance Microscopy (MRM) was performed on a 9.4T (400 MHz proton frequency) wide-bore vertical superconducting magnet (Jastec Superconductor Technology, Tokyo, Japan) connected to an NMR/MRI spectrometer (Tecmag, Houston TX, United States). Before the imaging, the tube with the sample was inserted in a Micro 2.5 gradient system with a 10 mm RF probe (Bruker, Ettlingen, Germany) of the magnet.
DTI of the nerves was performed using a three-dimensional (3D) pulsed gradient spin-echo (PGSE) imaging sequence with diffusion gradients in 19 different directions; however, all with the same b value of 1,150 s/mm2. The selected b value was chosen given the preliminary results, whereas we have tested various b values up to 1,800 s/mm2. The selected value provided optimal conditions for measuring the leading eigenvalue within the nerve fascicles. The theory also supports the selected b value for the two-point experiment with b1 = 0 and b2 = b > 0, where the optimal b value is equal to b = 1.1/D (Xing et al., 1997 (link)). Acquisition of an additional reference T2-weighted image with no diffusion weighting (b = 0) was needed for DTI calculation. The images were acquired with the following parameters: TE/TR = 36/880 ms; δ = 3 ms; ∆ = 27 ms; G0 = 0.26 T/m; field of view 9 × 4.5 × 10 mm3; matrix size, 256 × 128 × 16; and 4 signal averages. The image resolution along the in-plane directions was 35 μm. Scanning was performed at room temperature of 21°C with a total acquisition time of 1 day 16 h.
DTI of the nerves was performed using a three-dimensional (3D) pulsed gradient spin-echo (PGSE) imaging sequence with diffusion gradients in 19 different directions; however, all with the same b value of 1,150 s/mm2. The selected b value was chosen given the preliminary results, whereas we have tested various b values up to 1,800 s/mm2. The selected value provided optimal conditions for measuring the leading eigenvalue within the nerve fascicles. The theory also supports the selected b value for the two-point experiment with b1 = 0 and b2 = b > 0, where the optimal b value is equal to b = 1.1/D (Xing et al., 1997 (link)). Acquisition of an additional reference T2-weighted image with no diffusion weighting (b = 0) was needed for DTI calculation. The images were acquired with the following parameters: TE/TR = 36/880 ms; δ = 3 ms; ∆ = 27 ms; G0 = 0.26 T/m; field of view 9 × 4.5 × 10 mm3; matrix size, 256 × 128 × 16; and 4 signal averages. The image resolution along the in-plane directions was 35 μm. Scanning was performed at room temperature of 21°C with a total acquisition time of 1 day 16 h.
Free full text: Click here
