Nmi20 040v 1

Magnetic resonance imaging (MRI) analysis was performed using an NMR analyser (NMI20-040 V-I, Suzhou Niumag Analytical Instrument Co., Ltd., Suzhou, China). The sample was placed in the center of the radiofrequency coil of the magnet box and was imaged by MRI using a multilayer spin-echo (SE) sequence.

The duck jerky was cooled and placed in a desiccator for 2 h to balance the water. The samples were measured using an LF-NMR analyser (NMI20-040 V-I, Suzhou Niumag Analytical Instrument Co., Ltd., Suzhou, China) with a proton resonance of 20 MHz at 32°C and a magnetic field strength of 0.5 Tesla. The decay signal of CPMG sequence was collected by a 40 mm diameter radio frequency coil. The parameters were set as follows: 90° pulse width (P1) = 7.52 μs, 180° pulse width (P2) = 14.48 μs, waiting time (TW) = 2,500 ms, number of echoes (NECH) = 10,000, and number of scans (NS) = 8. Then, the transverse relaxation (T2) signals were obtained, including the relaxation amplitude and the time constant during relaxation.

To identify water movement and redistribution in crayfish, a 23 MHz NMR spectroscopy (NMI20-040V-I, Niumag, Shanghai, China) was used [19 (link)]. The Carr–Purcell–Meiboom–Gill pulse sequence was used to measure the spin-spin relaxation time (T₂), and the following settings were used: PRG = 2, RFD = 0. 002 ms, TE (ms) = 0.150, Tw = 1500 ms, NECH = 12,000, NS = 8. T₂₁, T_22, and T₂₃ represented the T₂ of bound water, immobilized water, and free water, respectively.