Low-Field NMR Study on T₂ Relaxation and MRI Imaging During Seed Water Absorption

I. Experimental Materials

 

Bauhinia seeds;

II. Experimental Instrumentation

 

NMI20-015V-I, resonance frequency: probe coil with a 15 mm diameter;

III. Sample Preparation

 

T₂ Relaxation Test: Bauhinia seeds were soaked in water for set intervals (0h, 1h, 2h, 4h, 6h, 8h, 12h, 16h, 20h, 24h, 48h);

MRI Test: Proton density imaging was performed on samples of Bauhinia seeds soaked for different durations.

IV. Experimental Parameters

CPMG: SF = 22 MHz, O1 = 107966 Hz;

MRI: SE sequence.

V. Experimental Methods

 

Soaked-seed T₂ spectra: CPMG sequence was used to test water-saturated seeds, and the SIRT algorithm was applied to invert and generate T₂ spectra;

MRI: Coronary-plane imaging of Bauhinia seeds was acquired using NMR imaging software with an SE sequence;

VI. Analysis and Results

 

(1) Analysis of T₂ spectra of Bauhinia seeds at different soaking times

The spectra reveal clear trends across the first three peaks, representing bound water, less-mobile water, and free water. After soaking, notable changes appear: the normalized T₂ spectra highlight shifts in peak positions and areas. Area A22 showed the strongest correlation with the total area (A_total), representing the dominant variation during seed hydration. Linear fitting of A_total to water absorption rate produced strong results, with seeds reaching hydration equilibrium after about 24 hours.

(2) Seed Imaging Experiments

The coronal images clearly show the hydration process from 0h to 12h: water uptake begins at the right-side embryo and gradually spreads throughout the seed before equilibrium is reached. Overall, LF-NMR analysis effectively reveals the distribution of water states in Bauhinia seeds, tracks the migration pathway during soaking, and identifies the time required to reach equilibrium.