Effect of b Value on Imaging Quality for Diffusion Tensor Imaging of the Spinal Cord at Ultrahigh Field Strength

This study investigates the ideal b value for diffusion tensor imaging (DTI) of rat spinal cords using a 7 Tesla MRI machine. DTI is a special MRI technique, can reflect the alterations of tissue microstructure by measuring the water diffusion motion, so it has important application prospects in evaluating the severity of SCI and its therapeutic effects. Researchers collected DTI data from 14 rats, both healthy and with spinal cord injuries, using various b values ranging from 200 to 1000 s/mm². Image quality (including image SNR and image distortion degree) and data quality (including data stability and data consistency) were calculated under different b value settings. The study concluded that a b value of 900 s/mm² is the most suitable for 7T spinal cord DTI scans, considering the limitations of lower b values in accurately depicting tissue microstructure. Considering the shortcomings of the ability of low b values to reflect the microstructure, b = 900 s/mm2 can be used as the optimal b value for 7 T spinal cord diffusion tensor scanning.

• 1
  Image signal-to-noise ratio (SNR) decreases as the b value increases, with the best image quality observed at b = 200 s/mm². The highest NMI result of the image appeared at b = 200 s/mm2 (0:381 ± 0:038) and the lowest at b = 1000 s/mm m2 (0:354 ± 0:044).
• 2
  Data quality, assessed by stability and consistency, peaks at b values of 800 and 900 s/mm². The overall data quality results reached the highest level at b = 800 and 900 s/mm2
• 3
  There was no significant difference in FA value for each b value, only group b = 400 s/mm2 was significantly lower than group b = 900 s/mm2 (Pcorrected = 0:00132).