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

Shu-Sheng Bao,Jia-Sheng Rao,Xing-Xing Bao,Can Zhao,Marco Giannelli

doi:10.1155/2021/4836804

Abstract

Objective To explore the optimal b value setting for diffusion tensor imaging of rats' spinal cord at ultrahigh field strength (7 T). Methods Spinal cord diffusion tensor imaging data were collected from 14 rats (5 healthy, 9 spinal cord injured) with a series of b values (200, 300, 400, 500, 600, 700, 800, 900, and 1000 s/mm2) under the condition that other scanning parameters were consistent. The image quality (including image signal-to-noise ratio and image distortion degree) and data quality (i.e., the stability and consistency of the DTI-derived parameters, referred to as data stability and data consistency) were quantitatively evaluated. The min-max normalization method was used to process the calculation results of the four indicators. Finally, the image and data quality under each b value were synthesized to determine the optimal b value. Results b = 200 s/mm2 and b = 900 s/mm2 ranked in the top two of the comprehensive evaluation, with the best image quality at b = 200 s/mm2 and the best data quality at b = 900 s/mm2. Conclusion 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.

Highlights

Magnetic resonance imaging (MRI) is an important imaging method to detect spinal cord injury (SCI) at present, but conventional MRI has deficiencies in detecting the microstructure of spinal cord tissue and the integrity of white matter fiber tracts [1]
A dual-channel surface receive coil was fixed on the back corresponding to the thoracic spinal cord, and the head was lifted by a head sheath to reduce the amplitude of respiratory movement and to avoid obvious movements during scanning
Our results showed that when b value was in low level (b = 200 − 600 s/mm2), mean diffusivity (MD) value increased with the increasing of it; MD was in stable when b value was in high level (b = 700 − 1000 s/mm2)

Summary

Introduction

Magnetic resonance imaging (MRI) is an important imaging method to detect spinal cord injury (SCI) at present, but conventional MRI has deficiencies in detecting the microstructure of spinal cord tissue and the integrity of white matter fiber tracts [1]. Diffusion tensor imaging (DTI), 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 [1,2,3]. It is proved that DTI technique can noninvasively reflect the spatiotemporal characteristics of SCI-induced white matter fiber bundles degeneration and can directly show the damage of white matter fiber tracts. Liu et al [5] investigated the dynamic correlation of DTI and neurological function scores in spinal cord-injured beagles and showed that DTI has the potential to accurately predict the recovery of neurological function after SCI

Methods

Results

Conclusion