Date Published: June 1, 2018
Publisher: JKL International LLC
Author(s): Wenzhi Sun, Jiewen Tan, Zhuo Li, Shibao Lu, Man Li, Chao Kong, Yong Hai, Chunjin Gao, Xuehua Liu.
This study aimed to evaluate the therapeutic effect of hyperbaric oxygen (HBO) on acute spinal cord injury (SCI) by measuring the in vivo diffusion tensor imaging (DTI) parameters apparent diffusion coefficient (ADC) and fractional anisotropy (FA) and observing diffusion tensor tractography (DTT) of fiber bundle morphology. The rats were randomly divided into sham-operated (SH), SCI, and SCI and hyperbaric oxygen treatment (SCI + HBO) groups (n = 6 in each group). The Basso-Bettie-Bresnahan (BBB) score was used to evaluate motor function recovery, and DTI was performed on days 3, 7, 14, and 21 after surgery. BBB scores and FA values decreased significantly after SCI, while the two values significantly improved in the SCI + HBO group compared with the SCI group on days 7, 14, and 21. ADC increased significantly on days 14 and 21 postoperatively in the SCI group compared with the SH group but did not significantly differ between the SCI and SCI + HBO groups at any time point. BBB scores had the same variation trend with ADC values and FA values in all three groups. In the SH group, DTT showed a well-organized spinal cord, but the spinal cord showed interruptions at sites of injury after SCI. In conclusion, HBO promotes the recovery of neuronal function after SCI. Parameters of DTI, especially FA, can quantitatively evaluate the efficacy of HBO treatment in SCI, while DTT enables the visualization of the fiber tracking of spinal cord tracts.
Conventional MRI is routinely used for the qualitative assessment of the pathology of injured spinal cord. In the present study, T1WI after SCI depicted less noticeable changes in signal intensity, T2WI on day 14 after SCI did not show too many changes compared with images on day 21 after SCI, and T2WI in the SCI group depicted less difference with T2WI in the SCI + HBO group at the same time points. Therefore, conventional MRI can display SCI but cannot visualize more details. DTI with parameters such as ADC and FA can provide quantitative information about tissue microstructure. The use of DTI to detect subtle changes in brain tumors, diffuse axonal injury, multiple sclerosis, Alzheimer’s disease, ischemic stroke, and spinal cord has been reported . ADC values represent the magnitude of diffusion, with high ADC values indicating the robust diffusive strength of extracellular water molecules. This information is derived from the DTI eigenvalues λ1, λ2, and λ3 that represent the magnitudes of diffusion along the three principal axes of the tissue structure . FA is a dimensionless measure varying between 0 and 1, where 0 represents isotropic diffusion and 1 represents infinite anisotropy . Unrestricted, isotropic diffusion is represented as a sphere in which all of the eigenvalues (λ) or diffusion coefficients are equal. Therefore, no directionality exists and FA is 0, for example, in pure water or cerebrospinal fluid . Diffusion is often anisotropic in highly organized biological tissue  because axonal membranes and myelin sheaths present barriers to the motion of water molecules in directions not parallel to their own orientation.