Assessment Of Neuroprotective Effects Of Low-Intensity Transcranial Ultrasound Stimulation In A Parkinson'S Disease Rat Model By Fractional Anisotropy And Relaxation Time T2*Value

Background: Low-intensity transcranial ultrasound (LITUS) may have a therapeutic effect on Parkinson's disease (PD) patients to some extent. Fractional anisotropy (FA) and relaxation time T2* that indicate the integrity of fiber tracts and iron concentrations in brain tissue have been used to evaluate the therapeutic effects of LITUS.Purpose: This study aims to use FA and T2* values to evaluate the therapeutic effects of LITUS in a PD rat model.Materials and Methods: Twenty Sprague-Dawley rats were randomly divided into a hemi-PD group (n = 10) and a LITUS group (n = 10). Single-shot spin echo echo-planar imaging and fast low-angle shot T2WI sequences at 3.0 T were used. The FA and T2* values on the right side of the substantia nigra (SN) pars compacta were measured to evaluate the therapeutic effect of LITUS in the rats.Results: One week after PD-like signs were induced in the rats, the FA value in the LITUS group was significantly larger compared with the PD group (0.214 +/- 0.027 vs. 0.340 +/- 0.032, t = 2.864, P = 0.011). At the 5th and 6th weeks, the FA values in the LITUS group were significantly smaller compared with the PD group (5th week: 0.290 +/- 0.037 vs. 0.405 +/- 0.027, t = 2.385, P = 0.030; 6th week: 0.299 +/- 0.021 vs. 0.525 +/- 0.028, t = 6.620, P < 0.0001). In the 5th and 6th weeks, the T2* values in the injected right SN of the LITUS group were significantly higher compared with the PD group (5th week, 12.169 +/- 0.826 in the LITUS group vs. 7.550 +/- 0.824 in the PD group; 6th week, 11.749 +/- 0.615 in the LITUS group vs. 7.550 +/- 0.849 in the PD group).Conclusion: LITUS had neuroprotective effects and can reduce the damage of 6-OHDA-induced neurotoxicity in hemi-PD rats. The combination of FA and T2* assessments can potentially serve as a new and effective method to evaluate the therapeutic effects of LITUS.