Abstract
Diffusion of water molecules closely related to physiological and pathological information of brain tissue. Low-intensity transcranial ultrasound stimulation (TUS) has advantages of noninvasive, high spatial resolution and penetration depth. Previous studies have demonstrate that TUS can modulate neuronal activity and alter cortical hemodynamic. However, how TUS affect diffusion of water molecules remain unclear. In this paper, in order to evaluate the effect of low-intensity TUS on the diffusion of water molecules in brain tissue, diffusion-weighted magnetic resonance (MR) imaging was performed in 19 healthy Sprague-Dawley rats in sham surgery group (six rats) and TUS group (thirteen rats) Subsequently, rats were stimulated by low-intensity transcranial ultrasound for 5 min in TUS group. Finally, rats of sham surgery group and TUS group were imaged again by diffusion-weighted MR imaging. The apparent diffusion coefficient (ADC) was measured in caudate putamen region and middle brain motor-related region of each rat in sham surgery group and TUS group. Surgery-related and TUS-related changes were calculated using a statistical analysis. The mean ADC values of marked regions of six rats in sham surgery group were 0.743 ± 0.031 (pre-surgery) and 0.745 ± 0.029 (post-surgery). The mean ADC values of marked regions of 13 rats in TUS group were 0.749 ± 0.032 (pre-TUS) and 0.712 ± 0.033 (post-TUS) Compared to the pre-TUS values, the mean ADC values of the rats decreased 4.9% (*P < 0.05) post-TUS. These results of this study demonstrate that low-intensity TUS can restrict the diffusion of water molecules in brain tissue.
Highlights
Diffusion-weighted magnetic resonance (MR) imaging, which is based on the random and irregular Brownian motion of water molecules, reflects the different states of water molecules in tissue (Engelbrecht et al, 2002; Fernández-Espejo et al, 2011)
We qualitatively analyzed the mean apparent diffusion coefficient (ADC) values of each rat in pre- and post-transcranial ultrasound stimulation (TUS) conditions, and we observed that TUS decreased the mean ADC values in 11 rats
We found that the mean ADC values of 13 rats were decreased by TUS, and the result has been expected statistical significance
Summary
Diffusion-weighted magnetic resonance (MR) imaging, which is based on the random and irregular Brownian motion of water molecules, reflects the different states of water molecules in tissue (Engelbrecht et al, 2002; Fernández-Espejo et al, 2011). It can effectively reflect the internal microstructure and micromotion and can provide the functional status of human tissues at the molecular level (Malayeri et al, 2011; Chavhan et al, 2014). It is of great significance that apparent diffusion coefficient (ADC) values can be used for the quantitative assessment of the aforementioned diseases (Schaefer et al, 2000).
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