In transcranial magnetic stimulation (TMS), the conductivity of brain tissue is obtained by using diffusion tensor imaging (DTI) data processing. However, the specific impact of different processing methods on the induced electric field in the tissue has not been thoroughly studied. In this paper, we first used magnetic resonance image (MRI) data to create a three-dimensional head model, and then estimated the conductivity of gray matter (GM) and white matter (WM) using four conductivity models, namely scalar (SC), direct mapping (DM), volume normalization (VN) and average conductivity (MC), respectively. Isotropic empirical conductivity values were used for the conductivity of other tissues such as the scalp, skull, and cerebrospinal fluid (CSF), and then the TMS simulations were performed when the coil was parallel and perpendicular to the gyrus of the target. When the coil was perpendicular to the gyrus where the target was located, it was easy to get the maximum electric field in the head model. The maximum electric field in the DM model was 45.66% higher than that in the SC model. The results showed that the conductivity component along the electric field direction of which conductivity model was smaller in TMS, the induced electric field in the corresponding domain corresponding to the conductivity model was larger. This study has guiding significance for TMS precise stimulation.
Transcranial Magnetic Stimulation ; Diffusion Tensor Imaging ; Electric Conductivity ; Electricity ; Scalp

OBJECTIVE To explore the protective effect of marein against alcoholic fatty liver （AFL） and its potential mechanisms. METHODS AFL mice model was established with strong wine by gavage. The mice were randomly divided into normal control group （n＝9， 0.5% sodium carboxymethyl cellulose solution）， model group （n＝10， 0.5% sodium carboxymethyl cellulose solution） and marein 75 and 150 mg/kg groups （n＝9）. Mice were given relevant medicine intragastrically， once a day， for consecutive 30 days. After the last medication， the levels of triglyceride （TG）， malondialdehyde （MDA）， and superoxide dismutase （SOD） in liver tissue were determined， and hepatic histopathological changes of liver tissue were observed； the protein expression levels of peroxisome proliferator-activated receptor α （PPARα）， carnitine palmitoyltransferase-1 （CPT-1）， and diacylglycerol acyltransferase （DGAT） were determined in liver tissue. BRL hepatocytes injury model was induced by ethanol combined with ferrous sulfate and oleic acid； after treatment with 3， 6 and 12 μmol/L of marein for 24 h， the distribution of lipid droplets， the levels of TG， MDA and SOD and protein expressions of PPARα， CPT-1 and DGAT in hepatocytes were examined. After pretreatment with MK886 （PPARα inhibitor， 10 μmol/L），modeled hepatocytes were treated with 12 μmol/L of marein for 24 h， and the protein expressions of PPARα， CPT-1 and DGAT were determined. RESULTS As the results showed in vivo， compared with the model group， after treatment with 75 and 150 mg/kg of marein， the degree of steatosis was significantly reduced， and the levels of TG and MDA and protein expression of DGAT were significantly decreased（P＜0.05 or P＜0.01）； the levels of SOD， protein expressions of PPARα and CPT-1 were significantly increased（P＜0.05 or P＜0.01）. As the results showed in vitro， after treatment with 3， 6 and 12 μmol/L of marein， the lipid accumulation of hepatocytes was significantly inhibited， and the levels of TG and MDA， protein expression of DGAT were significantly decreased（P＜0.05 or P＜0.01）， while the levels of SOD， protein expressions of PPARα and CPT-1 were significantly increased（P＜0.05 or P＜0.01）. After MK886 pretreatment， the effects of marein on the above protein expressions were abolished. CONCLUSIONS Marein might exert a protective effect against AFL. The mechanisms might be related to inhibiting oxidative stress-mediated injury and improving PPARα-mediated lipid metabolism signaling pathway.