According to the coupling relationship of electromagnetic field and acoustic field when electromagnetic field irradiates low conductivity objects, we carried out a study on the magnetoacoustic effect and thermoacoustic effect in pulsed magnetic excitation. In this paper, we provide the pressure wave equation in pulsed magnetic excitation based on the theory of electromagnetic field and acoustic wave propagation. A 2-dimensional coil carrying current and a circular thin sheet model were constructed to simulate the physical imaging environment. The transient electromagnetic field was simulated using finite element method. Numerical studies were conducted to simulate the pressures excited by magnetoacoustic effect and thermoacoustic effect according to the result of electromagnetic simulation. It was shown that the thermoacoustic effect played a leading role in the low conductivity objects on the microsecond Gauss pulsed magnetic excitation, and thermoacoustic effect and magnetoacoustic effect coexisted on the microsecond Gauss pulsed magnetic field and 0.2 T static magnetic field excitation. This study lays the foundation for the further application of magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging.
We investigated the effects and optimal treatment frequency of pulsed electromagnetic fields (PEMFs) on postmenopausal osteoporosis (PMO). A comparison was performed with the cyclical alendronate and a course of PEMFs in the treatment for postmenopausal osteoporosis on bone mineral density (BMD), pain intensity and balance function. There was no significant difference between the two groups on mean percentage changes from baseline of BMD within 24 weeks after random treatments (P≥0.05). However, at the ends of 48 weeks and 72 weeks, the BMD of the PEMFs group were significantly lower than that of the alendronate group (P<0.05). No significant difference was detected between the two groups with regard to treatment effects on Visual Analogue Scale score, the Timed Up & Go Test and Berg Balance Scale score. Compared with cyclical alendronate, a course of PEMFs was as effective as alendronate in treating PMO for at least 24weeks. So its optimal treatment frequency for PMO may be one course per six months.
Objective To investigate the changes of lumbar bone histomorphometry after exposure to low frequency pulsed electromagnetic fields (PEMFs), and to further understand the effect of PEMFs on osteoporosis (OP) in ovariectomizedOP rats. Methods Sixty-six 3-month-old Sprague Dawley rats were randomly divided into 4 groups: group A(n=12), groupB (n=12), group C (n=12), and group D (n=30). In group A, the ovaries were not resected as sham-ovariectomy; in groupsB, C, and D, the ovaries were resected. At 12 weeks after ovariectomy, the rats were exposed to PEMFs at 8 Hz, 3.8 mT, and 40 minutes/ day for 30 days in group B; the rats were administered with premarin [0.065 mg/(kg·d) by gavage for 30 days] in group C; in group D, the rats were housed as ovariectomy control. The hair and activity of rats were observed; the levels of serum estradiol were determined. At 30 days after intervention, all rats were sacrificed to harvest the L4 vertebrae for bone histomorphometry. Results General observation showed hair loss and decreased activity in group D, and no abnormal appearances in groups A, B, and C. The level of serum estradiol in group A was significantly higher than that in group D [(54.93 ± 23.52) pg/mL vs. (31.99 ± 23.45) pg/mL] (t=2.345, P=0.029). Histological observation showed thinness of sclerotin, bigger medullary cavity, and sparse and thinner bone trabecula in group D; uniform bone trabecula with no breakage in groups A, B, and C at 30 days after intervention. The ratio of trabecular bone area in group B was significantly higher than that in group D (P lt; 0.05); it was higher than that in groups A and C, showing no significant difference (P gt; 0.05). The trabecular thickness in group B was significantly higher than that in group D (P lt; 0.05), but it was lower than that in groups A and C, showing no significant difference (P gt; 0.05). The trabecular number in group B was significantly lower than that in group D (P lt; 0.05), but it was higher than that in groups A and C, showing no significant difference (P gt; 0.05). The trabecular separation in group B was higher than that in group D and lower than that in groups A and C, showing no significant difference (P gt; 0.05). Conclusion PEMFs at 8 Hz and 3.8 mT can significantly improve the character of bone microstructure in ovariectomized OP rats, increase the ratio of bone trabecular area and trabecular thickness, and decrease the trabecular number.
One of the main technical challenges when integrating magnetic resonance imaging (MRI) systems with medical linear accelerator is the strong interference of fringe magnetic fields from the MRI system with the electron beams of linear accelerator, making the linear accelerator not to work properly. In order to minimize the interference of magnetic fields, a magnetic shielding cylinder with an open structure made of high permeability materials is designed. ANSYS Maxwell was used to simulate Helmholtz coil which generate uniform magnetic field instead of the fringe magnetic fields which affect accelerator gun. The parameters of shielding tube, such as permeability, radius, length, side thickness, bottom thickness and fringe magnetic fields strength are simulated, and the data is processed by MATLAB to compare the shielding performance. This article gives out a list of magnetic shielding effectiveness with different side thickness and bottom thickness under the optimal radius and length, which showes that this design can meet the shielding requirement for the MRI-linear accelerator system.
Alzheimer’s disease (AD) is the most common degenerative disease of the nervous system. Studies have found that the 40 Hz pulsed magnetic field has the effect of improving cognitive ability in AD, but the mechanism of action is not clear. In this study, APP/PS1 double transgenic AD model mice were used as the research object, the water maze was used to group dementia, and 40 Hz/10 mT pulsed magnetic field stimulation was applied to AD model mice with different degrees of dementia. The behavioral indicators, mitochondrial samples of hippocampal CA1 region and electrocardiogram signals were collected from each group, and the effects of 40 Hz pulsed magnetic field on mouse behavior, mitochondrial kinetic indexes and heart rate variability (HRV) parameters were analyzed. The results showed that compared with the AD group, the loss of mitochondrial crest structure was alleviated and the mitochondrial dynamics related indexes were significantly improved in the AD + stimulated group (P < 0.001), sympathetic nerve excitation and parasympathetic nerve inhibition were improved, and the spatial cognitive memory ability of mice was significantly improved (P < 0.05). The preliminary results of this study show that 40 Hz pulsed magnetic field stimulation can improve the mitochondrial structure and mitochondrial kinetic homeostasis imbalance of AD mice, and significantly improve the autonomic neuromodulation ability and spatial cognition ability of AD mice, which lays a foundation for further exploring the mechanism of ultra-low frequency magnetic field in delaying the course of AD disease and realizing personalized neurofeedback therapy for AD.
The gradient field, one of the core magnetic fields in magnetic resonance imaging (MRI) systems, is generated by gradient coils and plays a critical role in spatial encoding and the generation of echo signals. The uniformity or linearity of the gradient field directly impacts the quality and distortion level of MRI images. However, traditional point measurement methods lack accuracy in assessing the linearity of gradient fields, making it difficult to provide effective parameters for image distortion correction. This paper introduced a spherical measurement-based method that involved measuring the magnetic field distribution on a sphere, followed by detailed magnetic field calculations and linearity analysis. This study, applied to assess the nonlinearity of asymmetric head gradient coils, demonstrated more comprehensive and precise results compared to point measurement methods. This advancement not only strengthens the scientific basis for the design of gradient coils but also provides more reliable parameters and methods for the accurate correction of MRI image distortions.
Several techniques were used to improve 0.3～0.5 mm microvascular anastomosis. These included (1) non-isolation of adventitia, (2) modified two—point anastomosis, (3) clamping only the inflow in veins anastomosis, (4) atraumatic measurement of vascular patency, (5) post operative stimulation by electromagnetic fields, which accelerated the healing of the vessels. The chance of patency following anastomosis in experimental group was significantly much greater than that in the control one (plt;0.001). We have have also used these techniques in 11 patients with fingers replantion or smaller lymphatic anastomosis. All of the operations were successful.
Studying effects of 50 Hz sinusoidal electromagnetic fields (SEMFs) with different intensities on peak bone mass (PBM) of rats may provide a theoretical basis for application of electromagnetic clinical field. 30 female SD rats, 6 weeks of age, were randomly divided into three groups: the control group, 0.1 mT electromagnetic field group (EMFs) and 0.6 mT EMFs. The EMFs groups were treated for 3 h/day. After 8 weeks, we examined their bone mineral densities (BMD), measured their bone biomechanical properties, and made serum levels of osteocalcin (OC), tartrate-resistant acid phosphatase 5b (TRACP 5b), and histomorphometry. It was found that the BMD (P < 0.01), maximum mechanical load (P < 0.01) in the 0.1 mT group were significantly higher than those in the control group, and Yield strength (P < 0.05), the analyses of serum bone turnover markers and histomorphometric parameters were better than those in the control group (P < 0.05). However, the 0.6 mT group did not have significantly difference comparing with that in the control group. This study proved that 50 Hz 0.1 mT SEMFs can increased BMD, bone strength, and bone tissue microstructure. Therefore, 50 Hz 0.1 mT SEMFs can improve peak bone mass of rats.
ObjectiveTo investigate whether signal molecule mitogen-activated protein kinases (MAPKs) involves in the process of the mineralization and maturation of rat calvarial osteoblasts promoted by 50 Hz, 0.6 mT pulsed electromagnetic fields. MethodsRat calvarial osteoblasts were obtained by enzyme digestion from the skull of 6 neonatal Wistar rats of SPF level. The primary osteoblasts were treated in 50 Hz and 0.6 mT pulsed electromagnetic fields for 0, 5, 10, 20, 40, 60, and 120 minutes; the protein expression of phosphorylated MAPKs was detected by Western blot. The osteoblasts were randomly divided into group A (control group), group B (low frequency pulse electromagnetic fields treatment group), group C (SB202190 group), and group D (SB202190+low frequency pulse electromagnetic fields treatment group); the alkaline phosphatase (ALP) activities were tested after corresponding treatment for 1, 4, and 7 days. The corresponding treated more than 90% confluenced osteoblasts were cultured under condition of osteogenic induction, then ALP staining and alizarin red staining were carried out at 9 and 12 days respectively. ResultsThe results of Western blot showed that there was no significant changes in the protein expressions of phosphorylated level of extracellular signal-related kinases 1/2 and c-Jun amino N-terminal kinases 1/2 in 50 Hz, 0.6 mT pulsed electromagnetic fields P>0.05), but the phosphorylated level of p38 began to increase at 5 minutes, peaked at 40 minutes, then gradually decreased, and it was significantly higher at 5-120 minutes than at 0 minute (P<0.05). After the activities of p-p38 was inhibited by inhibitor SB202190, the ALP activities, positive colonies and area of ALP and calcified nodules of group B were significantly higher than groups A, C, and D (P<0.05). Conclusionp38 is one of the signal molecules involved in the process of the mineralization and maturation of rat calvarial osteoblasts promoted by 50 Hz, 0.6 mT pulsed electromagnetic fields.
The possible influence of electromagnetic field (EMF) on the function of neural systems has been widely concerned. In this article, we intend to investigate the effects of long term power frequency EMF exposure on brain cognitive functions and it’s mechanism. The Sprague-Dawley (SD) rats were randomly divided into 3 groups: the rats in EMF Ⅰ group were placed in the 2 mT power frequency EMF for 24 days. The rats in EMF Ⅱ group were placed in the 2 mT power frequency EMF for 48 days. The rats in control group were not exposed to the EMF. Then, the 16 channel local field potentials (LFPs) were recorded from rats’ prefrontal cortex (PFC) in each group during the working memory (WM) tasks. The causal networks of LFPs were also established by applying the directed transfer function (DTF). Based on that, the differences of behavior and the LFPs network connection patterns between different groups were compared in order to investigate the influence of long term power frequency EMF exposure on working memory. The results showed the rats in the EMF Ⅱ group needed more training to reach the task correction criterion (over 80%). Moreover, the causal network connection strength and the global efficiency of the rats in EMF Ⅰ and EMF Ⅱ groups were significantly lower than the corresponding values of the control group. Meanwhile, significant differences of causal density values were found between EMF Ⅱ group and the other two groups. These results indicate that long term exposure to 2 mT power frequency EMF will reduce the connection strength and the information transfer efficiency of the LFPs causal network in the PFC, as well as the behavior performance of the rats. These results may explain the effect of EMF exposure on working memory from the view of neural network connectivity and provide a support for further studies on the mechanism of the effect of EMF on cognition.