As drug carriers, magnetic nanoparticles can specifically bind to tumors and have the potential for targeted therapy. It is of great significance to explore non-invasive imaging methods that can detect the distribution of magnetic nanoparticles. Based on the mechanism that magnetic nanoparticles can generate ultrasonic waves through the pulsed magnetic field excitation, the sound pressure wave equation containing the concentration information of magnetic nanoparticles was derived. Using the finite element method and the analytical solution, the consistent transient pulsed magnetic field was obtained. A three-dimensional simulation model was constructed for the coupling calculation of electromagnetic field and sound field. The simulation results verified that the sound pressure waveform at the detection point reflected the position of magnetic nanoparticles in biological tissue. Using the sound pressure data detected by the ultrasonic transducer, the B-scan imaging of the magnetic nanoparticles was achieved. The maximum error of the target area position was 1.56%, and the magnetic nanoparticles regions with different concentrations were distinguished by comparing the amplitude of the boundary signals in the image. Studies in this paper indicate that B-scan imaging can quickly and accurately obtain the dimensional and positional information of the target region and is expected to be used for the detection of magnetic nanoparticles in targeted therapy.
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.
In the present work, Monte Carlo simulations were employed to study the characteristics of the dose distribution of high energy electron beam in the presence of uniform transverse magnetic field. The simulations carried out the transport processes of the 30 MeV electron beam in the homogeneous water phantom with different magnetic field. It was found that the dose distribution of the 30 MeV electron beam had changed significantly because of the magnetic field. The result showed that the range of the electron beam was decreased obviously and it formed a very high dose peak at the end of the range, and the ratio of maximum dose to the dose of the surface was greatly increased. The results of this study demonstrated that we could change the depth dose distribution of electron beam which is analogous to the heavy ion by modulating the energy of the electron and magnetic field. It means that using magnetic fields in conjunction with electron radiation therapy has great application prospect, but it also has brought new challenges for the research of dose algorithm.
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.
With the acceleration of the aging in the world and our society, osteoarthritis has become a health concern for patients and health workers. At present, its treatment mainly relies on drug treatment, surgical treatment and rehabilitation. As a safe, non-invasive and simple treatment, pulsed electromagnetic field (PEMF) therapy has been used in clinical treatment of osteoporosis, promoting fracture healing and improving symptoms of osteoarthritis. However, the mechanism of PEMF in the treatment of knee osteoarthritis is still unclear. This paper reviews the effects of PEMF on apoptosis, cytokines, cartilage and subchondral bone in knee osteoarthritis in animal experiments, and the changes of chondrocyte morphology and extracellular matrix in cell experiments, aiming to enable medical workers to better understand the status and development of PEMF in the treatment of knee osteoarthritis in basic experimental researches.
This study aims to investigate the therapeutic efficacy of 50 Hz-0.6 mT low-frequency pulsed electromagnetic field (PEMF) on postmenopausal osteoporosis in ovariectomized rats. Thirty 3-month-old female SD rats were selected and divided into a sham operation group (Sham), an ovariectomized model group (OVX), and a low-frequency pulsed electromagnetic field (PEMF) treatment group, with 10 rats in each group. After 8 weeks, the whole-body bone mineral density (BMD) of each group of rats was measured. The treatment group began to receive PEMF stimulation for 90 minutes daily, while the OVX group only received a simulated placement without electricity. After 6 weeks of intervention, all rats were sacrificed and tested for in vitro BMD, micro-CT, biomechanics, serum biochemical indicators, and bone tissue-related proteins. The results showed that the BMD of the OVX group was significantly lower than that of the Sham group 8 weeks after surgery, indicating successful modeling. After 6 weeks of treatment, compared with the OVX group, the PEMF group exhibited significantly increased BMD in the whole body, femur, and vertebral bodies. Micro-CT analysis results showed improved bone microstructure, significantly increased maximum load and bending strength of the femur, elevated levels of serum bone formation markers, and increased expression of osteogenic-related proteins. In conclusion, this study demonstrates that daily 90-minute exposure to 50 Hz-0.6 mT PEMF effectively enhances BMD, improves bone biomechanical properties, optimizes bone microstructure, stimulates bone formation, and inhibits bone resorption in ovariectomized rats, highlighting its therapeutic potential for postmenopausal osteoporosis.
To observe the effect of pulsed electromagnetic fields (PEMFs) of different treatment time on bone mineral density of femur in ovariectomized rats, so as to find out the treatment time for the best therapeutic efficacy. Methods Fifty female SD rats were randomly divided into 5 groups: sham-ovariectomized (SHAM) group (no PEMFs treatment), ovariectomy (OVX) control group (no PEMFs treatment), OVX I, II and III groups (PEMFs treatment at 8 Hz frequency with 3. 8 ×10-10A/m intensity 20, 40, and 60 minutes daily for 30 days, respectively). All rats were given bilateral ovariectomy except those in the SHAM control group. Bone mineral density (BMD) of femur was assessed at 30 days after PEMFs treatment. Results In OVX control group, hypotrichosis, hypoactivity and l istlessness were observed after operation; and in SHAM group, OVX I group, OVX II group and OVX III group, pilus, psyche and activity were normal. The BMD values were (0.226 ± 0.011), (0.210 ± 0.011), (0.231 ± 0.013), (0.231 ± 0.017) and (0.229 ± 0.013) g/cm2 in SHAM group, OVX control group, OVX I group, OVX II group and OVX III group respectively, showing significant differences between OVX control group and other groups (P lt; 0.05), but showing no significant differences between other 4 groups (P gt; 0.05). Conclusion P EMFs of the three different treatment times can maintain the BMD in ovariectomized rats. It shows that PEMFs have the same effect of maintaining BMD with increasing of treatment time at the range of 20-60 minutes in ovariectomized rats.
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.
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.
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.
