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Objective:To study the influence of intensive magnet fields on radiation dose measurement, and to demonstrate the feasibility of measuring magnet field correction factor by a combination of medical linac with variable magnet fields in view of needing for accurate measurement of the doses from reference beam arising in MR image-guided radiotherapy.Methods:A photon radiation field and a variable field with 6 MV nominal high voltage were produced by using conventional medical electron linear accelerator equipped with a pair of electromagnets with magnetic field strength up to 1.5 T. Both PTW30013 and PTW31010 ionization chambers were used to test the responses of ionization chambers under different magnetic field strengths at four orientations in which the angles between ionization chamber axis and magnetic field direction were 0°, 180°, 90° and 270°, respectively. The magnetic factors, kB, M was calculated and compared with the reported values in literature. Results:The response of ionization chamber was proportional to the magnetic field strength before it reached to a peak around 1 T, and then fell down as the magnetic field continued to rise. When the magnetic field was 0.35 T, the magnetic factors of PTW31010 were 0.988 2±0.000 3 and 0.997 4±0.000 4 corresponding to 90° and 0° directions, the discrepancy between 0° scenario and literature was 0.05% ± 0.04%. When the magnetic field reached 1.5 T, the magnetic factor of PTW30013 was 0.958 9±0.000 5 at the situation of 90°, which was 0.60% ± 0.05% different from the literature value.Conclusions:Conventional 6 MV medical accelerator equipped with electromagnet can be used to measure the magnetic field factor of reference dosimetry for MRIgRT.
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Objective To investigate tumor cell killing effect of superparamagnetic Fe3O4 nanoparticles with cubic phase through magneto-mechanical force under a low-frequency vibrating magnetic field ( VMF). Methods A kind of strong magnetic and irregular-shaped Fe3O4 nanoparticles with cubic phase was synthesized by coprecipitation method. The Fe3O4 nanoparticles were exposed to a self-developed VMF and cell killing efficiency of the Fe3O4-mediated magneto-mechanical force was investigated. Results VMF alone had no effects on cell viability. After Fe3O4 nanoparticles were added, the cell viability significantly decreased with prolonging the VMF treatment time and increasing the Fe3O4 nanoparticle concentration. Lactate dehydrogenase released by damaged cells also increased with prolonging the VMF exposure time. Conclusions The irregular-shaped Fe3O4 nanoparticles can transfer magneto-mechanical force to tumor cells under VMF, cause structural damage of cells and result in cell death. The VMF generator developed in this study has simple structure and it is safe for use and convenient for operation. The developed magnetic nanoparticles and the corresponding cancer cell killing technique have the potential for clinical transformation.
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Objective:To study the method of intravascular angiography in vivo, analyze the clinical significance, and supply the basis of diagnosis and treatment of related orthopaedic diseases.Methods:The development was realized by improving the developer to increase the local concentration. Based on the study of Lijianmin-Chengkun Complexes and using the theory of magnetic microspheres, Fe 3O 4 magnetic microspheres with amino (negatively charged) shell are used to adsorb the aggregated ionic developer meglumine diatrizoate (positively charged diatrizoate). That is, by improving the method of developer, the magnetic microspheres can carry the developer to make new nanoparticles magnetic imaging composite particles. Under the action of external magnetic field, the magnetic imaging composite particles brought by blood circulation continue to stay and gather in the blood vessels in the magnetic field area, and the developer carried by the magnetic microspheres in the blood vessels in the magnetic field area is concentrated to reach the imaging concentration, so as to realize in vivo intravascular vascular imaging. By adjusting the ratio of the two reagents, the charge can be neutralized and condensed into small groups to improve the development efficiency. Thus, the electron microscope experiment, CT in vivo experiment, rabbit imaging experiment, experimental rabbit tissue picture confirmation, CT in vivo human body (the author is a volunteer) imaging experiment were carried out step by step. Results:Electron microscope experiment: meglumine diatrizoate, scanning electron microscope, the particle diameter is about 20 nm. Scanning electron microscope showed that the diameter of the magnetic microspheres was about 100 nm and the distribution was uniform. After the two reagents are mixed in a certain proportion, the neutralizing charge condenses into small groups, but it still has magnetohydrodynamic properties and strong paramagnetism. In vivo rabbit imaging experiment: the ideal intraosseous vascular imaging of the proximal tibia was captured. The tissue pictures of experimental rabbits confirmed that the distribution of Fe 3O 4 was obviously visible in the blood vessels in the proximal tibia on the side with magnetic field, but not on the side without magnetic field. In vivo human imaging experiment: the ideal intraosseous vascular imaging of the proximal fibula was captured. Conclusion:Through the preparation of new reagent of magnetic imaging composite particles (magnetic microspheres + meglumine diatrizoate), the concentration of in vivo bone developer can be achieved under the action of external magnetic field, and the in vivo external diameter ≥ 0.5mm can be achieved under CT thin-layer scanning.
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Objective:To evaluate the effects of orthogonal magnetic fields on the dose distribution of 6 MeV X-ray in a uniform water and heterogeneous phantoms.Methods:The Monte Carlo simulation software Gate v8.2 was used to investigate the dose distribution of X-ray beams of different field sizes in a uniform water phantom, water-air/bone-water layer phantom and" custom lung model" in the magnetic field strength of 0.0, 0.5, 1.0, 1.5, 3.0 T, respectively. The relationship between the intensity of magnetic field and the dose distribution of X-rays in the phantoms was analyzed.Results:The existence of a magnetic field would cause the X-ray to shorten the built-up area in the water phantom; when the field was 10 cm×10 cm, the maximum dose on the central axis could change by up to 56.22%(3.0 T). The transverse dose distribution of the radiation field in the direction of the vertical magnetic field shifted to one side by up to 43.64%(-44.55%). The average dose of the air layer in the water-air-water phantom could be reduced by 57.4%(3.0 T). In the water-bone-water phantom, the dose at the proximal end of the bone layer was decreased by 16.5%, whereas the dose at the distal end was increased by 22.6%(1.5 T). The dose change in each layer in the customed lung model was positively correlated with the magnetic field strength.Conclusion:The existence of the orthogonal magnetic field will cause the change of X-ray dose distribution on the built-up area and both sides of the radiation field in the phantoms, which is more obvious adjacent to the interface of heterogeneous phantom.
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Magnetic nanoparticles (MNP) have been widely used as biomaterials due to their unique magnetic responsiveness and biocompatibility, which also can promote osteogenic differentiation through their inherent micro-magnetic field. The MNP composite scaffold retains its superparamagnetism, which has good physical, mechanical and biological properties with significant osteogenic effects and . Magnetic field has been proved to promote bone tissue repair by affecting cell metabolic behavior. MNP composite scaffolds under magnetic field can synergically promote bone tissue repair and regeneration, which has great application potential in the field of bone tissue engineering. This article summarizes the performance of magnetic composite scaffold, the research progress on the effect of MNP composite scaffold with magnetic fields on osteogenesis, to provide reference for further research and clinical application.
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Cell Differentiation , Magnetite Nanoparticles , Osteogenesis , Tissue Engineering , Tissue ScaffoldsABSTRACT
Objective:Effects of pole-specific acupuncture combined with Bobath on upper limb function, daily life ability and nerve function after traumatic brain injury were observed.Methods:A total of 142 patients with cerebral hemiplegia after traumatic brain injury from January 2019 to December 2020, were divided into the Bobath group (47 cases), the pole-specific acupuncture group (47 cases) and combination group (48 cases) by the random number method. Bobath group received Bobath rehabilitation, the pole-specific acupuncture group received pole-specific acupuncture rehabilitation, and combination group was given pole-specific acupuncture rehabilitation and Bobath treatment. The overall rehabilitation efficiency, limb function Fugl-Meyer scale score, Barthel index of daily life ability, nerve function, and other indicators were observed and compared.Results:After treatment, the overall recovery efficiency (86.96%) in combination group was significantly higher than that of the Bobath group (65.96%) and acupuncture group (64.44%)( χ2=5.84, P=0.016). After treatment, the limb function Fugl-Meyer scale (including upper limb and lower limb function scores)( F=19.38, 24.83, all Ps<0.01), daily life ability Barthel index (including cognitive ability situation score, language ability score, self-care ability score, social adaptability score and total score) of combination group were significantly higher than those in the Bobath group and acupuncture group ( F=14.91, 15.87, 18.71, 18.88, 32.62, all Ps<0.001), while the NIHSS score of combination group was significantly lower than that of the Bobath group and acupuncture group ( F=31.71, P<0.01). After treatment, the NE[(58.29±9.82)μg/L vs. (86.29±12.35)μg/L, (88.34±12.87)μg/L, F=33.39], DA[(204.29±20.26)μg/L vs. (278.72±27.56)μg/L, (281.14±27.82)μg/L, F=55.50], 5-HT[(231.27±20.12)μg/L vs. (294.74±29.34)μg/L, (298.19±28.73)μg/L, F=13.86], E[(21.85±3.19)μg/L vs. (28.37±4.07)μg/L, (28.26±4.14)μg/L, F=9.34] of combination group were significantly lower than those in the Bobath group and acupuncture group ( P<0.01). Conclusion:Magnetic pole-specific acupuncture combined with Bobath can improve the function of limbs, daily quality of life and nerve function of the patients with traumatic craniocerebral injury with cerebral palsy.
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ABSTRACT Background: Brazil has a top position regarding scientific production on noninvasive neuromodulation worldwide. Knowledge of scientometric phenomena involving Brazilian researchers who produce science on this theme may aid confidence in Brazilian clinical and research professionals. Objective: To investigate the scenario of research on the theme of noninvasive neuromodulation in Brazil. Methods: This was a scientometric study for mapping scientific production on this subject involving network phenomena, the professions of researchers, institutional affiliation, main research unit, total number of scientific articles on noninvasive neuromodulation published in journals, research sub-area and year of obtaining the PhD title. Public data from Lattes Platform curricula vitae and from VOSViewer© were used. Results: A total of 54 Brazilian researchers were identified, of whom 16 are research productivity fellows. Most of them are linked to institutions in southeastern Brazil, involving the professions of biology, biochemistry, physical education, physiotherapy, speech therapy, gerontology, medicine and psychology, with 1175 articles published in journals. These studies involve experimental animal and human models to account for mechanisms, observational studies, case reports, randomized clinical trials, systematic reviews, meta-analyses, product and process development, computer modeling and guidelines. Conclusions: Brazil occupies a prominent place in the world scenario of research on noninvasive neuromodulation, which is used by different professions for treatment of brain dysfunctions, with a trend towards expansion to other fields.
RESUMO Antecedentes: O Brasil ocupa posição de destaque na produção científica de neuromodulação não invasiva no mundo. O conhecimento dos fenômenos cientométricos envolvendo pesquisadores brasileiros que produzem ciência neste tema pode auxiliar na confiança dos profissionais clínicos e pesquisadores brasileiros. Objetivo: Investigar o cenário das pesquisas sobre a temática da neuromodulação não invasiva no Brasil. Métodos: Estudo cienciométrico para mapeamento da produção científica sobre o tema envolvendo fenômenos de rede, profissão dos pesquisadores, afiliação à instituição, unidade principal de pesquisa, número total de artigos científicos publicados em periódicos sobre neuromodulação não invasiva, subárea de pesquisa e ano de obtenção do título de doutor. Utilizou-se dados públicos dos currículos da Plataforma Lattes e do sistema VOSViewer©. Resultados: Foram identificados 54 pesquisadores brasileiros, dos quais 16 são bolsistas de produtividade em pesquisa, a maioria deles vinculados a instituições do Sudeste do Brasil, envolvendo as profissões de Biologia, Bioquímica, Educação Física, Fisioterapia, Fonoaudiologia, Gerontologia, Medicina e Psicologia, com 1175 artigos publicados em periódicos. As pesquisas envolvem modelos experimentais animais e humanos para estudar dos mecanismos, estudos observacionais, relatos de casos, ensaios clínicos randomizados, revisões sistemáticas, meta-análises, desenvolvimento de produtos e processos, modelagem computacional e diretrizes. Conclusões: O Brasil ocupa lugar de destaque no cenário mundial das pesquisas em neuromodulação não invasiva, sendo utilizado por diferentes profissões para o tratamento de disfunções cerebrais, que tendem a se expandir para outros campos.
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Humans , Animals , Biomedical Research , Publications , Research Personnel , Brain , BrazilABSTRACT
SUMMARY OBJECTIVE: The aim of this study was to compare the effect of transcutaneous electrical nerve stimulation (TENS), ultrasound (US), and pulsed electromagnetic field (PEMF) combination with TENS and US therapy alone in patients with supraspinatus tear. METHODS: Forty patients were included in this study. The patients were randomly divided into two groups as follows: PEMF (n=20) and Sham (n=20) groups. PEMF was applied to the first group at a frequency of 50 Hz, 25 G intensity, and 20 min/session. The device was turned off while PEMF was applied to the second group. Diathermy (US) and electrotherapy (TENS) were applied to both groups for 10 sessions. Numerical Rating Scale (NRS), University of California-Los Angeles (UCLA) Shoulder Scale, and Shoulder Pain and Disability Index (SPADI) were used as outcome measures. RESULTS: In both groups, there was a significant improvement in the NRS, UCLA Shoulder Scale, and SPADI scores after treatment compared with pretreatment (p<0.05). In the comparison of the difference between the pretreatment and posttreatment measurement values between the groups, no significant difference was found between PEMF and Sham groups according to the NRS (p=0.165), UCLA Shoulder Scale (p=0.141), and SPADI (p=0.839) scores. CONCLUSIONS: In our study, a combination of PEMF therapy with conventional physical therapy modalities was not found to be superior to the conventional therapy alone, and adding it to the routine treatment of symptomatic supraspinatus tear would not provide any additional benefit.
Subject(s)
Humans , Electric Stimulation Therapy , Magnetic Field Therapy , Treatment Outcome , Rotator Cuff , Shoulder Pain/therapy , Electromagnetic FieldsABSTRACT
BACKGROUND: The clinical effect of spinal cord injury is usually unfavorable due to the lack of axon regeneration and the formation of glial scar. Schwann cells, as the support cells for nerve regeneration, have poor migration ability in the central nervous system with abundant astrocytes, which limit its effect on axon regeneration. OBJECTIVE: To explore the effect on the migration of Schwann cells containing superparamagnetic nanoparticles loaded with chondroitinase ABC (ChABC) in the region of astrocytes in the external magnetic field. METHODS: Schwann cells and astrocytes were extracted from sciatic nerves and brachial plexus and cerebral cortex of Sprague-Dawley rats of postnatal day 1 to 3. Cell purity was identified by immunofluorescence staining. The toxicity of superparamagnetic nanoparticles (PEI-SPIONs) to Schwann cells was analyzed by live/dead cell staining. Schwann cells were transfected with PEI-SPIONS in an external magnetic field of 1.4Td for 2 days. The optimal transfection concentration of PEI-SPIONS used was 2 mg/L and the optimal mass ratio of PEI-SPIONS to ChABC was 1:4. Cell migration test was used to evaluate the migration ability of not-treated Schwann cells, PEI-SPIONs/ ChABC transfected Schwann cells, and PEI-SPIONs/ChABC transfected Schwann cells in an external magnetic field. RESULTS AND CONCLUSION: The purity of Schwann cells and astrocytes reached to (91.7±1.2)% and (93.3±2.2)%, respectively. Compared with the Schwann cells group, the number of PEI-SPIONs/ChABC-transfected Schwann cells that entered the region of astrocytes was significantly increased (P < 0.05). Under the external magnetic field, the number of PEI-SPIONs/ChABC-transfected Schwann cells that entered the region of astrocytes and the cell migration distance were significantly increased as compared with the Schwann cells group (P < 0.005). In summary, PEI-SPIONs/ChABC transfection can enhance the ability of Schwann cells to break the glial scar, and increase the fusion of astrocytes. Under the guidance of external magnetic field, the migration ability of Schwann cells is significantly elevated. This method may be a new strategy to promote nerve regeneration after spinal cord injury.
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Objective To evaluate the impact of an external magnetic field on the dose distribution and electronic disequilibrium region around a Bebig type 60Co HDR brachytherapy source and to judge the feasibility of applying MRI scanner during brachytherapy.Methods The source model was established based on the Monte Carlo package Geant4 software.The simulated geometries consisted of the 60Co source inside a water phantom of 10.0cm× 10.0cm× 10.0cm in size.The magnetic field strength of the 0T,1.5T and 3.0T was considered,respectively.The voxels with a size of 0.2 mm,0.5 mm and 0.5 mm were established along the x-,y-and z-axis.The influence of the magnetic field on the Kerma (kinetic energy released to matter) distribution and dose distribution within the 10.0mm region from the source center was evaluated.Furthermore,the ratio of the Kerma to dose as a function of the distance to the center source was acquired.Results The 1.5T magnetic field exerted no effect on the dose distribution adjacent to 60Co HDR brachytherapy source,whereas3.0T magnetic field caused significant increase in the dose distribution within r＜6 mm from the source center.The dose distribution was increased by 40％ at r=5.4 mm from the source center.The ratio of Kerma to dose was less than 1 within the region of 1.2 mm＜r＜6.0 mm,suggesting that 3.0T magnetic field can lead to electronic disequilibrium within a larger region from the source center.Conclusions For Bebig 60Co HDR brachytherapy source,it is safe and reliable to apply1.5T external magnetic field.Nevertheless,3.0T magnetic field can cause high dose risk.Consequently,safety assessment and verification should be delivered prior to clinical application.
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OBJECTIVE: To analyze the current status of occupational exposure to power frequency electromagnetic field in converter stations. METHODS: Eight converter stations with voltage levels of ±500 kV and ±800 kV within normal operation were selected as the research subjects using the typical sampling method. Power frequency electric field and power frequency magnetic field strengths were measured and calculated according to the GBZ/T 189.3-2018 Measurement of Physical Agents in Workplace--Part 3: Electric Field and Magnetic Field between 1 Hz and 100 kHz. The GBZ 2.2-2007 Occupational Exposure Limits for Hazardous Factors in the Workplace--Part 2: Physical Factors were used to evaluate whether the power frequency electric field strength exceeds the regulatory limit(the occupational exposure limit of power frequency electric field in 8 hours workplace is 5.000 kV/m). Meanwhile, the test results were evaluated according to the short-term occupational exposure limit of 50 Hz electric field and magnetic field recommended by the International Committee on Nonionizing Radiation Protection in 2010 that are 10.000 kV/m and 1 000.00 μT. RESULTS: The power frequency electric field and magnetic field strengths of 582 working environment detection points were measured. The median and 0-100 th percentile of power frequency electric field and power frequency magnetic field strength were 4.342(0.001-12.003) kV/m and 5.51(0.10-186.90) μT, respectively.The exceeding standard rate of power frequency electric field strength in converter station workplaces was 37.8%(220/582), which concentrated in 500 kV alternating current filter area and 500 kV alternating current field area. Among them, 5 detection points had power frequency electric field strength exceeding 10.000 kV/m. The magnetic flux density of all the detection points did not exceed 1 000.00 μT. The power frequency electric field strength in ultra-high voltage region was higher than that in high voltage region(P<0.01). There was no significant difference in power frequency magnetic field strength(P>0.05). There was no significant difference in power frequency electric field and magnetic field between rectifier stations and inverter stations(P>0.05). The 8 hours time weighted average(TWA) value of power frequency electric field strength of 8 converter station operators was 1.044-2.335 kV/m, which did not exceed the occupational exposure limit. CONCLUSION: The converter station operators might be exposed to excessive power frequency electric fields for a short time, but the 8 hours TWA value of the power frequency electric field meets the requirements of standards, and the power frequency magnetic field exposure strength also meets the requirements of the relevant standards.
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Abstract Phenolic compounds are one of the main groups of secondary metabolites in plants and are known for their antioxidant activity. Rosmarinus officinalis L. (rosemary) contains different phenolic compounds including carnosol, carnosic acid and rosmarinic acid. In Cuba, rosemary cultivation is limited because it is difficult to propagate and has a low yield. As a result, it was removed from the Herbal Medicine National Formulary. However, the National Public Health System has a strong interest in rosemary because of its value as a natural antioxidant medicine. Irrigation with water treated with a static magnetic field (SMF) is a possible strategy to increase rosemary yield. This technology has been applied to accelerate plant growth and increase crop quality. The aim of this study was to evaluate the content of phenolic compounds and antioxidant activity in aqueous leaf extracts from plants irrigated with SMF-treated water in comparison to control plants. Significant differences in phenolic content and antioxidant activity were observed between aqueous extracts of control plants and plants irrigated with SMF-treated water. Therefore, irrigation with SMF-treated water is a promising technology to improve the cultivation of rosemary as a raw material to obtain pharmaceutical products with high antioxidant activities.
Subject(s)
Rosmarinus/chemistry , Agricultural Irrigation/methods , Magnetic Fields , Antioxidants/analysis , Chromatography, High Pressure LiquidABSTRACT
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.
Subject(s)
Acoustics , Computer Simulation , Magnetics , Magnetite Nanoparticles , TomographyABSTRACT
Portable low-cost magnetic resonance imaging (MRI) systems have the potential to enable “point-of-care” and timely MRI diagnosis, and to make this imaging modality available to routine scans and to people in underdeveloped countries and areas. With simplicity, no maintenance, no power consumption, and low cost, permanent magnets/magnet arrays/magnet assemblies are attractive to be used as a source of static magnetic field to realize the portability and to lower the cost for an MRI scanner. However, when taking the canonical Fourier imaging approach and using linear gradient fields, homogeneous fields are required in a scanner, resulting in the facts that either a bulky magnet/magnet array is needed, or the imaging volume is too small to image an organ if the magnet/magnet array is scaled down to a portable size. Recently, with the progress on image reconstruction based on non-linear gradient field, static field patterns without spatial linearity can be used as spatial encoding magnetic fields (SEMs) to encode MRI signals for imaging. As a result, the requirements for the homogeneity of the static field can be relaxed, which allows permanent magnets/magnet arrays with reduced sizes, reduced weight to image a bigger volume covering organs such as a head. It offers opportunities of constructing a truly portable low-cost MRI scanner. For this exciting potential application, permanent magnets/magnet arrays have attracted increased attention recently. A magnet/magnet array is strongly associated with the imaging volume of an MRI scanner, image reconstruction methods, and RF excitation and RF coils, etc. through field patterns and field homogeneity. This paper offers a review of permanent magnets and magnet arrays of different kinds, especially those that can be used for spatial encoding towards the development of a portable and low-cost MRI system. It is aimed to familiarize the readers with relevant knowledge, literature, and the latest updates of the development on permanent magnets and magnet arrays for MRI. Perspectives on and challenges of using a permanent magnet/magnet array to supply a patterned static magnetic field, which does not have spatial linearity nor high field homogeneity, for image reconstruction in a portable setup are discussed.
Subject(s)
Diagnosis , Head , Image Processing, Computer-Assisted , Magnetic Fields , Magnetic Resonance ImagingABSTRACT
Objective: To investigate the inhibitory effect of a combination of static magnetic field (SMF) and extremely low frequency-electromagnetic field (ELF-EMF) on the proliferation of tumor cells, and its causal relationship with the induction of intracellular reactive oxygen species (ROS) after exposure. Methods: The intensities of SMF and 50 Hz ELF-EMF both changed periodically and generated a magnetic field (MF) with a time-averaged intensity of 5.1 mT in the center of exposure area. The bronchial epithelium of human lung Beas-2B cells, human renal epithelial 293T cells, human nephroblastoma G401 cells, human gastric adenocarcinoma AGS cells, human pancreatic cancer BxPC cells and human neuroblastoma CHLA255 cells were exposured in MF for 2 h/d (continuous 3 days). The effects of the combined MF on the growth, proliferation, apoptosis and intracellular ROS concentration were detected by trype blue method, BrdU method, FCM method and DCFH-DA fluorescence probe method, respectively. Results: This combined MF showed no inhibitory effect on non-tumor cells including Beas-2B and 293T (both P > 0.05), while it showed inhibitory effect on tumor cells including G401, AGS, BxPC, and CHLA255 cells (all P < 0.01). G401 and CHLA255 cells were more sensitive to the MF, the inhibitory rate of G401 and CHLA255 cells at the third day of exposure was (29.41±0.81)% and (31.71±4.59)%, respectively. The apoptosis rate of G401 cells exposed to MF for 2 h/d was increased in 3 days (P < 0.05, P < 0.01 and P < 0.01). As compared with daily exposure for 2 h, the inhibition rate of daily exposure for 8 h induced another 10% increase (all P < 0.01). Furthermore, the combined MF exhibited more pronounced antitumor effect than that of SMF or ELF-EMF alone, including SMF with the same intensity of the combined field (all P < 0.01). The peak of intracellular ROS levels was reached shortly after initial exposure (1-2 h), for long before the peak of cell inhibition was reached (day 2-3 with accumulated exposure of 4-6 h). Continuous or intermittent increase of MF exposure did not result in further accumulation of intracellular ROS. However, the peak of ROS levels persisted to the next day after termination of exposure. Both SMF and ELF-EMF could induce the elevation of ROS, but without superimposition effect. Conclusion: Extending the exposure time of MF can improve its inhibitory effect on tumor cells. The antitumor effect of the combined MF is related to free radical damage, but this may be not the only mechanism.
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Objective: To investigate the impact of MR fringe magnetic field on the electron beam characteristics of the electron gun in the MRI-guided radiotherapy (MRIgRT). Methods Electromagnetic field analysis software was used to simulate the beam characteristics of both Litton L2087 electron gun and Varian 600C electron gun under different magnetic field strengths for the in-line MRIgRT configuration. Results Two electron guns exhibited qualitatively similar behavior in the fringe magnetic field. As field strength increased, the current emitted by the cathode increased slowly, which could increase up to 2.72% and 1.93% from the original value without external magnetic field for Litton L2087 and Varian 600C electron gun, respectively. The current at the anode exit started to decrease after the initial plateau, and after reaching a minimum value, the current started to increase slowly, and the current loss could reach up to 80.25% and 73.48% of the initial value, respectively. At high values of the field strength, the beam radius changed periodically. Beam root mean square emittance fluctuated under different magnetic field strengths. Conclusion For in-line MRIgRT configuration, the fringe magnetic field can affect the trajectory of the beam and cause a large amount of current loss in the electron gun, and the beam RMS emittance varies greatly.
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Objective To investigate the effect of pulsed magnetic radiation on BBB permeability of hippocampus in Sprague-Dawley rats at different exposure intensity.Methods A total of 72 male SD rats were randomly divided into sham exposure group,positive control group and magnetic field treatment groups (100,400,800,1 200 mT,30 pulses each group).At three hours after exposure,the morphological structure of hippocampus was evaluated by HE staining,the extravasation of albumin around microvessels in rat hippocampus was detected immunohistochemically,the EB extravasation around microvessels was observed with Evans blue (EB) fluorescence method,and the levels of BBB-related protein ZO-1 and Occludin in hippocampus were measured with Western blot assay.Results Compared with the control group,no significant change in the hippocampus morphology structure,the extravasation of albumin and EB around the microvessels were observed after the pulsed magnetic exposures.The protein levels of ZO-1 and Occludin had no changes in the exposed groups (P＞ 0.05) except that ZO-1 was significantly reduced in 1 200 mT exposure group (t =14.26,P ＜ 0.05).Conclusions Low-frequency pulsed magnetic field could not affect the permeability of BBB in SD rats but impairs the integrity of BBB at 1 200 mT.
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Introducción: La enfermedad cerebrovascular constituye un importante problema de salud a nivel mundial. En la actualidad se desarrollan investigaciones científicas dedicadas al estudio de los efectos del campo magnético de frecuencia extremadamente baja para su tratamiento. No es suficientemente clara la información acerca de su inocuidad en las dosis estudiadas. Objetivo: Estudiar la seguridad de la aplicación del campo magnético de frecuencia extremadamente baja a nivel del sistema nervioso central a través de un estudio toxicológico a dosis aguda, repetida y ensayo de micronúcleos en médula ósea. Métodos: Se conformaron tres grupos experimentales con ratas Sprague Dawley Cenp:SPRD jóvenes y sanas para los experimentos de toxicidad y ratones CENP: NMRI para la evaluación mutagénica. Se utilizaron controles negativos no tratados. En el ensayo de micronúcleos se incorporó un grupo control positivo al que se administró Ciclofosfamida por vía intraperitoneal. Se aplicó un campo magnético no homogéneo con niveles de inducción magnética de 6,5 y 15 mT, tomando como referencia el valor máximo sobre la superficie de la bobina. Para la aplicación del campo magnético la bobina estimuladora se colocó sobre la cabeza asegurando la exposición completa del encéfalo. Resultados: En ninguno de los ensayos se detectaron signos de toxicidad. Se comprobó así mismo que no se indujeron efectos genotóxicos ni citotóxicos sobre las células somáticas. Conclusiones: El tratamiento con campo magnético de frecuencia extremadamente baja a nivel del sistema nervioso central en las condiciones experimentales y dosis estudiadas es seguro(AU)
Introduction: Stroke is a major health problem all over the world. Nowadays are developed scientific researches devoted to the study of extremely low frequency magnetic field effects over this illness. The information about it safety is unclear yet. Objective: To study the safety of extremely low frequency magnetic field applied at central nervous system level wasby means ofa toxicological assay (Acute, repeated doses and micronucleus in bone marrow assay) Methods: Three experimental groups were made with Sprague Dawley Cenp: SPRD young and healthy rats for toxicity experiments and CENP: NMRI mice for mutagen evaluation. Untreated negative controls were used. In the micronucleus assay, an additional positive control group was included. This group received Cyclophosphamide by intraperitoneal administration. Was applied a non-homogenousmagnetic fieldof 6,5 and 15 mT, taken as reference the maximum value over the coil surface. The coil was positioned over the head, ensuring full exposure of brain to magnetic field. Results : In none of trials were detected any sign of toxicity. It was also found no genotoxic or cytotoxic effects induced on somatic cells. Conclusions : These results indicated the safety of treatmentwith extremely low frequency magnetic field at central nervous system level for experimental conditions and doses studied(AU)
Subject(s)
Animals , Cerebrovascular Disorders/therapy , Magnetic Field Therapy/methods , Toxicological Symptoms/toxicity , Rats, Sprague-Dawley , Neuroprotection , Mutagenicity Tests/methodsABSTRACT
This paper realized an electromagnetic tracking system based on electrically-controlled rotating magnetic field. A tracking system using the digital signal processor (DSP) as the control processing device was developed, including a controllable constant current source module, a magnetic field source module, a three-axis magnetic sensor and ADC interface circuit. The experimental results verified that each time the system could be stable positioning, average error of position was 0.282 cm, the average error of orientation was 0.696o, the positioning time was 1.572 s. Through calibration and further improvement of the hardware circuit, the performance of the system is expected to further improve.
Subject(s)
Calibration , Electromagnetic Phenomena , Equipment Design , Magnetic FieldsABSTRACT
Objective To develop a sinusoidal alternating magnetic field therapy system in order to overcome the disadvantages of the single output frequency and the low effective value of the output magnetic field strength of the alternating magnetic field therapy system in the market,of which the frequency and magnetic density both were continuously adjustable. Methods Multi winding Helmholtz coil was used as the magnetic field generator.On the basis of inverter technology,bipolar equivalent area method considering dead zone and variable speed integral incremental PID control algorithm were used to achieve the accuracy control of magnetic frequency and density in the coil.The accuracy of the resulting waveform and the accuracy of the magnetic field strength was verified by simulation calculation and system current and magnetic field strength test.Results The magnetic field treatment system gained high performance,total harmonic distortion (THD)of sine wave met the requirements of international standards.The obtained magnetic density was as expected of the simulation and calculation. Conclusion The device provides continuously adjustable magnetic field,which has a positive effect on the research for the medical staff, and technical references are provided to the research of magnetic field therapy system.