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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
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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@#Objective To investigate the effect of different dosage of pulsed magnetic field on expression of platelet-derived growth factor-A (PDGF-A) in rabbits with carotid atherosclerosis after carotid endarterectomy (CEA). Methods Carotid atherosclerosis were modeled in 50 New Zealand rabbits with air-drying lesion combined with high fat feed. All animals were treated with double side carotid endarterectomy after 2 months, and were randomly divided 3 groups: 0.6 T group, 1.0 T group and the blank control. The expression of platelet-derived growth factor-A were detected with immunohistochemistry 1 month, 2 months and 3 months after CEA. Results The expression of PDGF-A in treated groups were lower significantly than that in controls (P<0.05) 2 month after CEA, and it was the lowest in 1.0 T group, lower in 0.6 T group 3 month after CEA. Conclusion The pulsed magnetic field therapy can decrease the expression of PDGF-A, which might be helpful to prevent the carotid from restenosis.
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Objective To examine the neuroprotective effect of pulsed magnetic field in a animal focal cere-bral ischemica-reperfusion injury model. Methods Forty-eight Sprague-Dawley (SD) rats were randomized into 3 groups, a sham-operation group, a model group and a pulsed magnetic field group, with rats 16 in each group. Mid-dle cerebral artery occlusion (MCAO) method was employed to establish the focal cerebral ischemia-reperfusion inju-ry model in rats of model group and pulsed magnetic field group. Rats in sham-operation group was subject to the same operation procedure but not underwent ischemia-reperfusion. The infarction volume, histopathological damage and expressions of IGF-1 in ischemic brain tissue were investigated to evaluate the effect of pulsed magnetic field. Results The infarction volume was reduced, histopathological damage alleviated and expressions of IGF-1 in ische-mic brain tissue elevated in the pulsed magnetic field group as compared against the model group (P<0.05). Con-clusions Pulsed magnetic field might provide neuro-protection against cerebral ischemia-reperfusion injury.
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This paper introduces general guidelines for designing and constructing a magnetic stimulator (MS). These guidelines cover the theoretical concepts, hardware aspects and necessary components. RLC model producing the impulses in MS is focused on and the way to calculate the parameters of the model is presented. Some factors that influence induced magnetic field are discussed. Experiments are carried through with self-developed round coil and 8-shaped, and Tesla meter is used to detect the magnetic fields. The experiments data show that the distribution of the induced magnetic fields by the two coils are tailored to those of theoretical calculation adopted now. A simulation experiment to measure magnetic field in brain has been completed.
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Objective: To investigate the reversal effects of pulsed magnetic fields(PMF) on the drug resistant cell line K562/ADR in vitro and their mechanism.Methods: MTT assay was used to determine the IC50 of ADR on K562/S and K562/ ADR cell lines,the detriment of PMF on the K562/ADR cell line and the reversal effects of the drug resistance after treatment with different frequencies of PMF.Flow cytometry(FCM) was applied to the assessment of concentration of intracellular ADR.Results: The drug-resistance multiple of the K562/ADR cell line was 29.36.PMF did not affect the growth of the K562/ADR cell line.Different frequencies of PMF produced different effects on the IC50 of the K562/ADR cell line.In the same condition,70Hz PMF produced the most significant effect and increasea the concentration of intracellular ADR.Conclusion: PMF can reverse the multidrug resistance of K562/ADR by enhancing the drug concentration in K562/ADR cells,and its frequency is correlated with its reversal effect:low fregucncy produces better effect.