Existing neuroregulatory techniques can achieve precise stimulation of the whole brain or cortex, but high-focus deep brain stimulation has been a technical bottleneck in this field. In this paper, based on the theory of negative permeability emerged in recent years, a simulation model of magnetic replicator is established to study the distribution of the induced electric field in the deep brain and explore the possibility of deep focusing, which is compared with the traditional magnetic stimulation method. Simulation results show that a single magnetic replicator realized remote magnetic source. Under the condition of the same position and compared with the traditional method of stimulating, the former generated smaller induced electric field which sharply reduced with distance. By superposition of the magnetic field replicator, the induced electric field intensity could be increased and the focus could be improved, reducing the number of peripheral wires while guaranteeing good focus. The magnetic replicator model established in this paper provides a new idea for precise deep brain stimulation, which can be combined with neuroregulatory techniques in the future to lay a foundation for clinical application.
Brain ; Cerebral Cortex ; Computer Simulation ; Electricity ; Magnetic Fields

Currently, transcranial magnetic stimulation (TMS) has been widely used in the treatment of depression, Parkinson's disease and other neurological diseases. To be able to monitor the brain's internal activity during TMS in real time and achieve better treatment outcomes, the researchers proposed combining TMS with neuroimaging methods such as magnetic resonance imaging (MRI), both of which use Tesla-level magnetic fields. However, the combination of strong current, large magnetic field and small size is likely to bring physical concerns which can lead to mechanical and thermal instability. In this paper, the MRI static magnetic field, the TMS coil and human head model were built according to the actual situations. Through the coupling of the magnetic field and the heat transfer module in the finite element simulation software COMSOL, the force and temperature of the TMS coil and head were obtained when the TMS was used in combination with MRI (TMS-MRI technology). The results showed that in a 3 T MRI environment, the maximum force density on the coil could reach 2.51 × 10⁹ N/m³. Both the direction of the external magnetic field and the current direction in the coil affected the force distributions. The closer to the boundary of the external magnetic field, the greater the force. The magnetic field generated by the coil during TMS treatment increased the temperature of the brain tissue by about 0.16 °C, and the presence of the MRI static magnetic field did not cause additional thermal effects. The results of this paper can provide a reference for the development of the use guidelines and safety guidelines of TMS-MRI technology.
Brain/physiology* ; Humans ; Magnetic Fields ; Magnetic Resonance Imaging/methods* ; Temperature ; Transcranial Magnetic Stimulation/methods*

Cholangiocarcinoma is a highly malignant tumor. It is not sensitive to radiotherapy and chemotherapy and has a poor prognosis. At present, there is no effective treatment. As a new method for treating cancer, magnetic fluid hyperthermia has been clinically applied to a variety of cancers in recent years. This article introduces it to the cholangiocarcinoma model and systematically studies the effect of magnetic fluid hyperthermia on cholangiocarcinoma. Starting from the theory of magnetic fluid heating, the electromagnetic and heat transfer models were constructed in the finite element simulation software COMSOL using the Pennes biological heat transfer equation. The Helmholtz coil was used as an alternating magnetic field generating device. The relationship between the magnetic fluid-related properties and the heating power was analyzed according to Rosensweig's theory. After the multiphysics coupling simulation was performed, the electromagnetic field and thermal field distribution in the hyperthermia region were obtained. The results showed that the magnetic field distribution in the treatment area was uniform, and the thermal field distribution met the requirements of hyperthermia. After the magnetic fluid injection, the cholangiocarcinoma tissue warmed up rapidly, and the temperature of tumor tissues could reach above 42 °C, but the surrounding healthy tissues did not heat up significantly. At the same time, it was verified that the large blood vessels around the bile duct, the overflow of the magnetic fluid, and the eddy current heat had little effect on thermotherapy. The results of this article can provide a reference for the clinical application of magnetic fluid hyperthermia for cholangiocarcinoma.
Cholangiocarcinoma ; Humans ; Hyperthermia ; Hyperthermia, Induced ; Magnetic Fields ; Magnetics

The complex electromagnetic field environments in magnetic resonance imaging system(MRI) can have a significant impact on patients carrying implants, the RF heating problems being particularly important. To ensure the safety of the patients, it is necessary to understand the distribution of tissue temperature in the MRI environment and its changes over time. Based on the analysis of tissue temperature rise in MRI, this paper constructs a bird cage coil for generating RF field in MRI system, and constructs ASTM standard/improved phantom and single-cavity pacemaker finite element models, use time-domain finite difference (FDTD) to simulate. Firstly, the correctness of the simulation software and simulation method was validated according to the method of ISO. Then the distribution of the electric field, SAR and temperature field and the temperature change with time were calculated in the environment of 64 MHz, 2 W/kg. The difference in temperature rise with blood heat exchange and no blood heat exchange (standard/improved phantom) was specifically compared. The simulation results show that there are electric field and SAR hotspots near the electrode tip, the wire tail and the case of pacemaker. There are high SAR values on both sides of the phantom, and the shorter the distance from the coil, the higher the SAR. The temperature field distribution is similar to the SAR distribution; the temperature is higher in the area around the end of the wire and the case of pacemaker because the heat accumulation is higher around this area. At the same time, blood heat exchange can reduce the temperature rise to a certain extent.
Electromagnetic Fields ; Humans ; Magnetic Resonance Imaging ; Models, Theoretical ; Phantoms, Imaging ; Prostheses and Implants ; Temperature

OBJECTIVE: To investigate the effects of millimeter wave (MMW) exposure on apoptosis of human melanoma A375 cells and explore the mechanisms. METHODS: Through electromagnetic field calculation we simulated MMW exposure in cells and calculated the specific absorption rate (SAR). The optimal irradiation parameters were determined according to the uniformity and intensity of the SAR. A375 cells were then exposed to MMV for 15, 30, 60, or 90 min, with or without pretreatment with the caspase-3 inhibitor AC-DEVD-fmk (10 μmol/L) for 1 h at 90 min before the exposure. CCK-8 assay was used to assess the changes in the viability and Annexin-V/ PI staining was used to detect the apoptosis of the cells following the exposures; Western blotting was used to detect the expression of caspase-3 in the cells. RESULTS: The results of electromagnetic field calculation showed that for optimal MMV exposure, the incident field needed to be perpendicular to the bottom of the plastic Petri dish with the antenna placed below the dish. CCk-8 assay showed that MMW exposure significantly inhibited the cell viability in a time-dependent manner ( < 0.05); exposures for 15, 30, 60, and 90 min all resulted in significantly increased apoptosis of the cells ( < 0.05). The cells with MMW exposure showed significantly increased expression of caspase-3. The inhibitory effect of MMW on the cell viability was antagonized significantly by pretreatment of the cells with AC-DEVD-fmk ( < 0.05), which increased the cell viability rate from (36.7±0.09)% to (59.8±0.06)% ( < 0.05). CONCLUSIONS 35.2 GHz millimeter wave irradiation induces apoptosis in A375 cells by activating the caspase-3 protein.
Apoptosis ; Caspase 3 ; metabolism ; Caspase Inhibitors ; pharmacology ; Cell Line, Tumor ; Cell Survival ; Electromagnetic Fields ; Enzyme Activation ; Humans ; Magnetic Field Therapy ; Melanoma ; enzymology ; pathology ; therapy ; Time Factors

PURPOSE: We report a case of homonymous quadrantanopia caused by occipital lobe ulegyria. CASE SUMMARY: A 23-year-female was referred to our clinic because of a visual field defect incidentally discovered during preoperative evaluation for refractive surgery at another clinic. However, she did not report any symptoms. She had no systemic diseases. Visual acuity was 20/20 in both eyes, and the color vision test was normal. Both pupils exhibited normal responses to light and near stimulations. In fundus examinations, the right optic disc was normal and the left contained drusen. Automated perimetry revealed right lower homonymous quadrantanopia with macular sparing. Brain magnetic resonance imaging revealed areas of ulegyria involving the left occipital lobe, consistent with the visual field defect. A follow-up visual field test performed 5 months later yielded the same result. CONCLUSIONS: Neuroimaging should be performed in patients with homonymous visual field defects to determine the location and etiology of the brain lesions. Occipital lobe ulegyria can cause homonymous quadrantanopia in the absence of any neurological problem.
Brain ; Brain Injuries ; Color Vision ; Follow-Up Studies ; Hemianopsia ; Humans ; Magnetic Resonance Imaging ; Neuroimaging ; Occipital Lobe ; Pupil ; Refractive Surgical Procedures ; Visual Acuity ; Visual Field Tests ; Visual Fields

PURPOSE: Horizontal visual field defects are generally caused by lesions before the optic chiasm, but we report a case with bilateral inferior altitudinal defects secondary to bilateral occipital lobe infarction. CASE SUMMARY: A 57-year-old male with a history of diabetes and hypertension presented with a month of blurring in the inferior visual field. His corrected visual acuity was 1.0 in the right eye and 0.63 in the left eye, and the intraocular pressure was normal in each eye. Pupillary response, ocular movement, and color vision tests were normal in both eyes. There was no specific finding of the optic disc and macula on fundus examination. Visual field examination revealed an inferior congruous homonymous hemianopia with horizontal meridian sparing and a left incongruous homonymous quadrantanopia. Optical coherence tomography for peripapillary retinal nerve fiber layer thickness revealed a mild decrease in the inferior disc of both eyes. Brain magnetic resonance imaging confirmed the presence of an acute infarction confined with upper medial calcarine fissures of bilateral occipital lobe and the right splenium of the corpus callosum, which were consistent with inferior altitudinal hemianopia and left superior incongruous quadrantanopia, respectively. Brain magnetic resonance angiography showed multiple stenosis of bilateral posterior cerebral arteries. CONCLUSIONS: The altitudinal visual field defects could be caused by the occipital lesion medial to the calcarine fissure, and unusual visual defects could be due to a combination of multiple lesions.
Brain ; Color Vision ; Constriction, Pathologic ; Corpus Callosum ; Hemianopsia ; Humans ; Hypertension ; Infarction ; Infarction, Posterior Cerebral Artery ; Intraocular Pressure ; Magnetic Resonance Angiography ; Magnetic Resonance Imaging ; Male ; Middle Aged ; Nerve Fibers ; Occipital Lobe ; Optic Chiasm ; Posterior Cerebral Artery ; Retinaldehyde ; Tomography, Optical Coherence ; Visual Acuity ; Visual Fields

A 35-year-old female visited emergency department for a sudden onset of headache with vomiting after management for abortion at local department. Neurological examination revealed drowsy mentality without focal neurological deficits. CT showed 3.2×3.4 cm hyperdense intraventricular mass with intraventricular hemorrhage. The intraventricular hemorrhage was found in lateral, 3rd, and 4th ventricles. MRI showed well enhancing intraventricular mass abutting choroid plexus in the trigone of the right lateral ventricle. CT angiography showed tortuous prominent arteries from choroidal artery in tumor. Her neurological status deteriorated to stupor and contralateral hemiparesis during planned preoperative workup. Urgent transtemporal and transcortical approach with decompressive craniectomy for removal of intraventricular meningioma with hemorrhage was done. Grossly total removal of ventricular mass was achieved. Pathological finding was meningotheliomatous meningioma of World Health Organization (WHO) grade I. The patient recovered to alert mentality and no motor deficit after intensive care for increased intracranial pressure. However, visual field defect was developed due to posterior cerebral artery territory infarction. The visual deficit did not resolve during follow up period. Lateral ventricular meningioma with spontaneous intraventricular hemorrhage in pregnant woman is very uncommon. We report a surgical case of lateral ventricular meningioma with rapid neurological deterioration for intraventricular hemorrhage.
Adult ; Angiography ; Arteries ; Choroid ; Choroid Plexus ; Critical Care ; Decompressive Craniectomy ; Emergency Service, Hospital ; Female ; Follow-Up Studies ; Fourth Ventricle ; Headache ; Hemorrhage ; Humans ; Infarction ; Intracranial Pressure ; Lateral Ventricles ; Magnetic Resonance Imaging ; Meningioma ; Neurologic Examination ; Paresis ; Posterior Cerebral Artery ; Pregnancy ; Pregnant Women ; Stupor ; Visual Fields ; Vomiting ; World Health Organization

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.
Diagnosis ; Head ; Image Processing, Computer-Assisted ; Magnetic Fields ; Magnetic Resonance Imaging

In ultrasound/computed tomography (CT) fusion images, ultrasound allows visualization of the target in real time. CT provides a navigation for ultrasound scanning and improves the overview in areas of limited visualization with ultrasound. This study was performed to investigate the feasibility of ultrasound/CT fusion based on an electromagnetic tracking technique using external fiducial markers for canine ocular and periocular regions. In 7 Beagle dogs, contrast-enhanced CT images of the head were obtained with placing external fiducial markers over the frontal region and both sides of the forepaws of the dog. Ultrasonography was performed under a magnetic field by installing a position sensor in the linear probe, without changing the dog's position. The positions of the external fiducial markers were adjusted and matched, based on the CT images. The execution time of co-registration and the distance between the regions of interest and the co-registration points, the frontal bone, cornea, retina, and optic nerve, were estimated. Approximately 60% of external fiducial markers were properly recognized in all dogs. After adjustment, all external fiducial markers were precisely matched. The co-registration execution time was less than 1 min. The distances between the regions of interest and co-registration points were less than 3 mm in all dogs. The electromagnetic tracking technique using external fiducial markers was a simple and applicable method for fusion imaging of a canine head using real-time ultrasonography and CT. This technique can be useful for interventional procedures of retrobulbar and periorbital lesions.
Animals ; Cornea ; Dogs ; Fiducial Markers ; Frontal Bone ; Head ; Magnetic Fields ; Magnets ; Methods ; Optic Nerve ; Retina ; Tomography, X-Ray Computed ; Ultrasonography