In this work we have measured the dose distribution and the percent depth dose of 20 MeV electron beam using the X-OMAT films in order to verify the effects of transverse magnetic field on high energy elecrtron beam in a phantom. The result shows about 30% increase of the percent depth dose at 4.5 cm depth under the transverse magnetic field of 1.5 Tesla at 7.5 cm depth. We have verified that these were in an agreement with other theoretical results.
Magnetic Fields*

BACKGROUND: So many electronic devices have been introduced in the operating room. However, little was known about the hazards of electromagnetic fields (EMF) to the human body. We have studied about how much the anesthesiologists are exposed to EMF. METHODS: In 19 operating rooms of our hospital, the intensity of magnetic fields was measured by an ELF (Extremely low frequency) field strength measurement system. The distances were 30 cm, 50 cm and the anesthesiologist's proximity to the monitoring devices. RESULTS: The average strength of 19 operating rooms were 2.22 +/- 1.13 mG at 30 cm from the monitors, 1.29 +/- 0.84 mG at 50 cm and 1.00 +/- 0.78 mG at the anesthesiologist's stand. CONCLUSIONS: We found that in some of our operating rooms the exposure to EMF was measured above Sweden's TCO limit which has been accepted as the EMF radiation rule for computer monitors. Although the hazards of EMF have not been definitely confirmed yet, the effort not to be exposed to EMF should be considered by anesthesiologists.
Electromagnetic Fields* ; Human Body ; Magnetic Fields ; Magnets* ; Operating Rooms*

The purpose of this study was to evaluate the effects of magnetic field on cellular activity of MC3T3-El cells. The celular activity was monitored by alkaline phosphatase and DNA synthetic activity in control, static magnetic field and pulsed electromagnetic field groups. A static magnetic field was applied to the cell by placing one, two, three, four, and five samarium-cobalt magnets above and below each cell plate for 24hours per day. A pulsed electromagnetic field with a frequency of 100 herz was applied for 10 hours per day. After 10 days of magnetic field exposure, there were increase of alkaline phosphatase activity in static magnetic field groups consisted of one, two and three magnetic groups, Alkaline phosphatase activities were not significantly increased in four and five magnetic groups, Application of pulsed electromagnetic field did not result in significant increase in alkaline phosphatase activity compared to control. DNA synthetic activity in both static and pulsed electromagnetic field group were not significantly different from that in control group, The result of this study suggest that magnetic field could have effect on the metabolism of bone cells related to the cellular metabolic process,
Alkaline Phosphatase* ; DNA* ; Electromagnetic Fields* ; Magnetic Fields* ; Magnets* ; Metabolism

Electromagnetic Fields ; Magnetic Fields ; Microwaves ; adverse effects ; Television

To evaluate the effect of a static magnetic field on the bone producing potential of MC3T3 El cells, the alkaline phosphatase activity was measured after the cells having been cultured under 76.4mT static magnetic field using a SmCos magnets for 5days, 7days, lldays, 15days and 2ldays for each cell culture group. Also, the amount of bone nodule stained with Alizarin red S was observed. The results were as follows. · The alkaline phosphatase activity of the 7, 11, and 15 days group among the experimental groups was decreased as compared with the control groups, and the decrease of alkaline phosphatase activity in the 11 days group was the most evident among them. · Any stained bone nodules of both groups had not been observed until the 11th day. The stained bone nodules in the control groups were found on the 15th day, but not in the experimental groups. The stained bone nodules were observed in both groups on the 21st day, but the control groups have more bone nodules than the experimental groups.
Alkaline Phosphatase ; Cell Culture Techniques ; Magnetic Fields*

This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling.
Extracorporeal Circulation ; Magnetic Fields ; Magnetics ; Torque

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.
Calibration ; Electromagnetic Phenomena ; Equipment Design ; Magnetic Fields

Gaining a complete understanding of the physics of magnetic resonance imaging (MRI) is a daunting task. However, as cardiac MRI is being increasingly used in cardiovascular medicine, understanding the basics of MRI physics has become necessary for appropriate assessment of the images and correct interpretation of the findings. MRI is an imaging modality that utilizes the magnetic potential of the body. When the body is placed inside an extremely strong magnetic field, the protons of the water molecules inside the body align along the field, after which, the proton spins are exposed to a radiofrequency pulse with a frequency that matches the precession frequency of the protons in the body. This causes the precession of the protons to resonate and increase in amplitude. Simultaneously, three-dimensional magnetic gradients are applied for targeting specific slices of the body and discriminating the two-dimensional orientation of the organs; this is followed by emission of electromagnetic pulses generated by the resonance with varying frequencies and phases from various parts of the body. As soon as the input pulse has ceased, the machine starts absorbing the electromagnetic pulses that are being emitted by the body. These waves are mathematically converted into images of the internal organs and are visualized through rapid computer processing. To improve the contrast between tissues and abnormal structures, specific pulse sequences and weighting of the images are applied. This review summarizes the principles of MRI physics for clinicians who lack an understanding of fundamental physics.
Magnetic Fields ; Magnetic Resonance Imaging ; Magnets ; Protons ; Water

OBJECTIVE: Transcranial magnetic stimulation (TMS) is a new, noninvasive procedure of a localized pulsed magnetic field to the surface of the head to cause a depolarization of neurons in the brain cortex underneath. Knowledge of the neuroanatomic abnormalities of depression is serving as the background for TMS treatment in depression. Here we provide a summarized review of the therapeutic application of TMS in patients with depression. METHODS: We described the clinical and basic researches of TMS in depression and integrated the future direction using literature review and interview with experts. RESULTS: The field of TMS is beginning to address the issues of using TMS as a novel antidepressant. The ability to excite local areas of brain cortex has raised the possibility of the use of TMS as a novel therapeutic tool for depression. CONCLUSIONS: Many parameters, such as intensity, location, frequency, pulse width, intertrain interval, coil type, duration, numbers of sessions, and interval between sessions remain to be systematically explored. However TMS would be a relatively new and noninvasive method to investigate regional brain activity and to treat depression.
Brain ; Depression* ; Head ; Humans ; Magnetic Fields ; Neurons ; Transcranial Magnetic Stimulation*

To evaluate the typical appearance and the influence in the image interpretation of the metallic artifact which is known as one of the patient-related field artifacts, we analysed the magnetic resonance (MR) images of 40 patients (the total number of metallic materials were 45) acquired at MR 1.5T unit. All patients were screened for the presence of metal. The metallic implants were surgical wires and clips, orthopedic devices, and the other miscellaneous materials. The artifacts produced by metallic objects can be seen on MRI as the focal loss of signal and/or the local distortion of the image. Regardless of their ferromagnetic properties, metallic implants created regional artifacts in their images. Ferromagnetic materials, such as a lead fragment, showed severe artifacts and nonferromagnetic metals showed mild to moderate artifacts. The conspicuity of artifact was related tot he composition, mass, shape, orientation, and the location of the metallic objects in the body. Under high magnetic field strength, there were no significant differences between the various pulse sequences. Artifacts are particularly prominent on gradient-echo images. Our findings indicate that MR imaging of patients with standard nonferromagnetic metallic materials can be successfully performed and usefully interpretated.
Artifacts* ; Humans ; Magnetic Fields ; Magnetic Resonance Imaging* ; Magnets ; Metals ; Orthopedics