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Power Circuits and Communication Devices:  We use stationary and mobile telephones, in order to communicate on big distances, could not work without electromagnetism. The cooperation of the signals and the electromagnetic impulses make the telephones very convenient.  In power circuits, we use a device called relays, which has the potential to cut down a large current to the load, with the application of small amount of current. A small magnetic coil, which when energized, creates or breaks down the contact, thereby doing a greater amount of work on the other end. Not to forget the usage of electromagnetism in medical field. What is MRI?  Everyone must have heard about MRI scans. MRI- Magnetic resonance imaging is a method of scanning a person’s body using strong magnetic fields and radio waves to get the high-quality images that help in diagnosing a wide range of human states.    The description of how does it work? MRI scanners are large devices with a “bagel” shape. This process can be summed up as follows. First of all, the patient is placed inside the big magnet, where placed a really strong constant magnetic field. Patients lie horizontally on a special “couch”, so that they can be placed inside the MRI scanner. With the help of magnetic waves, it is possible to get the images of the head, spinal column and joints in the form of slices in three projections: axial, sagittal, coronal. For the image of blood vessels and ducts a 3D model is being constructed, for example, for arteries – angiography, for veins – venography, for bile ducts – cholangiography.  MR scanner consists of: magnetic gradients; the main magnet; data collection and processing systems; generator (transmitter) of radio pulses; receiver radio pulses; systems of power supply and cooling. The MRI procedure MRI can detect abnormalities of the brain, pituitary gland, intervertebral discs, meniscus, abdominal organs and small pelvis. The MRI method is safe for the body, since the patient isn’t presented to radioactive radiation amid the MRI system. Before scanning, you have to expel every single metal object and check for tattoos. Prior to the arrangement of a MRI, patients are encouraged to discover what data will be given and how this will influence the treatment procedure, regardless of whether there are contraindications for MRI, whether complexity will be utilized and for what. MRI scans usually take between 30 – 60 minutes. It depends on which part of your body is being inspected. You will be required to lie either head first or feet first on the MRI couch, depending on the area that will be scanned. The equipment will then be placed around the area that is inspecting. This equipment does not harm or hurt you; it picks up the signal that produces the images. The scanner is controlled by a computer which is placed outside the MRI rooms. The radiographer you can see though a glass panel at all time. Also, doctors can communicate with you through an “intercom”. However, the MRI scanner produces a very loud knocking noise which varies in sound throughout the scan, so you will be given a choice to wear the earplugs or the headphones to protect yourself from the loud noise. Through the headphones you will be able to listen to music during your scan if you wish. To ensure that the images are clear it is extremely important to remain still throughout the scan. You will be given a call bell to hold in your hand for the duration of the scanning process in case you should need the radiographer’s attention. The principle of the MRI scanner The transmitting coil generates resonant frequency waves and modulates them into pulses; A receiving coil representing a highly sensitive antenna located perpendicular to the direction of the main field (plane X-Y) transmits the received signal to the ADC; The analog-to-digital converter (ADC) sends data digitally to the operator computer for image reconstruction; The computer, in addition to obtaining an image from a tomograph, allows: centrally manage the entire system; process, record and print the image; perform a fast Fourier transform. Advantages: Brilliant contrast between various delicate tissues The resolution is higher than in computed tomography  No ionizing radiation Disadvantages: Little magnet bore prevents scanning in treatment position (particularly breast treatments) Some patients are unable to have the computer tomography due to an availability of sensitive equipment (pacemakers, cerebral aneurysm clips). 

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