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6 Cards in this Set
- Front
- Back
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PHOTOMULTIPLIER |
When the rays enter the iodine crystal, the light from the scintillation spreads through the crystal and the photomultiplier receives some of the total light. The photomultiplier then produce electric pulses, these pulses are then decoded and analysed creating an image. |
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PARTS OF THE BODY USED BY MRI |
brains; tumours, spinal cord damage, muscles, tendons, cartilage, joints; tears, parts other than bone. Soft tissue structures |
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HOW MRI WORK |
Eddy currents are induced in any nearby metallic material when the machine is operating, this is happening because there is a changing magnetic field in the MRI machine. A pulse of electromagnetic radiation, in the radio frequency range, is sent into the body. This pulse is then turned off. When the pulse is switched off the protons in the body react and line up. the aligned protons then release its own radio frequency pulse as a result of the pulse from the machine. The greater the density of hydrogen protons, the larger the signal and the brighter the image. Airy spaces show up dark. By examining the time it takes the protons to relax or reach the original energy states, the type of tissue can be identified. |
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MRI |
Body is placed into a strong magnetic field. Protons inside the body aligned with the magnet field due to their spin. An electromagnetic radiation pulse is sent into the body then switched off. Nuclei in your body react sending back a pulse while the protons return to their original energy state. The radio waves emitted are analysed. |
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LAMAR FREQUENCY |
Strong magnetic field aligns proton spin with field except protons still spin in a little wobbly, spin-top like motion creating a procession frequency called the lamar frequency. The lamar frequency can be manipulated by increasing the strength of the external magnetic field. |
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LOW AND HIGH ENERGY PROTONS |
The low and high level energy protons tend to cancel each other out. But because being low is easier, we find there is one more low then high proton, leaving and excess net of low protons. When a low energy proton is hit with a radio frequency pulse of energy equal to its lamar frequency it moves up to a high energy level. Low become high proton. When the pulse is switched off, the high proton releases energy and becomes a low energy proton and emits energy, this energy is read by the receiver coil and the MRI machine. |
