LEARNING WEEK/ I lavori degli studenti sulle tecniche avanzate di diagnostica medica
Applications of Technique of Examination of The Human Body in the Diagnostic Field/2 - Nowadays the most used techniques to look inside the human body are two: CT and MR. These high level technologies use different kinds of methods to achieve their goal, which is to give internal images of the human body, and are in constant update. Both these techniques follow the same path to obtain images; first there’s giving of energy to the patient, than this energy has an interaction with the matter that is read by a detector system, which finally gives the required image to the observer.
The source of energy is different between CT (computed tomography) and MR ( magnetic resonance); the first system is based on x-rays, a kind of electromagnetic radiations which are ionizing and quite penetrant. The process consists of sending a beam of photons with a definite amount of energy; then, passing through the body, the beam reaches the exposed plate and the detector system is able to convert the different amount of photons into different colours which create the image. This technique involves some risks because x-rays can break molecular bonds in the human body cells; for this reason it’s not wealthy to undergo too many CT procedures.
On other hand, the MR technique uses a harmless kind of radiations, the RF (radio frequency) waves. Although this process doesn’t involve any risks, it takes much more time than CT to obtain the image. As a matter of fact, in cases of emergency, Ct is used instead of MR despite the fact that MR technique gives higher definition images. The MR process takes advantage of the composition of the human body, which is made of water by 80 %, which contains hydrogen.
As a matter of fact MR uses a magnetic field, inside which the patient is put, which changes the orientation of the hydrogen protons, each one with a characteristic rotation (“spin”). At this point a coil sends a radio-electric pulse which is able to modify another time the orientation of the hydrogen protons; then the spring is turned off and there’s a relaxation of each proton which releases a different amount of energy. When this energy reaches the receiver coil, it is able to create the image with different colours according to the different amount of energy that is transported by the coil.
( Di Marco Frangi e Tommaso Zanchettin - Classi 3a e 4a Liceo Frassati, Seveso)
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