If someone lies in front of an MRI machine, it kills him. We will understand this machine in detail, but I have a case that you should see. The incident of Mumbai is 200 years ago that a boy took an oxygen cylinder with him in the room where the MRI machine is kept. And the oxygen cylinder was made of iron.
This boy had no idea how powerful this machine could be. As soon as he enters the room, the powerful strong magnetic field of the machine pulls this boy away from the distance and gives him death on the spot. My goal is not to scare you, but to understand the behavior of the MRI Machine.
Power of MRI Machine
The crane that picks up the garbage in the junkyard has the power of around 1 Tesla, which can easily pick up any car from a magnet. Tesla is a unit that shows the strength of the magnetic field.
But the MRI machine can be of 3 Tesla power. This MRI Machine has such a strong magnetic field that you can’t even take a nail of iron with it. We understand in detail. Basically, the MRI machine detects any problem in the body with proper detailing. So it is especially used for brain scanning.
Magnetic Coil of MRI
There is a coil type winding in the magnet which is made of niobium or titanium. The resistance of this coil is absolutely zero but for now this coil does not have any magnetic field so first of all this coil is charged. And as soon as it is charged, the current will start circulating in the coil and this current will generate a magnetic field around it.
But this field will not be very strong because if the current circulates, then the winding temperature will increase and the resistance will come in between. So to maintain the resistance to zero, this coil is provided with liquid helium cooling, whose temperature is -261 degrees centigrade (minus 261°C). And this liquid helium keeps the temperature of the coil at zero degrees centigrade, due to which this coil comes in the superconducting stage.
And it has a powerful strong magnetic field. Since the resistance of this coil is zero, then we don’t need to supply it from outside. Just charge this coil once and when it reaches the superconducting stage, its magnetic field will remain for a lifetime. Because the resistance loses power and here the resistance is zero. And after that the magnet is packed.
What is the Connection of MRI Machines to Our Body
Our body has 60% water and hydrogen atoms in the water. And if we are alive, then you know that these hydrogen atoms will have some energy. But they are the owners of their own will and randomly release their own energy. When the atoms come in a strong magnetic field, then this magnetic field will set all these atoms in a line and align them well.
The magnetic field of this magnet is homogeneous, which means that the magnetic field of the magnet equal force. So now the atoms of the whole body have set very well with the magnetic field.
The Radio Frequency Coil
When the brain is scanned through one circle set right next to our brain, which is called the radio frequency coil. Now we will increase our focus a little. What does this coil do? It sends radio frequency signals inside the brain, but not continuously. Once the pulse is sent, then it is closed again.
Let’s assume that this is a hydrogen atom and it is randomly releasing its energy according to the gravity of the natural earth. So first of all, let’s put a superconducting magnet field on it, then it will come under proper discipline.
Look at this animation. Now let’s put a 90 degree pulse of the radio frequency on this atom. And what will this pulse do? It will rotate this hydrogen atom at 90 degrees and immediately after that, it will stop the radio frequency. Now this hydrogen atom will try to align with the superconducting magnet field and when it will come back to its position, it will release some of the energy that the radio frequency coil gave.
The Receiver of the Radio Frequency Coil & resonance frequency.
The receiver of the radio frequency coil is placed very close to our brain, so as soon as all the atoms release their energy, the receiver of the radio frequency coil senses this energy. And the frequency at which this energy has returned is called the resonance frequency.
Let’s make it a little easier. Suppose your girlfriend slapped you. Now if you have the courage, you will try to slap again, but you will not be able to hit with the intensity of the girlfriend’s slap. So what happened here?
First, the girlfriend sent you a radio frequency in the form of a slap. And now you suddenly got energy. Now if you get angry, you have to release this energy again, then you will slap again. So this energy that has come back to the girlfriend is called resonance frequency.
Now the girlfriend, consider it a radio frequency coil, it is a kind of sensor that is attached to our brain and keeps checking how much energy has come back.
How Does MRI Machine Detect the Problems?
Radio frequency coils basically have an inductor and a capacitor, which are recharged and discharged from the frequency to make a graph. But even now, the doctor will not know where the problem is. All we know is that a problem has been found. Because we have to make an exact image so that the problem can be treated at any point.
The machine itself does not know that the problem that has been found is in which part of the brain. Because there should be some reference for measurement, right? Like if you say that the star in the sky is broken and the next day I ask you where the star was broken yesterday, then you can only tell an idea that it was broken on this side, but I want its exact position so that we can tell someone else.
MRI Machine Gradient Coil
Then the third component of the MRI Machine, the gradient coil, and the gradient coil helps to make the exact image. The gradient coil is in the position of circle bore.
The supply is given in the opposite direction in these two coils, which generates its field near the coil. Now, although so many field lines are generated there, but for simplicity, we assume only one field line there. So the magnetic field of the coil there is in the same direction as the main magnetic field, so these two will be added.
But the field of the coil there is in the opposite direction of the main field. But if you consider at the center point of these two coils, then the field of both the magnets there is in the opposite direction of each other, then it will cancel and become zero. So we can say that the field of the big magnet in the center point is available, the field of the coil on both sides has become zero.
Let’s assume that the strength of the field of the large magnet on the center point is 1 tesla. Now as we go here from this center point, then this field will increase by 1.1 tesla, 1.2 tesla, 1.3 tesla. Because the gradient coil and the main field there are connecting and the same field is decreasing on the opposite side of it.
Now this line is of Z axis and if there is any problem at this point, then the machine will know that the frequency is of a different type from the magnetic field of 1.2 tesla in Z axis. In the same way, there is a coil like this for X axis and Y axis.
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Conclusion
When an MRI is done on a patient, it can take 30 to 40 minutes because the radio frequency is sent multiple times to create an exact image. All the x-ray side effects of this MRI Machine, although it does not have any side effects, but if you have had any surgery in the past and you have put an iron part in your body, then you have to tell the doctor beforehand.
You don’t have to hide anything. Otherwise, when you go near the MRI Machine, the machine will tear your body and take out an iron piece. So whatever the doctor asks you, you have to tell the truth. Generally, MRI Machine works better in the muscles part of the body, where water content is more available.
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