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Magnetic Resonance Imaging: Summary and Applications

How does indeed Magnetic Resonance imaging work and how do it influence the future?

An Launch to Magnetic Resonance Imaging[1][2][3]:

Magnetic resonance imaging (MRI) can be used as a precise form of disease recognition which is usually used to verify a patients condition, as well as a method of considering trauma to the brain, examples of which could be hemorrhage and swelling. Alongside these uses MRI may be used to go through the soft cells, as well as home elevators the composition of joint parts.

Prior to the benefits, in order to for diagnosis for most of these problems were intrusive methods such as surgery, and x-rays or CT-scans which were less exact and ionizing, which could have a enduring effect upon our bodies. The usage of MRI scans is only a recent phenomenon, with the first image on a person being produced as later as 1977, by Paul Lauterbur and Sir Peter Mansfield who received a shared Nobel prize for his or her work on this subject. Both researchers were considering how nuclear magnetic resonance imaging could be utilized to look at solids and fluids, and both produced the theory behind it all, but it was Sir Peter Mansfield who developed the method found in MRI by first of all handling how to specify a slice of the matter, and also how to produce images from multiple-pulse experiments. Although the task on producing images for biological specimens only came into being consequently to the fact that it might be too hard to produce images of a solid.

How does indeed Magnetic Resonance Imaging work[4][5]?

Magnetic resonance imaging entails a series of steps which are explained below, to be able to produce the ultimate image that is employed for diagnostics.

Nuclear Spin

The body's mass is around 10% hydrogen, of which 70% is contained in water, and because of the fact that protons produce a large signal to a MRI scanning device a more appropriate image is produced, because they are in such large abundance in the body in the water.

 

The hydrogen nuclei in the body spin about an axis, this is illustrated in physique 1. 1. Due to the content spinning protons being priced, the spinning of your nuclei along an axis causes a small circulating electric energy, which in turn causes a small magnetic field.

If a collection of these nuclei were to be positioned in a more robust exterior magnetic field (B˜), the majority of the nuclei will align their spin in the same path as the external field.

As you can see from body 1. 2 not all of the hydrogen nuclei are aligned with the route of the magnetic field, which is because both alignments are possible, but the one with the field is a lower energy condition, whilst the protons from the field are in an increased energy condition. The protons are regularly oscillating back and forth between the two states, since there is a tendency for nuclei in a higher energy state to return to a lesser energy status by emitting some of its energy to encompassing nuclei. There is usually enough thermal energy in the materials for the nuclei to be flipped back again.

 

How do protons precess about an axis?[6]

Spinning protons when in the presence of an exterior magnetic field do not set up themselves properly parallel or anti-parallel to the magnetic field, as the nuclei always have equal but other magnetic charges they block out when there is no magnetic field. The particles tend to precess about the magnetic field lines, which is illustrated in physique 1. 3.

The nuclei complete a complete rotation about the magnetic field in a period that is immediately proportional to the effectiveness of the exterior magnetic field. As you can see from the figure 1. 4 the period gets smaller for a larger magnetic field and so the frequency of the precession rises. This rate of recurrence is fixed depending upon the effectiveness of the magnetic field, and is named the Larmor rate of recurrence and the partnership between them is distributed by:

f = (П‰)/ (2П)

Where ОҐ is a constant called the gyromagnetic regularity, which varies for every single kind of particle. In MRI the Larmor consistency is about 50 MHz, which is the radio consistency area of the magnetic frequency spectrum and the magnetic field has a magnitude of just one 1 or 2 2 Teslas.

Why is the Larmor occurrence is of this form?

TheLarmor frequencyinMRI is the speed of precession of the magnetic moment of the proton round the exterior magnetic field. The rate of recurrence of precession is related to the strength of the exterior magnetic field, B˜.

TheLarmor precession of nuclei of an substance put in a magnetic field B0 is determined from Larmor Formula, the Larmor precession is measured in Radians mere seconds-1:

П‰ = ОB˜

Where ОҐ is a frequent called the gyromagnetic regularity, which varies for each and every type of particle, however in the situation of MRI is a frequent when you are only affecting hydrogen nuclei. As the external magnetic field would be consistent and constant, to work out the Larmor frequency you need to divde the Larmor precession by 2Пf.

The frequency is measured in Hertz which is s-1 so that П‰ is measured in Radians moments-1 so to work through the rate of recurrence needed you separate this by 2Пf which results in the Larmor frequency which is per second.

The World wide web Magnetization Vector

The precession of the nuclei only has a tiny effect upon the total magnetic field, which is only a small upsurge in magnetic field along the exterior field axis.

This is because there are somewhat more nuclei in parallel to the external magnetic field, than nuclei that happen to be anti parallel to the exterior magnetic field. Although all the nuclei in the materials will be precessing at the Larmor rate of recurrence, they all may well not be in phase. Therefore the tranverse waves created by the nuclei get cancelled out which means that there will only be a tiny increase in field strength in direction of the exterior field as not absolutely all of the nuclei parallel to the exterior field are certain to get cancelled out.

Why do we need superconducting magnets to help make the protons resonate?

Superconducting magnets are used in magnetic resonance imaging of the human body because magnetic resonance imaging requires extremely uniform fields across the subject matter and extreme stableness as time passes. By getting the magnet coils in the superconducting status helps to achieve parts-per-million spacial uniformity over a space large enough to hold a person, and parts per million hour-1 stableness with time. This is the reason for using superconducting magnets alongside the fact that they are able to create a magnetic field of any magnituted of 1 one or two 2 Teslas.

How to help make the protons resonate?

In order to produce a magnetic resonance image we need to make the protons precess about the exterior field lines in phase with the other person ; that will produce a little net transverse field which rotates about the axis of the exterior field at the Larmor occurrence. This is actually the magnetic field that can be detected and in turn create a magnetic resonance image.

These three phases are all depend upon the nuclei precessing in phase with each other, this is performed by causing them absorb radio-frequency radiation of the same regularity of the Larmor consistency. The absorbtion of the vitality causes low-energy condition protons to flip in to the high-energy state, which means that the protons are anti-parallel to the external field lines and also precessing in period with the applied indication, which in turn mean that they are in phase with each other. The number of protons that flip is based upon the length of the radio rate of recurrence pulse, which is applied.

How a magnetic resonance image is produced:

In order for a magnetic resonance image to be produced, you should be able to discover the part of the body that has an ailment, to carry out this three smaller non even magnetic areas are added to the constant field. If you look at physique 1. 5 you are able to observe how these magnetic domains are applied, with one running the space of the patient's body, this is actually the z-axis which can be used to define slices through the body. The body in this diagram is the test, with the other magnetic domains being applied in the x-axis and y-axis, within the plane of a slice.

The magnetic field strength at any point is the amount of the four fields that sets a distinctive larmour rate of recurrence and phase at each point in the body.

To actually produce an image a pulse of electromagnetic rays is directed through your body at a place radio regularity. The protons with a Larmor rate of recurrence will absorb energy from the pulse and flip in to the higher energy state. Because of this a transverse field, which is revolving at the Larmor regularity, is produced for the precise part of the body. Due to Flemings Left hand rule, the revolving magnetic field that is actually an alternating field induces an electric current in the detector. The image is slowly but surely formed by sending a series of radio-frequency pulses through the body at different frequencies to choose the Larmor frequencies at different locations. The indicators produced and the leisure time included are processed by computer to put together the image.

How is a definite image is produced on the check?

The leisure time is the time considered for the protons to land back down with their lower energy condition after the radio-frequency pulse is switched off. The protons fall season to their lower energy point out by moving their energy on into neighboring atoms. The relaxation time is measured by the change in the depth of the signal induced in the detector. The leisure time can be used showing the contrast in tissue within an image, with the rest time dependent upon the type of atoms close to the stimulated protons. Thus a specific image of the muscle can be seen.

The safety of magnetic resonance imaging scanning:

MRI is regarded as one of the safest ways of confirming a medical diagnosis, although there are a few exceptions where a patient has form of steel in their body, which interferes with the powerful superconducting magnets, which allows a magnetic resonance image to be produced. A good example of something, that could cause a magnetic resonance image never to work, is tattoos which may have metallic fragments in the ink that can be used to create the image. The metal is dangerous because material items can be forcefully attracted to the magnet; if these material objects are inserted in your body, they can be attracted to the magnet and cause damage. The magnetic resonance image can also be dangerous for pregnant females.

Using magnetic resonance imaging to detect malignancy in the body

A future use of MRI is to discover cancer; cancer skin cells need a lot more energy than most other types of tissue in the body, so a fresh approach has just been developed where a patient suspected of having tumors is injected with glucose. This leads to a differing brightness on the image produced with the tumor showing up way brighter. Although this happens to be only a concept that is still a way from being used on the general public, and this is in part due to the fact that the magnetic field power used to create these results is much higher than used currently and we would need to see if the same results would be produced at a lower field durability.

Conclusion

In conclusion by firmly taking the simple model already in place MRI has a dazzling future in prognosis and recognition of diseases, with MRI being the safest form of diagnosis for soft cells because of this of its non-ionizing mother nature and clear results that this produces. The future for MRI will become brighter as the cost of using it comes over time, such that it could be more freely available and thus use for mass cancer tumor detection could happen for example.

MRI has recently had a major impact on procedures performed by doctors in examining a patients needs, and the use of MRI stands to keep these changes further as more uses are developed.

Bibliography

Introduction to MRI:

  • http://www. vistadiagnostics. co. uk/mri_explained. htm
  • http://www. teslasociety. com/mri. htm
  • http://www. nobelprize. org/nobel_prizes/medicine/laureates/2003/mansfield-bio. html

How does Magnetic Resonance imaging work?

  • http://technology. howstuffworks. com/mri. htm
  • http://www. magnet. fsu. edu/education/tutorials/java/mri/
  • http://www. ncbi. nlm. nih. gov/pmc/articles/PMC1121941/
  • Page 504-505 Advancing Physics By Steve Adams and Jonathon Allday

The larmor Frequency

http://radiopaedia. org/articles/larmor-frequency

The basic safety of MRI scanning

  • http://pain. about. com/od/testingdiagnosis/p/having_an_MRI. htm

Using MRI to find cancer in the body:

  • http://www. medicalnewstoday. com/articles/146309. php

Are there any modern alternatives to this technology?

  • http://www. medicinenet. com/mri_scan/page3. htm
  • http://www. nhs. uk/news/2013/07July/Pages/Could-new-tests-use-sugar-to-help-detect-cancer. aspx

Gihan Fernando1

[1] http://www. medicinenet. com/mri_scan/article. htm

[2] http://www. teslasociety. com/mri. htm

[3] http://www. vistadiagnostics. co. uk/mri_explained. htm

[4] Advanced Physics by Steve Adams and Jonathon Allday- Web page 504, Magnetic Resonance Imaging

[5] http://www. simplyphysics. com/page2_1. html

[6] http://radiopaedia. org/articles/net-magnitisation-vector

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