Magnetic resonance imaging

Under the supervision of:Dr.Mohamed Hesham

Prepared by :Ahmed Mostafa Hassan Elsayed Elsaghier

Magnetic Resonance Imaging :

Is the way medical imaging to illustrate the pathological changes in living tissue and magnetic resonance non-medical uses of physical hand they rely on the so-called nuclear magnetic tone RMN. Magnetic resonance imaging is costly tests and is permanently available in many hospitals, and there are difficulties when making this type of radiation in patients who are afraid of enclosed spaces or patients who complain of excessive obesity.

MRI :Start date and the birth of the idea of magnetic resonance in year 1945-1946 When won world Felix Bloch & Edward Purcell the Nobel Prize for his discovery of MRI. Developed by the world's Erwin Hahn in 1950. Developed for medical use in 1973 at the hands of the British and American worlds Peter Mansfield & Paul Aoterbr. 1976 published the first picture of a magnetic resonance toe. And in 1977 published the first full body imaging. It should be noted that the MRI initially use in chemical plants only after it has been updated to enter the medical field. Initially called nuclear magnetic resonance, but later changed the name to the public fear and sensitive of the word nuclear was intended by the nucleus of an atom of nuclear radiation itself.

The idea magnetic resonance :The idea MRI to stimulate the protons in the

atoms in the body to launch signal, and then picked up and determine its location in the body and displayed on a scale of gray color indicates the signal strength, and gradually be different tissues in the body.

More of these elements is hydrogen and stimulation that he was in abundance in living bodies & the of a single proton in the atomic nucleus, giving it more power than the rest of the items on the version of the signals used in magnetic resonance imaging.

MRI types :There are different types and multiple day with many

ideas for magnetic resonance imaging devices, in general, there are three main types of magnetic resonance: 

PermanentResistantAnd anti-resistance

- MRI generally contains part gives the strong magnetic field & part issued radio waves to stimulate the protons and captures the incoming signal & progressive part of the system.

  - Survey, which is used in the medical cost areas million

per Tesla and several hundreds of thousands of dollars are spent annually in maintenance. - Used computers mainly in MRI scans and advanced programs effectively help to give the best results.

Magnetic Resonance Physics :The device consists of an electromagnet coil huge for the formation of a magnetic field around the patient produces a magnetic field 2 Tesla equivalent to 20,000 Gauss. 

- This area makes hydrogen atoms Taatmgnt all tend to its magnetic north Vtaatouhd part in one direction. After piece displays the body to radiation Mveaih lead to increased energy these atoms and piece will change its direction to a certain degree, leaving us an atom of every million corn is the process of magnetic resonance imaging, a large number of atoms enough for the emergence of a clear picture of you very much to be photographed and sent a couple of energy reverse. This inverse receive energy from the device are calculated and composed in the form of a photo This picture shows the intensity of hydrogen in every region of the body. Using this image doctors can discover a lot of diseases.

the emergence of a clear picture of you very much to be photographed and sent a couple of energy reverse. This inverse receive energy from the device are calculated and composed in the form of a photo This picture shows the intensity of hydrogen in every region of the body. Using this image doctors can discover a lot of diseases.

- When provoked atoms in the body are protons movement with & against the direction of the magnetic field the main, getting protons approval to the direction of the main for protons anti small amounts but very important to get the picture later, and disturbed these protons, especially radio waves Climate of set of vertical to horizontal, but What soon return to equilibrium mode, but to return to equilibrium situation there important Toukatan.

Time horizontalTime the fastest time in the horizontal is the scattering of

protons on the horizontal axis.

Time verticalTime vertical a time when protons return to equilibrium mode - It should be noted that Altoqatn occur concurrently to each

other. - Measured energy magnets used in magnetic resonance imaging

unit tesla is equal to 10,000 Gauss, measuring the earth's average magnetic found to be equal to half Gauss.

 

Proton density - The number of active protons per unit volume of tissue, and vary the

density of the fabric to another fabric. 

Echo cycle - After the impact of protons by radio waves are broadcast waves again it

goes back 180 °, and measured the length of time between the first 90 ° impact and influence, 180 ° Time echo.

Echo cycle- After the impact of protons by radio waves

are broadcast waves again it goes back 180 °, and measured the length of time between the first 90 ° impact and influence, 180 ° Time

MRI uses :Using magnetic resonance diagnostic is for the purpose

of such imaging veins and arteries, or filming neurological changes in the brain, and magnetic resonance imaging is considered the best types to clarify the tissues and body fluids, as well as used to plan treatment plans based on radiation therapy. By magnetic resonance medical history should be reviewed fully and make sure there is no previous surgery or accidents led to the presence of metals in the body, such as shrapnel, and be sure that the cross-scan routine & passage of the patient through the metal detector. Often gives the patient a special dye is injected into the body so as to increase the contrast and clarify parts converged.

Magnetic resonance image :Composed image magnetic resonance of several columns and rows called another question matrix, each column description contains the boxes called pixel, distributes signals captured from the body on these boxes so arranged as arranged in the body, and this mechanism relies on a graded gives each segment of the body force specific signal, and the signal strength captured give color to grayscale, consists us a picture of magnetic resonance image gray gradient. - Private equation clarity is:

 Number of boxes per cm = 1 / size of the box - The contrast in the image depends on the vertical and

horizontal times and proton density and called (internal influences), and the echo time and repetition oukt considered (externalities.

Definition (IMAGE RESOLUTION)

More MRIs consists of two dimensions, each divided into a network of sham rectangular elements called (pixels) pixels.

 Intensity in each pixel depends on the strength

of the magnetic resonance wave emitted from the region that they contain.

 Image size depends on the number Baksalat,

and Most images consisting of 265 Pixels vertically and 256 horizontally Pixels.

Definition clarity (image resolution):is the system's ability to distinguish between two separate

points. Control sizes Alfoxlat (volumetric picture elements) (voxels) in

clarifying the image (image resolution) as the small-Alfoxlat images be good evacuation and thus make it easier for the system to differentiate between small body components. 

- Factors affecting the evacuation and size Alfoxl: Thickness of the slide.Field of view FOV.Matrix moot. - Factors that control the supply and field dimensions Alfoxl: The strength of the magnetic field out.Time taken for each sample (bandwidth) for the progressive

field.

Contrast (CONTRAST) :Signal strength klmazadt from pixel greater the brightness of the image at that pixel. 

To distinguish between tissues in the picture, every tissue has a different brightness These Aldahirh called mixed. 

And can be divided into the factors affecting the variance into two groups .

Internal factors: a change stromal factors .Proton density PD .

Longitudinal relaxation T1 :

Transverse relaxation T2 :

External factors: These are factors that can be changed by the operator: 

Repetition time TR .Time of excitement TE .And change the power of the wave with the

changing weights multiplied by three, namely: Proton density.T1 weighted: a guest T1 and TR .Weighted T2: a guest T2 and TE .This relationship can be represented in the

following equation :Signal = (p (H) [1-exp (-TR/T1)] × [exp (-TE/T2 ([

We can deduce from the equation that we can change the contrast by changing one of the external factors: 

For example: if we want weighted density proton must finish effect weights other T1 and T2 and we did it change in external factors, if we are weighted T1 must all be from the time of recurrence and time thrills short, and if we are weighted T2 must be Taiwilan, if we are likely proton density must be a long time repetition and thrills short time .

Safety in the Magnetic Resonance

No, as is the case in CT imaging and general risk ionization radiation, but no magnetic resonance as is the case in all the use of certain medical risks  .

Risk magnetization metals and grabbed the device  .

Loud sounds produced during the test .

Claustrophobia .A helium leak in the ultra

Delivery.

Index : 2 Magnetic Resonance Imaging

3 History

5 MRI types

6 Magnetic Resonance Physics

11 MRI uses

20 Safety in the Magnetic Resonance

References :

Physics Serway .http://ar.wikipedia.org .

In the end ……I hope to be able to benefit the reader