1. Magnetic Resonance Imaging (MRI)
By: Kiara Stone

2. Initial Questions What is the purpose of the shape of an MRI machine?
How are principles of physics applied in the scanning of body tissue?
How does the MRI machine create a picture of the tissue in a specific area of the body?

3. How does magnetic resonance imaging relate to real life?
Magnetic resonance imaging (MRI) scans are used in the medical field to develop images of soft body tissue.
Can be used to detect injuries or abnormalities in tissue.

4. What is the purpose of magnetic resonance imaging?
An MRI scan targets body tissue that contains hydrogen atoms.
The MRI machine uses radio frequency to detect signals from protons in the H atoms.
The signals provide data that can be displayed in an MRI image.
Dark areas indicate a lack of hydrogen protons (ex. bone). Lighter areas are different types of tissue.
This is why an MRI image shows different hues of gray.

5. Basic Summary
A superconductive magnet surrounds the person getting the MRI.
The superconductive magnet has an electric current, which creates a magnetic field.
Once inside the magnetic field, the hydrogen atoms in the person’s body align with the magnetic field.
A radio transceiver (RF coil) uses radio frequency waves to send pulse signals to hydrogen atoms.
Hydrogen atoms send back signals to RF coils so data can be displayed.

6. Superconductivity
“The property of having no electrical resistance, exhibited by some substances at very low temperatures (originally, close to absolute zero)” (Oxford English Dictionary).
What does this mean?
A superconducting magnet is one that does not lose energy in the process of making electricity when surrounded by something really cold.
This is unlike an electromagnet, which has resistance to electricity (current of electrons is hindered by some other material).

7. Why is Superconductivity important?
The really cold substance (liquid helium) slows the atoms in the wire so electric current can travel through the wire coils easily
No resistance
Superconductive magnet creates a strong magnetic field
Costs less than using an electromagnet
Shape of the MRI machine – special wires coiled and surrounded by liquid helium to eliminate resistance in current.
Drawing on board – resistance of electrons and what happens when wire is cooled
Cooling the wire cools the ATOMS, which makes it easier for current of electrons to move through the wire

8. What does an MRI machine’s magnetic field look like?
A magnetic resonance imagining machine is made of coils of wire that are surrounded by a very cold substance (liquid helium). The coiled wire produces a magnetic field that looks like this 
The wire is called a solenoid
North and south poles

9. TIME FOR A DEMOSTRATION…
What does a mini-solenoid look like?

10. Hydrogen Atoms Humans are mostly water (H2O).
The strong magnetic field aligns the spinning protons of H atoms in a way that half of them are in line with the field, the other half are aligned in the opposite direction
This is called the magnetic moment

11. Spin The nucleus of an atom has a property called spin.
When placed in a magnetic field, the nuclei of the atoms in a body line up with the axis of the magnetic field. Why?
Spin allows the nuclei to absorb energy (in this case, radio frequency)
Larmor frequency  vL = yB where y = gyromagnetic ratio, B = strength of magnetic field applied
A nucleus’s spin will flip in the opposite direction when it absorbs energy at the Larmor frequency
Apply this to the protons in the nucleus of H2O atoms in the body.
Gyromacnetic ratio is the ratio of a nucleus’s magnetic dipole moment to its angular momentum.
WHY??????

12. Alignment of H atoms
Protons lined up in opposite directions cancel each other out.
Not all protons cancel out. A few more line up in one direction than in the other.
education/tutorials/ magnetacademy/mri/fullarticl e.html

13. ANOTHER DEMONSTRATION…
Magnetic file and compasses
Represents the effect of an MRI machine’s magnetic field on hydrogen protons (on a much smaller and weaker scale)
No magnetic force applied
Magnetic force applied in direction of arrows

14. Radio Frequency (RF)
Radio frequency coils in the MRI machine send RF pulses that are absorbed the aligned protons.
The RF pulses cause the protons to flip on their axes and send a signal back to the machine.
The signals from the protons provide data that allows an image to be formed based off of the concentration of hydrogen protons in particular areas.

15. Questions I Still Have
Are the physics of magnetic resonance imaging similar to the principles of other types of scans such as:
computed tomography (CT) scans?
positron emission tomography (PET) scans?
Electroencephalograph (EEG) scans?

16. Works Cited
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agnetacademy/mri/fullarticle.html
agnetminute/superconductingmagnet- transcript.html
ools/2006/Medical_Imaging/mriphysics1.html