physics : MRI

Question 1

what does MRI stand for

Answer 1

magnetic resonance imaging

Question 2

how does MRI work

Answer 2

uses the magnetism of nuclei within the body

Question 3

MRI will prompt these reactions

Answer 3

• atoms line up depending on their magnetic moment
• atoms relax depending on what sort of perturbations given to mm
• atoms relax to original states => gives info that will build into an image

Question 4

atoms with an even number of protons

Answer 4

have no magnetism

Question 5

atoms with an odd number of protons

Answer 5

have slight magnetism

Question 6

hydrogen is the most common

Answer 6

atom with an odd no. of protons

Question 7

protons in a magnetic field

Answer 7

have a microscopic magnetisation & they spin within that magnetic field

Question 8

protons spin

Answer 8

in 2 diff directions or 2 diff axes in that magnetic field

Question 9

rate of precession is

Answer 9

resonance or larmor frequency

Question 10

radiofrequency… what & at the larmor frequency

Answer 10

an electromagnetic field

43Hz per tesla

Question 11

where to apply an RF pulse

Answer 11

at right angles to main field

Question 12

what happens with RF

Answer 12

• atoms absorb en preferentially
• spins of protons flip 90 degrees and now perpen to magnetic field
• magnetic moment changes direction

Question 13

what happens when the magnetic moment changes direction

Answer 13

• longitundal magnetism decreases , ,transverse on created
• protons spin together therefore theyre along the line of RT pulse
• theref giving a strong magnetic signal

Question 14

T1 spin lattice relaxation

Answer 14

• transverse magnetism goes back to longitundal
• kinda slow process… few secs
• 90 degree flips relaxes back to vertical direction