2: MRI Flashcards
What is the Larmor frequency for hydrogen?
42.58 MHz/T
The strength of the static magnetic field is determined by
current flow through the coil
The static magnetic field of MRI is _____ x stronger than Earth’s magnetic field.
100k
Different T (tesla) define…
the strength of the magnet
Homogeneity of the magnetic field (____) …
(equal magnet force throughout) is important to reduce noise. This can be achieved through coils wrapping over a longer distance with a smaller diameter.
Why do we focus on hydrogen atoms in MRI?
- They have a single proton (+vely charged) and they spin.
- A charge with a spin is required to form a magnetic field (each hydrogen nucleus is like a magnet)
- they align with the static magnetic field
- 70% of our bodies comprise of hydrogen
T2 decay results from…
changes in the synchronization of the hydrogen ions as they rotate in the x, y (transverse) plane
Following an RF pulse (90 degrees to the Z (B0) plane), the magnetic signals from hydrogen atoms are detected in the…
transverse (X, Y) plane
Axial slice selection in MRI involves the combined use of
Z Gradient coil and an appropriate radio-frequency (RF) pulse.
spatial encoding within a slice involves
changing the magnetic field in the Y and X directions (transverse plane) using gradient coils
TR refers to
the time interval between successive RF pulses, usually measured in seconds
TE refers to
Time from excitation to measurement
measurement = DAQ = Data accquisition
TE: Short | TR: intermediate
T1 contrast
TE: Intermediate | TR: long
T2 contrast
TE: Short | TR: long
Proton density imaging
