Introduction to MRI
• Magnetic
• Resonance
• Imaging
Bore
1.5-3.0 Tesla
Super conductive
Magnet, RF coils
Understanding and Reading
MRIs
How is this MRI Image produce?
Numbers
Transforming Radio Frequencies
into Images?
Let’s step back, and look at a device
that is familiar to all of us…the Radio
RF decoded
X 1021 / 5mm slice of tissue
Setting up the Machine
Surface coil
Reading the Images
The emitted energy of the protons
once the RF is stopped is affected by in
which tissue (the “lattice”) it resides:
fat, muscle, ligament, bone, brain, etc.
RF Pulse sequence parameters
which the technician adjusts
• The three pulse sequence parameters are
• Repetition time (TR) measured in msec
• Echo time (TE) measured in msec
• Flip angle measured in degrees
T1 and T2 relaxation times
Occur simultaneously and
independently of each other and form
the basis of tissue contrast in MRreconstructed images
T1
• Low TR (400-700 msec)
• Low TE (20-40 msec)
T2
• High TR (2,000-3,000 msec)
• High TE (40-70 msec)
Proton density
• High TE (2,000-3,000msec)
• Low TE (20-40 msec)
Basic Sequences
• T1 to view anatomy
• T2 to detect a pathologic process
(edema, swelling)
• Proton Density (PD)
great for ligamentous anatomy
Basic Pulse Sequences for MRI Imaging
Image type
Fat
Water
Advantage
T1
Bright
Dark
Anatomical detail
T2
Intermediate
Bright
++ edema
Fat
Suppressed
T2
Very Dark
Very Bright
++++ edema
Fat Suppression
A very valuable tool to define whether a
structure is composed of water (bright)
such as blood or fat (bone marrow)
Fat
Water
TI
Fat
Water
T2
Fat
Water
Intermediate
Bright
Fat
Water
T2 Fat Suppressed
Proton Density Fat Suppressed
(PD-S)
FAT
Water