Introduction to MRI• Magnetic

• Resonance

• Imaging

Bore1.5-3.0 TeslaSuper conductive Magnet, RF coils

Understanding and Reading MRIs

How is this MRI Image produce?

Numbers

Transforming Radio Frequenciesinto Images?

Let’s step back, and look at a device that is familiar to all of us…the Radio

Encoded RF “1060

on your dial”

RF decoded

X 1021 / 5mm slice of tissue

Setting up the Machine

Surface coil

Reading the Images

The emitted energy of the protonsonce the RF is stopped is affected by in which tissue (the “lattice”) it resides: fat, muscle, ligament, bone, brain, etc.

RF Pulse sequence parameterswhich 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 andindependently of each other and formthe basis of tissue contrast in MR-reconstructed 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)

TIFat

Water

T2Fat

Water

Fat Water

Intermediate Bright

T2 Fat Suppressed

Water

Fat

Proton Density Fat Suppressed (PD-S)

FAT

Water