Introduction to MRI Magnetic Resonance Imaging Bore 1

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

060 1 “ F R ed Encod dial” r on you RF decoded

X 1021 / 5 mm 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

T 1 and T 2 relaxation times Occur simultaneously and independently of each other and form the basis of tissue contrast in MRreconstructed images

T 1 • Low TR (400 -700 msec) • Low TE (20 -40 msec) T 2 • High TR (2, 000 -3, 000 msec) • High TE (40 -70 msec) Proton density • High TE (2, 000 -3, 000 msec) • Low TE (20 -40 msec)

Basic Sequences • T 1 to view anatomy • T 2 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 T 1 Bright Dark Anatomical detail T 2 Intermediate Bright ++ edema Fat Suppressed T 2 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 T 2 Fat Water Intermediate Bright

Fat Water T 2 Fat Suppressed

Proton Density Fat Suppressed (PD-S) FA T Water