james d. christensen, ph.d. iu school of medicine

BME 595 - Medical Imaging ApplicationsPart 2: INTRODUCTION TO MRI

Lecture 3 Multi-Dimensional Imaging

Feb. 28, 2005

James D. Christensen, Ph.D.IU School of Medicine

Department of RadiologyResearch II building, E002C

jadchris@iupui.edu317-274-3815

ReferencesOnline resources for introductory review of MRI physics:

Robert Cox’s book chapters online http://afni.nimh.nih.gov/afni/edu/See “Background Information on MRI” section

Mark Cohen’s intro Basic MR Physics slideshttp://porkpie.loni.ucla.edu/BMD_HTML/SharedCode/MiscShared.html

Douglas Noll’s Primer on MRI and Functional MRIhttp://www.bme.umich.edu/~dnoll/primer2.pdf

Joseph Hornak’s Web Tutorial, The Basics of MRIhttp://www.cis.rit.edu/htbooks/mri/mri-main.htm

Book covering Multi-Dimensional MRI:E. Mark Haacke, et al. Magnetic Resonance Imaging: Physical Principles and Sequence

Design, 1999.

Phase-Encoding

2D Gradient-Echo Pulse Sequence (a)

2D Gradient-Echo Pulse Sequence (b)

2D Gradient-Echo K-Space

Multi-Slice 2D Pulse Sequence

Multi-Slice 2D Slice Excitation

2D Echo-Planar Imaging (EPI)

Pulse Sequence K-Space Trajectory

3D Gradient-Echo Pulse SequencePhase Spoiling:

(RF or gradients) causes Incoherence in transverse magnetization

Fast-Imaging(Steady-State Incoherent pulse sequence)

The steady-state equilibrium magnetization is

where

The transverse magnetization following the nth RF pulse is

For a train of RF pulses repeated every TR seconds

The Steady-State Incoherent signal intensity is proportional to M

Flip Angle (θ), TR & T1 in Fast Imaging

where

Steady-State Incoherent (SSI) signal intensity:

Flip Angle (θ), TR & T1 in Fast Imaging

where

Steady-State Coherence Pulse Sequence

Steady-State Coherence Pulse Sequence

Chemical-Shift Imaging (CSI)

Chemical-Shift Imaging (CSI)

Chemical-Shift Imaging (CSI)

Chemical-Shift Imaging (CSI)

Homework

Problem 1