Magnetic Resonance Image Artifacts

Outline

Mind Map

Learning Objectives

Teaching Visuals

Online Module
(Requires Enrollment)

Text Reference

 

Outline and Learning Guide


INTRODUCTION AND OVERVIEW

MOTION-INDUCED ARTIFACTS

Phase-Encoded Direction

Cardiac Motion

Triggering

Flow Compensation

Respiratory Motion

Averaging

Ordered Phase Encoding

Regional Presaturation

Flow

Regional Presaturation

Flow Compensation

ALIASING ARTIFACTS

CHEMICAL-SHIFT ARTIFACTS

Field Strength

Bandwidth

MIND MAP and SUMMARY

 

 

Learning Objectives

 

  • Name and briefly describe the types of motion in a patient's body that can produce artifacts in MR images.
     

  • Describe the general appearance of typical MR image artifacts.
     

  • Briefly describe the types of MR image artifacts that are associated with the phase-encoded-direction.
     

  • Briefly describe the types of MR image artifacts that are associated with the frequency-encoded direction.
     

  • Briefly explain the general difference between motion blurringand motion artifacts in MR imaging.
     

  • Explain why motion artifacts appear as streaks in the phase encoded direction.
     

  • Describe the technique of cardiac triggering and why it is used in MR imaging.
     

  • Briefly describe the concept of flow compensation and why it is useful for artifact suppression.
     

  • Briefly explain why the technique of averaging can be useful in reducing artifacts from respiratory motion.
     

  • Describe the concept of ordered phase-encoding and how it is used.
     

  • Describe the process of using regional pre-saturation to suppress artifacts from respiratory motion.
     

  • Describe how the technique of regional pre-saturation is used to suppress artifacts produced by flowing blood.
     

  • Briefly explain why the technique of flow compensation might be useful in imaging procedures where you want to see bright rather than black blood.
     

  • Describe the type of artifact that can occur if the image FOV is smaller than the anatomical body section and appropriate suppression techniques are not used.
     

  • Explain and illustrate the concept of the over-sampling technique used to reduce fold-over or wraparound artifacts.
     

  • Explain and illustrate how regional pre-saturation can be used to reduce fold-over or wraparound artifacts.
     

  • Describe the chemical-shift artifact and what causes it.
     

  • Explain why there is a relationship between the chemical-shift artifact and magnetic field strength.
     

  • Describe the relationship between RF receiver bandwidth and the amount of chemical-shift artifact.
     

  • Explain why it is not usually good practice to select the widest possible bandwidth to reduce the chemical-shift artifact.
     

 

 

Text Reference

Chapter 1

Magnetic Resonance Imaging: Principles, Methods, and Techniques
Medical Physics Publishing,  http://www.medicalphysics.org

 

 

Mind Map