Essentials of Functional MRI

During the last two decades, new developments in functional MRI (magnetic resonance imaging) have made it possible to detect changes in the brain over time, as opposed to the "snapshot" produced by conventional MRI. Essentials of Functional MRI breaks down the technical challenges for physicians, researchers, and technologists who use functional MRI but may not be experts in the necessary math and physics. The author describes the theory and practical details of functional MRI (fMRI) methodology, including how to acquire and analyze images, and a wide range of examples demonstrate how fMRI has been used thus far. The author provides the essential information to study, understand, use, and teach the practical aspects of fMRI for those people who are most likely to extend its use into clinical practice.

Introduction

Basic Concepts

Basic Anatomy of an MRI System

Representing Images with Numbers and Vice Versa

Recurring Math Concepts: Representing Data as Sums of Meaningful Components

Source of the MR Signal and Its Properties

Origins of the MR Signal.

The Equilibrium State—Magnetization in Tissues Behavior of the Magnetization When Not at Equilibrium. Pushing the Magnetization Away from Equilibrium—The RF Pulse Detecting the MR Signal. Relaxation Back to Equilibrium Observing the Effects of Relaxation

The Fundamental Building Blocks of MRI Methods: Spin Echoes and Gradient Echoes

The Need for Echoes

Spin Echo

Gradient Echo.

Steady-State Methods and Stimulated Echoes.

Steady-State Methods

Stimulated Echoes.

Signal Weighting and Contrast

Inversion-Recovery Methods

Magnetization Transfer Contrast

Summary

Creating an Image from the Magnetic Resonance Signal

Spatially Selective Radio-Frequency Pulses

Encoding Spatial Information into the MR Signal to Create an Image

Constructing an Image from k-Space

Signal Strength, Imaging Speed, and Spatial Resolution—You Cannot Have It All Fast Imaging Methods Parallel Imaging Causes of Image Artifacts and Distortion

Principles and Practice of Functional MRI

How MRI Becomes Functional MRI

Contrast Mechanisms: Linking the MR Signal and Neural Function

General BOLD fMRI Methods

Special Regions.

Specific Examples of fMRI Applications—Setting the Acquisition Parameters Alternative Contrast Mechanisms

Functional MRI Study Design

Basic Principles of fMRI Study Design

Choice of Stimulation Method or Task

Choice of the fMRI Study Design

Order and Timing of Presentation of Tasks or Stimuli

Timing of Tasks or Stimuli, Duration, Sampling Rate.

Summary of Factors Influencing fMRI Study Design

Functional MRI Data Analysis

Hypothesis Testing

fMRI Analysis Software.

Preprocessing

Data Analysis Methods

Statistical Threshold, and Correction for Multiple Comparisons

Group Analysis

Interpretation of fMRI Results—What Do They Really Mean?

Clinical Applications of Functional MRI

Examples of Current Clinical Applications of fMRI.

Examples of Forthcoming Clinical Applications

Patrick. W. Stroman, Ph.D., is now an associate professor Queen’s University in Ontario, Canada. He holds a Canada research chair in imaging physics, and leads a research program that focuses on the development of spinal fMRI as a tool for clinical assessments and spinal cord research.