Transcript An Introduction to Functional MRI

Welcome to the fMRI course.
Please sign in before taking
your seat.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
An Introduction to
Functional MRI
FMRI Graduate Course (NBIO 381, PSY 362)
Dr. Scott Huettel, Course Director
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Some Introductions: People
Course Director:
Scott Huettel
Associate Professor, Psychology & Neuroscience, BIAC, CCN
Research Interests: Decision making, neuroeconomics
Teaching Assistant:
David V. Smith
Graduate Student, Psychology & Neuroscience, IPCN
Research Interests: Decision making, social rewards
Michele Diaz
FMRI – Week 1 – Introduction
Jim Voyvodic
Allen Song
Scott Huettel, Duke University
Some Introductions: Places
Duke-UNC
Brain Imaging &
Analysis Center (BIAC)
Duke Teaching and Learning
Center, “The Link”
BIAC Offices and Analysis
Laboratory, Bell Building
www.biac.duke.edu
MRI Scanners (3T, 4T), Duke Hospital
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Overview of the Course
•
Lectures
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•
Readings
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Wednesdays 3-4:30pm
Perkins -- “The Link”, Seminar Room 4
Functional Magnetic Resonance Imaging (Huettel, Song, McCarthy)
Original papers, posted to website (optional)
Laboratories
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–
Wednesdays 4:30-6:00pm
Additional times arranged with TAs and instructor (group)
• David is planning on office hours on Tuesdays (in the Link)
•
Grading Basis
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Attendance
Weekly laboratory exercises (group)
Self-assessment exercises
Mid-term examination
Project presentation (group)
Course auditors are welcome to attend lectures!
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Course Textbook
• First edition (2004): Required
• Selected chapters from new
edition (2008) will be provided by
instructor
• REQUIRED: Self-assessment
questions available on
accompanying CD
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Each week has lecture and laboratory components
Labs start next week.
In late September, you will form small groups for your
fMRI projects. We’ll go over the project phase of the
course in great detail around then.
We will introduce the analysis package FSL in a
session in this room.
The midterm on 10/8. Auditors are welcome to take it
for fun.
There may be slight changes to the order and coverage
of topics in the final weeks.
Each group will present their projects at a session during
the normal final examination period.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Course logistics…
or “What you need to do!”
1.
Get a copy of the course textbook.
2.
Find a partner for laboratory exercises. Most people
will be in groups of 2; we can have one group of 3 as
necessary.
3.
Be aware of TA and computer availability for
laboratories.
4.
During the semester, download course materials from
the class website:
http://www.biac.duke.edu/education/courses/fall07/fmri/
(all materials will also be available on BlackBoard)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Any questions?
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Outline for Today
• Lecture: Introducing fMRI
–
–
–
–
–
What is fMRI?
History
Key concepts
Parts of a MR scanner
MR safety
• Laboratory: Scanner Visit (Dr. Jim Voyvodic)
– Scanner hardware
– Stimulus presentation and recording hardware
– Demonstration of real-time fMRI (??)
Note: I will post all slides to the course web page!
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
1. What is fMRI ?
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
isn’t
1. What is fMRI ?
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
fMRI is not bumpology
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
• Phrenology claimed that
bumps on the skull reflected
exaggerated functions/traits
• It lacked any mechanism
underlying its claims.
from Gall (c. 1810)
• It used anecdotal, rather than
scientific, evidence.
• Nevertheless, its central idea
persisted:
Localization of Function
Franz Joseph Gall
(1758-1828)
FMRI – Week 1 – Introduction
Johann Spurzheim
(1776-1832)
Scott Huettel, Duke University
fMRI is not mind-reading
This is not a
thought.
This is not a thought.
This is not an anti-thought.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
fMRI is not a window on the brain
“Mirror neuron activity in the right posterior
inferior frontal gyrus – indicating
identification and empathy - while watching
the Disney/NFL ad.”
rIFG
vent
Str
“Ventral striatum activity – indicating
reward processing - while watching
the Disney/NFL ad.”
[Citations omitted to protect the offenders.]
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
fMRI is not invasive
Positron Emission
Tomography (PET)
Intracranial
Stimulation / Recording
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
FMRI is… a technique for measuring
metabolic correlates of neuronal activity
•
•
•
•
•
Uses a standard MRI scanner
Acquires a series of images (numbers)
Measures changes in blood oxygenation
Use non-invasive, non-ionizing radiation
Can be repeated many times; can be used for a wide
range of subjects
• Combines good spatial and reasonable temporal
resolution
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
fMRI is a Measurement Technique…
Manipulation Techniques
Lesions, TMS, Stimulation
BRAIN
BEHAVIOR
Measurement Techniques
fMRI, PET, EEG
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
… that provides information about a
wide range of topics.
From what we see…
(ocular dominance columns)
Cheng, Waggoner, & Tanaka (2001) Neuron
FMRI – Week 1 – Introduction
… to what we feel.
(the dread of an upcoming shock)
Berns et al. (2006) Science
Scott Huettel, Duke University
2. History of fMRI
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Timeline of MR Imaging
1924 - Pauli
suggests that
nuclear particles
may have angular
momentum (spin).
M
1920
1972 – Damadian
patents idea for large
NMR scanner to
detect malignant
tissue.
1937 – Rabi measures
magnetic moment of
nucleus. Coins
“magnetic resonance”.
1944 – Rabi wins
Nobel prize in
Physics.
1952 – Purcell and
Bloch share Nobel
prize in Physics.
1930
1940
R
1950
1946 – Purcell shows
that matter absorbs
energy at a resonant
frequency.
1946 – Bloch demonstrates
that nuclear precession can
be measured in detector
coils.
FMRI – Week 1 – Introduction
1960
1959 – Singer
measures blood flow
using NMR (in
mice).
1985 – Insurance
reimbursements for
MRI exams begin.
1973 – Lauterbur
publishes method for
generating images
using NMR gradients.
MRI scanners
become clinically
prevalent.
NMR becomes MRI
1970
1980
1973 – Mansfield
independently
publishes gradient
approach to MR.
1990
2000
1990 – Ogawa and
colleagues create
functional images
using endogenous,
blood-oxygenation
contrast.
1975 – Ernst
develops 2D-Fourier
transform for MR.
Scott Huettel, Duke University
Early Uses of NMR
• Most early NMR was used for chemical analysis
– No medical applications
• 1971 – Damadian publishes and patents idea for using
NMR to distinguish healthy and malignant tissues
– “Tumor detection by nuclear magnetic resonance”, Science
– Proposes using differences in relaxation times
– No image formation method proposed
• 1973 – Lauterbur describes projection method for
creating NMR images
– Mansfield (1973) independently describes similar approach
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
The First ZMR NMR Image
Lauterbur, P.C. (1973). Image formation by induced local interaction: Examples employing nuclear magnetic resonance. Nature, 242, 190-191.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Early Human MR
Images (Damadian)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Mink5 Image – Damadian (1977)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Digression: 2003 Nobel Controversy
Paul Lauterbur
FMRI – Week 1 – Introduction
Peter Mansfield
Scott Huettel, Duke University
Raymond Damadian
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
New York Times
October 9, 2003
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Nobel Press Release
October 6, 2003
Summary
Imaging of human internal organs with exact and non-invasive methods is very important for medical diagnosis,
treatment and follow-up. This year's Nobel Laureates in Physiology or Medicine have made seminal discoveries
concerning the use of magnetic resonance to visualize different structures. These discoveries have led to the
development of modern magnetic resonance imaging, MRI, which represents a breakthrough in medical
diagnostics and research. …
This year's Nobel Laureates in Physiology or Medicine are awarded for crucial achievements in the development of
applications of medical importance. In the beginning of the 1970s, they made seminal discoveries concerning the
development of the technique to visualize different structures. These findings provided the basis for the
development of magnetic resonance into a useful imaging method.
Paul Lauterbur discovered that introduction of gradients in the magnetic field made it possible to create twodimensional images of structures that could not be visualized by other techniques. In 1973, he described how
addition of gradient magnets to the main magnet made it possible to visualize a cross section of tubes with ordinary
water surrounded by heavy water. No other imaging method can differentiate between ordinary and heavy water.
Peter Mansfield utilized gradients in the magnetic field in order to more precisely show differences in the
resonance. He showed how the detected signals rapidly and effectively could be analysed and transformed to an
image. This was an essential step in order to obtain a practical method. Mansfield also showed how extremely rapid
imaging could be achieved by very fast gradient variations (so called echo-planar scanning). This technique became
useful in clinical practice a decade later.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Timeline of MR Imaging
1924 - Pauli suggests
that nuclear particles
may have angular
momentum (spin).
M
1920
1972 – Damadian
patents idea for large
NMR scanner to
detect malignant
tissue.
1937 – Rabi measures
magnetic moment of
nucleus. Coins
“magnetic resonance”.
1944 – Rabi wins
Nobel prize in
Physics.
1952 – Purcell and
Bloch share Nobel
prize in Physics.
1930
1940
R
1950
1946 – Purcell shows
that matter absorbs
energy at a resonant
frequency.
1946 – Bloch demonstrates
that nuclear precession can be
measured in detector coils.
FMRI – Week 1 – Introduction
1960
1959 – Singer
measures blood flow
using NMR (in
mice).
1985 – Insurance
reimbursements for
MRI exams begin.
1973 – Lauterbur
publishes method for
generating images
using NMR gradients.
I
1970
MRI scanners
become clinically
prevalent.
NMR becomes MRI
1980
1973 – Mansfield
independently
publishes gradient
approach to MR.
1990
f
2000
1990 – Ogawa and
colleagues create
functional images
using endogenous,
blood-oxygenation
contrast.
1975 – Ernst
develops 2D-Fourier
transform for MR.
Scott Huettel, Duke University
Physiology (BOLD Contrast)
Blood-OxygenationLevel Dependent
contrast
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Using MRI to Study Brain Function
Kwong, et al., 1992
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Visual Cortex
Scott Huettel, Duke University
Growth in fMRI : Published Studies
1990
1991
1992
1993
1994
1995
Medline search on “functional magnetic
resonance”, “functional MRI”, and “fMRI”.
1996
Year 2004 = ~1500; Years 2005+ > 2000
1997
1998
1999
2000
2001
2002
2003
…
2004
0
200
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400
600
800
1000
1200
1400
Scott Huettel, Duke University
3. Key Concepts
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Key Concepts
•
•
•
•
Contrast
Spatial Resolution
Temporal Resolution
Functional Resolution
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Contrast: Conceptual Overview
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Contrast: Anatomical
Contrast:
1) An intensity difference between quantities: “How much?”
2) The quantity being measured: “What?”
Contrast-to-noise: The magnitude of the intensity difference between quantities
divided by the variability in their measurements.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Contrast: Functional
Contrast-to-noise is critical for fMRI: How effectively can we decide
whether a given brain region has property X or property Y?
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Spatial Resolution: Voxels
Voxel: A small rectangular prism that is the basic sampling unit of fMRI.
Typical anatomical voxel: (1.5mm)3. Typical functional voxel: (4mm)3.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Spatial Resolution: Examples
~8mm2
~4mm2
~1.5mm2
FMRI – Week 1 – Introduction
~2mm2
~1mm2
Scott Huettel, Duke University
Temporal Resolution
• Determining factors
– Sampling rate, usually repetition time (TR)
– Dependent variable, usually BOLD response
• BOLD response is sluggish, taking 2-3 seconds to rise above baseline
and 4-6 seconds to peak
– Experimental design
• Most FMRI studies have temporal resolution on the order of a
few seconds
– With specialized designs and data acquisition, this can be
improved to ~100ms
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Functional Resolution
The ability of a measurement technique to identify the
relation between underlying neuronal activity and a
cognitive or behavioral phenomenon.
Functional resolution is limited both by the intrinsic
properties of our brain measure and by our ability to
manipulate the experimental design to allow variation
in the phenomenon of interest.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
4. MRI Scanners
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
GE 3T Scanner (cf. BIAC’s)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Phillips 3T Scanner (Vanderbilt)
Siemens 3T Scanner
Phillips 0.6T Open Scanner
FMRI – Week 1 – Introduction
FONAR 0.6T MR
Operating Room
Scott Huettel, Duke University
Main Components of a Scanner
1. Magnetic: Static Magnetic Field Coils
2. Resonance: Radiofrequency Coil
3. Imaging: Gradient Field Coils
•
•
•
Shimming Coils
Data transfer and storage computers
Physiological monitoring, stimulus display, and
behavioral recording hardware
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
1. Magnetic: Static Field Coils
The scanner contains large parallel
coilings of wires.
These generate the main magnetic field
(B0), which gives the scanner its field
strength (e.g., 3T).
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
2. Resonance: Radiofrequency Coils
Surface Coil
Volume Coil
Electronic coils tuned
to radio signals send
energy into the brain
and record an emitted
“echo”.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
3. Imaging: Gradient Coils
Three gradient coils are
used, one in each of the
cardinal directions.
These allow spatial
encoding of the MR signal.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
The scanner is
controlled by a
pulse sequence.
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Pulse Sequences
T1
T2
• Recipes for controlling scanner hardware
• Allow MR to be extremely flexible
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
5. MRI Safety
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Hospital Nightmare
Boy, 6, Killed in Freak MRI Accident
July 31, 2001 — A 6-year-old boy died after
undergoing an MRI exam at a New Yorkarea hospital when the machine's powerful
magnetic field jerked a metal oxygen tank
across the room, crushing the child's head.
…
ABCNews.com
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
MR Incidents
• Pacemaker malfunctions leading to death
– At least 5 as of 1998 (Schenck, JMRI, 2001)
– E.g., in 2000 an elderly man died in Australia after being twice
asked if he had a pacemaker
• Blinding due to movements of metal in the eye
– At least two incidents (1985, 1990)
• Dislodgment of aneurysm clip (1992)
• Projectile injuries (most common incident type)
– Injuries (e.g., cranial fractures) from oxygen canister (1991, 2001)
– Scissors hit patient in head, causing wounds (1993)
• Gun pulled out of policeman’s hand, hitting wall and firing
– Rochester, NY (2000)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Issues in MR Safety
• Known acute risks
– Projectiles, rapid field changes, RF heating,
claustrophobia, acoustic noise, etc.
• Potential acute/chronic risks
– Current induction in tissue at high fields?
– Changes in the developing brain?
• Epidemiological studies of chronic risks
– Extended exposure to magnetic fields does not cause harm
• Difficulty in assessing subjective experience
– In one study, 45% of subjects exposed to a 4T scanner
reported unusual sensations (Erhard et al., 1995)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Projectile Effects: External
The Scanner
is Never Off!
Chaljub (2001)
Schenck (1996)
“Large ferromagnetic objects that were reported as having been
drawn into the MR equipment include a defibrillator, a wheelchair, a
respirator, ankle weights, an IV pole, a tool box, sand bags containing
metal filings, a vacuum cleaner, and mop buckets.”
-Chaljub et al., (2001) AJR
Chaljub (2001)
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
Any questions?
FMRI – Week 1 – Introduction
Scott Huettel, Duke University
BIAC Scanner Tour
•
Dr. Jim Voyvodic will demonstrate real-time fMRI
–
–
•
We will see the 3T BIAC scanner in action
Go through the mock scanner
You’ll go through low-field areas of the MR center
–
–
Anyone with pacemaker, other implanted metal (shunts,
clips, etc.) should tell instructor
Fillings, piercings fine (for console room)
•
Please be considerate while walking through the
hospital!
•
Graduate students: We’ll meet at the entrance to the
Link in 5 minutes
–
Auditors: Remain here for quick info session
FMRI – Week 1 – Introduction
Scott Huettel, Duke University