Transcript Diffusion Tensor Imaging Physics Waves - cmaste

Diffusion TensorMagnetic Resonance
Imaging (DT-MRI)
Project
Physics 30 Outcomes
This lesson will address the following outcomes from:
Physics 30 Program-Of-Study
Forces & Fields
General Outcomes 3: Students will explain how the properties of electric and magnetic
fields are applied to numerous devices
30-B3.2sts: explain that the goal of technology is to provide solutions to practical problems
and that the appropriateness, risks and benefits of technologies need to be assessed for
each potential application from a variety of perspectives, including sustainability
International Baccalaureate HL Physics Program-of-Study
Option I – Medical Physics
I.2.12: Outline the basic principles of nuclear magnetic resonance (NMR) imaging
Introduction: Brain Tumours
Brain tumours can be benign or malignant as well as primary
or secondary:
Benign Tumours
Benign brain tumours do not contain cancer cells:
Usually, benign tumours can be removed, and they
seldom grow back.
The border or edge of a benign brain
tumour can be clearly seen. Cells from
benign tumours do not invade tissues
around them or spread to other parts
of the body. However, benign tumours
can press on sensitive areas of the
brain and cause serious health
problems.
Malignant Tumours
Malignant brain tumours contain cancer cells:
Malignant brain tumours are generally more serious and
often is life threatening.
They are likely to grow rapidly and crowd or invade the
surrounding healthy brain tissue.
Primary/Secondary Tumours
Primary brain tumours:
Tumours that begin in the brain tissue
Secondary brain tumours:
Cancer that spread from its original place to another part
of the body.
Secondary tumours in the brain are far more common
than primary brain tumours.
Treatments of Brain Tumours
Treatment of brain tumours (gliomas):
The standard treatment is to kill or remove the glioma
cells. Of course, this can only work if the surgeon or
radiologist can find these cells.
Unfortunately, there are inevitably
occult cancer cells, which may
infiltrate several centimeters
beyond the clinically apparent
lesion and are not found even by
today's sophisticated imaging
Occult cells
techniques.
surrounding
tumour
Treatment of Brain Tumours
Due to the limited ability to detect occult glioma cells,
clinicians currently add a uniform margin of 2cm or more
beyond the visible abnormality, and irradiate that volume.
However, researchers believe expanding the tumour 2cm in
every direction is killing more cells than necessary and that
some hidden cells may grow outside the 2cm envelope.
Treatment of Brain Tumours
Evidence, however, suggests that glioma growth is not
uniform - growth is favored in certain directions and impeded
in others. This means it is important to determine, for each
patient, which areas are at high risk of harboring occult cells.
Occult cells growing
towards the back of
the brain
Glioma has squished
this area of brain to be
‘abnormal’, during
scans they are also
classified as unhealthy
cells
What is a DT-MRI?
Diffusion Tensor Magnetic Resonance Imaging (DT-MRI)
and Machine Learning tries to predict the location of these
occult cells by learning the growth patterns exhibited by
gliomas in previous patients.
These new images allow
researchers to detect
direction and rate of
water flow
What is a DT-MRI?
Diffusion Tensor Magnetic Resonance Imaging (DT-MRI)
is a new technique in MRI that scans the fibrous muscle
structure of the brain to determine the rate of diffusion and a
preferred direction of diffusion of water.
It has been noted that occult cancer cells tend to grow with
these preferred rate and direction of diffusion of water
How does MRIs work?
MRI Magnetic Resonance Imaging (MRI) scanners contain
magnets. The magnetic field produced by an MRI is about
10 thousand times greater than the earth's.
MRI is based on the
way certain atomic
nuclei respond to
radio waves while in
the presence of a
magnetic field.
How does MRIs work?
The magnetic field forces hydrogen atoms in the body to line
up in a certain way (similar to how the needle on a compass
moves when you hold it near a magnet).
Hydrogen atoms are ideal to work with because they only
have one proton and have a large magnetic moment,
meaning these atoms will line up in the direction of a
magnetic field.
The hydrogen atoms in our bodies spin in all sorts of
directions.
How does MRIs work?
However, when a patient is inside the MRI, the hydrogen
protons will line up either towards the feet or the head.
Since the protons an align in
two directions, most will be
cancelled out, but one or two
out of each million will not be
cancelled out and hence create
a net magnetic force.
One or two in each millions is not a lot, but there are about
4.7x1027 hydrogen atoms in each human body
How does MRIs work?
When radio waves are sent towards the one or two (in each
million) unpaired hydrogen atom, the proton absorbs the
energy needed to create a spin.
This spin gives off a particular frequency in a specific
direction. This frequency is known as the Larmour
frequency.
Different types of tissues send back different
signals/frequencies. For example, healthy tissue sends back
a slightly different signal than cancerous tissue.
How does MRIs work?
Now that we have the signals, the machine will convert
these frequencies into a picture.
MRIs take pictures of 3-D bodies, but the images in 2-D of
MRIs are in 2-D. So how can we create the 3-D image using
these 2-D scans?
How does MRIs work?
Think of a loaf of bread, we
can slice it up and look at
each piece individually.
MRIs also create 2-D images
are called slices. The images
can be stacked to create the
3-D image that was scanned.
How does MRIs work?
Each column, T1, T1c, and T2 scan different aspects of the
brain
T1 weighted: An MRI that highlights
fat locations.
T1 Tissue
Bone
Air
Fat
Water
How it
appears
Dark
Dark
Bright
Dark
T1c weighted: An MRI that is taken
after the injection of the contrast agent
gadolinium, a contrast agent that can
make abnormalities such as tumours
clearer due to the element's special
magnetic properties.
T2 weighted: An MRI that highlights
water locations.
T2 Tissue
How it
appears
Bone
Air
Fat
Water
Dark
Dark
Dark
Bright
How does DT-MRI help?
With the new technique of DT-MRI provides more data for
researchers to learn the where occult are and predict the
direction of growth of the glioma cells.
What is Machine Learning?
Machine Learning is a scientific discipline concerned with
designing and developing programs that allow computers to
learn based on data (“thinking” computers). A program is
created to find gliomas and autonomously find the tumour
region within a brain image which may contain occult cancer
cells.
What are the advantages?
Result of this Medical and Computer Science collaboration:
•Advanced imaging techniques help us better
characterise gliomas in the future
•Create an image-based database to allow machine
learning analysis of all the clinically available data
•Through machine learning analysis, develop computer
algorithms to allow us to automate tumour segmentation,
predict tumour behaviour and predict location of clinically
occult glioma cells
Questions about MRIs?
MRIs are proving to be an extremely useful technique for
imaging blood flow and soft tissue in the body. It is the
preferred diagnostic imaging technique for studying the
brain and the central nervous system
1. Describe the basic principles employed to collect an MRI
scan of body tissues.
2. What properties of the hydrogen atom makes it such a
useful atom for MRI diagnosis?
Questions about MRIs?
3. Give two diagnostic
applications that MRI scans
are used for.
4. Discuss the advantages and
disadvantages that a MRI
scan has when compared to
other diagnostic techniques.
5. If the radio waves used to excite the hydrogen atoms
are 2.45x104 Hz, what is the corresponding wavelength?
Questions about MRIs?
6. A magnetic resonance imaging (MRI) machine uses an
enormous and extremely strong magnet to study a patient's
body. The magnet, which has its north pole at the patient's
head and its south pole at the patient's feet, is actually a coil
of superconducting wire through which electric charges
flow. This fancy electric system seems unnecessary; why
can't the technicians simply put
a large number of north
magnetic poles near the
patient's head and an equal
number of south magnetic
poles near the patient's feet?
Questions about MRIs?
7. Aluminum isn't normally magnetic, but as you carry a
large aluminum tray toward the magnet, you find that the
magnet repels the aluminum. Explain.
8. You eventually manage to get the aluminum tray up to the
magnet. As long as the tray doesn't move, it experiences no
magnetic forces. But when you drop it, it falls past the
magnet remarkably slowly. What slows down its fall?
What is an MRI?
Resources:
http://clinicaltrials.gov/ct2/show/NCT00330109
http://www.medicinenet.com/brain_tumor/page2.htm
http://www.physics247.com/physics-help/mri.shtml
http://www.phys.unsw.edu.au/~jw/FAQ.html#scan
http://healthguide.howstuffworks.com/mri-dictionary.htm
http://healthguide.howstuffworks.com/mri-dictionary.htm
http://rabi.phys.virginia.edu/1060/1999/PS3a.html
http://education.jlab.org/qa/mathatom_04.html
Centre for Mathematics Science and Technology Education (CMASTE)
382 Education South
University of Alberta
Edmonton AB T6G 2G5
www.CMASTE.ca
To download: select Outreach, Alberta Ingenuity Resources and Centre for Machine Learning
Filename: AICML6BrainTumourAnalysis
Centre for Machine Learning
Department of Computing Science
University of Alberta
2-21 Athabasca Hall
Edmonton AB T6G 2E8
(780) 492-4828
www.machinelearningcentre.ca
Alberta Ingenuity
2410 Manulife Place, 10180-101 Street
Edmonton AB T5J 3S4
(780) 423-5735
www.albertaingenuity.ca