Abstract
This is an engage lesson about Biomedical
Imaging and should be considered in the context of
the electromagnetic spectrum (the methods all use one
or multiple parts of the spectrum for imaging) and
the extension of the human senses through technology.
Students will compare one of two imaging methods, either
ultrasound or MRI, with another method of their choosing
and present their findings to the class. It is strongly
suggested, if the facilities are available, that this
presentation be done in PowerPoint.
Objectives
Students will:
1. Use guided questions and research to compare
two biomedical imaging methods and effectively present
their findings to the class (according to the rubric
below).
2. Use new technical knowledge to summarize and compare
new techniques with those they researched.
National
Science Standards
Content Standard A: Scientific
Inquiry
Identify questions that guide scientific inquiry
Content Standard B: Physical Science
Structure and properties of matter
Content Standard E: Science and Technology
Identify a problem or design an opportunity
Communicate the problem, process, and solution
Content Standard F: Science in personal and social perspectives
Personal and community health
Natural and human-induced hazards
Science & Technology in local, national and global challenges
Teacher Background
Many of the various types of imaging
have, at their root, a connection with the electromagnetic
spectrum. Students should consider this as they do
their research, and having a visual depiction of the
electromagnetic spectrum in the classroom can help
them do this. One example is here: http://kingfish.coastal.edu/marine/Animations/Images/Electromagnetic-Spectrum-2.png,
and a great written treatise is here:http://www.phys.unsw.edu.au/~jw/EMspectrum.html but
feel free to use another example. At the end of the
exercise, going back to this image and reviewing
what the students have learned in reference to the
electromagnetic spectrum can help them place this new
information in context. While it isn’t necessary
for the teacher to comprehensively understand all these
imaging techniques, below is a brief description of
each and at least one reference if more information
is desired.
Ultrasound- Ultrasound or sonography uses high
frequency sound waves and their reflected
waves to create pictures,
i.e. of internal organs. Ultrasound does not penetrate
bone and air-filled organs (bladder, lungs, etc.)
are opaque to the sound waves. http://www.radiologyinfo.org/content/ultrasound-general.htm.
MRI- Magnetic Resonance Imaging. This is a non-invasive
technique where a patient is put into a large doughnut
shaped machine and rapidly changing strong magnetic
fields orient protons within cells in the body. Once
molecules are oriented, radio waves are emitted by
the machine and cause the aligned particles in the
cells to emit signals, which are manipulated by altering
the magnetic fields. The response of the cells are
detected and translated into pictures of cross-sectional
slices of the body. http://www.radiologyinfo.org/content/safety/mri_safety.htm.
http://www.simplyphysics.com/page2_1.html is also
a useful page and goes into some depth.
X-rays- Oldest and most frequently used imaging
technique, small wavelength electromagnetic
rays that are emitted
when inner orbital electrons are excited. X-rays
are absorbed in varying amounts by different tissue.
A
film is used, and passing x-rays through a part
of the body will create an image, allowing
diagnosis.
Limitations: X-ray is generally used for bone and
joint diagnoses, soft tissue is not well shown
with this
technique. http://www.radiologyinfo.org/content/bone_radiography.htm
CAT
scan- CT stands for Computed Tomography, although
often called a CAT scan. This technology uses X-rays
to get multiple angled pictures to create a 3-D
image. Instead of a film, a detector takes measurements
at many angles, and then incorporates these images
into
a 3-D image. This technology can look at soft tissues,
and is often accompanied with contrast agents,
often
swallowed by the patient. Finer details of soft
tissues are difficult to see and might be better
seen with
MRI. http://www.radiologyinfo.org/content/ct_of_the_body.htm
PET
scan- PET stands for Positron Emission Tomography,
where positrons are emitted from a substance given
to the patient. The radioactive substance will
be attached to something that is used by the body
part
that is
to be imaged. (i.e. glucose for muscle tissue).
Once the patient is given the substance (usually
through
injection), they will be passed through a doughnut
shaped detector where readings will create a picture
of the body. Often used in combination with other
techniques, it shows body function. As such, if
a patient is somehow
chemically imbalanced (i.e. diabetic after a meal)
it can give false results. http://www.radiologyinfo.org/content/petomography.htm
Radar- (Radio Detection And Ranging) High frequency
radio waves are transmitted, and their reflection
is analyzed (active imaging). This allows the determination
of position and velocity (among other attributes).
http://www.answers.com/topic/radar?method=6. Radar
has a long range of use, ~60 miles.
http://www.ieee-virtual-museum.org/collection/tech.php?taid=&id=2345896&lid=1.
Proteomics- The detection and characterization
of proteins found in cells to determine their role
in
physiological functions. Many different techniques
exist.
As an example, in 2D protein gels, the proteins are tagged with radioactive
or fluorescent substances and then visualized in
some way. In 2D gels (for example),
they are run on a gel. On the gel, proteins are generally separated in two
dimensions- by size and by pH. Proteomics is often
used for assessing differences in cell
populations as they give functional information. http://en.wikipedia.org/wiki/Proteomics
Electron
Microscopy- the use of beams of electrons to image small objects.
SEM (Scanning Electron Microscopy) is used much like a dissection light microscope,
bouncing a beam of electrons (instead of light) off an object (in a vacuum)
and
collecting the reflected electrons in a detector to show surface contours
of the object. TEM (Transmission Electron Microscopy) is used much like a
transmission
or compound light microscope, passing electrons instead of light waves though
thin layers and detecting the passage of these electron beams by a detector
on the other side of the sample. The electrons have a smaller wavelength
than photons
(light), and so can show far greater detail. Also, having a charge, electrons
can be directed using electromagnetic fields. http://en.wikipedia.org/wiki/Electron_microscopy.
Polarized
light scattering spectroscopy- a new
technology used in screening for skin cancers,
this method uses polarized light to assess
tissues
by detecting the reflection of these polarized light waves off
of
epithelial tissue (among
other things). Cancerous cells often have atypical or enlarged
nuclei, and light
scatters off of these organelles differently than cytoplasm and
other organelles.
As such, tissues can be imaged in situ (they do not need to be
removed) and more can be sampled. http://www.bme.northwestern.edu/faculty/Backman_Polarized_Light.pdf (don’t be too scared of the math…the information is found
in the first page).
Nanocameras- Not yet medically used at this time,
nanotechnology represents a huge entity
on the horizon, and may well affect every
aspect of our lives
in
the future. The following is an interesting article: http://www.newscientist.com/popuparticle.ns?id=in64,
but the current idea with nanocameras is to use viruses that
had
incorporated heavy metals. The viruses would break into cells
and with something akin
to polarized light-scattering spectroscopy, could help give us
a detailed picture
of those
cells. http://www.newscientist.com/channel/mech-tech/nanotechnology/dn4615.
Infra-red
imaging- infrared is primarily heat radiation.
It can be used in medicine to show blood
flow problems and to assess
injury (example: http://www.ipac.caltech.edu/Outreach/Edu/Guess/img4.html)
Echolocation- Used by bats, dolphins and perhaps
whales, this is a biosonar, where sound
waves are emitted and the reflected
waves
are used to locate
objects in the surrounding area. http://en.wikipedia.org/wiki/Animal_echolocation
Sonar- Like echolocation, but with the sound emitted and
detected by machines. Sonar is used in submarines and in
other aquatic
applications to determine
location and velocity (among other aspects of objects). It
has been shown to cause problems
and serious injuries to marine mammals that use echolocation.
http://en.wikipedia.org/wiki/Sonar.
MALDI-TOF- Matrix-Assisted Laser Desorption/Ionization-Time
of Flight. Confusing name, this technology dissolves
a protein sample
in a matrix that allows
for both hydrophilic and hydrophobic samples to dissolve.
Then the matrix/sample solution is allowed to crystallize
and a
laser vaporizes primarily matrix
material
and thereby ionizes the sample. Then a mass spectrometer
(time of flight) is used to see what sorts of proteins
are there.
The proteins are detected
based
on mass to charge the ratio of ions. The masses are used
to characterize proteins. http://en.wikipedia.org/wiki/MALDI-TOF,
http://en.wikipedia.org/wiki/Mass_spectrometry.
Imaging
spectroscopy- Using near infrared and infrared
reflectance from the solar illumination (passive imaging),
surface images
can be created from
geographical features. Used for assessing the environment,
minerals, vegetation, land management
and other aspects of land. A remote sensing technique,
the composition of various materials can be ascertained
by different
reflectance
properties
detected with
a sensor. http://speclab.cr.usgs.gov/aboutimsp.html,
http://landsat.usgs.gov/resources/remote_sensing/images/Light.jpg.
*A
note on PowerPoint:
Once learned, this is an incredibly easy presentation
medium used extensively in higher education. It can
be used well,
but also
be used quite poorly.
Use your own discretion about whether you include
this in your lesson, but we highly
recommend it.
**A further note:
The presentations that are created by students
are going to be used by the students for the rest
of
the unit to
go over
these
different techniques more
fully. It
is imperative that they create informative presentations
that can translate into real student learning.
Guide them actively
in this.
Related
and Resource Websites
See
Above. |
