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Biomedical Imaging

Author: Charlene Stone. Ph.D. and Sarah Kenyon



Time: 3-4 class periods
Preparation
Time:
45 minutes
Gathering materials (projectors)
Reserving library or computer time
Potentially giving/getting a tutorial in PowerPoint
Making transparency of Electromagnetic Spectrum
Photocopying Project Description Handout, Proteomics sheet and MALDI-TOF sheet
Materials: Internet access, PowerPoint
Project Description Handout
Electromagnetic Spectrum transparency
Proteomics sheet
MALDI-TOF sheet

 


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.

 

 

Activity

Introduction:
1. Lead students in a discussion about biomedical imaging. Start by asking students “How do you know what is wrong with you when you are sick?” This should get a whole lot of different answers, but try to hone the students in on those that include sensing things being wrong, use of your senses (eyes, ears, touch) to see this, and how, ultimately, uncertainty is cleared up. Also, they should identify the notion that it is a change from a normal state, (homeostasis).

2. Ask “what sort of techniques have you heard of that help doctors to diagnose illness?”

3. Ask “Does it help doctors to see the affected parts?” “How can they do this?”

4. Tell students that this activity will give them a better idea about some of the ways that this is done, and that the general field they will be exploring is Biomedical Imaging.

5. Put students in pairs and alternately assign them ultrasound or MRI as one method they will be using. Then allow them to pick their second method for comparison from the following list:
X-rays
CAT scan
PET scan
Radar
Electron Microscopy
Polarized light scattering spectroscopy
Nanocameras
Infra-red imaging
Echolocation
Sonar
Imaging spectroscopy

6. Pass out the Project Description Sheet (please modify if you are unable to give students the opportunity to do PowerPoint presentations) Make sure that students understand that the rest of the class will be looking to them as experts on this topic and that the class will be drawing upon their expertise and understanding of biomedical imaging techniques.

7. Finally, before they begin, place a transparency of the electromagnetic spectrum on the overhead projector. Direct students to consider the electromagnetic spectrum in mind as they are comparing their two methods of imaging.

8. Once students begin to find information, via internet and library resources, pass out the following set of questions to help guide them in their investigation.

Suggested topics to include in your presentation:
1) How was this imaging method discovered? When? By whom?
2) What science principle(s) is (are) this imaging based on?
(e.g. reflection and absorption of sound waves for Ultrasound)
3) What are the limitations of this imaging method?
(e.g. How small an object can be imaged?)
4) What are the advantages and disadvantages of this method?
5) What are the applications of this method?
6) What (if any) connections are there to the electromagnetic spectrum?
On the second or third day, each student group will present their PowerPoint presentations to the class. Questions should be encouraged, as well as speculative answers. Although this is an engage piece, full coverage of the material is essential to the remainder of the class. Feel free to give an extra day either during the information collection part of the lesson, or even better, after the class presentation to allow students to modify or improve their presentations.

Closure

Class activity: At the end of the exercise, go back to the electromagnetic spectrum image and review what the students have learned in reference to it The electromagnetic spectrum can help them place this new information in context, you might even have them indicate what portions are used by their technology/method.
Individual activity: At the end, they will receive two sheets: one describing proteomics in general and another describing MALDI-TOF. They must both summarize the method and write a response comparing it to one of the methods they researched.

Assessment

Use the Project Description Sheet to guide your grading of the presentations.

Homework
To work on the presentation so that it is as professional as possible (according to the Project Description sheet guidelines)
At the end, they will receive two sheets: one describing proteomics in general and another describing MALDI-TOF. They must both summarize the method and write a response comparing it to one of the methods they researched.

 

Embedded Assessment
Initial discussion provides an opportunity to assess what pre-knowledge students have about biomedical imaging. In the closing discussion and in their presentations, students and the teacher have the opportunity to assess the students’ grasp of biomedical imaging and the electromagnetic spectrum in biomedical imaging. Assess how groups work together and their ability to efficiently research. Make sure to keep a close eye on whether or not the technical aspect (i.e. use of PowerPoint) is causing problems for some groups and offer assistance as needed. You may use members of other groups for this, or even designate a technical expert or two if you have them in class..

 


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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Supported by NIEHS grant # ES06694


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Last update: November 10, 2009
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