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PET Scans

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Effects and Medical Uses of Radiation
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Penetrating Ability of Emissions

An emission's penetrating ability is its ability to go through matter. Which type of particle has the least penetrating power, and why? Which is the most penetrating?

Positrons represent a special case because they annihilate when they hit electrons. What occurs during this sort of collision?

Blocking alpha particles can be easily accomplished. How do beta emissions differ? How can you block gamma rays?

Click here to find more info on this concept and to check your answers!

Effects of Radiation

Ionizing radiation on the cell disrupts the DNA strand. How does this affect cells?

Remember: DNA is responsible for protein synthesis and the regulation of many cellular functions, and RNA helps produce proteins.

There are two general types of effects when humans are exposed to radiation. Low-level exposure can lead to cancer. Why is this? What are some affects of acute exposure? What does radiation therapy do for cancer patients?

You can check your answers and find more info on the effects of radiation here.

Radioisotopes in Medical Diagnosis and Treatment

Radioisotopes are used to diagnose and treat disease. After administering isotopes, how do you locate them for diagnosis? What is possibly the most widely used radioisotope in diagnosis and treatment?

Isotopes are also useful in scans to locate cancer cells, as shown below:

Radioisotope scans can be used to detect tumors

License: CC BY-NC 3.0


This patient has a number of tumors that have metastasized, or spread, from the main tumor. How do antibodies play a part in locating tumors?

Check your answers and find more info on this concept here!

PET Scans

Positron emission tomography (PET), or a PET scan, is one of the more interesting and useful approaches to radioisotope applications in medicine, particularly when studying the processes in the brain.

Many compounds can't enter the brain because of the blood-brain barrier that acts as a filter to brain tissue. How does this protect the brain? How does this apply to PET scans?

PET scanners detect gamma emissions from the collisions of a positron with an electron and stores the data in a computer, forming a detailed picture of a brain.

A useful application of PET scanning is in the diagnosis of Alzheimer's disease. How does plaque affect the brain of those with Alzheimer's? (Hint: use the following image to help you explain)

Brain scans using Pittsburgh compound B

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Brain scans using Pittsburgh compound B to locate plaque. [Figure2]

Note: red indicates a high level of radioactivity and yellow indicates somewhat less activity.

Some studies have been done looking at the brain functioning of drug addicts! These studies are linked to the amount of dopamine action and therefore pleasure, possibly giving us a better understanding of the biochemical processes in addiction. 

PET scans of dopamine in normal and addicted individuals

License: CC BY-NC 3.0


How do the top row scans compare to the "normal" bottom row scans?

You can find more info on PET scans and check your answers here.

Image Attributions

  1. [1]^ License: CC BY-NC 3.0
  2. [2]^ License: CC BY-NC 3.0
  3. [3]^ License: CC BY-NC 3.0


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