Question

1. Of the three main radioactive emissions: alpha, beta, and gamma, which would be the least/most harmful to biology and why? Which would be the easiest/hardest to block and how?

2. In some medical procedures, radioactive isotopes are used that have very short half-lives. Why is this desirable and how would these isotopes be obtained since none would be found in supply due to their short half-life?f

3. Different types of imaging - CT, PET, MRI - use different methods to obtain an image. How would those differences go in deciding what would be the best type of image to take? In other words, how would one decide which type of image would give the best result for a given situation?

Please no handwritten or picture responses - only typed replies

Answer 1

1. Gamma rays have highest prenetration. So hardest to block. Most harmful to humans. Next are beta rays. Last are alpha rays.

2.when radio active isotopes administered to body will accumulate around certain type of cells like tumor or organ. Due to their small half life, they disintegrate and emmit radiation which can be studied by imaging. If isotope has long half life then doctor has to scan the body for a very long time to get proper image. These artificial isotopes are made in partical accelerators by colliding ions( eg is large hadron collider lhc).

3. Ct scan uses x rays to scan soft tissue like liver, lungs, tumors etc. Mri scan captures the magnetic fields and also uses radio waves to capture images. Pet scan uses radio active isotopes to make images of organs and tissues. The main deference between pet and other two is that, pet scan can also help understand the metabolic activity of scanned region. Depending on the requirement of part to be scanned different methods are used. Like brain scans are done by mri. But brain tumor scans are done by pet scan to identify whether medication is altering metabolic activity of tumor. For a pnemonia patient lung scan is done by ct scan etc.