Describe the critical importance of both the photoelectric effect and positron a

Question

Describe the critical importance of both the photoelectric effect and positron annihilation (positron decay) to the use of radionuclides for modern nuclear medical (NM) imaging. Provide an example of one NM nuclide that employs each process and the form of NM imaging for which it is used. ) The half life of Uranium-235 is 704 million years, yet it is unstable and naturally decays by alpha particle emission and can also undergo spontaneous fission. What is the binding energy per nucleon for the Uranium-235 and how does its binding energy per nucleon compare to that of the stable Carbon-12 nucleus that is ubiquitously present in biological systems? See the worked example for Carbon-12 shown in your lecture notes that is found throughout the human body as well as animal and plant kingdoms. Show your work! 4) Show the equations for positron (+) decay, negatron ( ) and alpha particle decay. Describe what happens with the parent radionuclide's atomic number and mass number following each type of decay. Give examples of radiolsotopes that decay by positron emission and by alpha particle emission.

Explanation / Answer

Photoelectric effect and positron annihilation processes of Radio nuclei have a similarly that both are emitted by Gamma photon intracting with matter.

In nuclear medical imaging, Gamma photons interact eith human tissues and special camera are used to detect and computers are used to make images of the body parts.

Photoelectric and positron annihilation provide energy of photons in tissues equal to full energy of photon(photopeak) and 0.511MeV(annihilation peak).

Cs137 will have photopeak of 662KeV.

While Na22 will give 511KeV annihilation peak and 1274photopeak.

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