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BETA (PLUS) DECAY-POSITRON EMISSION

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BETA (PLUS) DECAY-POSITRON EMISSION

1. A PROTON BECOMES A NEUTRON BY GIVING UP ITS POSITIVE CHARGE.

2. This occurs in proton rich nuclides (conversely, those with a neutron deficit). Accelerator-produced radionuclides are typically neutron deficient.

3. Proton is converted to a neutron by the emission of a positron, neutrino and radiation.

4. For Beta + decay to occur, the positron is emitted with high energy, hence the parent isotope must have at least 1022 keV excess energy.

5. Z decreases by 1 but A (loss of a proton, gain of a neutron) stays the same. The daughter is therefore a different element. Example: Fluorine-18.

6. Positrons react violently with their antiparticles (electrons) resulting in the entire rest mass of both particles being instantaneously converted to energy and emitted as two oppositely directed (i.e., ~180 degrees apart) 511-keV annihilation photons.


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REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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