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1. THE ATOM TRANSFORMS BY LOOSING A HELIUM NUCLEUS (decay by the emission of an alpha particle).

2. Alpha decay typically occurs with heavy nuclides (A > 150) and is often followed by gamma and characteristic x-ray emission.

3. These photon emissions are often accompanied by the competing processes of internal conversion and Auger electron emission.

4. Z (atomic number) decreases by 2 and A (mass number) decreases by 4. The daughter is therefore a different element.

5. Due to their relatively high mass, electrical charge and low speed, α particles readily interact with other atoms and are effectively stopped by a few centimetres of air.

6. High LET radiation which causes radiation damage through ionization, and pose serious health hazards, hence not used in imaging.


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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