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1. These have a threshold dose below which the effect will not occur.

2. The threshold dose is fairly constant between individuals.

3. Once the threshold dose is exceeded, the likelihood of the effect occurring increases rapidly, up to a level at which the effect will definitely occur.

4. Most deterministic effects have repair mechanisms such that the rate at which the dose is delivered influences the threshold dose (i.e. entire dose may be given in one shot or at multiple intervals).

5. For simplicity, cataract formation in the eye is taken as a deterministic effect.

6. Absorbed dose more accurately describes this as the severity of effects is proportional to dose, but will not occur below threshold.


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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