Inverse square law
Citation, DOI & article data
The inverse square law describes the principle of dose reduction as the distance from the source increases.
This assumes a point source. If radiation spreads over a spherical area, as the radius increases, the area over which the dose is distributed increases according to
where A is the area and r is the radius of the sphere.
Therefore, the dose is proportional to the inverse of the square of the radius. Thus if you double the distance you reduce the dose by a factor of four.
- 1. Shafiei SA, Hasanzadeh H, Shafiei SA. A simple calculation method for determination of equivalent square field. J Med Phys. 2012;37 (2): 107-11. doi:10.4103/0971-6203.94746 - Free text at pubmed - Pubmed citation
- 2. Rehani MM. Challenges in radiation protection of patients for the 21st century. AJR Am J Roentgenol. 2013;200 (4): 762-4. doi:10.2214/AJR.12.10244 - Pubmed citation
- 3. Curry TS, Dowdey JE, Murry RE. Christensen ́s physics of diagnostic radiology 4 Ed. Lippincott Williams & Wilkins. (1990) ISBN:0812113101. Read it at Google Books - Find it at Amazon