This routine combines the dose difference measurement with the distance to agreement (DTA) to provide one metric for each pixel. Gamma values greater than one indicate failure of both criteria. The calculation of gamma throughout the measured dose distribution provides a presentation that quantitatively indicates the delivery accuracy relative to the acceptance tolerances. The Gamma Function can be calculated for one or two dimensional dose distributions. You can also look at  Gamma Pass/Fail plots and Gamma Histograms. This routine is based on a technique by Lowe, Harms, Mutic and Purdy of Mallinckrodt Institute.



Low, Harms, Mutic, Purcy, "A Technique for the quantitative evaluation of dose distributions," Medical Physics, Vol 25, May 1998, 656-661.
Low, Dempsey, Mutic, “Evaluation of the gamma dose distribution comparison method”, Medical Physics, Vol. 30, #9, September 2003, 2455-2464.