Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs12976-018-0096-7/MediaObjects/12976_2018_96_Fig4_HTML.png)
(a) The number of cells without irradiation and (b) the number of survived cells after irradiated by 2 Gy were counted and fitted with the exponential function. Note that the x-axis represents the dates for cell counting, and the y-axis represents the number of the survived cells in millions