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. 2008 Sep 10;35(10):4342–4351. doi: 10.1118/1.2975147

Figure 3.

Figure 3

(a)–(c) Histograms of the dark images acquired with and without the presence of stray radiation. For all dark image acquisitions, the lens cover was placed on the lens and the entire CCD was covered with opaque black felt. The CCD was placed approximately 2 m from the gantry isocenter and the linac was run at a dose rate of 400 MU∕min. (a) Luca in normal mode, (b) U2000, and (c) Luca in electron-multiplying (EM) mode. (d) Histograms of the images exposed to light acquired with the U2000 CCD in normal mode under the same conditions as in (a)–(c) except the CCD was unshielded from ambient light.