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Figure 7. Differences between calculated and measured doses at the centre of the in-house inhomogeneity phantom for 6 MV and 10 MV open beams on three SL-series linear accelerators, LA 1, LA 2 and LA 3. Differences are shown for fields passing through 0.28 g cm-3 lung, 1.35 g cm-3 bone and 1.85 g cm-3 bone. A positive difference indicates that Pinnacle3 predicts a higher dose than is actually measured. The differences between Pinnacle3 and measurements in water have been subtracted from the results, so that the figure represents the differences due to inhomogeneities only, rather than differences due to the beam models.
