Figure 4.
Comparison of dose distributions with interplay effects at individual CT slice level illustrates that plans using large-spot machine (a) delivered higher dose to nearby healthy organs than the plan using (b) small-spot machine. There was statistically significant difference in (c) total lung V5Gy[RBE], (d) esophagus Dmean, (e) heart D33%, and (f) heart Dmean, illustrating plans using small-spot machine protected the lung, esophagus and heart better than large-spot machine. Averaged values from all 5 runs are shown. (c~f) Error bars indicate the minimum and maximum values among 5 runs. P values were calculated by Wilcoxon signed-rank testing. Abbreviations: RBE = relative biological effectiveness.