Figure 7.

Calculated probability motion functions (pmf) of intrafractional target motion without subtraction of target baseline motion (i.e., ultracyclic plus cyclic target motion (a)‐(f)), and with subtraction of the target baseline motion (i.e., cyclic target motion (g)–(l)), for a lower‐ and upper‐lobe tumor. Each red solid line represents the per‐100 s pmf, and the black solid line is the reference pmf calculated using the first 100 s motion data. The blue dotted line is the averaged pmf of the entire treatment. The upper‐lobe tumor is not only associated with noticeable baseline variation, but also associated with significant variability of target motion amplitude and period. The lower‐lobe tumor, on the other hand, is associated with excellent reproducibility of the pmf in spite of the baseline variations.