Fig. 2
Three examples of in-field recurrences (green) or marginal failures, together with the initial GTV (yellow) and PTVhigh (red) structures and dose distribution showing V59GyRBE and V66GyRBE (in color wash). The dose of 66 GyRBE corresponds to the 95% covering isodose (D95) in most cases. The first example (a) shows a marginal failure in the ethmoid/frontal sinus due to lack of elective coverage in this area. In the second example (b), the initial PTVhigh (red) nearly completely covers the recurrence (green) but because of the brainstem OAR constraint, the dose distribution is compromised in this area (right image). Example 3 (c) shows a marginal failure because of chiasm OAR constraints