Fig. 2

Adaptive re-planning reduces unplanned dose inhomogeneity and parotid gland overdose. These images are from the same case as presented in Fig. 1. At time of initial simulation (a), anticipated coverage of the high dose planned target volume (PTV) was 98.5% receiving 70Gy and the mean dose of the left and right superficial parotids were 25.0 and 24.5 Gy, respectively. However, by week 5 (b), there was wide variation in dose within the high dose PTV with cold spots down to 88.0% and hot spots up to 113.4% of the prescription. In addition, the mean left and right superficial parotids doses increased to 32.2 Gy and 36.7 Gy, respectively. With adaptive re-planning (c), dose homogeneity was improved with cold spots only being 94.8% and hot spots only being 104.4% inside of the high dose PTV, with reduction of the mean right and left superficial parotid dose back to 24.9 Gy and 24.6 Gy, respectively. The main benefit of A-ART in this case was sparing of the parotids, given there was an unplanned overdose of an additional 7.2 Gy to the left and 12.2 Gy to the right parotids which was mitigated with adaptive re-planning