Fig. 1.

Illustration of dose accumulation in adapt-to-position (ATP) plans. “Dose C1” is the fraction dose of one ATP plan. (A) Direct summation of fraction doses of all ATP plans creates the summed ATP dose, representing the planned delivered dose. (B) To generate the accumulated deformed dose, the “Dose C1” is first shifted to the corresponding daily MR space “MR D1” by using the isoshift obtained during treatment. Then rigid registration (RR) between “CT sim” and “MR sim” and deformable image registration (DIR) between “MR D1” and “MR sim” are combined to deform “Dose M1” to “CT sim” space for accumulation, creating the accumulated deformed dose.