@inproceedings{gerlach2022fast,
author = {S. Gerlach and T. Hofmann and C. Fuerweger and A. Schlaefer},
title = {TH-B-206-02: Fast Adaptive Replanning by Constrained Reoptimization for Intra-Fractional Non-Periodic Motion During SBRT of the Prostate.},
year = {2022},
volume = {49.},
number = {(6),},
pages = {E570-E570},
booktitle = {Medical Physics},
url = {https://aapm.onlinelibrary.wiley.com/doi/epdf/10.1002/mp.15769},
abstract = {Purpose: Periodic motion of the target can be compensated by translational motion of the treatment beams in robotic SBRT.  However,  spontaneous,  non-periodic  displacement  of  the  target  may  completely  change  the  treatment geometry.  In  this  case,  translation  is  not  sufficient  since  relative  motion  between  the  PTV  and  OARs  can  cause substantial deviations of dose in the OARs. Instead, solving a new optimization problem is required after partial dose delivery. We demonstrate this effect and propose a method for adaption by replanning which accounts for the change in  the  geometry.  Methods:In  contrast  to  typical  adaptive  strategies,  our  approach  is  based  on  complete  and constrained replanning of the optimization problem which guarantees that no side effects such as higher doses than prescribed  can  occur  in  the  treatment  plan.  We  adapt  the  linear  program  to  account  for  the  changed  treatment geometry which allows for fast reoptimization. For evaluation, we translate the target with random direction and length sampled from a truncated normal distribution with mean values from 12.5 to 30mm without overlap with OARs. We stu dy treatment plans with approximately 300 treatment beams and consider the motion to occur after 100 delivered beams. We solve in total 40,950 inverse planning problems for 45 patients. Re  sults: Replanning can compensate for coverage loss and avoid constraint violation. Runtime of reoptimization is on average 14s. When not compensating for movement, coverage can decrease from 95% to 20%. While translation of the beam source can compensate for loss in coverage, dose constraints can be violated. E.g. maximum dose in the rectum is violated in 62% of treatment plans with translational compensation.  Conclusion: For non-periodic target displacements, translational compensation can lead to suboptimal treatment plan delivery. Constrained replanning after partially delivery of the treatment plan can compensate for the negative impact on the delivered dose distribution}
}

@COMMENT{Bibtex file generated on 2026-5-28 with typo3 si_bibtex plugin. Data from https://www.tuhh.de/mtec/publications/2024-2020 }