Dose prescription with spatial uncertainty for peripheral lung SBRT.
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Date
2019-01ICR Author
Author
Bedford, JL
Blasiak-Wal, I
Hansen, VN
Type
Journal Article
Metadata
Show full item recordAbstract
Current clinical practice is to prescribe to 95% of the planning target volume (PTV) in 4D stereotactic body radiotherapy (SBRT) for lung. Frequently the PTV margin has a very low physical density so that the internal target volume (ITV) receives an unnecessarily high dose. This study investigates the alternative of prescribing to the ITV while including the effects of positional uncertainties. Five patients were retrospectively studied with volumetric modulated arc therapy treatment plans. Five plans were produced for each patient: a static plan prescribed to PTV D95% , three probabilistic plans prescribed to ITV D95% and a static plan re-prescribed to ITV D95% after inverse planning. For the three probabilistic plans, the scatter kernel in the dose calculation was convolved with a spatial uncertainty distribution consisting of either a uniform distribution extending ±5 mm in the three orthogonal directions, a distribution consisting of delta functions at ±5 mm, or a Gaussian distribution with standard deviation 5 mm. Median ITV D50% is 23% higher than the prescribed dose for static planning and only 10% higher than the prescribed dose for prescription to the ITV. The choice of uncertainty distribution has less than 2% effect on the median ITV dose. Re-prescribing a static plan and evaluating with a probabilistic dose calculation results in a median ITV D95% which is 1.5% higher than when planning probabilistically. This study shows that a robust probabilistic approach to planning SBRT lung treatments results in the ITV receiving a dose closer to the intended prescription. The exact form of the uncertainty distribution is not found to be critical.
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Subject
Humans
Lung Neoplasms
Radiosurgery
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Uncertainty
Retrospective Studies
Algorithms
Radiotherapy, Intensity-Modulated
Organs at Risk
Research team
Radiotherapy treatment planning
Language
eng
Date accepted
2018-10-26
License start date
2019-01
Citation
Journal of applied clinical medical physics, 2019, 20 (1), pp. 160 - 167