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Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
Normal tissue dose conformality measures to guide radiotherapy fractionation decisions
1Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. myerson@radonc.wustl.edu
Medical Physics
|June 2, 2011
Summary
Hypofractionation can be favorable for normal tissues by ensuring dose conformality. This study defines conditions and indices to achieve therapeutic gain with hypofractionated radiation therapy.
Area of Science:
- Radiation oncology
- Medical physics
Background:
- Hypofractionation, delivering larger doses per fraction, is increasingly used in radiation therapy.
- Determining optimal fractionation requires balancing tumor control and normal tissue toxicity.
Purpose of the Study:
- To identify conditions where hypofractionation benefits normal tissues, even with differing alpha/beta ratios between tumor and normal tissue.
- To establish a framework for evaluating the safety and efficacy of hypofractionated treatment plans.
Main Methods:
- Defined the hypofractionation sufficiency condition (HSC) as a dose conformality constraint.
- Utilized the extended equivalent uniform dose (EUD) model and linear-quadratic (LQ) principles.
- Introduced the hypofractionation sufficiency index (HSI) based on dose distribution and normal tissue parameters.
Main Results:
- The HSC is satisfied when the HSI is less than the normal tissue to tumor alpha/beta ratio.
- Satisfying HSC for all relevant normal tissues indicates a therapeutic gain with hypofractionation.
- Derived multifractionation sufficiency conditions (MSI) for assessing benefits with increasing fractions.
Conclusions:
- Conformality measures like HSI and MSI can guide radiation therapy fractionation decisions.
- The LQ/EUD models provide a basis for optimizing hypofractionated treatment planning.
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