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Introduction to Pencil Beam Scanning Proton Therapy

M Zhu1*, S Mossahebi2*, (1) Emory University School of Medicine, Atlanta, GA, (2) University of Maryland School of Medicine, Baltimore, MD


(Sunday, 7/12/2020) 3:30 PM - 4:30 PM [Eastern Time (GMT-4)]

Room: Track 6

Pencil Beam Scanning (PBS) is now the dominant treatment technique used in proton beam therapy. Its unique treatment planning, commissioning and quality assurance concepts are introduced. Proton therapy uncertainties such as range and radiobiological uncertainties are discussed in this course. Many planning concepts that are used in PBS are informed by these uncertainties and mitigation efforts. Plan robustness is used to assess the dosimetric effectiveness of mitigation techniques while robust optimization is used to optimize the robustness of a plan. Basic planning approaches such as single and multi-field optimization (SFO and MFO) are explained.
Commissioning procedures used for a Pencil Beam system include the collection of integrated depth dose (IDDs) curves and spot profile measurements over the entire range of energies available. Absolute calibration based on the TRS-398 protocol will be discussed. The concepts and associated measurement equipment will be introduced. Similar to any radiation therapy technique, routine quality assurance procedures include daily, monthly and annual check. Examples of each applied to PBS are provided.

Learning Objectives:
1. Understand uncertainties inherent to proton therapy in general and PBS in particular
2. Understand basic concepts of uncertainty mitigation and treatment planning
3. Understand data requirements and measurement techniques for PBS commissioning
4. Understand basics of daily, monthly and annual QA for PBS



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