Dissertation
Accurate and efficient dose calculation and treatment planning for the dynamic collimation system for pencil beam scanning proton therapy
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2024
DOI: 10.25820/etd.007416
Abstract
Purpose: To design and validate an analytical dose calculator for use with the Dynamic Collimation System (DCS) for pencil beam scanning proton therapy, to perform patient specific quality assurance (PSQA) on DCS-collimated patient plans developed in a TPS using this algorithm, and to assess the robustness of those plans to range error when compared with standard uncollimated pencil beam scanning (PBS) proton therapy.
Methods: The Pencil bEam TRimming Algorithm (PETRA) was derived by generalizing an existing pencil beam dose calculation model to account for DCS-specific effects on the final dose distribution. The model was validated against a measurement-validated Dynamic Collimation Monte Carlo (DCMC) model of the Miami Cancer Institute’s (MCI) IBA Proteus Plus system equipped with the DCS. DCS-collimated and standard uncollimated pencil beam scanning (PBS) treatment plans were developed in the Astroid Treatment Planning System (TPS) for three patient cases and delivered and measured at MCI using a MatriXX-PT ion chamber array. The plans were recalculated with ±3% adjustment to relative stopping power to simulate undershoot and overshoot errors and assess their sensitivity to range error.
Results: Integral depth dose (IDD) curves for energies 70-160 MeV among all simulated trimmer combinations with and without a range shifter agreed between PETRA and DCMC at the 1%/1mm 1-D gamma criteria for 99.9% of points. All DCS-collimated patient plans passed the 90% threshold pass rate for a 3%/3mm gamma criteria with a median pass rate of 98.3%. The median error in V_(95%) across all error scenarios for DCS-collimated plans was 98.8% compared with a median error of 99.2% for uncollimated PBS plans.
Conclusions: An analytical dose calculation algorithm has been developed, validated, and incorporated into an FDA-cleared TPS for use in developing DCS-collimated treatment plans. This work represents a significant step in moving the DCS from prototype to commercially available clinical device.
Details
- Title: Subtitle
- Accurate and efficient dose calculation and treatment planning for the dynamic collimation system for pencil beam scanning proton therapy
- Creators
- Laura Christine Bennett
- Contributors
- Ryan T. Flynn (Advisor)Daniel E. Hyer (Committee Member)Joseph M. Reinhardt (Committee Member)James A. Ankrum (Committee Member)Sarah C. Vigmostad (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biomedical Engineering
- Date degree season
- Spring 2024
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007416
- Number of pages
- xiv, 99 pages
- Copyright
- Copyright 2024 Laura Christine Bennett
- Language
- English
- Date submitted
- 04/08/2024
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 82-90).
- Public Abstract (ETD)
- Proton therapy is often used to treat cancer in patients for whom any excess radiation delivered outside of the target poses an unacceptable risk. Unlike traditional photon radiation therapy, the depth at which protons stop in tissue may be controlled by manipulating their energy. Additionally, protons may be magnetically steered across the target to control the lateral deposition of dose. While this usually results in treatments that largely conform to the target, shallow targets such as those in the head and neck or brain that must use lower energy beams or external devices naturally see a broadening of the beam that results in radiation spilling beyond the tumor margins. The Dynamic Collimation System (DCS) is a device that aims to mitigate this by using two pairs of orthogonal nickel blades to follow the beam as it delivers dose and block radiation where it would intersect with healthy tissue. In transitioning the device from research prototype to clinical device, it is imperative to be able to accurately and efficiently calculate the dose that would be delivered to a patient to design and safely deliver treatment plans. This work details the design and validation of an analytical dose calculation algorithm that is compatible with the DCS, its incorporation into an FDA-cleared treatment planning system (TPS), and design and delivery of patient-specific quality assurance measurements using DCS-collimated treatment plans generated within that TPS. Additionally, this work evaluated the sensitivity of DCS-plans to range errors relative to standard uncollimated proton plans.
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering
- Record Identifier
- 9984647356302771
Metrics
16 File views/ downloads
47 Record Views