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Session: Therapy General ePoster Viewing [Return to Session]

Application of Extracted Proton Energy Spectrum From Measured Integrated Depth Dose to Validating the Linear Energy Transfer Calculation in a Commercial TPS

W Yao1*, (1) University of Maryland School of Medicine, Baltimore, MD

Presentations

PO-GePV-T-126 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: To validate the calculated linear energy transfer (LET) in RayStation treatment planning system (TPS) by using measured integrated depth dose (IDD) of the protons of interest.

Methods: Energy spectrum of protons of interest was extracted by decomposing the IDD of the protons into mono-energetic proton IDDs. Track- and dose-averaged LETs (LETt and LETd) were calculated by using the energy spectrum and stopping power that is function of energy. In addition, without using the stopping power but the change of energy spectra in depth we calculated another form of LET (LETf) to validate LETt. In the TPS, water and water plus bone phantoms were generated, and proton single layer and SOBP beams were created. Dose and LETd from the beams were calculated in the TPS. IDDs from the protons of interest were obtained. IDDs were also acquired by a Bragg peak ion chamber and multi-layer ion chambers with a small-open collimator from delivering the beams. Our method is based on the integrated dose but the TPS considers each single event, and thus the validation is independent.

Results: For single layer beams, LETd from our method agreed with that from the TPS within 0.2 keV/μm in the proximal region, and had the same tread in the distal region. LET fluctuation in the distal region contributed the difference. For SOBP beams, the agreement was even better. The difference between LETt and LETf was within 0.1 keV/μm and 1 keV/μm in the proximal and distal regions for single layer beams, and the difference was even smaller for SOBP beams.

Conclusion: We validated a commercial TPS calculated LETd by our method in single layer and SOBP beams traversing water and water plus bone phantoms. Our LETt calculated with stopping power was also validated by LETf calculated from the change of energy spectra in depth.

Keywords

LET, Validation, Energy Spectrum

Taxonomy

TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

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