Technical Note: Using dual step wedge and 2D scintillator to achieve highly precise and robust proton range quality assurance

Purpose The main purpose of this study is to demonstrate the clinical implementation of a comprehensive pencil beam scanning (PBS) daily quality assurance (QA) program involving a number of novel QA devices including the Sphinx/Lynx/parallel‐plate (PPC05) ion chamber and HexaCheck/multiple imaging modality isocentricity (MIMI) imaging phantoms. Additionally, the study highlights the importance of testing the connectivity among oncology information system (OIS), beam delivery/imaging systems, and patient position system at a proton center with multi‐vendor equipment and software. Methods For dosimetry, a daily QA plan with spot map of four different energies (106, 145, 172, and 221 MeV) is delivered on the delivery system through the OIS. The delivery assesses the dose output, field homogeneity, beam coincidence, beam energy, width, distal‐fall‐off (DFO), and spot characteristics — for example, position, size, and skewness. As a part of mechanical and imaging QA, a treatment plan with the MIMI phantom serving as the patient is transferred from OIS to imaging system. The HexaCheck/MIMI phantoms are used to assess daily laser accuracy, imaging isocenter accuracy, image registration accuracy, and six‐dimensional (6D) positional correction accuracy for the kV imaging system and robotic couch. Results The daily QA results presented herein are based on 202 daily sets of measurements over a period of 10 months. Total time to perform daily QA tasks at our center is under 30 min. The relative difference (Δrel) of daily measurements with respect to baseline was within ± 1% for field homogeneity, ±0.5 mm for range, width and DFO, ±1 mm for spots positions, ±10% for in‐air spot sigma, ±0.5 spot skewness, and ±1 mm for beam coincidence (except 1 case: Δrel = 1.3 mm). The average Δrel in dose output was −0.2% (range: −1.1% to 1.5%). For 6D IGRT QA, the average absolute difference (Δabs) was ≤0.6 ± 0.4 mm for translational and ≤0.5° for rotational shifts. Conclusion The use of novel QA devices such as the Sphinx in conjunction with the Lynx, PPC05 ion chamber, HexaCheck/MIMI phantoms, and myQA software was shown to provide a comprehensive and efficient method for performing daily QA of a number of system parameters for a modern proton PBS‐dedicated treatment delivery unit.

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“…For better understanding on the range calculation using wedge, readers are advised to refer to work published by Shen et al . and Deng et al …”

Section: Methodsmentioning

confidence: 99%

Development and long‐term stability of a comprehensive daily QA program for a modern pencil beam scanning (PBS) proton therapy delivery system

Rana

Bennouna

Samuel

et al. 2019

J Applied Clin Med Phys

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“…19,20 Several studies have reported the dosimetric characteristics of scintillation detectors and their use as dosimeters for quality assurance (QA) in proton therapy. [21][22][23][24][25][26][27][28][29][30] These studies showed that scintillator-based dosimetry systems offered a fast response and could be used as high-resolution dosimeter tools if the quenching effects were corrected. A commercially available scintillator-based dosimeter tool, Lynx (IBA Dosimetry, Louvain-la-Neuve, Belgium), has been used in proton beam measurements.…”

Section: Introductionmentioning

confidence: 96%

“…Several studies have reported the dosimetric characteristics of scintillation detectors and their use as dosimeters for quality assurance (QA) in proton therapy . These studies showed that scintillator‐based dosimetry systems offered a fast response and could be used as high‐resolution dosimeter tools if the quenching effects were corrected.…”

Section: Introductionmentioning

confidence: 99%

Feasibility study of a plastic scintillating plate‐based treatment beam fluence monitoring system for use in pencil beam scanning proton therapy

et al. 2019

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Purpose The purpose of this study was to describe a plastic scintillating plate‐based gantry‐attachable dosimetry system for pencil beam scanning proton therapy to monitor entrance proton beam fluence, and to evaluate the dosimetric characteristics of this system and its feasibility for clinical use. Methods The dosimetry system, consisting of a plastic scintillating plate and a CMOS camera, was attached to a dedicated scanning nozzle and scintillation during proton beam irradiation was recorded. Dose distribution was calculated from the accumulated recorded frames. The dosimetric characteristics (energy dependency, dose linearity, dose rate dependency, and reproducibility) of the gantry‐attachable dosimetry system for use with therapeutic proton beams were measured, and the feasibility of this system during clinical use was evaluated by determining selected quality assurance items at our institution. Results The scintillating plate shortened the range of the proton beam by the water‐equivalent thickness of the plate and broadened the spatial profile of the single proton spot by 11% at 70 MeV. The developed system functioned independently of the beam energy (<1.3%) and showed dose linearity, and also functioned independently of the dose rate. The feasibility of the system for clinical use was evaluated by comparing the measured quality assurance dose distribution to that of the treatment planning system. The gamma passing rate with a criterion of 3%/3 mm was 97.58%. Conclusions This study evaluated the dosimetric characteristics of a plastic scintillating plate‐based dosimetry system for use with scanning proton beams. The ability to account for the interference of the dosimetry system on the therapeutic beam enabled offline monitoring of the entrance beam fluence of the pencil beam scanning proton therapy independent of the treatment system with high resolution and in a cost‐effective manner.

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Feasibility study of utilizing Sphinx Compact for quality assurance in uniform scanning proton therapy

Rana

Eckert²,

Tesfamicael³

2023

Physica Medica

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Technical Note: Using dual step wedge and 2D scintillator to achieve highly precise and robust proton range quality assurance

Abstract: The new method of using a dual step wedge and scintillator for proton range QA was efficient, highly reproducible, and robust. This method of proton range QA was highly feasible and appealing from a workflow point of view.

Cited by 4 publications

References 14 publications

Development and long‐term stability of a comprehensive daily QA program for a modern pencil beam scanning (PBS) proton therapy delivery system

Development and long‐term stability of a comprehensive daily QA program for a modern pencil beam scanning (PBS) proton therapy delivery system

Feasibility study of a plastic scintillating plate‐based treatment beam fluence monitoring system for use in pencil beam scanning proton therapy

Feasibility study of utilizing Sphinx Compact for quality assurance in uniform scanning proton therapy

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