Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy

Purpose: To commission MCsquare (a multi-cores CPU-based dose calculation engine) for pencil beam scanning (PBS) proton therapy, integrate it into RayStation treatment plan system (TPS) to create a dedicated platform for fast independent dose verification. Method: A MCsquare-based independent dose verification platform (MC2InRS) was developed to realize automatic dose re-calculation for clinical use, including data preparation, dose calculation, 2D/3D gamma analysis. MCsquare was commissioned based on in-air lateral dose profiles, integrated depth dose, and the absolute dose of different beam energies for Proteus®ONE. MC2InRS was validated with measurement data using various targets and depths in a water phantom. This study also investigated 15 clinical cases to demonstrate the feasibility and effectiveness of MC2InRS platform in clinic practice. Results: Between simulation and measurement, the distal range differences at 80% (R80) and 20% (R20) dose levels for each energy were below 0.05 mm, and 0.1 mm, respectively, and the absolute dose differences were below 0.5%. 29 out of 36 QA planes reached a 100% gamma passing rate (GPR) for 2%/2mm criteria, and a minimum of 98.3% gamma was obtained in water phantom between simulation and measurement. For the 15 clinical cases investigated, the average 2D GPR (2%/2mm) was 95.4%, 99.3% for MCsquare vs. measurement, MCsquare vs. TPS, respectively. The average 3D GPR (2%/2mm) was 98.9%, 95.3% for MCsquare vs. TPS in water, and computed tomography (CT), respectively. Conclusion: MC2InRS, a fast, independent dose verification platform, has been developed to perform dose verification with high accuracy and efficiency for Pencil Bream Scanning (PBS). Its potential to be applied in routine clinical practice has also been discussed.

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SU-F-T-161: The Effect of Pencil Beam Scanning Gantry Angle Dependent Spot Size Variations On Plan Quality

Medical Physics ◽

10.1118/1.4956297 ◽

2016 ◽

Vol 43 (6Part15) ◽

pp. 3499-3499

Author(s):

U Langner ◽

K Langen

Keyword(s):

Spot Size ◽

Pencil Beam ◽

Plan Quality ◽

Beam Scanning ◽

Pencil Beam Scanning ◽

Gantry Angle

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Parametrization of in-air spot size as a function of energy and air gap for the ProteusPLUS pencil beam scanning proton therapy system

Radiological Physics and Technology ◽

10.1007/s12194-020-00589-w ◽

2020 ◽

Vol 13 (4) ◽

pp. 392-397

Author(s):

Suresh Rana ◽

Anatoly B. Rosenfeld

Keyword(s):

Proton Therapy ◽

Spot Size ◽

Air Gap ◽

Pencil Beam ◽

Beam Scanning ◽

Pencil Beam Scanning

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Innovations and the Use of Collimators in the Delivery of Pencil Beam Scanning Proton Therapy

International Journal of Particle Therapy ◽

10.14338/ijpt-20-00039.1 ◽

2021 ◽

Vol 8 (1) ◽

pp. 73-83

Author(s):

Daniel E. Hyer ◽

Laura C. Bennett ◽

Theodore J. Geoghegan ◽

Martin Bues ◽

Blake R. Smith

Keyword(s):

Proton Therapy ◽

Spot Size ◽

Low Energy ◽

Healthy Tissue ◽

Pencil Beam ◽

New Paradigm ◽

Beam Scanning ◽

Multileaf Collimators ◽

Pencil Beam Scanning ◽

Tissue Sparing

Abstract Purpose The development of collimating technologies has become a recent focus in pencil beam scanning (PBS) proton therapy to improve the target conformity and healthy tissue sparing through field-specific or energy-layer–specific collimation. Given the growing popularity of collimators for low-energy treatments, the purpose of this work was to summarize the recent literature that has focused on the efficacy of collimators for PBS and highlight the development of clinical and preclinical collimators. Materials and Methods The collimators presented in this work were organized into 3 categories: per-field apertures, multileaf collimators (MLCs), and sliding-bar collimators. For each case, the system design and planning methodologies are summarized and intercompared from their existing literature. Energy-specific collimation is still a new paradigm in PBS and the 2 specific collimators tailored toward PBS are presented including the dynamic collimation system (DCS) and the Mevion Adaptive Aperture. Results Collimation during PBS can improve the target conformity and associated healthy tissue and critical structure avoidance. Between energy-specific collimators and static apertures, static apertures have the poorest dose conformity owing to collimating only the largest projection of a target in the beam's eye view but still provide an improvement over uncollimated treatments. While an external collimator increases secondary neutron production, the benefit of collimating the primary beam appears to outweigh the risk. The greatest benefit has been observed for low- energy treatment sites. Conclusion The consensus from current literature supports the use of external collimators in PBS under certain conditions, namely low-energy treatments or where the nominal spot size is large. While many recent studies paint a supportive picture, it is also important to understand the limitations of collimation in PBS that are specific to each collimator type. The emergence and paradigm of energy-specific collimation holds many promises for PBS proton therapy.

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