The Advance of Pencil Beam Scanning Proton Beam Therapy in Cancers

A special issue of Cancers (ISSN 2072-6694). This special issue belongs to the section "Cancer Therapy".

Deadline for manuscript submissions: 20 June 2025 | Viewed by 7222

Special Issue Editors

New York Proton Center, New York, NY 10035, USA
Interests: radiation oncology; proton therapy (PT); flash PT; adaptive; reirradiation
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Guest Editor
Department of Medical Physics and Biomedical Engineering, University College London, London, UK
Interests: proton therapy; ultra-high dose rate; FLASH radiotherapy; particle therapies

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Guest Editor
Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA
Interests: proton therapy; motion management; radiation therapy; imaging; radiation physics

Special Issue Information

Dear Colleagues,

Proton therapy (PT) has developed rapidly in recent years. Over 125 proton therapy centers are in operation, and around 36 are under construction, according to the statistics from PTCOG. As the most advanced delivery technique, pencil beam scanning (PBS) allows intensity-modulated proton therapy (IMPT) to be delivered in the most conformal format. Along with zero exit dose, IMPT delivers the prescribed dose to the tumor and maximizes the protection of the surrounding organs. Physicists and clinicians further explored the clinical applications of PBS PT in various practical scenarios, especially cases with complexities and challenges for conventional radiotherapy.  This Special Issue covers a wide range of PBS PT topics for cancer therapy and recent developments, including but not limited to:

  1. Novel approaches in improving proton planning, treatment quality, and clinical efficiency;
  2. Proton solutions for specific disease;
  3. Adaptive proton therapy;
  4. Imaging development and its applications in PT;
  5. Uncertainty mitigation and management;
  6. Biological models and treatment optimization;
  7. Applications of AI and machine learning;
  8. Spatially fractionated radiotherapy;
  9. New developments such as FLASH RT, proton arc, mini beam, to name a few;
  10. Combination of proton therapy and other therapies.

Other physics- and clinic-related studies on PBS PT are highly welcome.

Dr. Haibo Lin
Dr. Richard A. Amos
Dr. Heng Li
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Cancers is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

  • proton therapy
  • pencil beam scanning
  • robustness
  • adaptive radiotherapy
  • imaging guidance
  • radiobiological model
  • FLASH radiotherapy
  • spatially fractionated radiotherapy (SFRT)
  • proton arc

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Published Papers (4 papers)

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20 pages, 6969 KiB  
Article
Potential Therapeutic Improvements in Prostate Cancer Treatment Using Pencil Beam Scanning Proton Therapy with LETd Optimization and Disease-Specific RBE Models
by Michael Vieceli, Jiyeon Park, Wen Chien Hsi, Mo Saki, Nancy P. Mendenhall, Perry Johnson and Mark Artz
Cancers 2024, 16(4), 780; https://doi.org/10.3390/cancers16040780 - 14 Feb 2024
Cited by 1 | Viewed by 1825
Abstract
Purpose: To demonstrate the feasibility of improving prostate cancer patient outcomes with PBS proton LETd optimization. Methods: SFO, IPT-SIB, and LET-optimized plans were created for 12 patients, and generalized-tissue and disease-specific LET-dependent RBE models were applied. The mean LETd in several [...] Read more.
Purpose: To demonstrate the feasibility of improving prostate cancer patient outcomes with PBS proton LETd optimization. Methods: SFO, IPT-SIB, and LET-optimized plans were created for 12 patients, and generalized-tissue and disease-specific LET-dependent RBE models were applied. The mean LETd in several structures was determined and used to calculate mean RBEs. LETd- and dose–volume histograms (LVHs/DVHs) are shown. TODRs were defined based on clinical dose goals and compared between plans. The impact of robust perturbations on LETd, TODRs, and DVH spread was evaluated. Results: LETd optimization achieved statistically significant increased target volume LETd of ~4 keV/µm compared to SFO and IPT-SIB LETd of ~2 keV/µm while mitigating OAR LETd increases. A disease-specific RBE model predicted target volume RBEs > 1.5 for LET-optimized plans, up to 18% higher than for SFO plans. LET-optimized target LVHs/DVHs showed a large increase not present in OARs. All RBE models showed a statistically significant increase in TODRs from SFO to IPT-SIB to LET-optimized plans. RBE = 1.1 does not accurately represent TODRs when using LETd optimization. Robust evaluations demonstrated a trade-off between increased mean target LETd and decreased DVH spread. Conclusion: The demonstration of improved TODRs provided via LETd optimization shows potential for improved patient outcomes. Full article
(This article belongs to the Special Issue The Advance of Pencil Beam Scanning Proton Beam Therapy in Cancers)
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11 pages, 2174 KiB  
Article
Enhancement of Stopping Power Ratio (SPR) Estimation Accuracy through Image-Domain Dual-Energy Computer Tomography for Pencil Beam Scanning System: A Simulation Study
by Dong Han, Shuangyue Zhang, Sixia Chen, Hamed Hooshangnejad, Francis Yu, Kai Ding and Haibo Lin
Cancers 2024, 16(2), 467; https://doi.org/10.3390/cancers16020467 - 22 Jan 2024
Cited by 1 | Viewed by 1405
Abstract
Our study aims to quantify the impact of spectral separation on achieved theoretical prediction accuracy of proton-stopping power when the volume discrepancy between calibration phantom and scanned object is observed. Such discrepancy can be commonly seen in our CSI pediatric patients. One of [...] Read more.
Our study aims to quantify the impact of spectral separation on achieved theoretical prediction accuracy of proton-stopping power when the volume discrepancy between calibration phantom and scanned object is observed. Such discrepancy can be commonly seen in our CSI pediatric patients. One of the representative image-domain DECT models is employed on a virtual phantom to derive electron density and effective atomic number for a total of 34 ICRU standard human tissues. The spectral pairs used in this study are 90 kVp/140 kVp, without and with 0.1 mm to 0.5 mm additional tin filter. The two DECT images are reconstructed via a conventional filtered back projection algorithm (FBP) on simulated noiseless projection data. The best-predicted accuracy occurs at a spectral pair of 90 kVp/140 kVp with a 0.3 mm tin filter, and the root-mean-squared average error is 0.12% for tissue substitutes. The results reveal that the selected image-domain model is sensitive to spectral pair deviation when there is a discrepancy between calibration and scanning conditions. This study suggests that an optimization process may be needed for clinically available DECT scanners to yield the best proton-stopping power estimation. Full article
(This article belongs to the Special Issue The Advance of Pencil Beam Scanning Proton Beam Therapy in Cancers)
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12 pages, 2684 KiB  
Article
Feasibility of Synchrotron-Based Ultra-High Dose Rate (UHDR) Proton Irradiation with Pencil Beam Scanning for FLASH Research
by Lingshu Yin, Umezawa Masumi, Kan Ota, Daniel M. Sforza, Devin Miles, Mohammad Rezaee, John W. Wong, Xun Jia and Heng Li
Cancers 2024, 16(1), 221; https://doi.org/10.3390/cancers16010221 - 3 Jan 2024
Cited by 4 | Viewed by 1785
Abstract
Background: This study aims to present the feasibility of developing a synchrotron-based proton ultra-high dose rate (UHDR) pencil beam scanning (PBS) system. Methods: The RF extraction power in the synchrotron system was increased to generate 142.4 MeV pulsed proton beams for UHDR irradiation [...] Read more.
Background: This study aims to present the feasibility of developing a synchrotron-based proton ultra-high dose rate (UHDR) pencil beam scanning (PBS) system. Methods: The RF extraction power in the synchrotron system was increased to generate 142.4 MeV pulsed proton beams for UHDR irradiation at ~100 nA beam current. The charge per spill was measured using a Faraday cup. The spill length and microscopic time structure of each spill was measured with a 2D strip transmission ion chamber. The measured UHDR beam fluence was used to derive the spot dwell time for pencil beam scanning. Absolute dose distributions at various depths and spot spacings were measured using Gafchromic films in a solid-water phantom. Results: For proton UHDR beams at 142.4 MeV, the maximum charge per spill is 4.96 ± 0.10 nC with a maximum spill length of 50 ms. This translates to an average beam current of approximately 100 nA during each spill. Using a 2 × 2 spot delivery pattern, the delivered dose per spill at 5 cm and 13.5 cm depth is 36.3 Gy (726.3 Gy/s) and 56.2 Gy (1124.0 Gy/s), respectively. Conclusions: The synchrotron-based proton therapy system has the capability to deliver pulsed proton UHDR PBS beams. The maximum deliverable dose and field size per pulse are limited by the spill length and extraction charge. Full article
(This article belongs to the Special Issue The Advance of Pencil Beam Scanning Proton Beam Therapy in Cancers)
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13 pages, 803 KiB  
Brief Report
Emulating the Delivery of Sawtooth Proton Arc Therapy Plans on a Cyclotron-Based Proton Beam Therapy System
by Samuel Burford-Eyre, Adam Aitkenhead, Jack D. Aylward, Nicholas T. Henthorn, Samuel P. Ingram, Ranald Mackay, Samuel Manger, Michael J. Merchant, Peter Sitch, John-William Warmenhoven and Robert B. Appleby
Cancers 2024, 16(19), 3315; https://doi.org/10.3390/cancers16193315 - 27 Sep 2024
Viewed by 721
Abstract
Purpose: To evaluate and compare the deliverability of ‘sawtooth’ proton arc therapy (PAT) plans relative to static intensity modulated proton therapy (IMPT) at a cyclotron-based clinical facility. Methods: The delivery of single and dual arc Sawtooth PAT plans for an abdominal [...] Read more.
Purpose: To evaluate and compare the deliverability of ‘sawtooth’ proton arc therapy (PAT) plans relative to static intensity modulated proton therapy (IMPT) at a cyclotron-based clinical facility. Methods: The delivery of single and dual arc Sawtooth PAT plans for an abdominal CT phantom and multiple clinical cases of brain, head and neck (H&N) and base of skull (BoS) targets was emulated under the step-and-shoot and continuous PAT delivery regimes and compared to that of a corresponding static IMPT plan. Results: Continuous PAT delivery increased the time associated with beam delivery and gantry movement in single/dual PAT plans by 4.86/7.34 min (brain), 7.51/12.40 min (BoS) and 6.59/10.57 min (H&N) on average relative to static IMPT. Step-and-shoot PAT increased this delivery time further by 4.79 min on average as the delivery was limited by gantry motion. Conclusions: The emulator can approximately model clinical sawtooth PAT delivery but requires experimental validation. No clear benefit was observed regarding beam-on time for sawtooth PAT relative to static IMPT. Full article
(This article belongs to the Special Issue The Advance of Pencil Beam Scanning Proton Beam Therapy in Cancers)
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