@article{Jolly2020, abstract = {There is growing interest in the radiotherapy community in the application of FLASH radiotherapy, wherein the dose is delivered to the entire treatment volume in less than a second. Early pre-clinical evidence suggests that these extremely high dose rates provide significant sparing of healthy tissue compared to conventional radiotherapy without reducing the damage to cancerous cells. This interest has been reflected in the proton therapy community, with early tests indicating that the FLASH effect is also present with high dose rate proton irradiation. In order to deliver clinically relevant doses at FLASH dose rates significant technical hurdles must be overcome in the accelerator technology before FLASH proton therapy can be realised. Of these challenges, increasing the average current from the present clinical range of 1–10 nA to in excess of 100 nA is at least feasible with existing technology, while the necessity for rapid energy adjustment on the order of a few milliseconds is much more challenging, particularly for synchrotron-based systems. However, the greatest challenge is to implement full pencil beam scanning, where scanning speeds 2 orders of magnitude faster than the existing state-of-the-art will be necessary, along with similar improvements in the speed and accuracy of associated dosimetry. Hybrid systems utilising 3D-printed patient specific range modulators present the most likely route to clinical delivery. However, to correctly adapt and develop existing technology to meet the challenges of FLASH, more pre-clinical studies are needed to properly establish the beam parameters that are necessary to produce the FLASH effect.}, author = {Simon Jolly and Hywel Owen and Marco Schippers and Carsten Welsch}, doi = {10.1016/j.ejmp.2020.08.005}, issn = {1724191X}, journal = {Physica Medica}, title = {Technical challenges for FLASH proton therapy}, volume = {78}, year = {2020} } @ARTICLE{Fenwick2024, AUTHOR={Fenwick, John D. and Mayhew, Christopher and Jolly, Simon and Amos, Richard A. and Hawkins, Maria A. }, TITLE={Navigating the straits: realizing the potential of proton FLASH through physics advances and further pre-clinical characterization}, JOURNAL={Frontiers in Oncology}, VOLUME={Volume 14 - 2024}, YEAR={2024}, URL={https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2024.1420337}, DOI={10.3389/fonc.2024.1420337}, ISSN={2234-943X}, ABSTRACT={Ultra-high dose-rate 'FLASH' radiotherapy may be a pivotal step forward for cancer treatment, widening the therapeutic window between radiation tumour killing and damage to neighbouring normal tissues. The extent of normal tissue sparing reported in pre-clinical FLASH studies typically corresponds to an increase in isotoxic doselevels of 5-20%, though gains are larger at higher doses. Conditions currently thought necessary for FLASH normal tissue sparing are a dose-rate ³40 Gy s -1 , dose-perfraction ³5-10 Gy and irradiation duration £0.2-0.5 s. Cyclotron proton accelerators are the first clinical systems to be adapted to irradiate deep-seated tumours at FLASH dose-rates, but even using these machines it is challenging to meet the FLASH conditions. In this review we describe the challenges for delivering FLASH proton beam therapy, the compromises that ensue if these challenges are not addressed, and resulting dosimetric losses. Some of these losses are on the same scale as the gains from FLASH found pre-clinically. We therefore conclude that for FLASH to succeed clinically the challenges must be systematically overcome rather than accommodated, and we survey physical and pre-clinical routes for achieving this.}} @article{Kelleter2019, abstract = {Purpose: The purpose of this study is to characterize the magnitude and depth of dose buildup in pencil beam scanning proton therapy. Methods: We simulate the integrated depth–dose curve of realistic proton pencil beams in a water phantom using the Geant4 Monte Carlo toolkit. We independently characterize the electronic and protonic components of dose buildup as a function of proton beam energy from 40 to 400 MeV, both with and without an air gap. Results: At clinical energies, electronic buildup over a distance of about 1 mm leads to a dose reduction at depth of the basal layer (0.07 mm) by up to 6% compared to if no buildup effect were present. Protonic buildup reduces the dose to the basal layer by up to 16% and has effects at depths of up to 150 mm. Secondary particles with a mass number A > 1 do not contribute to dose buildup. An air gap of 1 m has no significant effect on protonic buildup but reduces electronic buildup below 1%. Conclusions: Protonic and electronic dose buildup are relevant for accurate dosimetry in proton therapy although a realistic air gap reduces the electronic buildup to levels where it can be safely neglected. We recommend including electrons and secondary protons in Monte Carlo-based treatment planning systems down to a predicted range of 10–20 μ m in order to accurately model the dose at depths of the basal layer, no matter the size of the air gap between nozzle and patient.}, author = {Laurent Kelleter and Benjamin Zhen-Hong Tham and Ruben Saakyan and Jennifer Griffiths and Richard Amos and Simon Jolly and Adam Gibson}, doi = {10.1002/mp.13660}, issn = {24734209}, issue = {8}, journal = {Medical Physics}, title = {Technical Note: Simulation of dose buildup in proton pencil beams}, volume = {46}, year = {2019} } @article{Yap2020, abstract = {The Clatterbridge Cancer Centre (CCC) in the United Kingdom is the world's first hospital proton beam therapy facility, providing treatment for ocular cancers since 1989. A 62 MeV beam of protons is produced by a Scanditronix cyclotron and transported through a passive delivery system. In addition to the long history of clinical use, the facility supports a wide programme of experimental work and as such, an accurate and reliable simulation model of the treatment beamline is highly valuable. However, as the facility has seen several changes to the accelerator and beamline over the years, a comprehensive study of the CCC beam dynamics is needed to firstly examine the beam optics. An extensive analysis was required to overcome facility related constraints to determine fundamental beamline parameters and define an optical lattice written with the Methodical Accelerator Design (MAD-X) and the particle tracking Beam Delivery Simulation (BDSIM) code. An optimised case is presented and simulated results of the optical functions, beam distribution, losses and the transverse rms beam sizes along the beamline are discussed. Corresponding optical and beam information was used in TOPAS to simulate transverse beam profiles and compared to EBT3 film measurements. We provide an overview of the magnetic components, beam transport, cyclotron, beam and treatment related parameters necessary for the development of a present day optical model of the facility. This work represents the first comprehensive study of the CCC facility to date, as a basis to determine input beam parameters to accurately simulate and completely characterise the beamline.}, author = {Jacinta Yap and Javier Resta-Lopez and Andrzej Kacperek and Roland Schnuerer and Simon Jolly and Stewart Boogert and Carsten Welsch}, doi = {10.1016/j.ejmp.2020.08.002}, issn = {1724191X}, journal = {Physica Medica}, title = {Beam characterisation studies of the 62 MeV proton therapy beamline at the Clatterbridge Cancer Centre}, volume = {77}, year = {2020} } @article{Owen2016, abstract = {The past few years have seen significant developments both of the technologies available for proton and other charged particle therapies, and of the number and spread of therapy centres. In this review we give an overview of these technology developments, and outline the principal challenges and opportunities we see as important in the next decade. Notable amongst these is the ever-increasing use of superconductivity both in particle sources and for treatment delivery, which is likely to greatly increase the accessibility of charged particle therapy treatments to hospital centres worldwide.}, author = {Hywel Owen and Antony Lomax and Simon Jolly}, doi = {10.1016/j.nima.2015.08.038}, issn = {01689002}, journal = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, title = {Current and future accelerator technologies for charged particle therapy}, volume = {809}, year = {2016} }