China
Africa
Explore chapters and articles related to this topic
Proton and Other Heavy Charged-Particle Beams
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Alejandro Mazal, Ludovic de Marzi
With pencil-beam scanning, the field shape can be defined by the area over which the beamlet is scanned. With such a method, special attention must be paid to the beam parameters that determine the steepness of the lateral fall-off. These are essentially the pencil-beam diameter, the relative weights of the lateral spots and the spot-grid spacing. Strategies for improving the penumbra of scanned proton beams have been discussed (see for example Winterhalter et al. 2018). In particular, the use of a field collimation system as well as un-collimated edge-enhancement by pencil-beam weight optimisation greatly reduces the spread of the lateral penumbra of proton beams. The improvement is particularly significant at low energies. This type of collimation can be achieved with fixed apertures (as done with scattered beams) or a dynamic collimation system based on two pairs of travelling trimmer blades (Hyer et al. 2014). This latter technique allows the best use of the pencil-beam scanning performances, as it provides collimation to each energy layer.
Primary Bone Tumors
Published in Pat Price, Karol Sikora, Treatment of Cancer, 2020
Jeremy S. Whelan, Rob C. Pollock, Rachael E. Windsor, Mahbubl Ahmed
The pattern of toxicity differs between the radiotherapy beam and technique used. In a prospective randomized trial comparing 3D-conformal radiotherapy and IMRT the rates of acute skin toxicity were 49% and 32% respectively (p = 0.02). Late toxicity for 3D-conformal radiotherapy versus IMRT for fracture (9.1%, 4.1%, p = 0.18), joint stiffness (11%, 14.5%, p = 0.40), lymphedema (7.9%, 14.9%, p = 0.05), nerve damage (1.6%, 3.5%, p = 0.45).16 For patients undergoing proton radiotherapy for bone sarcoma approximately 33% develop high-grade toxicities, and the majority of these are skin toxicities.13 Improving proton beam technology such as pencil beam scanning is likely to reduce acute and late skin toxicities.
Physics of Treatment Planning Using Scanned Beams *
Published in Harald Paganetti, Proton Therapy Physics, 2018
It is becoming increasingly clear that the most flexible method of delivering proton (or particle) therapy is by the use of pencil beam scanning (PBS). In this approach, narrow pencil beams of particles are scanned across the target volume in three-dimensions, using deflector magnets in the directions orthogonal to the beam direction, and some form of energy modulation for positioning of the Bragg peak in depth. In its most flexible form, such delivery systems are capable of complete control of the dose delivered by each such pencil beam, resulting in a true fluence modulation in three dimensions from each individual incident field direction [1]. This is the particle therapy equivalent of intensity-modulated radiotherapy (IMRT) with photons, and brings similar (if somewhat more) advantages and potential disadvantages. In this chapter, we will look into both the physics and methods of treatment planning for scanned particle beams, starting with the similarities to conventional IMRT (henceforth referred to here as IMXT) and the main dissimilarities to passive scattering proton therapy. In addition, we will look at different modes of optimizing scanned proton therapy treatments and how possible delivery uncertainties can be dealt with. Finally, a number of case studies will be presented to indicate the potential of these techniques and some of the remaining challenges of treatment planning for PBS proton therapy.
The first direct method of spot sparsity optimization for proton arc therapy
Published in Acta Oncologica, 2023
Lewei Zhao, Juntao You, Gang Liu, Sophie Wuyckens, Xiliang Lu, Xuanfeng Ding
One of the challenges in the clinical implementation of proton arc therapy is to minimize its beam delivery time (BDT), as the plan might contain numerous energy layers and spots. In the beginning stage of the pencil beam scanning (PBS) clinical implementation, energy layer switching time (ELST) is the bottleneck due to the technical limitation that prolongs the treatment delivery time. Thus, several studies focused on reducing energy layer switching time through energy sequence optimization [3–7]. However, a recent study [8] found that the BDT is approximately proportional to the spot number for IBA’s ProteusONE PBS proton therapy system in Beaumont where about half the treatment delivery time is spent on the spot switching [9]. It becomes a new bottleneck of SPArc therapy, which normally contains thousands of spots making it very challenging to deliver in a timely manner. Thus, it is critical to reducing the spot number while maintaining the optimal treatment plan quality.
Cardiotoxicity model-based patient selection for Hodgkin lymphoma proton therapy
Published in Acta Oncologica, 2022
Pierre Loap, Ester Orlandi, Ludovic De Marzi, Viviana Vitolo, Amelia Barcellini, Alberto Iannalfi, Rémi Dendale, Youlia Kirova, Alfredo Mirandola
Intensity modulated proton therapy (IMPT) with quasi-discrete active scanning was retrospectively re-planned at the National Center for Oncological Hadrontherapy (CNAO, Pavia, Italy) on the initial simulation CT scans aiming to achieve a similar CTV coverage. Robust optimization with multifield optimization was used for IMPT plan calculations on CTV; 2 mm isotropic setup error and 3% range uncertainty were applied. Cardiac motion was not specifically taken into account. Spot spacing was 3 mm with an energy step of 2 mm in water. One to four pencil beam scanning (PBS) fields were planned, depending on the target localization and on the patient anatomy. For complex target volumes, targets could be divided for multifield planning based on the anatomical localization (upper mediastinum, lower mediastinum, neck, axillary, etc.); in cases of diffuse mediastinal targets, a combination of anterior and posterior fields could be notably used to optimize cardiac and lung sparing. No systematic class solution was used for beam arrangement, which was defined on a case-by-case basis. Use of range shifter depended on the target shape and localization. Proton plans were made by physicists experienced in proton therapy planning for HL. This study was reviewed and approved by the institutional review board of the Institut Curie (Paris, France) and conducted in accordance with the STROBE guidelines [16] (Supplementary Material).
Is proton beam therapy ready for single fraction spine SBRS? – a feasibility study to use spot-scanning proton arc (SPArc) therapy to improve the robustness and dosimetric plan quality
Published in Acta Oncologica, 2021
Gang Liu, Xiaoqiang Li, An Qin, Jun Zhou, Weili Zheng, Lewei Zhao, Jun Han, Sheng Zhang, Di Yan, Craig Stevens, Inga Grills, Xuanfeng Ding
In the past decades, proton beam therapy has been implemented clinically, taking advantage of its unique physical characteristics of dose deposition from the ‘Bragg peak’. The development of the Pencil Beam Scanning (PBS) technique allows the proton system to optimize the energies and numerous spots to deliver the radiation dose layer by layer and spot by spot in 3-dimensional, just like a 3D-printer [9]. However, due to the prolonged proton PBS treatment delivery time, only a limited number of beam angles are normally used in the proton clinic [10,11]. Additionally, compared to the photon treatment, IMPT alone cannot provide high dose conformity and sharp dose fall-off, which is critical to SBRS/SBRT due to the large lateral penumbra from each individual proton spot [12–14]. As a result, only passive-scattering proton beam therapy using a collimator system was occasionally used in spine SBRT proton treatment cases through five or more fractions instead of a newer technique, PBS [15,16]. Single fractionation SBRS proton beam therapy for spine metastasis is not possible in most cases, even with passive-scattering technique due to the needs in the matching line feathering [17].