Purpose: The focus of this article is to describe the configuration, testing, and commissioning of a novel gantry-less synchrotron-based proton therapy (PT) facility.Materials and methods: The described PT system delivers protons with a water equivalent range between 4 and 38 cm in 1800 energy layers. The fixed beam delivery permits a maximum field size of 28 × 30 cm². The patient positioning and imaging system includes a six-degree-of-freedom robotic arm, a convertible patient chair, a vertical 4DCT, and an orthogonal 2D X-ray imaging system.Results: The spot positioning reproducibility was consistent within ±1 mm. The width (σ) of the beam profile at the isocenter was energy dependent and ranged from 2.8 mm to 7.7 mm. Absolute dose reproducibility was measured and deviations were found to be <0.62% for all possible beam scenarios. The built-in dose monitoring system was successfully tested for its ability to generate interlocks under specific conditions (beam spot deviation ≥2 mm, individual spot dose ≥10% or ≥0.25 Gy, spot energy deviation ≥0.5 MeV). The robot positioning exhibited a consistent reproducibility within ±1 mm. All tested scenarios achieved laser-free initial 3D/3D image-guided positioning within ±5 mm. Subsequent 2D/3D positioning showed an accuracy of ±1 mm. A single 2D/3D image registration event corrected positions in all cases. Results of gamma analysis (3%, 3 mm) demonstrated pass rates greater than 95% for head and neck, thorax, abdomen treatment plans.Conclusions: We report on the performance of a novel single-room gantry-less PT system comprised of a compact synchrotron and an adjustable (from nearly horizontal to almost vertical) patient positioning system. The commissioning results show high accuracy and reproducibility of the main proton beam parameters and the patient positioning system. The new PT facility started patient treatments in March 2023, which were the first in Israel and the Middle Eastern region.

To evaluate the patient's positioning reproducibility during upright treatment with image-guided adaptive proton therapy (IGAPT) for head and neck cancers. 10 head and neck (H&N) patients were treated with gantry-less IGAPT, which includes daily 3D computed tomography (CT) and two 2D kilovoltage radiographs before treatment and weekly 3DCT immediately after irradiation. All procedures were performed in the carbon chair on the 6 degrees of freedom robotic positioner. Prior to treatment we registered shifts in patient positioning using 3D/3D registration at the imaging isocenter: X = -0.1 ± 3.9 (mean ± standard deviation) mm, Y = -3.7 ± 3.5 mm, Z = 0.5 ± 6.2 mm. The corresponding vector was applied to the robotic positioner to compensate for the registered shifts, after which the patients were moved to the treatment isocenter and the following shifts were obtained there using 2D/3D registration: X = -0.31 ± 1.37 mm, Y = -0.02 ± 1.33 mm, Z = 0.59 ± 1.55 mm. Finally, the weekly follow-up 3D/3D registration showed X = -0.2 ± 1.2 mm, Y = -0.0 ± 1.4 mm, Z = 2.3 ± 2.0 mm. A novel image-guided gantry-less PT facility showed reliable results in terms of patient positioning for H&N cases during clinical trials. This fact confirmed the suitability of using gantry-less PT for H&N treatment. A small, systematic shift in the vertical direction was detected in the follow-up 3D/3D registration. The effect of this shift will be investigated in further studies with pre/post treatment 2D/3D registration. The next phase of the clinical trial of this facility is dedicated to the thorax region.

Purpose: To evaluate intrafractional motion effects as a function of peak-to-peak motion and period during single -field, single-fraction and single -field, multifraction irradiation of the moving target in spot-scanning proton therapy. Materials and Methods: An in -house dynamic phantom was used to simulate peak-to-peak motion of 5, 10, and 20 mm with periods of 2, 4, and 8 seconds. The dose distribution in the moving target was measured using radiochromic films. During the perpendicular motion, the film was fixed and moved perpendicular to the beam direction without changing the water equivalent thickness (WET). During longitudinal motion, the film was fixed and moved along the beam direction, causing a change in WET. Gamma index analysis was used with criteria of 3%/3 mm and 3%/2 mm to analyze the dose distributions. Results: For single-fraction irradiation, varying the period did not result in a significant difference in any of the metrics used ( P > .05), except for the local dose within the planning target volume ( P < .001). In contrast, varying peak-to-peak motion was significant ( P < .001) for all metrics except for the mean planning target volume dose ( P approximate to .88) and the local dose ( P approximate to .47). The perpendicular motion caused a greater decrease in gamma passing rate (3%/3 mm) than WET variations (65% +/- 5% vs 85% +/- 4%) at 20 mm peak-to-peak motion. Conclusion: The implementation of multifraction irradiation allowed to reduce hot and cold spots but did not reduce dose blurring. The motion threshold varied from 7 to 11 mm and depended on the number of fractions, the type of motion, the acceptance criteria, and the calculation method used.

Objective. Recently, a new and promising approach for range verification was proposed. This method requires the use of two different ion species. Due to their equal magnetic rigidity, fully ionized carbon and helium ions can be simultaneously accelerated in accelerators like synchrotrons. At sufficiently high treatment energies, helium ions can exit the patient distally, reaching approximately three times the range of carbon ions at an equal energy per nucleon. Therefore, the proposal involves adding a small helium fluence to the carbon ion beam and utilizing helium as an online range probe during radiation therapy. This work aims to develop a software framework for treatment planning and motion verification in range-guided radiation therapy using mixed carbon–helium beams. Approach. The developed framework is based on the open-source treatment planning toolkit matRad. Dose distributions and helium radiographs were simulated using the open-source Monte Carlo package TOPAS. Beam delivery system parameters were obtained from the Heidelberg Ion Therapy Center, and imaging detectors along with reconstruction were facilitated by ProtonVDA. Methods for reconstructing the most likely patient positioning error scenarios and the motion phase of 4DCT are presented for prostate and lung cancer sites. Main results. The developed framework provides the capability to calculate and optimize treatment plans for mixed carbon–helium ion therapy. It can simulate the treatment process and generate helium radiographs for simulated patient geometry, including small beam views. Furthermore, motion reconstruction based on these radiographs seems possible with preliminary validation. Significance. The developed framework can be applied for further experimental work with the promising mixed carbon–helium ion implementation of range-guided radiotherapy. It offers opportunities for adaptation in particle therapy, improving dose accumulation, and enabling patient anatomy reconstruction during radiotherapy.

The advent of commercially available vertical CT systems has renewed interest in gantry-less proton therapy (PT), in which patients are treated in an upright position using a fixed beamline and robotic positioning. This study evaluates the feasibility, safety, and preliminary efficacy of novel gantry-less image-guided adaptive PT (IGAPT) for recurrent head and neck (HN) and brain malignancies. A planned interim analysis was performed on 20 adult patients with recurrent HN (80 %) and brain (20 %) cancers, median age 62 years, with Eastern Cooperative Oncology Group (ECOG) performance status ≤2. Patients underwent upright and supine imaging and simulation, followed by treatment planning comparing upright PT to conventional supine intensity-modulated radiotherapy (IMRT). Dosimetric analyses focused on organ-at-risk (OAR) sparing and target coverage. Toxicities were assessed prospectively every three months using the Common Terminology Criteria for Adverse Events (CTCAE). Gantry-less PT demonstrated significant dosimetric advantages over photon IMRT, including reduced doses to critical OARs including brainstem (6 Gy(RBE) vs. 19.1 Gy; p < 0.001) and spinal cord (12.5 Gy(RBE) vs. 18.3 Gy; p < 0.006). At 3-month follow-up (n = 14), a complete response was observed in 64.3 % of evaluable patients and a partial response in 21.4 %. Most toxicities were mild-to-moderate (grades 1-2), primarily dermatitis (55 %), fatigue (45 %), and mucositis (31.3 %). Grade 3 toxicities occurred in four patients (20 %). There were no device-related deaths. This first clinical evaluation of a novel gantry-less IGAPT system confirms its feasibility, safety, and promising efficacy for recurrent HN and brain cancer, with superior dosimetry and high local control rates. Its cost-effective design may improve global access to the IGAPT.