First experimental results of motion mitigation by continuous line scanning of protons

Schätti, A; Meer, D.; Lomax, Anthony

doi:10.1088/0031-9155/59/19/5707

Cited by 29 publications

(19 citation statements)

References 36 publications

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“…The volumetric rescanning and layer-by-layer rescanning (or layered rescanning) are distinguished in scanning methodologies [91,92]. Volumetric rescanning delivers a subfractional daily dose (d/n, where n is rescanning number, d is daily dose) to the whole volume of target on each scan and repeats the 3D depth scanning multiple times [91,93]. The layered rescanning method delivers a subfractional dose at each energy layer and repeats this multiple times at that isoenergy layer and then moves to the next layer [92].…”

Section: ) Rescanningmentioning

confidence: 99%

“…It's dose distributions are comparable with those of discrete spot scanning, with only a modest degradation of lateral penumbra in the scanning direction-which is one of the drawbacks of the rescanning method with free breathing. For large tumor motion (>1 cm) rescanning needs to be combined with gating or BH to achieve the desired level of dosimetric benefit [93].…”

Section: ) Rescanningmentioning

confidence: 99%

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Current status of proton therapy techniques for lung cancer

Han

2019

Radiat Oncol J

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Proton beams have been used for cancer treatment for more than 28 years, and several technological advancements have been made to achieve improved clinical outcomes by delivering more accurate and conformal doses to the target cancer cells while minimizing the dose to normal tissues. The state-of-the-art intensity modulated proton therapy is now prevailing as a major treatment technique in proton facilities worldwide, but still faces many challenges in being applied to the lung. Thus, in this article, the current status of proton therapy technique is reviewed and issues regarding the relevant uncertainty in proton therapy in the lung are summarized.

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Section: ) Rescanningmentioning

confidence: 99%

Section: ) Rescanningmentioning

confidence: 99%

Current status of proton therapy techniques for lung cancer

Han

2019

Radiat Oncol J

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“…In addition, Sato et al [100] has shown that the intensity control of a synchrotron [34] can be performed within less than 1 ms time. Both parameters are important for implementation of new scanning techniques which are expected to be advantageous for moving target treatment [103,54]. Another synchrotron-based facility which operates a carbon-ion gantry, HIT, does not have a possibility to change the energy within one spill but implemented the dynamic intensity control and uses it in clinical standard operation [107].…”

Section: D Beam Deliverymentioning

confidence: 99%

“…Cyclotrons, instead, are designed to accelerate only one type of particles, but offer almost continuous beam extraction releasing protons every ∼30 ns. This type of accelerators is compatible with continuous (line) scanning, implemented by Sumitomo Heavy Industries, Ltd. and at PSI [103]. In comparison to pencil beam scanning (PBS), line scanning allows avoiding dead time between spots resulting in a reduction of the total dose delivery time.…”

Section: D Beam Deliverymentioning

confidence: 99%

Clinical implementations of 4D pencil beam scanned particle therapy: Report on the 4D treatment planning workshop 2016 and 2017

et al. 2018

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In 2016 and 2017, the 8th and 9th 4D treatment planning workshop took place in Groningen (the Netherlands) and Vienna (Austria), respectively. This annual workshop brings together international experts to discuss research, advances in clinical implementation as well as problems and challenges in 4D treatment planning, mainly in spot scanned proton therapy. In the last two years several aspects like treatment planning, beam delivery, Monte Carlo simulations, motion modeling and monitoring, QA phantoms as well as 4D imaging were thoroughly discussed.This report provides an overview of discussed topics, recent findings and literature review from the last two years. Its main focus is to highlight translation of 4D research into clinical practice and to discuss remaining challenges and pitfalls that still need to be addressed and to be overcome.

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“…For this purpose, fast PBS irradiation could help: with less time needed to scan through the tumor volume, motion mitigation techniques such as gating, breath‐hold, and rescanning (or their combination) can be used more efficiently. The main ingredients for a fast PBS irradiation are high, stable beam currents, fast lateral movement of the beam, and fast energy switching. In the context of motion mitigation techniques, switching energy layers in less than 1 s would be an advantage (it may allow, for example, irradiation of a whole target in a 10–20 s single breath‐hold).…”

Section: Introductionmentioning

confidence: 99%

A predictive algorithm for spot position corrections after fast energy switching in proton pencil beam scanning

et al. 2018

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Purpose Fast energy switching is of fundamental importance to implement motion mitigation techniques in pencil beam scanning proton therapy, allowing efficient irradiation and high patient throughput. However, depending on magnet design, when switching between different energy layers, eddy currents arise in the bending magnets’ yoke, damping the speed of the magnetic field change and lengthening the settling time of the magnetic field. In a proton therapy gantry, this can cause a temporary displacement of the beam trajectory and consequently an incorrect beam position in the bending direction, resulting in an unacceptable loss of position precision at isocenter. The precision can be recovered by either increasing the beam off time after an energy change (waiting until the magnetic field is fully settled) or by actively correcting for the misplacement. We studied the transient magnetic field effects at PSI Gantry 2 in order to develop a correction strategy for this beam position misplacement. Methods We used position and proton range sensitive detectors (segmented strip chamber and multilayer ionization chambers respectively) to measure the difference between expected and actual proton beam position and range as a function of time. The detectors are automatically triggered, read out, and analyzed by the treatment control system. We studied the effects due to the magnets on the gantry and those upstream of the gantry separately, in order to identify which elements contribute the most to the beam position instability. We then designed a spot position algorithm to be applied with the gantry scanning magnets, to correct for the displacement observed as a function of time and achieve the PSI Gantry 2 clinical target of 1 mm precision at isocenter at all times, even after an energy change. Results When switching energy layers in a field, we observed an exponentially decaying spot position displacement at isocenter. The effect increases with increasing energy difference between energy layers (ΔE). The initial residuals between expected and measured position are higher than 1 mm for most of the clinical cases at Gantry 2 and fall below 1 mm within about 1 s or more (depending on ΔE). We found no time dependence for the proton range, thus confirming that the displacement is purely due to a beam trajectory displacement resulting from the longer settling time of the magnetic field. A double exponential model, with two time constants and amplitudes depending on ΔE, fits the data and provides an easy model for the correction function. We implemented this correction as a spot position correction, applied by the scanning magnets during field application. After correction, the residuals were below 0.5 mm right after the energy change. Conclusions We developed a spot position correction for PSI Gantry 2 which reduces the beam off time needed in current state‐of‐the‐art gantries to settle the magnetic fields in the bending magnets. Thanks to this correction, the spot position is stable within 100 ms of an energy change at Gantry 2....

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First experimental results of motion mitigation by continuous line scanning of protons

Cited by 29 publications

References 36 publications

Current status of proton therapy techniques for lung cancer

Current status of proton therapy techniques for lung cancer

Clinical implementations of 4D pencil beam scanned particle therapy: Report on the 4D treatment planning workshop 2016 and 2017

A predictive algorithm for spot position corrections after fast energy switching in proton pencil beam scanning

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