The SC cyclotron and beam lines of PSI’s new protontherapy facility PROSCAN

Schippers, Jacobus Maarten; Dölling, R.; Duppich, Jürgen; Goitein, Gudrun; Jermann, Martin; Mezger, A.; Pedroni, E.; Reist, H.W.; Vranković, V.

doi:10.1016/j.nimb.2007.04.052

Cited by 57 publications

(39 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, for tentative modelling purposes an average value is assumed. The beam can be either switched off when moving between the consecutive spots (''discrete spot scanning'') [20], or the beam is moved to the next voxel without turning it off (''raster scanning'') [21]. Discrete spot scanning may offer some advantages in terms of reoxygenation, as the beam is off between spots, allowing some more time for rediffusion of oxygen before the same voxel is treated again.…”

Section: Reoxygenation Effect During Spot Scanningmentioning

confidence: 99%

Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions

Wilson

Jones²,

Yokoi³

et al. 2012

BJR

View full text Add to dashboard Cite

Objective: To reinvestigate ultra-high dose rate radiation (UHDRR) radiobiology and consider potential implications for hadrontherapy. Methods: A literature search of cellular UHDRR exposures was performed. Standard oxygen diffusion equations were used to estimate the time taken to replace UHDRRrelated oxygen depletion. Dose rates from conventional and novel methods of hadrontherapy accelerators were considered, including spot scanning beam delivery, which intensifies dose rate. Results: The literature findings were that, for X-ray and electron dose rates of around 10 9 Gy s -1 , 5-10 Gy depletes cellular oxygen, significantly changing the radiosensitivity of cells already in low oxygen tension (around 3 mmHg or 0.4 kPa). The time taken to reverse the oxygen depletion of such cells is estimated to be over 20-30 s at distances of over 100 mm from a tumour blood vessel. In this time window, tumours have a higher hypoxic fraction (capable of reducing tumour control), so the next application of radiation within the same fraction should be at a time that exceeds these estimates in the case of scanned beams or with ultra-fast laser-generated particles. Conclusion: This study has potential implications for particle therapy, including lasergenerated particles, where dose rate is greatly increased. Conventional accelerators probably do not achieve the critical UHDRR conditions. However, specific UHDRR oxygen depletion experiments using proton and ion beams are indicated.

show abstract

Section: Reoxygenation Effect During Spot Scanningmentioning

confidence: 99%

Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions

Wilson

Jones²,

Yokoi³

et al. 2012

BJR

View full text Add to dashboard Cite

show abstract

“…The PROSCAN facility at PSI includes: (a) the medical accelerator COMET; (b) the beamlines and ESS for the different treatment rooms; and c) the treatment rooms (Gantry 1, Gantry 2, and Optis 2; a fourth treatment room, Gantry 3, is currently under commissioning). Correspondingly, three independent but interfaced control systems are responsible for the beam delivery in the treatment rooms: (a) the COMET control system, responsible solely for the operation of the cyclotron; (b) the machine control system (MCS), controlling the beamlines; and (c) the therapy control systems (TCSs) of the different rooms.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2018

View full text Add to dashboard Cite

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....

show abstract

“…The degrader is followed by two collimators: the first (Col1) in copper is used to define the beam size and the second (Col2) in graphite to limit the scattered particles from Col1. Two strip monitors installed before the degrader (Mon1) and after Col2 (Mon2) are used to measure beam size and current during the normal operation of the facility [29]. The accuracy of the MC models on the growth of the transverse phase space impacts the correct evaluation of the beam transmission after the collimators.…”

Section: Beamline Transmissionmentioning

confidence: 99%

On the accuracy of Monte Carlo based beam dynamics models for the degrader in proton therapy facilities

Rizzoglio

Adelmann

Baumgarten

et al. 2018

Nuclear Instruments and Methods in Physics Research Section A:

View full text Add to dashboard Cite

In a cyclotron-based proton therapy facility, the energy changes are performed by means of a degrader of variable thickness. The interaction of the proton beam with the degrader creates energy tails and increases the beam emittance. A precise model of the degraded beam properties is important not only to better understand the performance of a facility already in operation, but also to support the development of new proton therapy concepts. The accuracy of the degraded beam properties, in terms of energy spectrum and transverse phase space, is influenced by the approximations in the model of the particle-matter interaction. In this work the model of a graphite degrader has been developed with four Monte Carlo codes: three conventional Monte Carlo codes (FLUKA, GEANT4 and MCNPX) and the multi-purpose particle tracking code OPAL equipped with a simplified Monte Carlo routine. From the comparison between the different codes, we can deduce how the accuracy of the degrader model influences the precision of the beam dynamics model of a possible transport line downstream of the degrader.

show abstract

The SC cyclotron and beam lines of PSI’s new protontherapy facility PROSCAN

Cited by 57 publications

References 2 publications

Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions

Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions

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

On the accuracy of Monte Carlo based beam dynamics models for the degrader in proton therapy facilities

Contact Info

Product

Resources

About