arXiv subjects

K. P. Nesteruk

Publications and source records attributed to K. P. Nesteruk.

4 recordsLinked to original sources

arXiv2021

Commissioning of a clinical pencil beam scanning proton therapy unit for ultrahigh dose rates (FLASH)

Purpose: The purpose of this work was to provide a flexible platform for FLASH research with protons by adapting a former clinical pencil beam scanning gantry to irradiations with ultrahigh dose rates. Methods: PSI Gantry 1 treated patients until December 2018. We optimized the beamline parameters to transport the 250 MeV beam extracted from the PSI COMET accelerator to the treatment room, maximizing the transmission of beam intensity to the sample. We characterized a dose monitor on the gantry to ensure good control of the dose, delivered in spot-scanning mode. We characterized the beam for different dose rates and field sizes for transmission irradiations. We explored scanning possibilities in order to enable conformal irradiations or transmission irradiations of large targets (with transverse scanning). Results: We achieved a transmission of 86 % from the cyclotron to the treatment room. We reached a peak dose rate of 9000 Gy/s at 3 mm water equivalent depth, along the central axis of a single pencil beam. Field sizes of up to 5x5 mm$^{2}$ were achieved for single spot FLASH irradiations. Fast transverse scanning allowed to cover a field of 16x1.2 cm$^{2}$. With the use of a nozzle-mounted range shifter we are able to span depths in water ranging from 19.6 to 37.9 cm. Various dose levels were delivered with a precision within less than 1 %. Conclusions: We have realized a proton FLASH irradiation setup able to investigate continuously a wide dose rate spectrum, from 1 to 9000 Gy/s in a single spot irradiation as well as in the pencil beam scanning mode. As such, we have developed a versatile test bench for FLASH research.

physics.med-ph↗

arXiv2019

Large energy acceptance gantry for proton therapy utilizing superconducting technology

When using superconducting (SC) magnets in a gantry for proton therapy, the gantry will benefit from some reduction in size and a large reduction in weight. In this contribution we show an important additional advantage of SC magnets in proton therapy treatments. We present the design of a gantry with a SC bending section and achromatic beam optics with a very large beam momentum acceptance of $\pm15\%$. Due to the related very large energy acceptance, approximately 70% of the treatments can be performed without changing the magnetic field for synchronization with energy modulation. In our design this is combined with a 2D lateral scanning system and a fast degrader mounted in the gantry, so that this gantry will be able to perform pencil beam scanning with very rapid energy variations at the patient, allowing a significant reduction of the irradiation time. We describe the iterative process we have applied to design the magnets and the beam transport, for which we have used different codes. COSY Infinity and OPAL have been used to design the beam transport optics and to track the particles in the magnetic fields, which are produced by the magnets designed in Opera. With beam optics calculations we have derived an optimal achromatic beam transport with the large momentum acceptance of the proton pencil beam and we show the agreement with particle tracking calculations in the 3D magnetic field map. A new cyclotron based facility with this gantry will have a significantly smaller footprint, since one can refrain from the degrader and energy selection system behind the cyclotron. In the treatments, this gantry will enable a very fast proton beam delivery sequence, which may be of advantage for treatments in moving tissue.

physics.med-ph↗

arXiv2018

A system for online beam emittance measurements and proton beam characterization

A system for online measurement of the transverse beam emittance was developed. It is named $^{4}$PrOB$\varepsilon$aM (4-Profiler Online Beam Emittance Measurement) and was conceived to measure the emittance in a fast and efficient way using the multiple beam profiler method. The core of the system is constituted by four consecutive UniBEaM profilers, which are based on silica fibers passing across the beam. The $^{4}$PrOB$\varepsilon$aM system was deployed for characterization studies of the 18~MeV proton beam produced by the IBA Cyclone 18 MeV cyclotron at Bern University Hospital (Inselspital). The machine serves daily radioisotope production and multi-disciplinary research, which is carried out with a specifically conceived Beam Transport Line (BTL). The transverse RMS beam emittance of the cyclotron was measured as a function of several machine parameters, such as the magnetic field, RF peak voltage, and azimuthal angle of the stripper. The beam emittance was also measured using the method based on the quadrupole strength variation. The results obtained with both techniques were compared and a good agreement was found. In order to characterize the longitudinal dynamics, the proton energy distribution was measured. For this purpose, a method was developed based on aluminum absorbers of different thicknesses, a UniBEaM detector, and a Faraday cup. The results were an input for a simulation of the BTL developed in the MAD-X software. This tool allows machine parameters to be tuned online and the beam characteristics to be optimized for specific applications.

physics.acc-ph↗

arXiv2012

A beam monitor detector based on doped silica and optical fibres

A beam monitor detector prototype based on doped silica fibres coupled to optical fibres has been designed, constructed and tested, mainly for accelerators used in medical applications. Scintillation light produced by Ce and Sb doped silica fibres moving across the beam has been measured, giving information on beam position, shape and intensity. Mostly based on commercial components, the detector is easy to install, to operate and no electronic components are located near the beam. Tests have been performed with a 2 MeV proton pulsed beam at an average current of 0.8 μA. The response characteristics of Sb doped silica fibres have been studied for the first time.

physics.ins-det↗