Development of a compact proton scanning system in Uppsala with a moveable second magnet

Abstract

A scanned proton beam yields dose distributions that in most cases are superior to passively scattered proton beams and to other external radiation treatment modalities. The present paper gives a description of the scanning system that has been developed at the Svedberg Laboratory (TSL) in Uppsala. The scanning technique and the technical design are described. The solution with a small pole gap of the magnets and a moveable second magnet results in a very compact scanning head, which can therefore be incorporated in a gantry of relatively limited size. A prototype was constructed that has been used to realize various dose distributions with a scanned beam of 180 MeV protons at TSL.

Development and verification of the pulsed scanned proton beam at The Svedberg Laboratory in Uppsala

“…The TSL nozzle construction with the movable second scanning magnet enables full threedimensional scanning with small pole gaps, 10 mm, and can be combined with a compact gantry with a diameter of approximately 6 m and a length of 4.5 m (Lorin et al 2000). This is considerably smaller than other gantries used for protons.…”

“…Finally, the current in the second magnet providing the fast vertical scan is started at a selected distance from the field edge and the triggering of pulses is only performed within the field. The current in the fast vertical scan magnet is then returned to the starting value of the next scanning line without triggering pulses so that the beam is turned off while the current in the second magnet is returned to the starting value (see Lorin et al (2000) for further details).…”

“…The basic design and functioning of a control system for the scanned proton beam has been described by Lorin et al (2000). The recent development mainly involves a new software package including a control and supervising system, and the dosimetry system and procedures.…”

“…At TSL we have used a unique solution to this problem, namely, to make the second magnet movable, rotating around the centre of the first scanning magnet. Therefore, it can always be positioned synchronized with the deflection of the beam in the first scanning magnet as reported by Lorin et al (2000).…”

Evaluation of radiobiological effects in intensity modulated proton therapy: New strategies for inverse treatment planning

“…Kanai et al 1980). This can be done either using two sweeping magnets (Lorin et al 2000), or by combining one sweeping magnet with a moveable patient couch to cover the second direction (Pedroni et al 1995).…”