A general solution to charged particle beam flattening using an optimized dual-scattering-foil technique, with application to proton therapy beams

Abstract

This paper describes a dual-scattering-foil technique for flattening of radiotherapeutic charged particle beams. A theory for optimization of shapes and thicknesses of the scattering foils is presented. The result is a universal optimal secondary-scatterer profile, which can be adapted to any charged particle beam by a simple scaling procedure. The calculation of the mean square scattering angle of the beam after passing through the scattering foils is done using the generalized Fermi-Eyges model for charged particle transport. It is shown that the fluence profile in the plane of interest can be made flat to better than 1% inside a predefined beam radius provided the shaped secondary scatterer has the universal radial thickness profile. The thicknesses of the two foils are optimized to minimize the total energy loss. The theory has been tested experimentally in an 180 MeV clinical proton beam. The measured distributions agree well with the calculations.

A Study on Beam Flattening Based on Compact Double Scatterer Applicable to Rotational Beam Irradiation System in the Proton Therapy Facility at CYRIC, Tohoku University

“…To achieve SOBP, several types of ridge filters are employed in front of proton beam to give desired homogeneous dose in depth 4) . In lateral direction, broad and uniform beam profile is produced using double scattering technique [5][6][7] or single scattering in combination with beam wobbling system 8) . The wobbling system includes two separate magnets in series for horizontal and vertical deflecting of protons along their central axis in a circular fashion.…”

Range and modulation dependencies for proton beam dose per monitor unit calculations

“…[10][11][12][13] For beam ranges between 6 and 27 cm, a single physical modulator device is used for a defined modulation width. In this system, the lateral dose uniformity in the plane of the isocenter is optimized for different beam ranges by displacing the first scatterer towards or away from the isocenter.…”

The CNAO dose delivery system for modulated scanning ion beam radiotherapy

“…The CNAO synchrotron [14] has been designed to accelerate protons or carbon ions to energies corresponding to depth from 3 to 32 g/cm 2 and from 3 to 27 g/cm 2 , respectively. Two identical ion sources, the radio frequency quadrupole and a linear accelerator are located inside the 25 m diameter ring of the synchrotron.…”

“…The pioneer passive beam delivery systems [1,2,3] are being replaced by active systems [4,5,6,7] which provide highly conformal dose distributions using pristine 70 monoenergetic pencil beams at well-defined penetration depths without any need for patient-specific hardware. The scanned ion beam technique is currently used only in few centers worldwide [8,9,10], but several existing and proposed facilities are developing scanning capabilities in Asia, Europe, and USA [11,12,13].…”