Design of ridge filters for spread-out Bragg peaks with Monte Carlo simulation in carbon ion therapy

Abstract

Spread-out Bragg peaks made by ridge filters or wheel range modulators are used in charged particle therapy with passive methods to achieve uniform biological responses in irradiated tumors. Following the biological responses needed to design the ridge filters, which were developed at the National Institute of Radiological Sciences in Japan, new ridge filters were designed using recent developments in heavy-ion reactions and dosimetry. The Monte Carlo code of Geant4 was used to calculate the qualities of carbon ion beams in a water phantom. The results obtained from the simulation were corrected so that they agreed with the measurements of depth dose distributions. The calculations of biological responses to fragments other than carbon ions were assumed to be for helium ions. The measured dose distributions with the designed ridge filters were compared to the calculated distributions. A beam modifying system using this adaptable method was successively applied to carbon ion therapy at Gunma University.

Correction to: Estimation of linear energy transfer distribution for broad-beam carbon-ion radiotherapy at the National Institute of Radiological Sciences, Japan

“…The indifference to the fragments may also be justified by their theoretical difficulty such that even advanced Monte Carlo simulation required empirical correction for them [21]. To select either polyline to apply for a singleL D value, we took the RBE at the proximal end of SOBP, or at d = R − M , as the RBE threshold r BEth per energy per modulation.…”

A preliminary Monte Carlo study for the treatment head of a carbon-ion radiotherapy facility using TOPAS

“…The ridge filter is a stationary plate shaped device made of aluminum typically (mass density ȡ=2.7 kg/m3), and consists of about a total of 40 ridge bars abreast placed every 5 mm in this modelling. The beam energy will be degraded by bring in the ridge filter [21,22]. After the ridge filter, the Spread-Out Bragg peak will be produced to cover the target in depth with a relatively homogeneous RBE-weighted dose [2][3][4].…”

A Mathematic Method to Adjust MLC Leaf End Position for Accuracy Dose Calculation in Carbon Ion Beam Radiation Therapy Treatment Planning System

“…The struggling range of carbon ion beam in MLC saves troubles with the rounded leaf end design caused by photon attenuation in MLC [5]. One of the most important principles of MLC design is to reduce the differences between the dose 50% points and the projected light field edge on axis [6]. The characteristic of the projected light field edge locations and the definition of MLC position as well as the dose 50% points in photon treatment planning system need to be corrected before patients' treatment monitor units are calculated.…”