Application of lung substitute material as ripple filter for multi-ion therapy with helium-, carbon-, oxygen-, and neon-ion beams

Abstract

A development project for hypo-fractionated multi-ion therapy has been initiated at the National Institute of Radiological Sciences in Japan. In the treatment, helium, carbon, oxygen, and neon ions will be used as primary beams with pencil beam scanning. A ripple filter (RiFi), consisting of a thin plastic or aluminum plate with a fine periodic ridge and groove structure, has been used to broaden the Bragg peak of heavy-ion beams in the beam direction. To sufficiently broaden the Bragg peak of helium-, carbon-, oxygen-, and neon-ion beams with suppressed lateral scattering and surface dose inhomogeneity, in this study, we tested a plate made of a lung substitute material, Gammex LN300, as the RiFi. The planar integrated dose distribution of a 183.5 MeV u−1 neon-ion beam was measured behind a 3 cm thick LN300 plate in water. The Bragg peak of the pristine beam was broadened following the normal distribution with the standard deviation σ value of 1.29 mm, while the range of the beam was reduced by 8.8 mm by the plate. To verify the LN300 performance as the RiFi in multi-ion therapy, we measured the pencil beam data of helium-, carbon-, oxygen- and neon-ion beams penetrating the 3 cm thick LN300 plate. The data were then modeled and used in a treatment planning system to achieve a uniform 10% survival of human undifferentiated carcinoma cells within a cuboid target by the beam for each of the different ion species. The measured survival fractions were reasonably reproduced by the planned ones for all the ion species. No surface dose inhomogeneity was observed for any ion species even when the plate was placed close to the phantom surface. The plate made of lung substitute material, Gammex LN300, is applicable as the RiFi in multi-ion therapy with helium-, carbon-, oxygen- and neon-ion beams.

Development of ripple filter composed of metal mesh for charged-particle therapy

“…The principle of the Bragg peak broadening by porous material uses the randomness of its microstructure, and has been well described by the binary voxel model (Titt et al 2015, Baumann et al 2017, Ringbaek et al 2017, Inaniwa et al 2021. In the model, a plate of porous material is modeled as regularly arrayed fine cubic voxels filled with either a high-density material or air.…”

“…The RiFi in multi ion irradiation is required to: sufficiently broaden the Bragg peak, suppress surface dose inhomogeneity, and suppress the lateral beam spread for all the particle species used. As a RiFi that satisfies these requirements, a RiFi using porous material with a random microstructure has been studied (Ringbaek et al 2017, Inaniwa et al 2021. The random microstructure of a porous material broadens the Bragg peak width without causing surface dose inhomogeneity.…”

Adaptation of stochastic microdosimetric kinetic model to hypoxia for hypo-fractionated multi-ion therapy treatment planning

“…n,D ¯These parameters depend only on the cell line, and they are independent of the radiation type. We assumed r n = 8.1 μm for all cell lines following our previous studies (Inaniwa andKanematsu 2018, Inaniwa et al 2020b). = K 3 mmHg has been experimentally determined for several cell lines exposed to photon radiation (Wouters andBrown 1997, Hall andGiaccia 2006).…”

“…A development project for hypo-fractionated multi-ion therapy (HFMIT) has been initiated at the National Institutes for Quantum Science and Technology (QST) in Japan for further improvement of clinical results of charged-particle therapy especially for radioresistant tumors. In the treatment, helium-, carbon-, oxygen-, and neon-ion beams will be used as primary beams with wide linear energy transfer (LET) ranges (Inaniwa et al 2020a(Inaniwa et al , 2020b(Inaniwa et al , 2021. To carry out the HFMIT, the biological effectiveness of these radiation beams has to be predicted for individual clinical cases based on biological models (Kanai et al 1999, Krämer and Scholz 2000, Inaniwa et al 2015c.…”

“…The SMK model was developed and verified for in vitro experiments under aerobic conditions (Inaniwa andKanematsu 2018, Inaniwa et al 2020b). The response of cells to radiation is however strongly dependent on oxygen conditions in addition to radiation type, LET and absorbed dose (Furusawa et al 2000(Furusawa et al , 2012.…”