Simulation studies of field shaping in rotational radiation therapy

Abstract

This article presents simulation studies of field shaping in rotational radiation therapy by means of two categories of beam modifying devices: protectors and shapers. The protectors used are diminished copies of the organs at risk (OARs) and stay parallel to them during gantry rotation. Thus, each protector always keeps the corresponding OAR in its shadow, significantly reducing the irradiation. The shapers are used in order to obtain a more uniform dose distribution in the planning target volume (PTV) while preserving their initial orientation during gantry rotation. Thus, the use of beam modifying devices allows modulation of the beam intensity, to better fit irradiation requirements, at every gantry position. A software tool for calculations of geometrical position and dimensions of the beam modifying devices, using information about the shape, size, and position of the protected organ or area at risk as input, was developed. This tool was integrated into the in-house-developed Monte Carlo radiation therapy simulator (MCRTS), used to simulate the particle transport through the designed system. The verification of the software tool showed good agreement between experimental and simulation data, with discrepancies of less than 3%. Dose distributions in solid-geometry and voxel-based neck models were evaluated. Furthermore, the effectiveness of the shapers to modify the dose distribution outside the protected area was studied. Results demonstrated that the use of the shapers effectively improves dose uniformity. Studies using shapers of different materials were also carried out and resulted in similar dose distributions. The results of the simulation studies with a voxel-based model showed that rotational therapy with beam modifying devices offers adequate protection of the OAR and a uniform dose distribution outside the protected region.

Using Nano Tungsten Oxide Polymer Composite as a Gamma Radiation Shielding

“…In the study by Ivanova et al, [7] high density polymer metal composites are used for radiation protection in radiotherapy. In the preparation of this composite, wolfram powder and polymer were created by mixing high-density and low X-ray transmittance.…”

Radiation attenuation capability and flow characteristics of HDPE composite loaded with W, MoS2, and B4C

“…Presence of wolfram metal powder in styrene‐butadiene‐styrene copolymer matrix created a new high energy radiation shielding material . In another work, prepared high density polymer‐wolfram composites were studied and showed low x‐ray transmittance .…”

Modeling and simulation of filters and devices for conformal radiotherapy

“…The dose homogeneity outside the OAR, opposite, is worsening. The dose homogeneity can be improved by use of beam shapers, as it was shown both by experimental (Danciu 2001) and by simulation (Ivanova et al 2005) studies.…”

“…Nevertheless, adequate protection of the OAR and uniform dose at the target volume has to be provided. Cylindrical attenuator inserted in the treatment beam can effectively be used for a protection of the spinal cord in the case of rotational therapy (Proimos 1961, Danciu 2001, Jena et al 2004, Ivanova et al 2006. The idea of the protection is simple, evident and elegant.…”