Shielding analysis of the proton therapy facility at China Medical University Hospital: comparison of a simplified approach with Monte Carlo simulations.

This study comprehensively compared two approaches for analyzing the shielding design of the proton therapy facility at China Medical University Hospital. The first approach essentially involved two approximate models: one for estimating the transmitted radiation through thick shields, and one for estimating radiation streaming at locations near a maze entrance. The second approach relied on Monte Carlo simulations for predicting the radiation field in a complex environment. A total of 22 beam loss scenarios were considered, and dose rates at 32 locations around the facility were estimated using the two approaches. The comparison results demonstrated that the simplified approach proposed in this study can yield fairly accurate or conservative estimates for quickly performing shielding design or dose assessment in a real-world proton therapy facility.

Comparison of different methods for the shielding analysis of an AB-BNCT facility based on the Be(p,xn) reaction with 30-MeV protons.

Five shielding calculation methods were employed to estimate the dose rate distribution around an accelerator-based boron neutron capture therapy facility. Their performances were compared in terms of accuracy and efficiency. The results indicate that the hybrid deterministic/Monte Carlo method is the most efficient in the context of accurate modeling and simulation, whereas the analytical approximation with pre-generated source terms and attenuation lengths is preferable in the design phase because of its simplicity and ease of verification while retaining a reasonable accuracy.

SCOPING ANALYSIS OF MATERIAL ACTIVATION AT A BORON NEUTRON CAPTURE THERAPY FACILITY BASED ON THE Be(p,xn) REACTION WITH 30 MeV PROTONS.

Material activation assessment of a proposed accelerator-based boron neutron capture therapy facility was performed using the FLUKA Monte Carlo code to quantify the magnitude of the problem in terms of the isotope inventories, induced activities, and residual dose rates. Two simplified operation scenarios were considered: a 30-min proton bombardment to simulate a typical session of patient treatment and a long-term 1 year continuous operation to estimate the accumulation of long-lived radionuclides. Following the generation and transport of decay radiation, the space- and time-dependent inventories of induced radionuclides in materials and residual dose rates after shutdown were obtained. The predicted results were compared with the corresponding regulatory limits. Moreover, the effectiveness of various measures to reduce the impact of material activation was demonstrated.

Neutron yield and induced radioactivity: a study of 235-MeV proton and 3-GeV electron accelerators.

This study evaluated the magnitude of potential neutron yield and induced radioactivity of two new accelerators in Taiwan: a 235-MeV proton cyclotron for radiation therapy and a 3-GeV electron synchrotron serving as the injector for the Taiwan Photon Source. From a nuclear interaction point of view, neutron production from targets bombarded with high-energy particles is intrinsically related to the resulting target activation. Two multi-particle interaction and transport codes, FLUKA and MCNPX, were used in this study. To ensure prediction quality, much effort was devoted to the associated benchmark calculations. Comparisons of the accelerators' results for three target materials (copper, stainless steel and tissue) are presented. Although the proton-induced neutron yields were higher than those induced by electrons, the maximal neutron production rates of both accelerators were comparable according to their respective beam outputs during typical operation. Activation products in the targets of the two accelerators were unexpectedly similar because the primary reaction channels for proton- and electron-induced activation are (p,pn) and (γ,n), respectively. The resulting residual activities and remnant dose rates as a function of time were examined and discussed.

Shielding analysis of proton therapy accelerators: a demonstration using Monte Carlo-generated source terms and attenuation lengths.

Monte Carlo simulations are generally considered the most accurate method for complex accelerator shielding analysis. Simplified models based on point-source line-of-sight approximation are often preferable in practice because they are intuitive and easy to use. A set of shielding data, including source terms and attenuation lengths for several common targets (iron, graphite, tissue, and copper) and shielding materials (concrete, iron, and lead) were generated by performing Monte Carlo simulations for 100-300 MeV protons. Possible applications and a proper use of the data set were demonstrated through a practical case study, in which shielding analysis on a typical proton treatment room was conducted. A thorough and consistent comparison between the predictions of our point-source line-of-sight model and those obtained by Monte Carlo simulations for a 360° dose distribution around the room perimeter showed that the data set can yield fairly accurate or conservative estimates for the transmitted doses, except for those near the maze exit. In addition, this study demonstrated that appropriate coupling between the generated source term and empirical formulae for radiation streaming can be used to predict a reasonable dose distribution along the maze. This case study proved the effectiveness and advantage of applying the data set to a quick shielding design and dose evaluation for proton therapy accelerators.

Source terms and attenuation lengths for estimating shielding requirements or dose analyses of proton therapy accelerators.

Proton therapy accelerators in the energy range of 100-300 MeV could potentially produce intense secondary radiation, which must be carefully evaluated and shielded for the purpose of radiation safety in a densely populated hospital. Monte Carlo simulations are generally the most accurate method for accelerator shielding design. However, simplified approaches such as the commonly used point-source line-of-sight model are usually preferable on many practical occasions, especially for scoping shielding design or quick sensitivity studies. This work provides a set of reliable shielding data with reasonable coverage of common target and shielding materials for 100-300 MeV proton accelerators. The shielding data, including source terms and attenuation lengths, were derived from a consistent curve fitting process of a number of depth-dose distributions within the shield, which were systematically calculated by using MCNPX for various beam-target shield configurations. The general characteristics and qualities of this data set are presented. Possible applications in cases of single- and double-layer shielding are considered and demonstrated.