High‐density dental implants and radiotherapy planning: evaluation of effects on dose distribution using pencil beam convolution algorithm and Monte Carlo method

Abstract

High atomic number and density of dental implants leads to major problems at providing an accurate dose distribution in radiotherapy and contouring tumors and organs caused by the artifact in head and neck tumors. The limits and deficiencies of the algorithms using in the treatment planning systems can lead to large errors in dose calculation, and this may adversely affect the patient's treatment. In the present study, four commercial dental implants were used: pure titanium, titanium alloy (Ti‐6Al‐4V), amalgam, and crown. The effects of dental implants on dose distribution are determined with two methods: pencil beam convolution (PBC) algorithm and Monte Carlo code for 6 MV photon beam. The central axis depth doses were calculated on the phantom for a source–skin distance (SSD) of 100 cm and a 10×10 cm2 field using both of algorithms. The results of Monte Carlo method and Eclipse TPS were compared to each other and to those previously reported. In the present study, dose increases in tissue at a distance of 2 mm in front of the dental implants were seen due to the backscatter of electrons for dental implants at 6 MV using the Monte Carlo method. The Eclipse treatment planning system (TPS) couldn't precisely account for the backscatter radiation caused by the dental prostheses. TPS underestimated the back scatter dose and overestimated the dose after the dental implants. The large errors found for TPS in this study are due to the limits and deficiencies of the algorithms. The accuracy of the PBC algorithm of Eclipse TPS was evaluated in comparison to Monte Carlo calculations in consideration of the recommendations of the American Association of Physicists in Medicine Radiation Therapy Committee Task Group 65. From the comparisons of the TPS and Monte Carlo calculations, it is verified that the Monte Carlo simulation is a good approach to derive the dose distribution in heterogeneous media.PACS numbers: 87.55.K‐

Investigating the effect of dental implant materials with different densities on radiotherapy dose distribution using Monte-Carlo simulation and pencil beam convolution algorithm

“…8 The algorithms used for dose calculations in treatment planning systems (TPS) cannot accurately calculate the scattered dose. 9 The Monte Carlo (MC) simulation is the best way to model the radiation beam and its interactions. More accurate results are obtained in dose calculations using MC simulation.…”

“…More accurate results are obtained in dose calculations using MC simulation. 1,5,9 Several groups have made measurements to investigate dental implant materials effect on the dose distribution. Ozen et al 8 and Beyzadeoglu et al 10 evaluated dose increment related to scattered radiation from bone-dental implant surface and beam incidence angle.…”

Feasibility of optimizing intensity‐modulated radiation therapy plans based on measured mucosal dose adjacent to dental fillings and toxicity outcomes

“…Possible reasons for the noted disagreement between the measured and calculated doses include a large dose gradient present in oral cavity, a dose variation from positioning uncertainties of the dosimeters, radiation scattering caused by the metallic fillings, and potentially inaccurate calculation on TPS due to streaking artifacts on CT images caused by metals. A number of previous studies have revealed the need for more accurate dose calculation techniques, such as Monte Carlo algorithm, especially when the structure is very close to the metallic implants and the local dose gradient is high, for example the abutting buccal or lingual mucosa as being studied here 14, 15, 16. Novel dose distributions generated by varying beam intensity and geometry within the IMRT software may explain the discrepancy in the trend of dose perturbations between this study and previous studies17, 18 most of which were done based on conventional RT techniques.…”

Photon and electron backscatter dose and energy spectrum analysis around Lipiodol using flattened and unflattened beams

“…4,5 We revealed the factor of the dose enhancement that was defined as the probability of electron generation. 9 They showed that the large errors were caused for the treatment planning without Monte Carlo calculation (MC). The backscatter around high-Z materials, that is dental implants, results in local dose enhancement.…”

“…[6][7][8] Çatli reported that a high atomic number and density of dental implants led to major problems with regard to providing an accurate dose distribution in radiotherapy, and also with regard to contouring tumors caused by artifacts in head and neck tumors. 9 They showed that the large errors were caused for the treatment planning without Monte Carlo calculation (MC). The MC method is a good approach toward deriving the dose distribution in heterogeneous media.…”