In external radiotherapy for head and neck cancer, it is possible that some patients have metal dental materials. In this situation, a critical problem is that electronic backscatter from the upstream surface of these materials may damage the surrounding soft tissue. The purpose of this study was to determine the impact of electronic backscatter from dental materials with high-energy external X-ray irradiation and also to determine the optimal thickness of a protecting device (PMMA) for preventing its effect by using EGS5 Monte Carlo simulation. First, four high-energy X-rays (4, 6, 10, and 15 MV) and five dental materials (three metals and two ceramics) of 1 × 1 × 0.2 cm3 were used to investigate the impact of electronic backscatter from dental materials and also to investigate the correlation between these impacts and X-ray energies. Then, based on these results, optimal thickness of protective PMMA was investigated. Results of 6 MV and 10 M V, backscatter effects from the surfaces of dental materials (1 mm distance) caused increases of up to 132.1% and 134.6% (gold-silver-palladium alloy), and 141.7% and 146.2% (Metal-ceramic-gold alloy) of the simulation without dental material, respectively. Shielded with a 3 mm PMMA, these effects reduced to 101.4% and 104.4% (gold-silver-palladium alloy), and 102.5% and 106.7% (metal-ceramic-gold-alloy) respectively. The results showed that the impact of electronic backscatter was greater for materials with higher Z. The impact of electronic backscatter was also greater when X-ray energy was increased. Therefore, in order to protect soft tissue from the impact of electronic backscatter, it is necessary to make an optimal protective material according to patient-specific treatment.
|Number of pages||8|
|Publication status||Published - 2014 Oct 1|
|Event||2014 21st EGS Users' Meeting in Japan - Tsukuba, Japan|
Duration: 2014 Aug 4 → 2014 Aug 5
|Conference||2014 21st EGS Users' Meeting in Japan|
|Period||14/8/4 → 14/8/5|
ASJC Scopus subject areas