Abstract
The presence of dental metals creates radiation dose perturbation due to scattered radiation during radiation therapy for the head and neck region. The purpose of our study was to compare the scatter doses resulting from various dental metals in the direction of the buccal mucosa among a single‐field technique, three‐dimensional conformal radiation therapy (3D CRT), and intensity‐modulated radiation therapy (IMRT) during radiation therapy for the head and neck region. We used nine metal cubes with 10 mm sides, which were placed inside a water phantom. The scatter doses from the cubes in the direction of the buccal mucosa were measured using radiochromic films. The films were placed perpendicularly to the surface of the cubes. The phantom was irradiated with a 4 MV photon energy by a linear accelerator for all techniques. In the single‐field technique, the scatter doses from dental metals showed 3.7%–19.3% dose increases, and gold showed the largest dose increase. In 3D CRT, the scatter doses from dental metals showed 1.4%–6.9% dose increases, which were within the measurement uncertainty (except for gold). In IMRT, the scatter doses from dental metals showed only 1.4%–4.3% dose increases, which were all within the measurement uncertainty. During radiation therapy for the head and neck region, the scatter doses from the tested dental metals in the direction of the buccal mucosa in 3D CRT or IMRT were lower than those using the single‐field technique. However, there were no differences between the scatter doses resulting from particular dental metals in the direction of the buccal mucosa in 3D CRT and those in IMRT, except for gold.PACS number: 87
Highlights
234 Shimamoto et al.: Scatter doses from dental metals observed: 1) an upstream dose increase due to backscatter, which may be the primary source of intraoral mucositis in the surrounding normal tissue in a clinical setting, and 2) a downstream dose decrease due to attenuation over the influence of the dose increase due to forward scatter, which might cause an underprescribed dose being administered to the tumor.[5]. The magnitude of the dose increase due to backscatter strongly depends on the atomic number of the scatterer for both photons[1,2,3,4] and electrons.[6,7,8,9]
All data from dental metals were normalized at a depth of 22 mm, where there was no influence of the scattered radiation, to correct the variability of measurement doses and compare the scatter doses from dental metals
In 3D CRT, the scatter doses from dental metals showed 1.4%–6.9% dose increases, which were within the measurement uncertainty, except for Au (Figs. 5(c) and 5(d))
Summary
234 Shimamoto et al.: Scatter doses from dental metals observed: 1) an upstream dose increase due to backscatter, which may be the primary source of intraoral mucositis in the surrounding normal tissue in a clinical setting, and 2) a downstream dose decrease due to attenuation over the influence of the dose increase due to forward scatter, which might cause an underprescribed dose being administered to the tumor.[5]. Mail et al[13] reported that the scatter doses in the direction of the buccal mucosa from a dental metal for single, parallel-opposed fields and volumetric-modulated arc therapy (VMAT) were significantly different. They evaluated only a single dental metal. We suggest that the evaluation of the scatter doses from various dental metals in the direction of the buccal mucosa among different irradiation methods is needed, as many kinds of metals are used clinically, and the magnitude of scatter doses differs according to their atomic number or composition. The aim of this study was to compare the scatter doses resulting from various dental metals in the direction of the buccal mucosa, and to compare these doses among the conventional single-field technique, three-dimensional conformal radiation therapy (3D CRT), and intensitymodulated radiation therapy (IMRT) during radiation therapy for the head and neck region
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