Measurement of absorbed doses near metal and dental material interfaces irradiated by x- and gamma-ray therapy beams.
Soft-tissue damage adjacent to dental restorations is a deleterious side effect of radiation therapy which is associated with low-energy electron scatter from dental materials of high electron density. This study was designed to investigate the enhancement of dose to soft tissue (or water) close to high electron-density materials and to measure the detailed lateral and depth-dose profiles in soft-tissue-simulating polymer adjacent to planar interfaces of several higher atomic-number materials: 18-carat gold dental casting alloy; Ag-Hg dental amalgam alloy; Ni-Cr dental casting alloy; and natural human tooth structure. Interleaved stacks of calibrated thin radiochromic dosimeter films and tissue-simulating polymer were used for these measurements. Assemblies of these polymer-dosimeter stacks on both sides of the dental materials were irradiated in one fixed direction by collimated 60Co gamma-ray or 10 MV x-ray beams directed perpendicularly to the material interfaces. In another test, designed to simulate more closely therapeutic treatment conditions, a phantom constructed on both sides of a row of restored and unrestored whole teeth (restoration materials: gold alloy crown; Ni-Cr alloy crown; Ag-Hg mesial-occlusal-distal (MOD) amalgam filling; unrestored tooth) was irradiated in one fixed direction by the collimated photon beams. Results indicate that the dose-enhancement in 'tissue' is as great as a factor of 2 on the backscatter side adjacent to gold and a factor of 1.2 adjacent to tooth tissue, but is insignificant on the forward-scatter side because of the predominant effect of attenuation by the high-density, high atomic-number absorbing material.
Farahani
M
M
ADAHF Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD 20899.
Eichmiller
F C
FC
McLaughlin
W L
WL
D002858:Chromium Alloys / Q000528:radiation effects; D003037:Cobalt Radioisotopes; D003722:Dental Alloys / Q000528:radiation effects*; D003723:Dental Amalgam / Q000528:radiation effects; D005720:Gamma Rays; D006047:Gold Alloys / Q000528:radiation effects; D006801:Humans; D011829:Radiation Dosage; D011878:Radiotherapy / Q000009:adverse effects; D012542:Scattering, Radiation; D014070:Tooth / Q000528:radiation effects*
D002858:Chromium Alloys; D003037:Cobalt Radioisotopes; D003722:Dental Alloys; D006047:Gold Alloys; D003723:Dental Amalgam