Premium
SU‐E‐T‐65: Dose Enhancement Measurements at High‐Z Dental Materials Using Radiochromic EBT‐2 Films
Author(s) -
Schoenfeld A,
Poppinga D,
Poppe B,
Chofor N
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4735121
Subject(s) - materials science , dosimetry , titanium , alloy , monte carlo method , biomedical engineering , nuclear medicine , optics , composite material , physics , metallurgy , medicine , statistics , mathematics
Purpose: The purpose of this work is to investigate the dose enhancement at high‐Z interfaces using radiochromic films. In radiation therapy the problem occurs for instance in H&N treatments. The dose enhancement at dental crowns and implants may cause necrosis of tissue or damage to the jawbone. In this study, typical dental materials like dental gold, Wirobond (Co‐Cr alloy) zirconium dioxide and titanium were investigated. Methods: Dose enhancement effects were investigated for the following materials: dental gold alloy (73% gold, 16% aurum, 11% other), cobalt‐chromium alloy (61%cobalt, 29% chromium, 10% other), zirconium dioxide (stabilized with 5% Y2O3) and titanium. The proximal and distal dose distribution near the robe's interfaces was measured with a slab geometry setup consisting of four EBT‐2 films separated by 0.5mm/0.5mm/1mm RW3. This setup was placed between two 6cm stacks of RW3 functioning as build‐up material. At a Siemens Primus linac, a 6MV photon beam with a field size of 10×10cm 2 and a source to surface distance of 100cm was used. The EBT2 films were digitized at a scanning resolution of 72dpi using an Epson 10000XL flatbed scanner with a transparency unit. Furthermore the films were fixed in analignment frame to prevent Newton rings in the scanned image. The results were verified with Monte Carlo simulations using DOSRZnrc/EGSnrc. Results: The dose enhancement at the proximal surface of the dental gold alloy is 59%, while the other three materials showed enhancements ranging between 20%–25%. The Monte Carlo simulations confirmed these results. In all cases, the dose enhancement decreases to less than 10% at a proximal distance of 3mm. Conclusions: The dose enhancements near dental implant materials should be properly accounted for in treatment plans and, if possible, a safety distance should be created around crowns withapproximately 3mm of water equivalent material.