Program including abstracts as pdf available here

P 92
Title
DOSIMETRy OF uPPER STANDARD DIGITAL OCCLuSAL RADIOGRAPHy
Authors
J. DAVIES 1 , D. DARIOS 2
Affiliations
1 Kings College London Dental Institute, London, UNITED KINGDOM, 2 Medical Physics Department,
Guys Hospital, London, UNITED KINGDOM
Body
Objective: The aim of this study was to investigate the effects of a thyroid shield and X-ray
beam collimation (circular/ rectangular) on the effective dose when taking the upper standard
occlusal radiograph.
Methods: Experiments were performed using a tissue-equivalent RANDO head phantom and
dental x-ray tube (60 kVp, 7 mA and 0.25 s) at a 65° downwards angulated beam. The absorbed
dose to various sensitive organs was measured at 24 different positions with thermoluminescent
dosimeters and the effective dose was determined using the tissue weighting factors
from the 2007 ICRP recommendations. Each individual radiographic exposure was repeated 10
times and each experimental method was repeated twice.
Results: Using circular collimation the mean effective dose was 0.93 µSv ±30% (E2007), adding
a thyroid shield the dose decreased to 0.61 µSv ±30% (E2007). Utilising a rectangular collimator
the mean effective dose was 0.68 µSv ±30% (E2007), adding a thyroid shield the mean
effective dose decreased to 0.41 µSv ±30% (E2007). The absorbed dose to the thyroid is reduced
by approximately 50% when using a thyroid shield, from 13.4 mGy to 6.7 mGy when using
circular collimation and from 10.0 mGy to 3.8 mGy when using a rectangular collimator.
Conclusion: The effective dose and absorbed dose to radiossensitive organs such as the thyroid
gland can be reduced significantly when using rectangular collimation and a thyroid collar
which is in keeping with the ICRP recommendations of optimisation and dose limitation.
Keywords
Dental Radiography,Thermoluminescent Dosimetry,Radiation Dosimetry
POSTerS
207