Proposals for revised factors in intra-oral radiography shielding calculations.
The current value for weighted average primary plus scatter kerma at 1 m for intra-oral radiography shielding assessment is based on scatter radiation measurements made with the trunk of a RANDO phantom and an assessment of primary transmission that is unverified. Measurements of primary transmission and scatter radiation during intra-oral radiography were made at 30° intervals through a full 360° rotation using two anthropomorphic head phantoms and similar equipment at three different sites. The results suggest that a scatter factor of 5 µGy (Gy cm(2))(-1) and a primary transmission of 0.03% of the entrance surface dose are more appropriate and, therefore, we recommend that the weighted average primary plus scatter kerma used for shielding calculations can be reduced from 1 to 0.5 µGy per exposure at 1 m. This factor will adequately account for exposures made at 60 and 70 kV using a range of intra-oral units.
Radiation Physics, Department of Medical Physics, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK. markworrall@nhs.net
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D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011861:Radiography, Dental / Q000295:instrumentation; D011874:Radiometry / Q000379:methods*; D018570:Risk Assessment; D012542:Scattering, Radiation