Erbium filtration for dose reduction in dental radiography.

Previous work has suggested that rare-earth filtration of diagnostic X rays is an effective means of dose reduction in radiology. Erbium (atomic number 68) is particularly promising in this respect. The effects on the X-ray beam and surface dose of the addition of 0.1 mm of erbium foil to the conventional filtration of a GE1000 dental X-ray set were investigated. Filtration by 0.1 mm of erbium produced a beam of narrower spectrum, greater penetration but lower intensity than that filtered conventionally by aluminium alone. The overall dose reduction achieved in dental radiography was greater than 30% between 65 and 85 kVp with a maximum dose reduction of 42% at 65 kVp. The question of the cost-effectiveness of erbium filtration as a radiation protection measure is also addressed.