Low-dose dental CT.

Purpose: The intention of this study was to reduce patient dose during dent al CT in the planning for osseointegrated implants. Methods and Materials: Dental CTs were performed with a spiral CT (Somatom Plus4, Siemens) and a d ental software package. Use of the usual dental CT technique [1] (120 kVp; 165 mA, 1 s rotation time, 165 mAs; pitch factor 1) was compared with a new protocol (120 kVp; 50 mA; 0.7 s rotation time; 35 mAs; pitch factor 2) whi ch delivered the best image quality at the lowest possible radiation dose, as tested in a preceding study. Image quality was analysed using a human an atomic head preparation. Four radiologists analysed the images independentl y. A Wilcoxon rank pair-test was used for statistic evaluation. The doses t o the thyroid gland, the active bone marrow, the salivary glands, and the e ye lens were determined in a tissue-equivalent phantom (Alderson-Rando Phan tom) with lithium fluoride thermoluminescent dosimeters at the appropriate locations. Results: By mAs reduction from 165 to 35 and using a pitch facto r of 2, the radiation dose could be reduced by a factor of nine (max.) (e.g ., the bone marrow dose could be reduced from 23.6 mSv to 2.9 mSv, eye lens from 0.5 mSv to 0.3 mSv, thyroid gland from 2.5 mSv to 0.5 mSv, parotid gl ands from 2.3 m5v to 0.4 mSv). The dose reduction did not lead to an actual loss of image quality or diagnostic information. Conclusion: A considerabl e dose reduction without loss of diagnostic information is achievable in de ntal CT. Dose-reducing examination protocols like the one presented may fur ther expand the use of preoperative dental CT.