Rustemeyer P, Streubühr U, Hohn H P, Rustemeyer R, Eich H T, John-Mikolajewski V, Müller R D
Zentralinstitut für Röntgendiagnostik, Universität Essen.
Rofo. 1999 Aug;171(2):130-5. doi: 10.1055/s-1999-243.
The intention of this study was to reduce patient dose during dental CT in the planning for osseointegrated implants.
Dental CTs were performed with a spiral CT (Somatom Plus 4, Siemens) and a dental 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) which delivered the best image quality at the lowest possible radiation dose, as tested in a preceding study. Image quality was analysed using a human anatomic head preparation. Four radiologists analysed the images independently. A Wilcoxon rank pair-test was used for statistic evaluation. The doses to the thyroid gland, the active bone marrow, the salivary glands, and the eye lens were determined in a tissue-equivalent phantom (Alderson-Rando Phantom) with lithium fluoride thermoluminescent dosimeters at the appropriate locations.
By mAs reduction from 165 to 35 and using a pitch factor 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 glands from 2.3 mSv to 0.4 mSv). The dose reduction did not lead to an actual loss of image quality or diagnostic information.
A considerable dose reduction without loss of diagnostic information is achievable in dental CT. Dose-reducing examination protocols like the one presented may further expand the use of preoperative dental CT.
本研究旨在减少牙种植体植入计划中牙科CT检查时的患者辐射剂量。
使用螺旋CT（西门子Somatom Plus 4）及牙科软件包进行牙科CT扫描。将常规牙科CT技术[1]（120 kVp；165 mA，旋转时间1秒，165 mAs；螺距因子1）与一种新方案（120 kVp；50 mA；旋转时间0.7秒；35 mAs；螺距因子2）进行比较，在前一项研究中已测试该新方案能在尽可能低的辐射剂量下提供最佳图像质量。使用人体解剖头部模型分析图像质量。四名放射科医生独立分析图像。采用Wilcoxon秩和检验进行统计学评估。在组织等效体模（Alderson-Rando体模）的适当位置，使用氟化锂热释光剂量计测定甲状腺、活性骨髓、唾液腺和晶状体所接受的剂量。
通过将mAs从165降低至35并使用螺距因子2，辐射剂量最多可降低9倍（例如，骨髓剂量可从23.6 mSv降至2.9 mSv，晶状体剂量从0.5 mSv降至0.3 mSv，甲状腺剂量从2.5 mSv降至0.5 mSv，腮腺剂量从2.3 mSv降至0.4 mSv）。剂量降低并未导致图像质量或诊断信息的实际损失。
牙科CT检查可在不损失诊断信息的情况下大幅降低辐射剂量。像本文所介绍的这种降低剂量的检查方案可能会进一步扩大术前牙科CT的应用范围。
