Universitat Rovira i Virgili. Servei de Protecci Radiològica Sant Llorenç 21, 43201 Reus, Spain.
Dentomaxillofac Radiol. 2013;42(3):92555893. doi: 10.1259/dmfr/92555893. Epub 2012 Aug 29.
The aim of this study was to calculate organ and effective doses for a range of available protocols in a particular cone beam CT (CBCT) scanner dedicated to dentistry and to derive effective dose conversion factors.
Monte Carlo simulations were used to calculate organ and effective doses using the International Commission on Radiological Protection voxel adult male and female reference phantoms (AM and AF) in an i-CAT CBCT. Nine different fields of view (FOVs) were simulated considering full- and half-rotation modes, and also a high-resolution acquisition for a particular protocol. Dose-area product (DAP) was measured.
Dose to organs varied for the different FOVs, usually being higher in the AF phantom. For 360°, effective doses were in the range of 25-66 μSv, and 46 μSv for full head. Higher contributions to the effective dose corresponded to the remainder (31%; 27-36 range), salivary glands (23%; 20-29%), thyroid (13%; 8-17%), red bone marrow (10%; 9-11%) and oesophagus (7%; 4-10%). The high-resolution protocol doubled the standard resolution doses. DAP values were between 181 mGy cm(2) and 556 mGy cm(2) for 360°. For 180° protocols, dose to organs, effective dose and DAP were approximately 40% lower. A conversion factor (DAP to effective dose) of 0.130 ± 0.006 μSv mGy(-1) cm(-2) was derived for all the protocols, excluding full head. A wide variation in dose to eye lens and thyroid was found when shifting the FOV in the AF phantom.
Organ and effective doses varied according to field size, acquisition angle and positioning of the beam relative to radiosensitive organs. Good positive correlation between calculated effective dose and measured DAP was found.
本研究旨在计算特定牙科专用锥形束 CT（CBCT）扫描仪中一系列现有方案的器官和有效剂量，并推导有效剂量转换因子。
使用蒙特卡罗模拟方法，使用国际辐射防护委员会体素成年男性和女性参考体模（AM 和 AF）在 i-CAT CBCT 中计算器官和有效剂量。模拟了 9 种不同的视野（FOV），考虑了全旋转和半旋转模式，以及特定方案的高分辨率采集。测量剂量面积乘积（DAP）。
不同 FOV 的器官剂量不同，AF 体模中的剂量通常更高。对于 360°，有效剂量范围为 25-66 μSv，全头部为 46 μSv。对有效剂量的贡献较高的依次为余部（31%；27-36 范围）、唾液腺（23%；20-29%）、甲状腺（13%；8-17%）、红骨髓（10%；9-11%）和食管（7%；4-10%）。高分辨率方案将标准分辨率剂量增加了一倍。对于 360°，DAP 值在 181 mGy·cm(-2) 和 556 mGy·cm(-2) 之间。对于 180°方案，器官剂量、有效剂量和 DAP 约降低 40%。对于所有方案（不包括全头部），推导了一个转换因子（DAP 到有效剂量）为 0.130±0.006 μSv·mGy(-1)·cm(-2)。当在 AF 体模中移动 FOV 时，发现眼晶体和甲状腺的剂量有很大的变化。
器官和有效剂量根据射束相对于敏感器官的大小、采集角度和位置而变化。发现计算的有效剂量与测量的 DAP 之间存在良好的正相关性。
