Pauwels Ruben
Department of Dentistry and Oral Health, Aarhus University, Denmark; Aarhus Institute of Advanced Studies, Aarhus University, Denmark; Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
Phys Med. 2023 Aug;112:102639. doi: 10.1016/j.ejmp.2023.102639. Epub 2023 Jul 11.
The purpose of this study was to determine a dedicated conversion formula between dose-area product (DAP) and effective dose (E) for dental CBCT, which incorporates X-ray beam energy as well as geometric factors.
CBCT exposures of an adult phantom were simulated using PCXMC 2.0 (STUK, Finland). Fifty-seven fields of view (FOV) were included, ranging from Ø4x4cm to Ø21x19cm. Six tube voltages (70 kV to 120 kV), eight combinations of Al (2.5 to 10 mm) and Cu (0 to 0.5 mm) filtration, and four source-isocentre distances (35 to 65 cm) were used, resulting in 10 896 simulated scan protocols. In addition, 10 944 random combinations of scan parameters within the aforementioned ranges were simulated, resulting in 21 840 scan protocols that were used for fitting a formula using multiple linear regression with 8 independent variables. Finally, 2304 random scan protocols were simulated as validation data to evaluate the formula's generalizability.
E/DAP ranged between 0.031 µSv/mGy.cm and 0.294 µSv/mGy.cm, with a mean of 0.150 µSv/mGy.cm. Due to extensive clustering of the E/DAP, three formulas were determined according to FOV categories (Small: <100 cm, Medium: 100-400 cm, Large: >400 cm). The resulting formulas showed mean absolute errors of 7.9%, 4.0% and 3.6%, respectively, for the validation data.
The new formulas allow for a straightforward, yet accurate, estimation of the effective dose for dental CBCT based on DAP. Further fine-tuning of the model could be achieved by incorporating, for example, bowtie filtration and off-axis beam geometries.
本研究的目的是确定牙科锥形束计算机断层扫描（CBCT）中剂量面积乘积（DAP）与有效剂量（E）之间的专用转换公式，该公式纳入了X射线束能量以及几何因素。
使用PCXMC 2.0（芬兰STUK）模拟成人模体的CBCT曝光。包括57个视野（FOV），范围从Ø4x4cm到Ø21x19cm。使用六种管电压（70 kV至120 kV）、八种铝（2.5至10 mm）和铜（0至0.5 mm）过滤组合以及四种源-等中心距离（35至65 cm），产生10896个模拟扫描方案。此外，模拟了上述范围内扫描参数的10944个随机组合，产生21840个扫描方案，用于使用具有8个自变量的多元线性回归拟合公式。最后，模拟2304个随机扫描方案作为验证数据，以评估公式的通用性。
E/DAP范围在0.031 µSv/mGy.cm至0.294 µSv/mGy.cm之间，平均值为0.150 µSv/mGy.cm。由于E/DAP的广泛聚类，根据视野类别（小：<100 cm，中：100 - 400 cm，大：>400 cm）确定了三个公式。对于验证数据，所得公式的平均绝对误差分别为7.9%、4.0%和3.6%。
新公式允许基于DAP对牙科CBCT的有效剂量进行直接而准确的估计。通过纳入例如蝴蝶结滤波器和离轴光束几何形状等因素，可以对模型进行进一步微调。
