Department of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Jl. Prof. Soedarto SH, Tembalang, Semarang, Central Java, Indonesia.
Discipline of Medical Imaging Science, Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, C42 Cumberland Campus, NSW, Australia.
J Xray Sci Technol. 2020;28(4):695-708. doi: 10.3233/XST-200667.
The objective of this study is to determine X-ray dose distribution and the correlation between central, peripheral and weighted-centre peripheral doses for various phantom sizes and tube voltages in computed tomography (CT). We used phantoms developed in-house, with various water-equivalent diameters (Dw) from 8.5 up to 42.1 cm. The phantoms have one hole in the centre and four holes at the periphery. By using these five holes, it is possible to measure the size-specific central dose (Ds,c), peripheral dose (Ds,p), and weighted dose (Ds,w).The phantoms are scanned using a CT scanner (Siemens Somatom Definition AS), with the tube voltage varied from 80 up to 140 kVps. The doses are measured using a pencil ionization chamber (Ray safe X2 CT Sensor) in every hole for all phantoms. The relationships between Ds,c, Ds,p, and Ds,w, and the water-equivalent diameter are established. The size-conversion factors are calculated. Comparisons between Ds,c, Ds,p, and Ds,ware also established. We observe that the dose is relatively homogeneous over the phantom for water-equivalent diameters of 12-14 cm. For water-equivalent diameters less than 12 cm, the dose in the centre is higher than at the periphery, whereas for water-equivalent diameters greater than 14 cm, the dose at the centre is lower than that at the periphery. We also find that the distribution of the doses is influenced by the tube voltage. These dose distributions may be useful for calculating organ doses for specific patients using their CT images in future clinical practice.
本研究旨在确定不同大小的体模和管电压在计算机断层扫描（CT）中的 X 射线剂量分布以及中心剂量、外周剂量和加权中心外周剂量之间的相关性。我们使用了内部开发的体模，水当量直径（Dw）从 8.5 厘米到 42.1 厘米不等。体模中心有一个孔，周围有四个孔。通过使用这五个孔，可以测量特定尺寸的中心剂量（Ds,c）、外周剂量（Ds,p）和加权剂量（Ds,w）。体模使用 CT 扫描仪（西门子 Somatom Definition AS）进行扫描，管电压从 80 千伏到 140 千伏不等。对于所有体模，使用铅笔电离室（Ray safe X2 CT 传感器）在每个孔中测量剂量。建立了 Ds,c、Ds,p 和 Ds,w 与水当量直径之间的关系。计算了尺寸转换因子。还比较了 Ds,c、Ds,p 和 Ds,w。我们观察到，对于水当量直径为 12-14 厘米的体模，剂量在整个体模中相对均匀。对于水当量直径小于 12 厘米的体模，中心的剂量高于周围的剂量，而对于水当量直径大于 14 厘米的体模，中心的剂量低于周围的剂量。我们还发现，剂量的分布受到管电压的影响。这些剂量分布将来可能有助于在临床实践中使用患者的 CT 图像计算特定患者的器官剂量。
