Anam Choirul, Fujibuchi Toshioh, Toyoda Takatoshi, Sato Naoki, Haryanto Freddy, Widita Rena, Arif Idam, Dougherty Geoff
Department of Physics, Faculty of Mathematics and Natural Sciences, Diponegoro University, Jl. Prof. Soedarto SH, Semarang 50275, Central Java, Indonesia.
Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Ganesha 10, Bandung 40132, West Java, Indonesia.
Radiat Prot Dosimetry. 2018 Apr 1;179(2):158-168. doi: 10.1093/rpd/ncx241.
The purpose of this study is to establish the relationship between the pixel value (I) of the CT localizer radiograph and water-equivalent thickness (tw) in a straightforward procedure. We used a body CTDI phantom, which was scanned in the AP and LAT projections. After transformation from the pixel values of the images to tw, water-equivalent diameter (Dw) and size-specific dose estimate were calculated on an anthropomorphic phantom and 30 patients retrospectively. We found a linear correlation between I and tw, with R2 ≥ 0.980. The Dw values based on the CT localizer radiograph were comparable to those calculated using axial images. The Dw difference for the anthropomorphic phantom between AP projection and axial images was 5.4 ± 4.2%, and between LAT projection and axial images was 6.7 ± 5.3%. The Dw differences for the patients between CT localizer radiograph and axial images was 2.3 ± 3.2%.
本研究的目的是通过一种直接的方法建立CT定位片的像素值（I）与水等效厚度（tw）之间的关系。我们使用了一个体部CTDI模体，对其进行前后位（AP）和侧位（LAT）扫描。在将图像的像素值转换为tw后，回顾性地计算了一个仿真人体模体和30例患者的水等效直径（Dw）及尺寸特异性剂量估计值。我们发现I与tw之间存在线性相关性，R2≥0.980。基于CT定位片的Dw值与使用轴向图像计算得到的值相当。仿真人体模体在前后位投影与轴向图像之间的Dw差异为5.4±4.2%，在侧位投影与轴向图像之间的Dw差异为6.7±5.3%。患者在CT定位片与轴向图像之间的Dw差异为2.3±3.2%。
