Huo Jie, Zhu Xianfeng, Dong Yang, Yuan Zhiyong, Wang Ping, Wang Xuemin, Wang Gang, Hu Xin-Hua, Feng Yuanming
Department of Biomedical Engineering, Tianjin University, Tianjin, China.
Department of Radiation Oncology, Tianjin Cancer Hospital, Tianjin, China.
PLoS One. 2014 Sep 30;9(9):e108823. doi: 10.1371/journal.pone.0108823. eCollection 2014.
Dual-energy (DE) radiographic imaging improves tissue discrimination by separating soft from hard tissues in the acquired images. This study was to establish a mathematic model of DE imaging based on intrinsic properties of tissues and quantitatively evaluate the feasibility of applying the DE imaging technique to tumor localization in radiotherapy.
We investigated the dependence of DE image quality on the radiological equivalent path length (EPL) of tissues with two phantoms using a stereoscopic x-ray imaging unit. 10 lung cancer patients who underwent radiotherapy each with gold markers implanted in the tumor were enrolled in the study approved by the hospital's Ethics Committee. The displacements of the centroids of the delineated gross tumor volumes (GTVs) in the digitally reconstructed radiograph (DRR) and in the bone-canceled DE image were compared with the averaged displacements of the centroids of gold markers to evaluate the feasibility of using DE imaging for tumor localization.
The results of the phantom study indicated that the contrast-to-noise ratio (CNR) was linearly dependent on the difference of EPL and a mathematical model was established. The objects and backgrounds corresponding to ΔEPL less than 0.08 are visually indistinguishable in the bone-canceled DE image. The analysis of patient data showed that the tumor contrast in the bone-canceled images was improved significantly as compared with that in the original radiographic images and the accuracy of tumor localization using the DE imaging technique was comparable with that of using fiducial makers.
It is feasible to apply the technique for tumor localization in radiotherapy.
双能（DE）射线成像通过在采集的图像中将软组织与硬组织分离来改善组织辨别能力。本研究旨在基于组织的固有特性建立DE成像的数学模型，并定量评估将DE成像技术应用于放射治疗中肿瘤定位的可行性。
我们使用立体X射线成像单元，通过两个体模研究了DE图像质量对组织放射等效路径长度（EPL）的依赖性。10名接受放射治疗且肿瘤内植入了金标记物的肺癌患者参与了本研究，该研究经医院伦理委员会批准。将数字重建射线照片（DRR）和去骨DE图像中勾勒出的大体肿瘤体积（GTV）质心的位移与金标记物质心的平均位移进行比较，以评估使用DE成像进行肿瘤定位的可行性。
体模研究结果表明，对比噪声比（CNR）与EPL的差值呈线性相关，并建立了数学模型。在去骨DE图像中，对应于ΔEPL小于0.08的物体和背景在视觉上无法区分。对患者数据的分析表明，与原始射线图像相比，去骨图像中的肿瘤对比度显著提高，并且使用DE成像技术进行肿瘤定位的准确性与使用基准标记物相当。
将该技术应用于放射治疗中的肿瘤定位是可行的。
