title: Feasibility study of dual energy radiographic imaging for target localization in radiotherapy for lung tumors.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  It is feasible to apply the technique for tumor localization in radiotherapy.
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Huo
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Radiation Oncology, Tianjin Cancer Hospital, Tianjin, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Department of Radiation Oncology, Tianjin Cancer Hospital, Tianjin, China.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Department of Radiation Oncology, Tianjin Cancer Hospital, Tianjin, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Physics, East Carolina University, Greenville, North Carolina, United States of America.
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Hu
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China; Department of Radiation Oncology, Tianjin Cancer Hospital, Tianjin, China; Department of Radiation Oncology, East Carolina University, Greenville, North Carolina, United States of America.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Feng
mesh_terms: D000465:Algorithms; D005240:Feasibility Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000295:instrumentation