title: Sequential dual-energy subtraction technique with a dynamic flat-panel detector (FPD): primary study for image-guided radiation therapy (IGRT).
abstract: A sequential dual-energy subtraction technique for image-guided radiation therapy (IGRT) was developed. Here, we report on a computerized method for creating sequential soft-tissue images and the accuracy of tracking targets on the images obtained, in comparison to conventional fluoroscopic images. Two sets of sequential chest images during respiration of a normal subject were obtained with X-rays of different energy separately with a flat-panel detector (FPD). Sequential soft-tissue images were created from the two sets of sequential images consisting of real-time images and reference template images, respectively. The creation of sequential soft-tissue images consisted of three steps: one-to-one image correspondence of the two sequential images, image registration, and image subtraction in each frame. Motion tracking of lung vessels was then performed by the template-matching technique. For evaluation of the accuracy of motion tracking on the sequential soft-tissue images, the results were compared with those on the original sequential images. Sequential soft-tissue images provided more accurate tracking than the original images (P < 0.01). There was no significant error throughout all frames in the soft-tissue images, whereas the rib shadow introduced a tracking error in the original images. The maximum errors were 4.1 +/- 0.3 mm in the sequential soft-tissue images and 28.1 +/- 20.0 mm in the original images. In conclusion, sequential soft-tissue images were helpful for tracking of a target affected by respiratory motion. Dual-energy subtraction has the potential to improve the accuracy of IGRT without implanted markers.
authors.affiliation: Division of Health Sciences, Radiology, Graduate School of Medical Science, Kanazawa University, Kodatsuno, Kanazawa, Japan. rie44@mhs.mp.kanazawa-u.ac.jp
authors.forename: Rie
authors.initials: R
authors.lastname: Tanaka
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sanada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsui
authors.forename: Norio
authors.initials: N
authors.lastname: Hayashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsui
mesh_terms: D005471:Fluoroscopy / Q000379:methods; D008175:Lung Neoplasms / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D012983:Soft Tissue Neoplasms / Q000532:radiotherapy*; D013382:Subtraction Technique / Q000295:instrumentation*
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