title: Amorphous silicon, flat-panel, x-ray detector: reliability of digital image fusion regarding angle and distance measurements in long-leg radiography.
abstract: OBJECTIVE
  To evaluate composed long-leg images acquired with a large-area, flat-panel x-ray detector with regard to angle and distance measurements.
  
  
  METHODS
  Radiographs of a long-leg phantom were acquired at 13 different angle settings with a 43-cm x 43-cm digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology. Three overlapping single images of the phantom were reconstructed at a workstation using a generalized correlation method. Four blinded observers were instructed to determine the angle of the axis of the long-legs as well as the length of "femur" and "tibia" on soft-copy displays. For that, the angle and distance measurement software integrated in the workstation was used. The images were analyzed with and without prior manual fine tuning of the primary composition result according to a mapped scale. Standard of reference was angle and distance determination at the phantom.
  
  
  RESULTS
  On average, the difference between the observers' angle measurements and the standard of reference was 0.4 degrees for both images with and without prior manual correction. Regarding distance measurements, the average discrepancies to the standard were 0.2 cm (femur) and 0.1 cm (tibia) when analyzing images that had undergone manual fine tuning and 0.5 cm and 0.7 cm, respectively, for images without manual correction.
  
  
  CONCLUSIONS
  The evaluated image fusion algorithm in conjunction with a 43-cm x 43-cm flat-panel detector is feasible regarding angle and distance measurements on long-leg images. In the case of inaccurate primary composition, results can be corrected easily by manual fine tuning.
authors.affiliation: Department of Diagnostic Radiology, University Hospital of Regensburg, Regensburg, Germany. o.hamer@gmx.de
authors.forename: Okka W
authors.initials: OW
authors.lastname: Hamer
authors.forename: Michael
authors.initials: M
authors.lastname: Strotzer
authors.forename: Niels
authors.initials: N
authors.lastname: Zorger
authors.forename: Christian
authors.initials: C
authors.lastname: Paetzel
authors.forename: Klaus
authors.initials: K
authors.lastname: Lerch
authors.forename: Stefan
authors.initials: S
authors.lastname: Feuerbach
authors.forename: Markus
authors.initials: M
authors.lastname: Völk
mesh_terms: D000465:Algorithms; D002586:Cesium; D006801:Humans; D007454:Iodides; D007867:Leg Bones / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D012015:Reference Standards; D012825:Silicon
chemical_list: D007454:Iodides; D002586:Cesium; C040050:cesium iodide; D012825:Silicon