title: Nonlinear geometric warping of the mask image: a new method for reducing misregistration artifacts in digital subtraction angiography.
abstract: OBJECTIVE
  Misregistration artifact is the major cause of image degradation in digital subtraction angiography (DSA). The purpose of this study was to evaluate the efficacy of a newly developed nonlinear geometric warping method to reduce misregistration artifact in DSA.
  
  
  METHODS
  The processing of the images was carried out on a workstation with a fully automatic computerized program. After making differential images with a lapracian filter, 49 regions of interest (ROIs) were set in the image to be processed. Each ROI of the live image scanned the corresponding ROI of the mask image searching for the best position to match itself. Each pixel of the mask image was shifted individually following the data calculated from the shifts of the ROIs. Five radiologists compared the images produced by the conventional parallel shift technique and those processed with this new method in 16 series of cerebral DSA.
  
  
  RESULTS
  In 14 of 16 series (88%), more radiologists judged the images processed with the new method to be better in quality. Small arteries near the skull base and veins of low density were clearly visualized in the images processed by the new method.
  
  
  CONCLUSIONS
  This newly proposed method could be a simple and practical way to automatically reduce misregistration artifacts in DSA.
authors.affiliation: Department of Radiology, Fukui Medical School, 23 Shimoaizuki, Matsuoka-cho, Yoshida-gun, Fukui 910-11, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Sakai
authors.forename: M
authors.initials: M
authors.lastname: Kitagawa
authors.forename: R
authors.initials: R
authors.lastname: Inagaki
authors.forename: N
authors.initials: N
authors.lastname: Sadato
authors.forename: Y
authors.initials: Y
authors.lastname: Ishii
authors.forename: Y
authors.initials: Y
authors.lastname: Nishimoto
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Fukushima
authors.forename: H
authors.initials: H
authors.lastname: Komuro
authors.forename: H
authors.initials: H
authors.lastname: Ogura
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Kubota
mesh_terms: D015901:Angiography, Digital Subtraction / Q000379:methods*; D016477:Artifacts; D002533:Cerebral Angiography; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*