title: A novel image toggle tool for comparison of serial mammograms: automatic density normalization and alignment-development of the tool and initial experience.
abstract: OBJECTIVE
  The purpose is to develop a new image toggle tool with automatic density normalization (ADN) and automatic alignment (AA) for comparing serial digital mammograms (DMGs).
  
  
  METHODS
  We developed an ADN and AA process to compare the images of serial DMGs. In image density normalization, a linear interpolation was applied by taking two points of high- and low-brightness areas. The alignment was calculated by determining the point of the greatest correlation while shifting the alignment between the current and prior images. These processes were performed on a PC with a 3.20-GHz Xeon processor and 8 GB of main memory. We selected 12 suspected breast cancer patients who had undergone screening DMGs in the past. Automatic processing was retrospectively performed on these images. Two radiologists subjectively evaluated them.
  
  
  RESULTS
  The process of the developed algorithm took approximately 1 s per image. In our preliminary experience, two images could not be aligned approximately. When they were aligned, image toggling allowed detection of differences between examinations easily.
  
  
  CONCLUSIONS
  We developed a new tool to facilitate comparative reading of DMGs on a mammography viewing system. Using this tool for toggling comparisons might improve the interpretation efficiency of serial DMGs.
authors.affiliation: Department of Radiology, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo, 104-8561, Japan, honda.mrad@tmd.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Honda
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsunoda
authors.forename: Wataru
authors.initials: W
authors.lastname: Fukuda
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Saida
mesh_terms: D000465:Algorithms; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies