title: Automated registration of breast lesions in temporal pairs of mammograms for interval change analysis--local affine transformation for improved localization.
abstract: Analysis of interval change is important for mammographic interpretation. The aim of this study is to evaluate the use of an automated registration technique for computer-aided interval change analysis in mammography. Previously we developed a regional registration technique for identifying masses on temporal pairs of mammograms. In the current study, we improved lesion registration by including a local alignment step. Initially, the lesion position on the prior mammogram was estimated based on the breast geometry. An initial fan-shaped search region was then defined on the prior mammogram. In the second stage, the location of the fan-shaped region on the prior mammogram was refined by warping, based on an affine transformation and simplex optimization in a local region. In the third stage, a search for the best match between the lesion template from the current mammogram and a structure on the prior mammogram was carried out within the search region. This technique was evaluated on 124 temporal pairs of mammograms containing biopsyproven masses. Eighty-seven percent of the estimated lesion locations resulted in an area overlap of at least 50% with the true lesion locations and an average distance of 2.4 +/- 2.1 mm between their centroids. The average distance between the estimated and the true centroid of the lesions on the prior mammogram over all 124 temporal pairs was 4.2 +/- 5.7 mm. The registration accuracy was improved in comparison with our previous study that used a data set of 74 temporal pairs of mammograms. This improvement in accuracy resulted from the improved geometry estimation and the local affine transformation.
authors: Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, USA.lhadjiiski@umich.edu
authors: L
authors: L
authors: Hadjiiski
authors: H P
authors: HP
authors: Chan
authors: B
authors: B
authors: Sahiner
authors: N
authors: N
authors: Petrick
authors: M A
authors: MA
authors: Helvie
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D017711:Nonlinear Dynamics; D011857:Radiographic Image Interpretation, Computer-Assisted; D013997:Time Factors