title: Classification of galactograms with ramification matrices: preliminary results.
abstract: OBJECTIVE
  The poor specificity of galactography, the imaging modality generally indicated in cases of nipple discharge, has led to a large number of biopsies with negative results. A quantitative scheme for classifying galactographic findings might help reduce the number of such biopsies in the future. As a first step toward that goal, the authors have studied one quantitative method for describing the branching of ducts by using ramification matrices (R matrices), and the correlation of the values of the matrix elements with clinical findings.
  
  
  METHODS
  The ductal trees were manually segmented for 25 galactographic views from 15 patients, and corresponding R matrices were calculated. Patients were divided into two groups: those with no reported galactographic findings (NF) and those with reported findings (RF) of ductal ectasia, cysts, or papilloma. In a leave-one-out fashion, the authors evaluated a classification scheme that was based on R-matrix coefficients and used a Bayesian decision rule. The effects of segmentation were tested by successively removing each of the terminal ducts and computing the corresponding matrices of the pruned trees.
  
  
  RESULTS
  With use of a single R-matrix element, 92% and 62% of NF and RF cases were correctly classified, respectively (P = .007). With use of two elements, 83% and 77% of NF and RF cases were correctly classified, but this result was not statistically significant (P = .108). In a test of robustness, an analysis of pruned trees yielded an average root-mean-square fractional difference of 9.7% between the elements of the original and the R matrix averaged over all pruned trees.
  
  
  CONCLUSIONS
  The preliminary analysis indicates that it may be possible to identify cases with reported galactographic findings by using R matrices.
authors.affiliation: Department of Radiology, Thomas Jefferson University, Suite 3390 Gibbon Bldg, 111 S 11th St, Philadelphia, PA 19107-5563, USA.
authors.forename: Predrag R
authors.initials: PR
authors.lastname: Bakic
authors.forename: Michael
authors.initials: M
authors.lastname: Albert
authors.forename: Andrew D A
authors.initials: AD
authors.lastname: Maidment
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods*; D008875:Middle Aged; D009558:Nipples / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D010212:Papilloma / Q000000981:diagnostic imaging / Q000473:pathology*