title: Development and evaluation of a robust algorithm for computer-assisted detection of sentinel lymph node micrometastases.
abstract: OBJECTIVE
  Increasing the sectioning rate for breast sentinel lymph nodes can increase the likelihood of detecting micrometastases. To make serial sectioning feasible, we have developed an algorithm for computer-assisted detection (CAD) with digitized lymph node sections.
  
  
  RESULTS
  K-means clustering assigned image pixels to one of four areas in a colourspace (representing tumour, unstained background, counterstained background and microtomy artefacts). Four filters then removed 'false-positive' pixels from the tumour cluster. A set of 43 sections containing tumour (a total of 259 foci) and 59 sections negative for malignancy was defined by two pathologists, using light microscopy, and CAD was applied. For the clinically relevant task of identifying the largest focus in each section (micrometastasis in 22/43 sections), the sensitivity and specificity were 100%. Isolated tumour cells (ITCs) were identified in one slide initially considered to be negative. Identification of all 259 foci yielded sensitivities of 57.5% for ITCs (<0.200 mm), 89.5% for micrometastases, and 100% for larger metastases, with one false-positive. Reduced sensitivity was ascribed to variable staining. Nine additional metastases (<0.01-0.3 mm) that were not initially identified were detected by CAD.
  
  
  CONCLUSIONS
  This algorithm is well suited to the task of sentinel lymph node evaluation and may enhance the detection of occult micrometastases.
authors.affiliation: Imaging Research, Sunnybrook Health Sciences Centre, Department of Surgical Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada. gina.clarke@sunnybrook.ca
authors.forename: Gina M
authors.initials: GM
authors.lastname: Clarke
authors.forename: Chris
authors.initials: C
authors.lastname: Peressotti
authors.forename: Claire M B
authors.initials: CM
authors.lastname: Holloway
authors.forename: Judit T
authors.initials: JT
authors.lastname: Zubovits
authors.forename: Kela
authors.initials: K
authors.lastname: Liu
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Yaffe
mesh_terms: D000465:Algorithms; D001943:Breast Neoplasms / Q000175:diagnosis; D016000:Cluster Analysis; D003936:Diagnosis, Computer-Assisted / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000175:diagnosis*; D008853:Microscopy; D061206:Neoplasm Micrometastasis / Q000175:diagnosis*; D010338:Pathology, Clinical / Q000706:statistics & numerical data; D012189:Retrospective Studies; D021701:Sentinel Lymph Node Biopsy