title: Creating individual-specific biomechanical models of the breast for medical image analysis.
abstract: OBJECTIVE
  Anatomically realistic biomechanical models of the breast potentially provide a reliable way of mapping tissue locations across medical images, such as mammograms, magnetic resonance imaging (MRI), and ultrasound. This work presents a new modeling framework that enables us to create biomechanical models of the breast that are customized to the individual. We demonstrate the framework's capabilities by creating models of the left breasts of two volunteers and tracking their deformations across MRIs.
  
  
  METHODS
  We generate customized finite element models by automatically fitting geometrical models to segmented data from breast MRIs, and characterizing the in vivo mechanical properties (assuming homogeneity) of the breast tissues. For each volunteer, we identified the unloaded configuration by acquiring MRIs of the breast under neutral buoyancy (immersed in water). Such imaging is clearly not practical in the clinical setting; however, these previously unavailable data provide us with important data with which to validate models of breast biomechanics. Internal tissue features were identified in the neutral buoyancy images and tracked to the prone gravity-loaded state using the modeling framework.
  
  
  RESULTS
  The models predicted deformations with root-mean-square errors of 4.2 and 3.6 mm in predicting the skin surface of the gravity-loaded state for each volunteer. Internal tissue features were tracked with a mean error of 3.7 and 4.7 mm for each volunteer.
  
  
  CONCLUSIONS
  The models capture breast shape and internal deformations across the images with clinically acceptable accuracy. Further refinement of the framework and incorporation of more anatomic detail will make these models useful for breast cancer diagnosis.
authors.affiliation: Auckland Bioengineering Institute, University of Auckland, Auckland City, Auckland, New Zealand. v.rajagopal@auckland.ac.nz
authors.forename: Vijay
authors.initials: V
authors.lastname: Rajagopal
authors.forename: Angela
authors.initials: A
authors.lastname: Lee
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Chung
authors.forename: Ruth
authors.initials: R
authors.lastname: Warren
authors.forename: Ralph P
authors.initials: RP
authors.lastname: Highnam
authors.forename: Martyn P
authors.initials: MP
authors.lastname: Nash
authors.forename: Poul M F
authors.initials: PM
authors.lastname: Nielsen
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001940:Breast / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological