Development and Implementation of a Corriedale Ovine Brain Atlas for Use in Atlas-Based Segmentation

PLoS One. 2016 Jun 10;11(6):e0155974. doi: 10.1371/journal.pone.0155974. eCollection 2016.

Abstract

Segmentation is the process of partitioning an image into subdivisions and can be applied to medical images to isolate anatomical or pathological areas for further analysis. This process can be done manually or automated by the use of image processing computer packages. Atlas-based segmentation automates this process by the use of a pre-labelled template and a registration algorithm. We developed an ovine brain atlas that can be used as a model for neurological conditions such as Parkinson's disease and focal epilepsy. 17 female Corriedale ovine brains were imaged in-vivo in a 1.5T (low-resolution) MRI scanner. 13 of the low-resolution images were combined using a template construction algorithm to form a low-resolution template. The template was labelled to form an atlas and tested by comparing manual with atlas-based segmentations against the remaining four low-resolution images. The comparisons were in the form of similarity metrics used in previous segmentation research. Dice Similarity Coefficients were utilised to determine the degree of overlap between eight independent, manual and atlas-based segmentations, with values ranging from 0 (no overlap) to 1 (complete overlap). For 7 of these 8 segmented areas, we achieved a Dice Similarity Coefficient of 0.5-0.8. The amygdala was difficult to segment due to its variable location and similar intensity to surrounding tissues resulting in Dice Coefficients of 0.0-0.2. We developed a low resolution ovine brain atlas with eight clinically relevant areas labelled. This brain atlas performed comparably to prior human atlases described in the literature and to intra-observer error providing an atlas that can be used to guide further research using ovine brains as a model and is hosted online for public access.

MeSH terms

  • Algorithms
  • Anatomy, Artistic / methods*
  • Anatomy, Cross-Sectional / methods
  • Anatomy, Veterinary
  • Animals
  • Atlases as Topic*
  • Brain / anatomy & histology*
  • Brain / diagnostic imaging
  • Brain Mapping* / methods
  • Brain Mapping* / veterinary
  • Image Interpretation, Computer-Assisted
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging / methods
  • Sheep / anatomy & histology*

Grants and funding

The research was supported by Defense Advanced Research Projects Agency (DARPA) MTO Contract No. N66001-12-1-4045 (TJO); Office of Naval Research (ONR) Global No. N62909-14-1- N020 (TJO); National Health and Medical Research Council of Australia (NHMRC) Project Grant APP1062532 (TJO) and Development Grant APP1075117 (TJO); Defence Health Foundation, Australia (Booster Grant) (TJO); Defence Science Institute, Australia, grant (TJO); Brain Foundation, Australia, research gift (TJO), and the Victorian Government’s Operational Infrastructure Support Program (TJO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.