title: Optimization of abdominal fat quantification on CT imaging through use of standardized anatomic space: a novel approach.
abstract: OBJECTIVE
  The quantification of body fat plays an important role in the study of numerous diseases. It is common current practice to use the fat area at a single abdominal computed tomography (CT) slice as a marker of the body fat content in studying various disease processes. This paper sets out to answer three questions related to this issue which have not been addressed in the literature. At what single anatomic slice location do the areas of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) estimated from the slice correlate maximally with the corresponding fat volume measures? How does one ensure that the slices used for correlation calculation from different subjects are at the same anatomic location? Are there combinations of multiple slices (not necessarily contiguous) whose area sum correlates better with volume than does single slice area with volume?
  
  
  METHODS
  The authors propose a novel strategy for mapping slice locations to a standardized anatomic space so that same anatomic slice locations are identified in different subjects. The authors then study the volume-to-area correlations and determine where they become maximal. To address the third issue, the authors carry out similar correlation studies by utilizing two and three slices for calculating area sum.
  
  
  RESULTS
  Based on 50 abdominal CT data sets, the proposed mapping achieves significantly improved consistency of anatomic localization compared to current practice. Maximum correlations are achieved at different anatomic locations for SAT and VAT which are both different from the L4-L5 junction commonly utilized currently for single slice area estimation as a marker.
  
  
  CONCLUSIONS
  The maximum area-to-volume correlation achieved is quite high, suggesting that it may be reasonable to estimate body fat by measuring the area of fat from a single anatomic slice at the site of maximum correlation and use this as a marker. The site of maximum correlation is not at L4-L5 as commonly assumed, but is more superiorly located at T12-L1 for SAT and at L3-L4 for VAT. Furthermore, the optimal anatomic locations for SAT and VAT estimation are not the same, contrary to common assumption. The proposed standardized space mapping achieves high consistency of anatomic localization by accurately managing nonlinearities in the relationships among landmarks. Multiple slices achieve greater improvement in correlation for VAT than for SAT. The optimal locations in the case of multiple slices are not contiguous.
authors.affiliation: Department of Radiology, Medical Image Processing Group, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6021.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Tong
authors.affiliation: Department of Radiology, Medical Image Processing Group, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6021.
authors.forename: Jayaram K
authors.initials: JK
authors.lastname: Udupa
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6021.
authors.forename: Drew A
authors.initials: DA
authors.lastname: Torigian
mesh_terms: D050153:Abdominal Fat / Q000000981:diagnostic imaging*; D050218:Body Fat Distribution / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D050152:Intra-Abdominal Fat / Q000000981:diagnostic imaging; D016014:Linear Models; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D011860:Radiography, Abdominal / Q000379:methods*; D012189:Retrospective Studies; D050151:Subcutaneous Fat / Q000000981:diagnostic imaging; D013904:Thoracic Vertebrae; D014057:Tomography, X-Ray Computed / Q000379:methods*