title: Prospects and challenges of rendering tissue density in Hounsfield units for cone beam computed tomography.
abstract: OBJECTIVE
  Limitations in rendering of tissue density in Hounsfield units (HUs) for cone beam computed tomography (CBCT) are described and illustrated using a phantom and two CBCT systems to demonstrate grayscale measurement variability.
  
  
  METHODS
  The basis of the HU scale, its correlation with measured computed tomography (CT) numbers, and the limitations in the accuracy of such correlation due to artifacts are discussed. Rendering of tissue densities based on HU values of two CBCT systems [NewTom VGi and Hyperion X9, respectively large and small field of view (FOV)] are measured using a phantom.
  
  
  RESULTS
  Data produced from small FOV CBCT acquisition are generally less affected by artifacts compared with large FOV CBCT.
  
  
  CONCLUSIONS
  Artifacts challenge the accurate conversion of density values into HUs. Care should be taken when interpreting quantitative density measurements obtained with CBCT. With more advanced software and methods, it may be possible to improve the consistency and accuracy of density measurements.
authors.affiliation: robertodocmolteni@yahoo.com
authors.forename: Roberto
authors.initials: R
authors.lastname: Molteni
mesh_terms: D016477:Artifacts; D015519:Bone Density; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results