title: How accurate is CBCT in measuring bone density? A comparative CBCT-CT in vitro study.
abstract: OBJECTIVE
  Recently, cone beam computed tomography (CBCT) has become widely used for oral and maxillofacial imaging. Twenty dry mandibles were CBCT and conventional multislice CT scanned to evaluate if there is a statistically significant difference between the bone density values they produce, defined as gray density values, and to determine any correlation between them.
  
  
  METHODS
  Using software and a radiographic template, the CT and CBCT scan images were overlapped, and two data sets were created, each one giving the respective gray values (voxel value [VV] or Hounsfield unit [HU]) of the same area with the same spatial coordinates. For the statistical analysis, t-test, Pearson's correlation, and Pearson's r were used.
  
  
  RESULTS
  The differences between the CBCT (VV) and CT (HU) gray density values were statistically significant (p ≤ .05), whereas the Pearson's correlation coefficients and Pearson's r-values demonstrated a statistically significant linear correlation between VV and HU gray density values.
  
  
  CONCLUSIONS
  The lower radiation dose and reduced costs of CBCT make this a useful substitute for CT; however, this study has shown that, in order to more accurately define the bone density with CBCT, a conversion ratio needs to be applied to the VV.
authors.affiliation: Department of Oral and Maxillofacial Sciences, School of Dentistry, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Cassetta
authors.forename: Luigi Vito
authors.initials: LV
authors.lastname: Stefanelli
authors.forename: Andrea
authors.initials: A
authors.lastname: Pacifici
authors.forename: Luciano
authors.initials: L
authors.lastname: Pacifici
authors.forename: Ersilia
authors.initials: E
authors.lastname: Barbato
mesh_terms: D015519:Bone Density; D054893:Cone-Beam Computed Tomography; D006801:Humans; D066298:In Vitro Techniques; D008334:Mandible / Q000000981:diagnostic imaging*; D061330:Multidetector Computed Tomography; D011857:Radiographic Image Interpretation, Computer-Assisted; D012984:Software
keywords: Hounsfield value; bone density; computed tomography; cone beam