title: Comparison of Tissue Density in Hounsfield Units in Computed Tomography and Cone Beam Computed Tomography.
abstract: OBJECTIVE
  Bone quality and quantity assessment is one of the most important steps in implant treatment planning. Different methods such as computed tomography (CT) and recently suggested cone beam computed tomography (CBCT) with lower radiation dose and less time and cost are used for bone density assessment. This in vitro study aimed to compare the tissue density values in Hounsfield units (HUs) in CBCT and CT scans of different tissue phantoms with two different thicknesses, two different image acquisition settings and in three locations in the phantoms.
  
  
  METHODS
  Four different tissue phantoms namely hard tissue, soft tissue, air and water were scanned by three different CBCT and a CT system in two thicknesses (full and half) and two image acquisition settings (high and low kVp and mA). The images were analyzed at three sites (middle, periphery and intermediate) using eFilm software. The difference in density values was analyzed by ANOVA and correction coefficient test (P<0.05).
  
  
  RESULTS
  There was a significant difference between density values in CBCT and CT scans in most situations, and CBCT values were not similar to CT values in any of the phantoms in different thicknesses and acquisition parameters or the three different sites. The correction coefficients confirmed the results.
  
  
  CONCLUSIONS
  CBCT is not reliable for tissue density assessment. The results were not affected by changes in thickness, acquisition parameters or locations.
authors.affiliation: Oral and Maxillofacial Radiologist, Tehran, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Varshowsaz
authors.affiliation: Oral and Maxillofacial Radiologist, Tehran, Iran.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Goorang
authors.affiliation: Oral and Maxillofacial Radiologist, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Ehsani
authors.affiliation: Assistant Professor of Oral and Maxillofacial Radiology, Oral and Maxillofacial Radiology Department, Shahed University of Medical Sciences, Dental School, Tehran, Iran.
authors.forename: Zeynab
authors.initials: Z
authors.lastname: Azizi
authors.affiliation: Assistant Professor of Oral and Maxillofacial Radiology, Oral and Maxillofacial Radiology Department, Shahid Beheshti University of Medical Sciences, Dental School, Tehran, Iran.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Rahimian
keywords: Bone Density; Cone-Beam Computed Tomography; Tomography, X-Ray Computed