title: Reference line-pair values of panoramic radiographs using an arch-form phantom stand to assess clinical image quality.
abstract: OBJECTIVE
  This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand.
  
  
  METHODS
  The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points.
  
  
  RESULTS
  The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region.
  
  
  CONCLUSIONS
  Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.
authors.affiliation: Department of Oral and Maxillofacial Radiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Da-Hye
authors.initials: DH
authors.lastname: Choi
authors.forename: Bo-Ram
authors.initials: BR
authors.lastname: Choi
authors.forename: Jin-Woo
authors.initials: JW
authors.lastname: Choi
authors.forename: Kyung-Hoe
authors.initials: KH
authors.lastname: Huh
authors.forename: Won-Jin
authors.initials: WJ
authors.lastname: Yi
authors.forename: Min-Suk
authors.initials: MS
authors.lastname: Heo
authors.forename: Soon-Chul
authors.initials: SC
authors.lastname: Choi
authors.forename: Sam-Sun
authors.initials: SS
authors.lastname: Lee
keywords: Phantom, Imaging; Quality Assurance; Radiography, Panoramic