title: Alveolar bone measurement precision for phosphor-plate images.
abstract: OBJECTIVE
  The aim was to demonstrate methods for determining measurement precision and to determine the precision of alveolar bone measurements made with a vacuum-coupled positioning device and phosphor plate images.
  
  
  METHODS
  Subjects were rigidly attached to the x-ray tube by means of a vacuum coupling device and custom cross-arch bite plates. Original and repeat radiographs (taken within minutes of each other) were obtained of the mandibular posterior teeth of 51 subjects, and cementoenamel junction-alveolar crest (CEJ-AC) distances were measured on both sets of images. In addition, x-ray transmission (radiodensity) and AC height differences were determined by subtracting one image from the other. Image subtractions and measurements were performed twice. Based on duplicate measurements, the root mean square standard deviation (precision) and least significant change (LSC) were calculated. LSC is the magnitude of change in a measurement needed to indicate that a true biologic change has occurred.
  
  
  RESULTS
  The LSCs were 4% for x-ray transmission, 0.49 mm for CEJ-AC distance, and 0.06 mm for crest height.
  
  
  CONCLUSIONS
  The LSCs for our CEJ-AC and x-ray transmission measurements were similar to what has been previously reported. The LSC for AC height (determined with image subtraction) was <0.1 mm. Compared with findings from earlier studies, this represents a highly precise measurement of AC height. The methods demonstrated for calculating LSC can be used by investigators to determine how large changes in radiographic measurements need to be before the changes can be considered to be (with 95% confidence) true biologic changes and not noise (i.e., equipment/observer error).
authors.affiliation: Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. hildeboltc@mir.wustl.edu
authors.forename: Charles F
authors.initials: CF
authors.lastname: Hildebolt
authors.forename: Rex
authors.initials: R
authors.lastname: Couture
authors.forename: Nathalia M
authors.initials: NM
authors.lastname: Garcia
authors.forename: Debra
authors.initials: D
authors.lastname: Dixon
authors.forename: D Doug
authors.initials: DD
authors.lastname: Miley
authors.forename: William
authors.initials: W
authors.lastname: Shannon
authors.forename: Cheryl
authors.initials: C
authors.lastname: Mueller
authors.forename: Eric
authors.initials: E
authors.lastname: Langenwalter
authors.forename: Cathy Anderson
authors.initials: CA
authors.lastname: Spearie
authors.forename: R
authors.initials: R
authors.lastname: Civitelli
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging*; D015519:Bone Density / Q000502:physiology; D002508:Cephalometry / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D019252:Radiography, Dental, Digital / Q000379:methods* / Q000706:statistics & numerical data; D013382:Subtraction Technique / Q000706:statistics & numerical data; D019237:Tooth Cervix / Q000000981:diagnostic imaging