title: Effect of bone chip orientation on quantitative estimates of changes in bone mass using digital subtraction radiography.
abstract: OBJECTIVE
  To assess the effect of the orientation of arbitrarily shaped bone chips on the correlation between radiographic estimates of bone loss and true mineral loss using digital subtraction radiography.
  
  
  METHODS
  Twenty arbitrarily shaped bone chips (dry weight 1-10 mg) were placed individually on the superior lingual aspect of the interdental alveolar bone of a dry dentate hemi-mandible. After acquiring the first baseline image, each chip was rotated 90 degrees and a second radiograph was captured. Follow-up images were created without the bone chips and after rotating the mandible 0, 1, 2, 4, and 6 degrees around a vertical axis. Aluminum step tablet intensities were used to normalize image intensities for each image pair. Follow-up images were registered and geometrically standardized using projective standardization. Bone chips were dry ashed and analyzed for calcium content using atomic absorption.
  
  
  RESULTS
  No significant difference was found between the radiographic estimates of bone loss from the different bone chip orientations (Wilcoxon: P > 0.05). The correlation between the two series of estimates for all rotations was 0.93 (Spearman: P < 0.05). Linear regression analysis indicated that both correlates did not differ appreciably ( and ).
  
  
  CONCLUSIONS
  It is concluded that the spatial orientation of arbitrarily shaped bone chips does not have a significant impact on quantitative estimates of changes in bone mass in digital subtraction radiography. These results were obtained in the presence of irreversible projection errors of up to six degrees and after application of projective standardization for image reconstruction and image registration.
authors.affiliation: Division of Oral and Maxillofacial Radiology, Department of Diagnostic Sciences and General Dentistry, School of Dentistry, University of North Carolina at Chapel Hill, North Carolina 27599-7450, USA. Andre_Mol@dentistry.unc.edu
authors.forename: André
authors.initials: A
authors.lastname: Mol
authors.forename: Stanley M
authors.initials: SM
authors.lastname: Dunn
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging; D018488:Bone Demineralization, Pathologic / Q000000981:diagnostic imaging; D015519:Bone Density; D001862:Bone Resorption / Q000000981:diagnostic imaging; D001842:Bone and Bones / Q000737:chemistry / Q000000981:diagnostic imaging*; D002118:Calcium / Q000032:analysis; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016015:Logistic Models; D008334:Mandible / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement / Q000379:methods; D013054:Spectrophotometry, Atomic; D018709:Statistics, Nonparametric; D013382:Subtraction Technique
chemical_list: D002118:Calcium