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Time‐Related Changes of In Vivo Projection Errors in Standardized Radiographs
Author(s) -
Zappa Urs,
Simona Claudio,
Graf Hans,
van Aken Jan
Publication year - 1993
Publication title -
journal of periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.036
H-Index - 156
eISSN - 1943-3670
pISSN - 0022-3492
DOI - 10.1902/jop.1993.64.4.278
Subject(s) - radiography , observational error , projection (relational algebra) , interval (graph theory) , subtraction , nuclear medicine , mathematics , optics , medicine , physics , statistics , surgery , algorithm , arithmetic , combinatorics
S ubtraction radiography requires radiographs made with identical projection geometry. Recently a new radiographic aiming device and an x‐ray beam manipulator made it possible to repeat radiographic exposures in vivo with small angular errors and to measure the angular errors occurring. The purpose of the present investigation was to study in vivo the measuring error and the angular errors produced by this new method at different time points (0, 6, and 12 months) and to assess the effect of different time intervals between exposures (0, 6, and 12 months). Ten sites were investigated. At each time point 2 exposures were made, resulting in 6 radiographs per site. For each pair of radiographs the measuring errors occurring during analysis and the projection errors were determined for each time point and for each time interval. Friedman's test and t ‐test were used to evaluate the errors. A difference in the measuring error of the system and in the angular errors at the timepoints 0, 6, and 12 months could not be detected. A time interval between exposures also did not have an effect on the measuring error. Time did not affect the vertical and horizontal angular errors measured between the radiographs producing the smallest oblique error. A combination of radiographs producing the largest oblique angular error showed an increase of the horizontal and vertical angular errors when the time interval increases. These effects, however, were not statistically significant. From these results it appears that the new radiographic aiming device and x‐ray beam manipulator produce radiographs with small changes in angular projection errors between radiographs taken with a time interval of 0, 6, or 12 months when they are selected from duplicate exposures. This new radiographic aiming device and x‐ray beam manipulator will greatly assist in providing standardized radiographs for computer analysis of changes in alveolar bone over time. J Periodontol 1993; 64:278–284 .