| Objective. To evaluate the effects on observer depth discrimination and vertical reading error of using linear, conical, and random x-ray beam arrays to make basis images for tomosynthetic reconstruction using Tuned-Aperture Computed Tomography (TACT(TM)) for assessing mandibular implant positioning with respect to simulated mandibular canals.; Materials and methods. Two tissue-equivalent test devices were constructed to replicate the position of a dental implant in relation to simulated mandibular canals. The x-ray generator was a Diamatic AP (Villa Systemi Medicali, Buccinasco, Italy) operating at 70 kVp, and 8 mA with 2 mm Al equivalent filtration. The receptor was a CDR #2 size CCD sensor (Schick Technologies, Long Island City, NY). The source-to-object and object-to-receptor distances were standardized using a specially fabricated optical bench. Beam geometries used to acquire the basis images for TACT(TM) integration included linear horizontal, linear vertical, symmetric conical, asymmetric conical, and random arrays.; Statistical analysis. Data for depth discrimination and vertical reading errors were entered into Microsoft Excel and analyzed by SPSS software Version 9.0 for Windows using a one-way ANOVA. The Tukey HSD was performed for comparison of reading errors using each type of projection.; Results. The means of reading errors for TACT images constructed using the various different projection arrays were small (0.09--1.24 mm). Horizontal linear, vertical linear, symmetric conical and asymmetric conical projections performed with no statistical difference (p > 0.05).; Conclusion. No statistical differences were shown between linear and conical projection arrays for TACT images for determining the relationship between a dental implant and a simulated mandibular canal. |
