Some properties of six different types of dental x-ray unit

Forty-four x-ray machines were tested for reliability of timer and for output. A distinction was made between different types of errors, and large differences between these categories of errors were found

A study of the radiographic aluminum equivalent values of the mandible

A longitudinal study of bone changes in the mandible was conducted. Duplicate radiographs were taken at 3-month intevals with the use of a positioning instrument, which included an aluminum calibrating wedge. The in-duplicate values obtained over the investigation period made it possible to assess the precision of the method and to analyze effects that take place with time. Significant bone changes were observed in seven volunteers between various observation periods at intervals of 6 and 9 months

Evaluation of postprocessing dual-energy methods in quantitative computed tomography. Part 2. Pracital aspects

Three facets of dual-energy quantitative computed tomography are studied: (1) the algorithm for postprocessing data (the methods of Cann, Laval-Jeantet et al, Goodsitt et al [two methods], and Nickoloff et al); (2) the influence of choice of tissue-equivalent materials for calibration; and (3) the difference between central and peripheral calibration. The different tissueequivalent materials include bone mineral-equivalent (K2HPO4 solutions and calcium hydroxyapatite), fat-equivalent (liquid paraffin, polyethylene, and 70% ethanol solution), and red marrow-equivalent (plastic). Deviation from the manufacturer's quoted content is least with central positioning of the calibration materials. The accuracy of estimates is best when the same tissueequivalent materials are used for calibration that are being measured. The deviations produced by the use of different tissueequivalent materials indicate the importance of using materials that mimic the components of bone most closely. The two methods of Goodsitt et al and the method of Nickoloff et al produced the best results