Effect of region-of-interest in computerized densitometric analysis of radiographs.

The region-of-interest (ROI) in computer-assisted densitometric image analysis (CADIA) is defined by its size and location. This study evaluated the effects of these variables on two quantitative parameters, the change in density and the area with change in density. Pairs of radiographs for these analyses were obtained from sites with "no change" or "known loss" in Cynomolgus monkeys during a study of ligature-induced periodontitis. The size and location of the ROI had clear effects on the two CADIA parameters. To reduce these effects, a corrective procedure hypothesizing a linear relationship between the ROI size and the area with change in density was tested. While this procedure was sufficient to correct for ROI size-dependent differences among "no change" images, it was not effective in images with "known loss". In such images, additional adjustments by increasing threshold levels for the registered change in density were found to reduce but not to eliminate differences between ROIs of different size and location. When densitometric radiographic analysis is used for quantitative comparison of different sites, it is primarily recommended to select ROIs of similar size and location. Application of corrective procedures should follow only after careful evaluation of their effects on sensitivity and specificity.

The relationship between probing attachment loss and computerized radiographic analysis in monitoring progression of periodontitis.

This study attempted to evaluate quantitative changes in radiographic density as an indicator of progression of periodontitis. Twenty-one subjects with a history of periodontitis were monitored at baseline, 3, 6, and 9 months using duplicate probing attachment level (PAL) measurements from stents and computer assisted densitometric image analysis (CADIA) of standardized radiographs. Results indicate that the majority of sites exhibited no PAL change during the 9-month period; however, the percentage of sites with loss increased with time. A mean of 6.1% of the sites/patient exhibited probing attachment loss during the study, as compared to a mean of 38.3% of the sites/patient that exhibited a loss of radiographic density. Due to the two dimensional nature of radiographs, density analysis was calculated in terms of radiographic "complexes" of multiple probing sites. There was significantly more density loss at complexes with greater than or equal to 2 mm of attachment loss than at sites with no change in PAL at 9 months; there was no such difference noted at 3 and 6 months. Also, density loss tended to increase as more sites within each complex experienced PAL. Although there was a significant correlation between mean density and PAL changes during the same time interval, there were wide variations at individual sites. This study suggests that there is a complex relationship between density change on radiographs and PAL change. The difficulties inherent in comparing highly sensitive new technologies to relatively imprecise clinical measurements of the attachment level are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Correction of density changes caused by methodological errors in CADIA.

Quantitative evaluation of radiographic changes by computer-assisted densitometric image analysis (CADIA) requires exact knowledge about method errors. In the present study, density change errors were determined from pairs of films with "no change". From this distribution of error values, a series of threshold values for correction of changes due to method errors was selected. The threshold values were then applied to results from analysis of densitometric changes in sites with "known loss" or "no change" of the alveolar bone among films from cynomolgus monkeys. The density errors formed non-normal distributions with no difference in magnitudes between the absolute values expressing density decreases and density increases in the same areas. Calculation of sensitivity, specificity, type 1 and type 2 errors showed that these variables were clearly influenced by selection of different threshold values for correction of the density change errors. It is therefore recommended that threshold values be determined for each analytical system initially as well as following any equipment or computer program modification. Before selecting the threshold value for a specific radiographic analysis, the desired level of sensitivity and specificity should be evaluated.

Vitrectomy and Whipple's disease.

We diagnosed Whipple's disease from the vitreous aspirate of two patients who underwent vitrectomies . In one case, the vitrectomy specimen would have indicated the diagnosis three years before the jejunal biopsy was performed had the appropriate PAS stain been used. In the second case, the PAS-positive macrophages were identified at the time of surgery.