The study of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error.
- Author:
Bong Hae CHO
1
Author Information
1. Department of Dental Radiology, College of Dentistry, Pusan National University, Korea.
- Publication Type:Original Article
- Keywords:
radiography;
dental;
digital subtraction;
computer-assisted;
periodontal
- MeSH:
Radiography*
- From:Journal of Korean Academy of Oral and Maxillofacial Radiology
1999;29(2):417-422
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
PURPOSE: The aim of this study was to assess the validity of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error. MATERIALS AND METHODS: Twenty periapical radiographs used baseline images were copied to exclude the influence of exposure geomety and contrast differences. These subsequent images were displaced by 0.1-0.5 mm in the x-, y- and xy-directions, rotated by 0.5-3o and distorted by angular contraction of 1-5o in x- and y-axis before subtraction. Pearson correlation coefficients(r) were calculated between the standard deviation of gray levels in the subtracted image and misplacement and paired t-tests were performed to compare standard deviations. RESULTS: Linear displacement showed high correlation coefficients of 0.997, 0.997 and 0.995 in x-, y- and xy-axis respectively. Statistically significant different standard deviation existed among all linearly displaced groups(p<0.05). Relatively low correlation coefficients of 0.982 and 0.959 in x- and y-axis distortion were demonstrated. The standard deviations between the two distortion groups were statistically significantly different(p<0.05). CONCLUSION: Standard deviation of gray level distribution in digital subtraction images is satisfactory but not perfect similarity measure to assess superimposition errors.
