Precision and accuracy of measurements in digital panoramic radiography

Objectives: To evaluate the precision and accuracy of digital measurements in digital panoramic radiography. Methods: A series of 70 digital panoramic radiographs were obtained of a dry skull in seven different positions with metallic pins and spheres fixed to the mandible. Three replicate measurements were performed with the mouse-driven cursor by one reader at 1:1 and 2:1 magnification. Precision was assessed with tbe reliability index (R) and Malony/Rastogi test and the effect of magnification on accuracy by paired Wilcoxon test. Results: Vertical measurements were less reproducible than horizontal measurements. There were significant differences in assessments between images at 1:1 and 2:1 magnification (P < 0.05). The maximum variation in mean difference was 0.4% of actual object length for pins and 1.2% for spheres. The difference did not exceed 0.1 mm. R was lower for 2: 1 magnification and consistently lower for spheres compared with pins. Conclusion: The most reliable measurements were obtained of linear objects in the horizontal plane, Digital measurements are sufficiently accurate for clinical use.