Theoretical Analysis of the Deviation of the Landmarks on Postero-anterior Cephalogram
1993 Volume 13 Issue 2 Pages 168-180
Details
1993 Volume 13 Issue 2 Pages 168-180
The location of the landmark on the postero-anterior (PA) cephalogram changed by the rotation of the patient head. The geometrical error induced by the rotation will be simulated by using a personal computer. The human head was rotated +10° in vertical or horizontal direction. All positions of cephalometric landmarks on the radiogram were calculated in every degree of head position.
The results were follows : The error induced by the vertical rotation was larger than that of horizontal rotation. For instance, upper incisor (U1) was moved 31. 7 mm in vertical direction. The width of Gonions, and the length of Crista Galli (CG) to Menton (Me) were changed in 1. 27 mm, 2. 87 mm respectively. The angle of CG-Gonionl (Gol) to Gol-Me was changed 19. 22°. On the other hand, Ul was moved 31. 4 mm in horizontal direction. The width of Gonions, and the length of CG to Me were changed in 1. 51 mm, O. 10 mm respectively. The angle of CG-Gol to Gol-Me was changed 9.82°
The results indicate that the error of PA cephalogram was smaller in horizontal width (like Gol-Go2) than in vertical height (like CG-Me). The error in linear is generally smaller than that in angular.
