Computer modeling of selected projectional factors of the 84-in focal film distance anteroposterior full spine radiograph compared with 40-in focal film distance sectional views

ObjectiveThe purpose of this study was to compare the 84-in focal film distance anteroposterior (A-P) full spine view to selected sectional views taken at a 40-in focal film distance for angles of divergence and changes produced by lateral translation and variation in source object distance.MethodsComputer models were used to determine angles of divergence and study the effects of lateral translation and changes in source object distance.ResultsLateral translation produced less projected axial (y-axis) vertebral rotation on the 84-in A-P full spine view than the film at 40 in. Angles of divergence are equal on the 14 × 17-in film at 40 in compared with the 84-in A-P full spine, and 70% of the 84-in full spine view is within the angles of divergence of the 40-in 10 × 12. The 84-in A-P full spine produced lowering and lengthening of the projected ilium when source object distance was reduced.ConclusionIn this study, the 84-in A-P full spine produced less projected vertebral rotation on lateral translation. Its angles of divergence were greater than the 40-in 10 × 12 and equal to the 40-in 14 × 17-in film. Except for a 5.4-in section at both the upper and lower margins, the 84-in full spine view was within the angles of divergence of a 40-in 10 × 12. The full spine film produced projected ilium lengthening and lowering.