A method for three-projection infant cephalometry

Objective: To assess morphology and growth in infants and children with cra niofacial anomalies based on comprehensive digitization of radiographic fil ms in three, mutually orthogonal projections. Method: The method consists of (1) acquisition of radiographic films in a h ighly standardized three-projection (lateral, frontal, and axial) cephalome ter, (2) marking and digitization of a total of 279 anatomical landmarks in the three projections, and (3) computation and presentation (tabular and g raphical) of 356 linear and angular variables describing the craniofacial m orphology, including soft tissue. Computation of statistical entities descr ibing a patient, a group of patients, the differences between patients or g roups of patients was carried out, Error assessment of the method involved investigation of error distribution among a number of error sources. Duplic ate digitization of radiographic films from 30 randomly selected patients, and from in dry skulls, was carried out to determine the errors contributed by the procedure of landmark digitization and the distribution of error am ong landmarks and variables, as well as between projections. Results: The average error due to landmark digitization, s(i), determined b y duplicate digitization and calculated by use of Dahlberg's formula was 0. 8 mm for linear variables and 1.6 degrees for angular variables. Conclusion: This method of infant cephalometry has been shown to be highly accurate and reproducible, and it adds significant new potential for, e.g., asymmetry detection, population comparison, and growth measurements compar ed to other cephalometric techniques due to its standardized acquisition an d digitization protocol, inclusion of an axial projection, and the large nu mber of well-defined landmarks and variables involved.