Evaluation of the CT scanogram for assessment of craniofacial morphology

Abstract

The purpose of this prospective laboratory study was to investigate the suitability of the computed tomography scanogram (CT) as compared with conventional (CC) or storage phosphor digital (SP) lateral cephalograms. Twenty intact, adult-sized, dry human skulls were used. Each skull was fixed in a custom-made plastic box and imaged in each of the three radiographic machines. All 60 hard copy radiographs were directly digitized using a customized cephalometric program, and all skulls were measured with an external caliper. All measurements were carried out twice, 2 weeks apart. "A priori" ranges were defined in advance for all 18 craniofacial parameters. Linear measurements were corrected for radiographic magnification. Data were analyzed using coefficients of repeatability, limits of agreement, and paired t-tests. Direct skull, anterior face height, sella-nasion, and cephalometric SnMx, SNA, SNB, and ANB (except CT) measurements were repeatable. Sella-basion, basion-nasion, most posterior face height measurements, MxMn, and incisor angulations were either not repeatable or not in agreement. When statistical significance was noted, however, the mean difference was of small magnitude for nearly all parameters. Depending on the clinical situation and the degree of precision required, the scanogram is a viable alternative to lateral cephalometry for assessment of sella-nasion, anterior face height, skeletal planes angles (SnMx, MxMn), SNA, SNB, and ANB, but not of sella-basion, basion-nasion, posterior face height measurements, and incisor angulations.