Evaluation of the accuracy of linear measurements on spiral computed tomography-derived three-dimensional images and its comparison with digital cephalometric radiography.
OBJECTIVE
The aim of the study was to evaluate the accuracy of linear measurements obtained from reconstructed spiral CT images of human dry skulls in three planes by comparing them with direct skull measurements, and then to compare these with measurements made on photostimulable phosphor cephalograms.


METHODS
Using a Siemens Somatom Sensation spiral CT scanner (Munich, Germany), CT images of six human dry skulls were imported into imaging software (Mimics 11.02 Materialise, Leuven, Belgium) and the measurements made were compared to the direct measurements made using a digital calliper (500-171, CD-6C, Mitutoyo, Kawasaki, Japan). The measurements were also compared to those made on frontal and lateral cephalograms taken using a digital cephalostat (Planmeca Oy, Helsinki, Finland). The mean of the 15 linear measurements obtained were compared using the paired Student's t-test.


RESULTS
CT measurements did not show a significant difference from the direct skull measurements (P < 0.05) in all three planes except for two midsagittal measurements in the anteroposterior plane. Cephalometric measurements were comparable to direct skull measurements for midsagittal measurements in the anteroposterior plane, but showed a significant difference when bilateral measurements were considered. Cephalometric measurements also showed a significant difference in the transverse plane from direct measurements and CT measurements; however, they did not display a significant difference between direct skull measurements and CT measurements for most parameters in the vertical plane.


CONCLUSIONS
Linear measurements on the spiral CT were comparable to anatomical measurements and were more reliable than cephalometric measurements. Cephalometric measurements were acceptable for midsagittal measurements in the anteroposterior plane, but showed a significant variation from anatomical and CT measurements in most other parameters.
Varghese
S
S
Department of Orthodontics, Sri Ramachandra Dental College, No.1 Ramachandra Nagar, Porur, Chennai-600116, India.
Kailasam
V
V
Padmanabhan
S
S
Vikraman
B
B
Chithranjan
A
A
D002508:Cephalometry / Q000379:methods*; D002680:Chin / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging; D008335:Mandibular Condyle / Q000000981:diagnostic imaging; D009295:Nasal Bone / Q000000981:diagnostic imaging; D009915:Orbit / Q000000981:diagnostic imaging; D021362:Palate, Hard / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012658:Sella Turcica / Q000000981:diagnostic imaging; D012886:Skull / Q000000981:diagnostic imaging; D019291:Skull Base / Q000000981:diagnostic imaging; D012984:Software; D015898:Tomography Scanners, X-Ray Computed; D036542:Tomography, Spiral Computed / Q000379:methods*
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