隨著錐狀射東電腦斷層掃描(cone-beam computed tomography, CBCT)的快速發展,它在牙科學的應用也包括了矯正病例診斷和治療計劃擬定。透過CBCT所獲得的顱顏結構三維影像,可免除平面影像放大率的問題。本研究使用三個完整之人類頭顱骨來探討傳統手繪測顱分析、電腦測顱分析、與CBCT三維立體影像線性測量之準確性,研究方法是使用電子游標尺測量頭顱骨以獲得真實值做為黃金標準,再分別與使用各分析方法所得的影像測量值作比較,包括測顱手繪測量、電腦軟體測量(WinCeph 8.0)、以及利用CBCT資料重組之三維立體影像測量(i-CAT/ Simplant Pro 12.02),除了驗證不同系統之影像放大率,並探討各種測量方法與實體測量之間的相關性,以探討各測量值的準確度。研究結果發現不同方式之影像測量與其實值之間皆具極高相關性,且真實值與CBCT三維立體影像測量的相關係數(0.996),略高於與WinCeph軟體測量(0.989)或手繪測量之相關係數(0.988),顯示在CBCT三維立體影像的線性測量結果具有相當高的準確性;然而,在連續曲線或曲面上的界標點(例如Co點與Jr點)仍可能受限於觀測者視線角度或參考線之有無,而影響測量值的準確性。
Introduction: The purpose of this study was to investigate the correlation between the actual linear measurements on human skull and the cephalometric measurements obtained from conventional digital cephalogram and cone-beam computed tomography (CBCT) 3-D images. Materials and Methods: Lateral and postero-anterior cephalograms of 3 skulls were assessed by measuring the commonly used 11 linear measurements. The CBCT volume images were obtained and measured by using 3-D image software (i-CAT/Simplant Pro 12.02). The measurements with conventionally manual tracing method, WinCeph software (2-D), and those on 3-D images were compared with the gold standards derived from repeated caliper measurements of the skulls. Correlations between the gold standard and the software measurements from 2D/3D images were assessed with Pearson's correlation coefficients. Results: The linear measurements on midsagittal plane were significantly more reliable than those from bilateral landmarks regardless of measurement technique. The Pearson's correlation coefficient between caliper method and CBCT 3-D measurements was 0.996, 0.989 between caliper measurements and conventional method, and 0.988 between caliper measurements and WinCeph measurement. Conclusions: Both conventional 2-D digital cephalograms and CBCT 3-D techniques provide acceptably accuracy of linear cephalometric measurements.