3次元ステレオフォトグラメトリの精度。3dMDとBellus3Dの顔面スキャンシステムの相互比較と直接人体計測の比較

Accuracy of 3-dimensional stereophotogrammetry: Comparison of the 3dMD and Bellus3D facial scanning systems with one another and with direct anthropometry.

抄録

はじめに:

本研究の目的は、Bellus3D Face Camera Pro (Bellus3D) (Bellus3D Inc, Los Gatos, Calif) と3dMDfaceシステム (3dMD) (3dMD Inc, Atlanta, Ga) で撮影した3次元 (3D) デジタル顔写真の正確さを、互いに、および直接人体計測 (DA) と比較することである。

INTRODUCTION: The objective of this study was to compare the accuracy of 3-dimensional (3D) digital facial photographs taken by the Bellus3D Face Camera Pro (Bellus3D) (Bellus3D Inc, Los Gatos, Calif) and the 3dMDface system (3dMD) (3dMD Inc, Atlanta, Ga) with one another and with direct anthropometry (DA).

方法:

研究対象として，マネキン頭部を選択した．20個の顔面ランドマークは，8個のランドマーク間距離と5個の角度を定義してラベリングした．ランドマーク間距離の測定には，精度が0.02mmの150mmデジタルノギス（株式会社ミツトヨ，東京）を用い，角度は余弦の法則に基づき算出した．測定はすべて同一条件下で各オペレータが3回ずつ行った。その後，各スキャナーで5回3次元写真を撮影し，10枚のデジタル立体写真を作成した。オープンソースの MeshLab ソフトウェア（ISTI [Italian National Research Council], Rome, Italy）を用いて再構成した顔面3D写真について，直線距離と角度を測定した．各直線距離と角度は，1 人のオペレータが 3 回測定し，3 人の検者が独立に測定した．真偽を確認するために，2 台のスキャナーと DA の測定値を比較するために同等性検定を適用した。また，Bellus3D vs 3dMD vs DA の 3 種類の測定法の真偽を直接比較するため，平均絶対偏差を算出した。最後に、観察者間一致と2つのスキャナーの精度を評価するために、クラス内相関係数が用いられた。

METHODS: A mannequin head was selected as the research object. Twenty facial landmarks were labeled on the basis of the 8 interlandmark distances and 5 angles that were defined. A 150-mm digital Vernier caliper (Mitutoyo Inc, Tokyo, Japan) with an accuracy of 0.02 mm was applied to directly measure the interlandmark distances, and the angles were calculated according to the law of cosines. All the measurements were conducted 3 times by each operator under identical conditions. Then, each scanner was used to acquire 3D photographs 5 times, generating 10 digital stereophotographs. Linear distances and angles were measured on the 3D facial photographs reconstructed with open-source MeshLab software (ISTI [Italian National Research Council], Rome, Italy). Each linear distance and angle were measured 3 times by 1 operator, and 3 examiners conducted the measurements independently. To obtain the trueness, equivalence tests were applied to compare the measurements of the 2 scanners and DA. In addition, the average absolute deviations were calculated to directly compare the trueness of 3 methods (Bellus3D vs 3dMD vs DA). Finally, the intraclass correlation coefficient was used to assess the interobserver agreement and the precision of 2 scanners.

結果:

3dMDで測定した直線距離（N-Pn, Sn-Pog, ORE-IRE, OLE-ILE, RLC-RMC, LLC-LMC, CR-CL）および角度測定（MLA, NFA, INI）は5件中3件でDAと同等であった。Bellus3Dで得られた8つの測定値のうち5つ（N-Pn, Sn-Pog, RLC-RMC, LLC-LMC, CR-CL）、5つの角度測定値のうち1つ（MLA）はDAで得られた測定値と同等であった。Bellus3Dで得られた3つの測定値（ORE-IRE、NFA、INI）を除くすべての測定値は3dMDと同等であった。3dMDとDAの平均絶対差は0.36±0.20mm、0.45°±0.56°、Bellus3DとDAの偏差は0.61±0.47mm、0.45°±0.56°であった。また、Bellus3Dと3dMDの偏差は、0.38±0.37mm、0.62°±0.39°であった。2 台のスキャナの精度は，3dMD のクラス内相関係数が約 1.00，Bellus3Dが 0.99であった。また，直線および角度の各測定における観察者間一致度は0.99であった．

RESULTS: As for the trueness, 7 out of 8 of the linear distance measurements (N-Pn, Sn-Pog, ORE-IRE, OLE-ILE, RLC-RMC, LLC-LMC, and CR-CL) and 3 out of 5 of the angular measurements (MLA, NFA, and INI) obtained by 3dMD were equivalent to those obtained by DA. Five out of 8 measurements (N-Pn, Sn-Pog, RLC-RMC, LLC-LMC, and CR-CL) and 1 out of 5 of the angular measurements (MLA) obtained by Bellus3D were equivalent to the measurements obtained with DA. All but 3 of the measurements (ORE-IRE, NFA, and INI) obtained with Bellus3D were equivalent to 3dMD. The mean absolute difference between 3dMD and DA was 0.36 ± 0.20 mm and 0.45° ± 0.56°; the deviation between Bellus3D and DA was 0.61 ± 0.47 mm and 0.99° ± 0.61°; and the deviation between Bellus3D and 3dMD was 0.38 ± 0.37 mm and 0.62° ± 0.39°. Regarding the precision of the 2 scanners, the intraclass correlation coefficient value of 3dMD was approximately 1.00, and that of Bellus3D was 0.99. The interobserver agreement for each linear and angular measurement was 0.99.

結論:

各スキャナーの真偽は，診断や治療計画において臨床的に許容されるものであった．3dMDとBellus3Dで得られた3D写真の精度は，良好なスキャニングの再現性を示した．3人のオペレーターの観察者間一致度は0.99と良好であった．

CONCLUSIONS: The trueness of each scanner was clinically acceptable for diagnosis and treatment planning. The precision of 3D photographs obtained by 3dMD and Bellus3D showed good scanning repeatability. The interobserver agreement between the 3 operators was rated as excellent (0.99).