基于激光扫描的面部软组织三维模型准确性评估

目的 评估基于激光扫描所建立的面部软组织三维模型和软组织测量标志点的准确性.方法 在一受试者的面部进行标志点标记,直接测量各标记点间的距离,之后使用Minolta Vivid 9i三维激光扫描仪进行面部扫描合成三维图像后,应用软件测量标记点间距离,对比两种方法的差异.另选择10名成年女性,在激光扫描前预先标记左右耳屏中点为固定标志点,再选取面部其余测量标志点22个.直接测量耳屏点与测量标志点间的距离,之后测量三维成像后耳屏点与测量标志点间距离,对比两者的差异.所有数据进行配对t检验.结果 基于激光扫描所建立的面部软组织三维模型的准确度为（0.72±0.51）mm.其中水平向、垂直向和前后向的准确度分别为（0.70±0.41）mm、（0.73±0.47）mm和（0.72±0.54）mm.59％的软组织测量标志点具有较高的准确性.结论 基于激光扫描的面部软组织三维模型具有较好的准确性.     

基于立体摄影技术的三维照相系统获取畸形面部影像的精确性研究

目的 探究基于立体摄影技术的三维照相系统获取畸形面部影像的精确性及其影响因素。方法 采用基于立体摄影技术的三维照相系统采集45个面部畸形的蜡制脸模的表面数据,测量19个面部软组织特征线距,以三坐标仪采集测量结果作为标准值,分析三维照相系统获取畸形面部影像的精确性,以及不同畸形形态与面部区域对测量结果精确性的影响。结果 三维照相系统获取的特征线距的测量值与标准值具有统计学差异（P<0.001）。凸起畸形对三维照相系统的测量误差有显著性影响（P<0.05）,裂隙畸形对三维照相系统的测量误差无显著性影响（P>0.05）。不同面部区域的三维照相系统测量误差有统计学差异（P<0.05）。畸形形态对三维照相系统测量偏大百分比无显著性影响（P>0.05）。中间区域与面部两侧区域的测量偏大百分比具有统计学差异（P<0.05）,左侧区域与右侧区域的测量偏大百分比无统计学差异（P>0.05）。结论 对畸形面部影像的分析,基于立体摄影技术的三维照相系统测量正畸临床常规线性项目的精确性受畸形形态与面部区域的影响,但误差在临床可接受范围内。     

面部软组织三维重建及测量系统的研制与应用

目的 研究和开发可应用于正畸临床诊断的数字化三维重建和测量系统,进行颌面部软组织结构的三维测量研究。方法 应用4个高精度的数码相机获取颌面部软组织的三维信息,自行研制和开发出应用于面部重建和测量的数字化立体摄影测量硬件系统,在专业计算机立体显示卡上开发面部软组织三维重建和测量软件系统,同时完成面部软组织三维测量分析和旋转观察。结果 应用研制的面部软组织三维重建和测量硬件及软件系统,可以重建出具有真实感的三维图像并在计算机中任意旋转、移动、缩放;面部软组织三维立体测量精度,左侧数码相机对为0．483mm,右侧数码相机为0．419mm。结论 本项研究所建立的面部软组织三维重建和测量系统,具有精度高、速度快、非介入性等特点,为口腔正畸学面部软组织三维结构的诊断、分析提供了一条新途径。     

新疆喀什地区维吾尔族青年面部三维扫描的形态学研究

目的:利用三维扫描技术获取新疆喀什地区维吾尔族青年人群颌面部二维及三维数据,比较维吾尔族男性与女性面部差异性。方法:采用3DCaMega光学三维扫描仪收集341例维吾尔族样本,男性116例,女性225例,应用Geomagic studio软件对数据进行重建、定点、测量、验证测量值可重复性、测量标志点间的平面距离及曲面距离,应用SPSS24.0软件进行统计学分析。结果:9个测量指标重复性好(P>0.05),比较维吾尔族男性及女性面部距离参数,其中两眼间距、外眦间距、鼻长、面下1/3高度,平面与曲面测量值男女间均存在显著差异(P<0.05);额高、鼻宽平面测量值无统计学意义(P>0.05),曲面测量值有统计学差异(P<0.05)。结论:三维面部测量的方法在反映面部复杂结构的差异性方面更加精确,是一个有价值、可靠人体测量学工具。     

激光扫描在面部畸形三维重建及测量中的初步应用

目的开发建立一套面部三维结构重建、测量及诊断分析系统。方法应用系统建立标准石膏立方体试件以及石膏头像三维计算机模型并进行定点、测量,测量值与标准值比较获得系统建模误差以及定点误差范围;2例面部畸形患者进行了面部三维扫描建模,应用系统对患者面部计算机模型进行了定点、线距、角度测量以及初步对称性分析。结果三维计算机模型的建模误差在0.2 mm以内,定点误差在0.5 mm以内。应用本系统可以完成三维计算机模型的定点、线距、角度测量及对称性分析工作,基本能够达到临床要求。结论三维激光扫描技术为颌面部畸形患者面部软组织三维结构重建和非接触式测量提供了一种简便、精确、高效的方法。     

面部软组织数字化三维重建及测量系统的研制与应用

目的研制和开发一套可应用于正畸临床诊断的数字化三维重建和测量系统,进行颌面部软组织结构的三维测量和研究,并可在计算机中将重建的面部三维图象进行旋转观测、储存和分析。材料方法应用4对高精度的数字相机获取颌面部软组织的三维信息,自行研制和开发出了应用于面部测量和重建的数字化立体摄影测量硬件系统,在专业计算机三维显示卡上开发出面部软组织三维重建和测量软件系统,可同时进行面部软组织三维测量分析与旋转观测。结果应用研制的面部软组织三维重建和测量的硬件和软件系统,可以重建出具有真实感的面部三维图象,并可在计算机中进行任意旋转、移动、缩放重建;建立的面部软组织三维测量系统的测量精度可达到0.5mm,足以满足口腔正畸临床诊断和治疗的需要。结论本研究所建立的面部软组织三维重建和测量系统,具有高精度、高速、非介入性等特点,为口腔正畸学临床诊断和治疗提供了一个崭新的途径。     

锥形束CT用于评价离体牙槽骨高度准确性的研究

目的评价锥形束CT（CBCT）图像测量离体牙槽骨高度的准确性和可重复性,为其应用于牙周病的临床诊断和预后评价提供理论依据。方法使用CBCT对8具干燥下颌骨进行扫描,在图像上重复测量236个人工选择标志点处牙槽嵴顶至釉牙骨质界的距离;同时使用游标卡尺直接测量以上标志点处牙槽嵴顶至釉牙骨质界的距离。应用SPSS 13.0软件对所得数据进行统计学分析。结果CBCT图像对牙槽嵴顶至釉牙骨质界距离的重复测量结果间差异无统计学意义（P>0.05）;CBCT图像与游标卡尺对牙槽嵴顶至釉牙骨质界距离的测量结果间差异也无统计学意义（P>0.05）。结论CBCT图像可清晰显示牙与牙槽骨之间的空间解剖关系,其对牙槽骨高度体外测量的结果具有准确性和可重复性。     

新型层析反求测量系统牙颌建模的应用研究

目的对新型层析反求测量系统的断层图像获取及定位精度等进行评估,并进行上下牙颌的建模应用。方法使用新型层析反求测量系统获取同心圆测量标定板图像,通过5次模拟层析及图像获取过程,测量圆心及四个不同方向的圆形半径变化,分析图像变形率,评估图像重复定位精度。并应用该系统对具有咬合关系的上下颌牙列模型进行逐层切削,数据运算,重建牙颌数字模型。结果新型层析测量系统各个方向上5次测量结果间无统计学差异P>0.05,在距离上测量结果存在显著性差异P<0.05,Student-Newman-Keuls两两对比统计发现,5mm到25mm距离变形差异不显著P>0.05,25mm和30mm时距离变形有统计学差异。重复定位测量表明,最大误差小于0.026mm。通过层析测量数据,可以建立具有咬合关系的牙颌数字模型。结论新型层析反求测量系统具有较高的图像获取及定位精度,能够适用于口腔牙颌的三维建模。     

基于X线的颅面部骨组织三维重建及测量

目的：利用头颅定位X线片实现颅面部骨组织三维重建及测量。方法：受试者面部贴450个金属标志点。拍摄侧位,45°和正位头颅定位X线片,采用相关视觉原理首先建立颅面部软组织的三维模型,用面部的软组织厚度对三维模型进行校正,得到颅面部骨组织的三维模型;选取14个标志点,进行22项测量,并与受试者的X线测量进行比较。结果：颅面部骨组织三维模型的面部横向测量项目较正位片上测得的值小,眶横径和下颌支长的测量值较X线片的测量值大。结论：本研究基于两张X线片建立的颅面部骨组织三维模型能够反映受试者的面部三维特征,达到了一定的准确度。     

面部轮廓三维彩色成像系统精确度的研究

目的探讨基于位相测量轮廓术（phase measuring profilometry, PMP）原理的面部轮廓三维彩色成像系统（DSC-2型）成像的精确度及临床实用性。方法使用DSC-2型面部三维成像照相机进行实际拍摄检验，测量规则几何条纹宽度并在石膏头像模型表面确定彩色标志点，定义并测量15项测量项目。对比3名医师两次计算机三维测量结果与两次实物测量结果之间的差异。结果几何条纹宽度的三维测量均值为19．5mm，与实物测量结果（20mm）比较，差异无统计学意义（P〉0．05）。石膏头像上15项测量项目的计算机三维测量结果与实物测量结果比较，差异无统计学意义（P〉0．05），不同医师测量结果的差异无统计学意义（P〉0．05）。结论基于位相轮廓术的面部轮廓三维彩色成像系统可为准确评估和预测正畸疗效提供一种可靠的方法。     

Technical validation of the Di3D stereophotogrammetry surface imaging system

The purpose of this work was to assess the technical performance of a three-dimensional surface imaging system for geometric accuracy and maximum field of view. The system was designed for stereophotogrammetry capture of digital images from three-dimensional surfaces of the head, face, and neck. A mannequin head was prepared for imaging by adding texture in the form of red paint, and facial landmarks as black ink dots. The mannequin was imaged at the manufacturer's recommended settings for human studies. Colour-coded surface difference images among repeated exposures were computed. We compared measurements of physical linear distance with digital measurements. The three-dimensional stereophotogrammetry system had a mean error in the three-dimensional surfaces of 0.057mm, a repeatability error (variance) of 0.0016mm, a mean error of 0.6mm in linear measurements compared with manual measurements, and a field of view of 170 degrees horizontally and 102 degrees vertically.     

Three-dimensional facial imaging: accuracy and considerations for clinical applications in orthodontics

This study determined the accuracy of a camera system capable of recording three-dimensional facial images. A Rainbow 3D Camera Model 250 system (Genex Technologies Inc, Kensington, Md) was used to capture images of specific models: (1) a precalibrated precision model and (2) a mannequin model that served to simulate the human condition. To assess the accuracy of the camera system, repeated images of both models were recorded at two time points, one week apart. Repeated measurements of specific distances were recorded directly on the models and from each image. Means and standard deviations were calculated for all the repeated measurements at each time point. A two-tailed t-test was used to test for significant differences between (1) each distance measured directly on the precision model and the same distance measured on the images of the precision model, (2) each distance measured directly on the mannequin and the same distance measured on the images of the mannequin, and (3) the mean differences between the same distances measured at the two times. The findings showed that substantial image distortion occurred when images of sharp angles (90 degrees) were captured. Also, those images captured from the frontal perspective +/- 15 degrees were the most accurate.     

Digital three-dimensional photogrammetry: evaluation of anthropometric precision and accuracy using a Genex 3D camera system.

OBJECTIVE: To determine the precision and accuracy of facial anthropometric measurements obtained through digital three-dimensional (3D) photogrammetry. DESIGN: Nineteen standard craniofacial measurements were repeatedly obtained on 20 subjects by two independent observers, using calipers and 3D photos (obtained with a Genex 3D camera system), both with and without facial landmarks labeled. Four different precision estimates were then calculated and compared statistically across techniques. In addition, mean measurements from 3D photos were compared statistically with those from direct anthropometry. RESULTS: In terms of measurement precision, the 3D photos were clearly better than direct anthropometry. In almost all cases, the 3D photo with landmarks labeled had the highest overall precision. In addition, labeling landmarks prior to taking measurements improved precision, regardless of method. Good congruence was observed between means derived from the 3D photos and direct anthropometry. Statistically significant differences were noted for seven measurements; however, the magnitude of these differences was often clinically insignificant (< 2 mm). CONCLUSIONS: Digital 3D photogrammetry with the Genex camera system is sufficiently precise and accurate for the anthropometric needs of most medical and craniofacial research designs.     

The clinical application of three-dimensional motion capture (4D): a novel approach to quantify the dynamics of facial animations

The aim of this pilot study was to evaluate the feasibility of measuring the change in magnitude, speed, and motion similarity of facial animations in head and neck oncology patients, before and after lip split mandibulotomy. Seven subjects (four males, three females) aged 42–80 years were recruited. The subjects were asked to perform four facial animations (maximal smile, lip purse, cheek puff, and grimace) from rest to maximal position. The animations were captured using a Di4D motion capture system, which recorded 60 frames/s. Nine facial soft tissue landmarks were manually digitized on the first frame of the three-dimensional image of each animation by the same operator and were tracked automatically for the sequential frames. The intra-operator digitization error was within 0.4 mm. Lip purse and maximal smile animations showed the least amount of change in magnitude (0.2 mm) following surgery; speed difference was least for smile animation (−0.1 mm/s). Motion similarity was found to be highest for lip purse animation (0.78). This pilot study confirmed that surgery did influence the dynamics of facial animations, and the Di4D capture system can be regarded as a feasible objective tool for assessing the impact of surgical interventions on facial soft tissue movements.     

Accuracy and repeatability of cone-beam computed tomography (CBCT) measurements used in the determination of facial indices in the laboratory setup

AIM: To assess the three dimensional (3D) surface accuracy of a phantom's face acquired from a cone-beam computed tomography (CBCT) scan and to determine the reliability of selected cephalometric measurements performed with Maxilim software (Medicim N.V., Mechelen, Belgium). MATERIAL AND METHODS: A mannequin head was imaged with a CBCT (I-CAT, Imaging Sciences International, Inc., Hatfield, USA). The data were used to produce 3D surface meshes (Maxilim and Mimics, Materialise N.V., Leuven, Belgium) which were compared with an optical surface scan of the head using Focus Inspection software (Metris N.V., Leuven, Belgium). The intra- and inter-observer reliability for the measurement of distances between facial landmarks with Maxilim 3D cephalometry were determined by calculating Pearson correlation coefficients and intraclass correlation (ICC). The Dahlberg formula was used to assess the method error (ME). RESULTS: (1) The maximal range of the 3D mesh deviations was 1.9 mm for Maxilim, and 1.8mm for Mimics segmentation. (2) Test-retest and inter-observer reliability were high; Pearson's correlation coefficient was 1.000 and the ICC was 0.9998. The ME of the vertical measurements was a little larger than that calculated for the width measurements. Maximum ME was 1.33 mm. CONCLUSIONS: The 3D surface accuracy of CBCT scans segmented with Maxilim and Mimics software is high. Maxilim also shows satisfactory intra- and inter-assessor reliability for measurement of distances on a rigid facial surface.     

Validation and reproducibility of a high-resolution three-dimensional facial imaging system

OBJECTIVE: To assess the accuracy and reproducibility of a high-resolution three-dimensional imaging system (Di3D). DESIGN: The three-dimensional imaging system was validated in vitro using 12 adult facial plaster casts, which had landmarks marked, and the positions of the landmarks on the three-dimensional images captured by Di3D were compared with those obtained by a coordinate measuring machine (CMM). METHODS: Operator error was measured by repeatedly locating landmarks on the three-dimensional image. Reproducibility error of the images was calculated by capturing three-dimensional images of the facial casts on two separate occasions; the Euclidean distance between the two matched sets of coordinates was then calculated. The Di3D system error was assessed by calculating the three-dimensional global positions of landmarks on the three-dimensional images and comparing them with those obtained by CMM (gold standard). RESULTS: The operator error in placement of landmarks on the three-dimensional model was 0.07mm, range 0.02-0.11mm. The reproducibility of the Di3D capture was 0.13mm, range 0.11-0.14mm. The mean distance between the CMM and Di3D landmarks, which constitutes the Di3D system error, was an average of 0.21mm, range 0.14-0.32mm. CONCLUSIONS: The Di3D system error was within 0.2mm, which is clinically acceptable, and offers considerable improvement in stereophotogrammetry for facial capture and analysis.     

A comparison study of different facial soft tissue analysis methods

ObjectivesThe purpose of this study was to evaluate several different facial soft tissue measurement methods.Materials and methodsAfter marking 15 landmarks in the facial area of 12 mannequin heads of different sizes and shapes, facial soft tissue measurements were performed by the following 5 methods: Direct anthropometry, Digitizer, 3D CT, 3D scanner, and DI3D system. With these measurement methods, 10 measurement values representing the facial width, height, and depth were determined twice with a one week interval by one examiner. These data were analyzed with the SPSS program.ResultsThe position created based on multi-dimensional scaling showed that direct anthropometry, 3D CT, digitizer, 3D scanner demonstrated relatively similar values, while the DI3D system showed slightly different values. All 5 methods demonstrated good accuracy and had a high coefficient of reliability (>0.92) and a low technical error (<0.9 mm). The measured value of the distance between the right and left medial canthus obtained by using the DI3D system was statistically significantly different from that obtained by using the digital caliper, digitizer and laser scanner (p < 0.05), but the other measured values were not significantly different. On evaluating the reproducibility of measurement methods, two measurement values (Ls–Li, G–Pg) obtained by using direct anthropometry, one measurement value (N′–Prn) obtained by using the digitizer, and four measurement values (En_Rt–En_Lt, Ala_Rt–Ala_Lt, Ch_Rt–Ch_Lt, Sn–Pg) obtained by using the DI3D system, were statistically significantly different. However, the mean measurement error in every measurement method was low (<0.7 mm). All measurement values obtained by using the 3D CT and 3D scanner did not show any statistically significant difference.ConclusionThe results of this study show that all 3D facial soft tissue analysis methods demonstrate favorable accuracy and reproducibility, and hence they can be used in clinical practice and research studies.