Variation of the face in rest using 3D stereophotogrammetry

To evaluate treatment outcomes following oral and maxillofacial surgery, pre- and post-treatment three-dimensional (3D) photographs of the patient's face can assessed, but this procedure is accurate only if the face is captured with the same facial expression every time. The purpose of this prospective study was to determine variations in the face at rest; 100 3D photographs of the same individual were acquired at different times. Initially, 50 3D photographs were obtained; 25 using a wax bite to ensure similar occlusion between subsequent photographs and 25 without wax bite. This procedure was repeated 6 weeks later. Variation of the face at rest was computed. The influence of time and wax bite was investigated. Different anatomical regions were investigated separately. A mean variation of 0.25 mm (0.21-0.27 mm) was found (standard deviation 0.157 mm). No large differences were found between different time points or use of wax bite. Regarding separate anatomical regions, there were small variations in the nose and forehead regions; the largest variations were found in the mouth and eyes. This study showed small overall variation within the face at rest. In conclusion, different 3D photographs can be reproduced accurately and used in a clinical setting for treatment follow-up and evaluation.     

Validity of the 3D VECTRA photogrammetric surface imaging system for cranio-maxillofacial anthropometric measurements

Purpose

The use of three-dimensional (3D) photography for anthropometric measurements is of increasing interest, especially in the cranio-maxillofacial field. Before standard implementation, accurate determination of the precision and accuracy of each system is mandatory.

Methods

A mannequin head was labelled with 52 landmarks, and 28 three-dimensional images were taken using a commercially available five-pod 3D photosystem (3D VECTRA; Canfield, Fairfield, NJ) in different head positions. Distances between the landmarks were measured manually using a conventional calliper and compared with the digitally calculated distances acquired from labelling by two independent observers. The experimental set-up accounted for clinical circumstances by varying the positioning (vertical, horizontal, sagittal) of the phantom.

Results

In the entire calliper measurement data set (n?=?410), a significant difference (p?=?0.02) between the directly measured and corresponding virtually calculated distances was found. The mean aberration between both modalities covering all data was 7.96 mm. No differences (p?=?0.94) between the two groups were found using a cut-off of 10 % (leaving n?=?369 distances) due to considerable errors in direct measurements and the necessary manual data translation. The mean diversity of both measurement modalities after cut-off was 1.33 mm (maximum, 6.70 mm). Inter-observer analysis of all 1,326 distances showed no difference (p?=?0.99; maximal difference, 0.58 mm) in the digital measurements.

Conclusion

The precision and accuracy of this five-pod 3D photosystem suggests its suitability for clinical applications, particularly anthropometric studies. Three-hundred-and-sixty degree surface-contour mapping of the craniofacial region within milliseconds is particularly useful in paediatric patients. Proper patient positioning is essential for high-quality imaging.     

Evaluation of reproducibility and reliability of 3D soft tissue analysis using 3D stereophotogrammetry

In 3D photographs the bony structures are neither available nor palpable, therefore, the bone-related landmarks, such as the soft tissue gonion, need to be redefined. The purpose of this study was to determine the reproducibility and reliability of 49 soft tissue landmarks, including newly defined 3D bone-related soft tissue landmarks with the use of 3D stereophotogrammetric images. Two observers carried out soft-tissue analysis on 3D photographs twice for 20 patients. A reference frame and 49 landmarks were identified on each 3D photograph. Paired Student's t-test was used to test the reproducibility and Pearson's correlation coefficient to determine the reliability of the landmark identification. Intra- and interobserver reproducibility of the landmarks were high. The study showed a high reliability coefficient for intraobserver (0.97 (0.90 – 0.99)) and interobserver reliability (0.94 (0.69 – 0.99)). Identification of the landmarks in the midline was more precise than identification of the paired landmarks. In conclusion, the redefinition of bone-related soft tissue 3D landmarks in combination with the 3D photograph reference system resulted in an accurate and reliable 3D photograph based soft tissue analysis. This shows that hard tissue data are not needed to perform accurate soft tissue analysis.     

Esthetic evaluation of facial cheek volume: A study using 3D stereophotogrammetry

Objectives:To investigate the influence of cheek volume on facial esthetics judged by orthodontists and non-specialists.Materials and Methods:A 25-year-old female''s natural and smiling face was captured by 3D stereophotogrammetry. Cheek volume of the 3D image was altered to different degrees three-dimensionally. For the natural and smiling face, seven groups of facial images were created: decreased grade I/II/III, increased grade I/II/III, and the original one. Thirty orthodontists and 30 nonspecialists were invited to perform esthetic evaluation of the original and transformed images using a questionnaire. Data were calculated with one-way analysis of variance (least significant difference test) and independent samples t test.Results:Compared to nonspecialists, orthodontists gave lower esthetic scores to the decreased grade III facial images (maximum deformation degree: 7.500 mm and 7.327 mm in natural and smiling face-oriented image groups, respectively). The decreased grade III facial images also received the highest age ranks. However, the increased grade III facial images received the lowest scores and highest age ranks from nonspecialists (maximum deformation degree: 6.994 mm and 5.300 mm in natural and smiling face-oriented image groups, respectively) (P < .01).Conclusions:Orthodontists and nonspecialists showed different esthetic evaluation of varied cheek volume. The influence of cheek volume in orthodontic diagnostic analysis needs further consideration.     

Root surface measurements of mandibular molars using stereophotogrammetry

Ten mandibular first molars were hemisected and the root surface of each root was measured using stereophotogrammetry and computer analysis. In each tooth the mesial root was determined to have a greater surface area than the distal root. This difference was statistically significant. The fact that the mesial root has the larger surface area must be a consideration when hemisection is planned.     

Validity and reproducibility of the 3D VECTRA photogrammetric surface imaging system for the maxillofacial anthropometric measurement on cleft patients

Clinical Oral Investigations - To validate the accuracy and reproducibility of linear measurements of three-dimensional (3D) images and to compare the measurements with the direct anthropometry...     

Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry

Objective:To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined.Materials and Methods:Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement.Results:The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Pro parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2.Conclusions:Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics.     

3D surface imaging in dentistry - what we are looking at

3D imaging has been widely used within various fields of dentistry to aid diagnosis, in treatment planning and appliance construction. Whereas traditionally this has involved the use of impression materials together with plaster or stone models, modern techniques are continually evolving which use virtual 3D images. These electronic virtual images are created using either contact or non-contact optical scanning techniques, but there are limitations, the most important of which is that any new virtual surface image is created from a series of discrete data points. It is not created from a continuous stream of data relating to the original object. This means that computer software has to be used to recreate a possible best fit, virtual surface from the data obtained. This paper describes the principles behind 3D scanning technology, the limitations of 3D imaging as well as current and possible uses of such imaging in clinical dentistry.     

CBCT三维成像在口腔种植术中的临床应用

目的:随着口腔种植修复的发展和技术的不断革新,种植外科趋于更精确和微创.计算机辅助设计在种植术前可以帮助医生完成患者颌骨结构的三维图像重建,对术区进行准确定位,分析可利用的骨量,确定最佳植入方向,从而制定完善的手术方案.方法:利用CBCT的影像诊断系统对口腔上下颌骨进行MPR多平面重建:标准轴面、冠状面、矢状面;VR:...     

基于最短曲面距离对3dMD立体摄影系统测量精度和稳定性的研究

目的：利用最短曲面距离验证3dMD立体摄影系统测量的精度和稳定性,对3dMD立体摄影系统的测量精度进行更为客观的评价。方法：被测物是表面贴有坐标格的直径14 cm的圆柱体模型,用3dMD立体摄影系统获取模型的表面数据,并利用该系统的测量工具测量模型上42个曲面距离,分别与对应的标准值进行统计学分析。结果：横向2格组、横向5格组、横向7格组和竖向7格组的测量值与标准值之间的差异有统计学意义（P<0．05）;竖向2格组、竖向5格组的差异无统计学意义（P>0．05）,但各组的误差均值都不超过0．3 mm;描述统计分析得出6组特征曲线长度的标准差均<0．1 mm,各测量组四分位数间距均≤0．15 mm。结论：3dMD立体摄影系统在测量曲面距离时精度高,稳定性好。     

3D surface imaging in medicine: a review of working principles and implications for imaging the unsedated child

This article provides an overview of the methods used for optical surface imaging during the last 30 years, with the primary focus on the imaging of the unsedated child. The goal is to provide the reader with an overview of the working methods behind the published articles. This will enable the reader to better interpret current data and decide if a certain approach is suitable for their particular research question.     

Intraoperative imaging of zygomaticomaxillary complex fractures using a 3D C-arm system

After preclinical studies and evaluation of radiation exposures, intraoperative three-dimensional (3D) C-arm based imaging is now available for the facial skeleton. Fourteen patients admitted for surgical treatment of zygomaticomaxillary complex (ZMC) fractures were included in the study. Preoperative diagnostics and surgical treatment were performed as usual. Intraoperatively, after open reduction, a cone-beam computed tomography (CBCT) dataset was generated using the SIREMOBIL Iso-C3D (Siemens Medical Solutions, Erlangen, Germany). After DICOM-import in eFilm Workstation axial, coronal and sagittal reconstructions were evaluated by five examiners with the help of six defined criteria. In our study, secondary reconstructions were available after 6 min, excluding the time needed for the evaluation of the images. Especially the positioning of the isocentre of the SIREMOBIL Iso-C3D proved to be uncomplicated. Because of the size of the datasets, assessment of the symmetry of the malar projection proved difficult. Best scoring results were found regarding the visualization of the fragment position, bony anchorage of the screws and the fitting of the plates. Remarkable was the low level of metal artefacts in primary and secondary reconstructions. In conclusion, our results demonstrate intraoperative CBCT using the SIREMOBIL Iso-C3D suitable for assessment of postoperative results following ZMC reduction.     

Evaluation of a portable low-budget three-dimensional stereophotogrammetry system for nasal analysis

Background

Three-dimensional (3D) photogrammetry has reached high standards and accuracy but is mainly conducted with stationary and expensive systems. The purpose of this study was to evaluate the accuracy of a low-budget portable system with special regard to the gracile and challenging nasal region.

Three dimensional evaluation of facial asymmetry after mandibular reconstruction: validation of a new method using stereophotogrammetry

The scientific literature is sparse on reports that evaluate facial asymmetry after mandibular reconstructive surgery objectively. The aim of this study is to introduce and validate a new method, using three dimensional (3D) stereophotogrammetry, that quantifies soft-tissue facial asymmetry in patients who have undergone mandibular reconstruction. To validate the new method, two observers applied the method on 3D photographs of five patients and five controls. An inter-observer difference of 0.04 mm (?0.08 to 0.17) was found with a measurement error of 0.13 mm. 15 3D photographs of the mandibular reconstructed patients were compared with 24 3D photographs of healthy controls. A significant difference (1.19 mm) in asymmetry was found between patients and controls. It is concluded that this new measuring method is a valid, fast and clinically applicable technique to quantify soft-tissue facial asymmetry. It is concluded that facial symmetry in patients is not restored to the level of the control group with the mandibular reconstruction method applied.