Three-dimensional imaging of the craniofacial complex

Orthodontic treatment requires the rearrangement of craniofacial complex elements in three planes of space, but oddly the diagnosis is done with two-dimensional images. Here we report on a three-dimensional (3D) imaging system that employs the stereoimaging method of structured light to capture the facial image. The images can be subsequently integrated with 3D cephalometric tracings derived from lateral and PA films (www.clinorthodres.com/cor-c-070). The accuracy of the reconstruction obtained with this inexpensive system is about 400 μ.     

Three-dimensional imaging andmotion animation

Orthodontic treatment is aimed at affecting the craniofacial relationships in three planes of space. Yet strangely enough, the critical diagnostic records are two-dimensional. In an orthodontic setting, the techniques of imaging the human face in a three-dimensional manner have been either stereo photography, or projection of optical grids or the structured light. These projections enable the operator to capture the facial image in a three-dimensional manner. Unfortunately, all these methods are static in nature. The laser scanning techniques and the availability of sophisticated software for image manipulation, make image animation possible. Here we report the first ever motion animation of the human face from laser-generated images for clinical purposes.     

Three-dimensional architectural and structural analysis—a transition in concept and design from Delaire's cephalometric analysis

The aim of this study was to present a systematic sequence for three-dimensional (3D) measurement and cephalometry, provide the norm data for computed tomography-based 3D architectural and structural cephalometric analysis, and validate the 3D data through comparison with Delaire's two-dimensional (2D) lateral cephalometric data for the same Korean adults. 2D and 3D cephalometric analyses were performed for 27 healthy subjects and the measurements of both analyses were then individually and comparatively analyzed. Essential diagnostic tools for 3D cephalometry with modified definitions of the points, planes, and measurements were set up based on a review of the conceptual differences between two and three dimensions. Some 2D and 3D analysis results were similar, though significant differences were found with regard to craniofacial angle (C1–F1), incisal axis angles, cranial base length (C2), and cranial height (C3). The discrepancy in C2 and C3 appeared to be directly related to the magnification of 2D cephalometric images. Considering measurement discrepancies between 2D and 3D Delaire's analyses due to differences in concept and design, 3D architectural and structural analysis needs to be conducted based on norms and a sound 3D basis for the sake of its accurate application and widespread adoption.     

计算机对颅颌面影像的自动识别

目的 采用现代图像处理技术,进行X线颅颌面影像的计算机自动识别研究,为计算机对X线颅颌面影像的全自动识别、定点、测量分析奠定基础。方法 ①图像信息的获取:在头颅定位仪定位下,拍摄研究对象的正中咬合位时X线颅颌侧位片。拍摄的X线片通过扫描仪将图像信息输入计算机。②图像信息的处理:首先是图像增强,按照需要突出、削弱或去除图像中的某些信息;随后,进行图像分层,利用X线颅颌面侧位片图像灰度分布的特征,将原始图像分层;最后,进行图像重建。结果 图像信息的表达:提取了颅面软、硬组织外轮廓及部分颅颌面硬组织内部结构。结论 初步建立了计算机对X线颅颌面影像的自动识别,为进一步研究奠定了基础。     

A three-dimensional comparison of a morphometric and conventional cephalometric midsagittal planes for craniofacial asymmetry

Morphometric methods are used in biology to study object symmetry in living organisms and to determine the true plane of symmetry. The aim of this study was to determine if there are clinical differences between three-dimensional (3D) cephalometric midsagittal planes used to describe craniofacial asymmetry and a true symmetry plane derived from a morphometric method based on visible facial features. The sample consisted of 14 dry skulls (9 symmetric and 5 asymmetric) with metallic markers which were imaged with cone-beam computed tomography. An error study and statistical analysis were performed to validate the morphometric method. The morphometric and conventional cephalometric planes were constructed and compared. The 3D cephalometric planes constructed as perpendiculars to the Frankfort horizontal plane resembled the morphometric plane the most in both the symmetric and asymmetric groups with mean differences of less than 1.00 mm for most variables. However, the standard deviations were often large and clinically significant for these variables. There were clinically relevant differences (>1.00 mm) between the different 3D cephalometric midsagittal planes and the true plane of symmetry determined by the visible facial features. The difference between 3D cephalometric midsagittal planes and the true plane of symmetry determined by the visible facial features were clinically relevant. Care has to be taken using cephalometric midsagittal planes for diagnosis and treatment planning of craniofacial asymmetry as they might differ from the true plane of symmetry as determined by morphometrics.     

Three‐dimensional imaging of the craniofacial complex

Orthodontic treatment requires the rearrangement of craniofacial complex elements in three planes of space, but oddly the diagnosis is done with two‐dimensional images. Here we report on a three‐dimensional (3D) imaging system that employs the stereoimaging method of structured light to capture the facial image. The images can be subsequently integrated with 3D cephalometric tracings derived from lateral and PA films ( http://www.clinorthodres.com/cor‐c‐070 ). The accuracy of the reconstruction obtained with this inexpensive system is about 400 μ.     

三维头影测量的研究现状与展望

随着锥体束CT(cone beam computed tomography,CBCT)在正畸领域的广泛使用,越来越多正畸医生开始研究使用CBCT影像进行三维头影测量分析.三维头影测量分析是需要基于CT或者CBCT获得患者的三维头颅影像,并使用具有三维分析功能的软件进行测量与分析.本文就三维头影测量的定义与发展、头颅定位、定点、测量项目及参考值的确定和影像重叠五个方面进行综述,并对其今后发展方向进行展望.     

Simple technique to achieve a natural position of the head for cone beam computed tomography

We developed a modified laser level technique to record the natural position of the head in all three planes of space. This is a simple method for use with three-dimensional images and may be valuable in routine craniofacial assessment.     

基于深度学习的二维头影测量定点分析系统的研究

目的 探讨基于深度学习的图像高斯金字塔和卷积神经网络方法,构建和训练一种高精准度的自动化二维头影测量标志点定位与分析系统模型。方法 收集2021年1月至12月期间本院所摄的400张年龄在18至50周岁且无牙列缺损的头颅侧位影像,在3D slicer（NIH美国）上完成每张44个牙颌和颅面软硬组织结构标志点的标注,并构建和训练基于图像高斯金字塔和卷积神经网络的自动化二维头影测量标志点定位和分析系统。结果 运用图像高斯金字塔和卷积神经网络方法能高精准获取44个牙颌和颅面的软硬组织结构标志点,在 2.0 mm、2.5 mm、3.0 mm、4.0 mm 精度范围内预测的平均准确率分别为 85.61 %、90.72 %、93.82 %、96.34 %;44个牙颌和颅面软硬组织结构标志点的平均误差为 1.22 mm,平均标准差为 1.27 mm;常见头影测量项目（ANB、SNA、SNB、ODI、APDI、FHI、FMA、MW）的平均预测准确率为 85.00 % 。结论 运用图像高斯金字塔和卷积神经网络方法能高精准获取牙颌和颅面的软硬组织结构标志点,并且对牙颌和颅面形态分析诊断具有良好的准确性,该技术将有助于推进自动化头影测量的临床运用。     

Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro.

PURPOSE: This study evaluated the measurement accuracy of three-dimensional (3D) volumetric images from spiral computed tomography (CT) in vitro. MATERIALS AND METHODS: The study sample consisted of nine cadaver heads that were submitted to an impact force by a special device to promote blunt traumatic craniofacial fractures. The heads were subsequently scanned by a spiral CT scanner (Toshiba Xpress S/X). The archived CT data were transferred to networked computer workstations (Sun Microsystems with Cemax VIP version 1.4 software) to generate 3D volumetric images. The visualization software was used to make interactive linear measurements on the 3D images. Measurements were made on the images twice by two observers, based on conventional craniofacial anatomic landmarks. The soft tissues were subsequently removed, and the same measurements were repeated on the cadaver heads with an electromagnetic digitizer (3 Space, Polhemus, Colchester, VT). RESULTS: The results showed no statistically significant differences between the 3D-CT and the physical measurements, with P>.05 for all measurements. The mean difference between the image and real measurements was less than 2 mm in all instances. CONCLUSIONS: It is concluded that measurement of the skull and facial bone landmarks by 3D reconstruction is quantitatively accurate for surgical planning and treatment evaluation of craniofacial fractures.     

Development of a non-radiographic cephalometric system

The purpose of the present study was to develop a three-dimensional (3D) non-radiographic cephalometric system based on Simon's three planes. In pursuit of cephalometry without irradiation of patients, readiness of data and simplicity of the system, a portable 3D computer-aided, contact-method cephalometric system, equipped with newly developed cephalometric software for chairside use, was developed. The feasibility of its clinical use was examined based on comparison of the measurements obtained with those from conventional radiographic cephalometry on a human dry skull, as well as on three living subjects. From a total of nine measurements, a statistically significant difference was seen in six measurements: FMPA, U1/FH, FMIA, ANB, IMPA, and A-Np for the dry skull; in four measurements: FPA, FMPA, U1/FH, and Pog-Np for subject A; in five measurements: FMPA, U1/FH, FMIA, AN/FH, and A-Np for subject B; and in seven measurements: FMA, FMPA, U1/FH, FMIA, ANB, IMPA, and AN/FH for subject C. A clinically significant difference was found only in one measurement, U1/FH for the dry skull, in four measurements FPA, FMPA, U1/FH, and Pog-Np for subject A, in one measurement AN/FH for subject B, and in three measurements U1/FH, FMIA, and AN/FH for subject C. While demonstrating workability as a chairside tool and whilst there is a need for further refinement in measurement accuracy, this newly developed cephalometric system shows potential applicability, not only in the clinic as an auxiliary to or as a substitute for existing radiographic cephalometry, but also outside the clinic as an epidemiological tool.     

New Methods to Evaluate Craniofacial Deformity and to Plan Surgical Correction

The success of cranio-maxillofacial (CMF) surgery depends not only on surgical techniques, but also upon an accurate surgical plan. Unfortunately, traditional planning methods are often inadequate for planning complex cranio-maxillofacial deformities. To this end, we developed 3D computer-aided surgical simulation (CASS) technique. Using our CASS method, we are able to treat patients with significant asymmetries in a single operation which in the past was usually completed in two stages. The purpose of this article is to introduce our CASS method in evaluating craniofacial deformities and planning surgical correction. In addition, we discuss the problems associated with the traditional surgical planning methods. Finally, we discuss the strength and pitfalls of using three-dimensional measurements to evaluate craniofacial deformity.     

A three-dimensional cephalometric analysis of Japanese adults and its usefulness in orthognathic surgery: A retrospective study

This study aimed to establish a three-dimensional (3D) cephalometric analysis of craniofacial morphology and discuss its theoretical usefulness in orthognathic patients.Cone-beam computed tomography (CBCT) images of Japanese subjects with skeletal Class I malocclusion before treatment were selected from among 1000 patients so that samples matched a historic 2D cephalometric cohort with normal occlusion using propensity score matching. In each CBCT image, 67 3D measurements were calculated based on manually identified landmarks. The mean and standard deviation of the measurements were calculated and used as the normative range for each sex. To confirm the usefulness of the 3D measurements, pre- and post-treatment CT data of nine jaw deformity patients who underwent orthognathic surgery with two-dimensional planning (2DP) in the past were used. Pre- and post-treatment CT values were evaluated with a paired t-test as well as a Z-score, which was calculated using the aforementioned normative range, and then categorized into five groups (“deteriorated”, “no improvement”, “over-treatment”, “no change”, “improvement”) with ?1 < Z-score < 1 considered normal.Fifty-six patients were matched to normal skeletal 1 subjects. The normative range of 67 items indicating 3D craniofacial morphology of the Japanese was calculated. Postoperatively, the horizontal position of the pogonion to the mid-sagittal plane significantly decreased (p = 0.043) and “improved”; however, the ramus axis on the right side significantly increased (p = 0.005) and “deteriorated”. Maxillary yaw and the horizontal position of the gonion also tended to “deteriorated”.The normative range for the 3D cephalometric analysis in Japanese has been established. Given findings of deteriorated maxillomandibular yawing after surgery when using conventional 2DP, 3D cephalometric measurements should be used when planning jaw positions after surgery for orthognathic patients.     

A new method for assessment of craniofacial malformations

Many assessments of craniofacial malformations are generally undertaken to assist in surgical intervention including physical examination, cephalometric radiographs in anteroposterior and lateral views, stereolithographic models, and anthropometric measurements integrated with three-dimensional computed tomography (3-D CT) reconstructions to quantify skeletal deformities. In the present report, the use of 3-D Malformation Analysis, a three-dimensional methodology for planning craniofacial operative procedures, is presented. In addition to cephalometric and anthropometric databases, the measurements from 3-D surface reconstructions from CT were used intraoperatively to establish the correct position of skeletal segments.     

三维CT影像在颌骨骨折诊断与治疗中的临床价值

目的 :探讨三维CT影像在颌面部骨折中的诊断价值。方法 :对 17例颌骨骨折的三维CT影像及二维CT影像进行观察 ,分析其各自的特征并进行比较。结果 :三维CT影像在显示骨折的空间位置方面 ,如骨折线的行走路线 ,骨折片的移位距离与方向等都有独到的优势 ,但在显示上窦前壁线型骨折 ,骨折断端周围的软组织改变等方面不如二维CT影像。结论 :三维CT影像在显示颌面骨折处的空间关系上有很大的诊断意义及治疗指导意义 ,可以弥补二维CT影像的不足 ,但不能取代二维CT影像。     

Cone-beam computed tomography: accuracy of three-dimensional cephalometry analysis and influence of patient scanning position

The aim of this research was to analyze the influence of the position of the skull during cone-beam computed tomography (CBCT) scan and if the three-dimensional cephalometric measurements are influenced by skull orientation during CBCT scan.The study consisted of 5 CBCT scanning (KODAK 9500 Cone Beam 3D System unit) in 5 different positions of a dry skull. The data were imported in SIMPLANT OMS Software version 13.0. Fifteen three-dimensional cephalometric measurements were calculated; moreover, the mean, the SD, the maximum/minimum Δ, and the maximum/minimum Δ percentage were calculated. The statistical analysis was performed by an independent-samples t-test to evaluate differences between the 5 scans.No difference was found in all the three-dimensional analysis. Twelve of 15 measurements have a Δ greater than 1.5, and 7 of 15 measurements have a Δ greater than 2. Nine of 15 have a Δ percentage greater than 5%. The preliminary results suggest that the three-dimensional cephalometric analysis is influenced by patient scanning position.     

Accuracy of craniofacial measurements: computed tomography and three-dimensional computed tomography compared with stereolithographic models

In a retrospective study, distance measurements of nine children with craniofacial malformation were analyzed. The accuracy of measurements was compared when measured on a workstation using a 16-slice multidetector spiral computed tomography and on a stereolithographic model. Three different methods of defining distances were investigated: 1) on the stereolithographic plastic models, 14 distances connecting landmarks were identified with a digitizer (Polaris Tracker); 2) the same distances were defined at axial, coronal, and sagittal reformats of the computed tomography data set and measured using a Philips MX View workstation; and 3) the same 14 distances were defined at three-dimensional virtual reality models of the skulls at the same workstation. All measurements were performed with all three methods by three different readers. The following conclusions could be drawn: stereolithographic models provide a highly exact reproduction of the skull in children with craniofacial malformations. They are a reliable basis for all analytic and probatory endeavors preparing complicated surgical corrections. Three-dimensional virtual reality display modes serve significantly better for exact distance measurements on the complex surface of the human skull than planar reformats of the same computed tomography data sets.     

Craniofacial morphology and obstructive sleep apnoea: a cephalometric analysis

The craniofacial morphology of 31 male patients diagnosed with obstructive sleep apnoea syndrome (OSAS) and 37 healthy male subjects were compared using cephalometric evaluation of lateral skull radiographs. The aim was to evaluate which cephalometric variables related to craniofacial morphology discriminate between OSAS patients and non-OSAS subjects. Sixteen cephalometric measurements were determined to study the craniofacial morphology. Differences in cephalometric variables between the two groups were analysed with unpaired Student t-tests (significance level 0.05). A multiple regression analysis was used to evaluate the joint predictive value of selected variables. With regard to five variables, significant differences were observed between OSAS patients and non-OSAS subjects (P < 0.05). Data indicated a relatively anterior position of the maxilla, an increase of the mid-facial height and a more inferiorly located hyoid bone in the OSAS patient group. The multiple regression analysis yielded a model discriminating between OSAS patients and non-OSAS subjects, which included two hyoid bone variables and one related with the intermaxillary relationship. A causal relationship between cephalometric variables of craniofacial morphology and OSAS is not sufficiently supported by our data. Presumably, hyoid bone position is of predictive value in the cephalometric discrimination between OSAS patients and non-OSAS subjects.     

Changes in orthodontic cephalometric reference points on application of orthopedic force to jaw: three-dimensional finite element analysis

The present study investigated the effects of two orthodontic appliances on changes in the cephalometric reference planes using the three-dimensional finite element method. We simulated the use of a headgear and an orthopedic facial mask, two devices for the application of orthodontic force to the jaw. Using a finite element model of the skull, orthodontic force was applied to the maxillary first molar in a posterior or anterior direction. Changes in the maxilla, mandible and cephalometric reference planes were ascertained by the three-dimensional finite element method. The results showed that posterior force caused a slight posterior displacement and clockwise rotation of the reference planes, while anterior force caused anterior displacement and counterclockwise rotation. Since the maxilla was displaced and rotated in the same direction, the degrees of cephalometric displacement and rotation of the maxilla were smaller than the actual values.     

计算机辅助颅颌面畸形的三维诊断

利用侧位Ｘ线头影测量对颅颌面畸形进行诊断分析，已有相当长的时间．但因该方法取自颅颌面结构左右两侧的均值，用其测量分析不对称颅颌面畸形，有很大局限性．本文报告一种将正位和侧位两张Ｘ线头影片结合起来的三维Ｘ线头影测量分析方法，以及标准化与个体化相结合的诊断方法在复杂、不对称颅颌面畸形诊断中的应用．