Bewertung von Präzision und Genauigkeit der digitalen Oberflächenphotogrammetrie mit dem DSP 400 System / Assessment of Precision and Accuracy of Digital Surface Photogrammetry with the DSP 400 System

3D assessment of the nasolabial region in cleft models comparing an intraoral and a facial scanner to a validated baseline

We aimed to validate the metric accuracy of a 3-dimensional (3D) facial scanner (FS) and an intraoral scanner (IOS) in capturing the nasolabial region in ex vivo unilateral cleft lip and palate (UCLP) models. The nasolabial region of 10 UCLP models was scanned using a 3D FS as well as an IOS and a previously validated stationary 3D scanner as a reference. Intraoral scan was performed directly on the UCLP models. In order to apply the FS on the models, they were embedded in a 3D printed sample face. Both test groups were aligned to the reference by applying a section-based best-fit algorithm. Subsequent analysis of the metric deviation from the reference was performed with a 3D analysis tool. Mean distance and integrated distance served as main parameters for surface and volume comparison. Point comparison served as an additional parameter. Statistical analysis was carried out using t-test for unconnected samples. Considering mean distance and integrated distance as main parameters for 3D evaluation of the scanner's accuracy, FS and IOS differ significantly in their metric precision in scanning the cleft model compared to the reference. The IOS proved to be significantly more accurate than the FS compared to the previously described stationary 3D scanner as reference and validated baseline. Further validation of the tested IOS and FS for 3D assessment of the nasolabial region is presented by adding the previously validated ATOS III Triple Scan blue light scanner as a reference. The IOS shows, compared to a validated baseline scan, significantly higher metric precision in experimental cleft model scanning. The collected data provides a basis for clinical application of the IOS for 3D assessment of the nasolabial region.

Three-Dimensional Quantification of Facial Asymmetry in Children with Positional Cranial Deformity

BACKGROUND

The extent of facial involvement in positional plagiocephaly is only little investigated so far. Investigation methods that take into account the challenging anatomical conditions and growth of infants' faces are desirable. In this study, the authors established a new three-dimensional photogrammetry quantification method evaluating pretherapeutic and posttherapeutic facial asymmetry in positional plagiocephaly. Furthermore, a facial asymmetry index was established and evaluated.

METHODS

Three-dimensional photographs of 100 children undergoing treatment with head orthoses were analyzed by constructing a standardized interindividual coordinate system. Defining landmarks, section planes, and point coordinates with a computer-aided design software, both sides of the faces were compared. Facial asymmetry was quantified by measuring differences between left and right sides and pretherapeutic and posttherapeutic changes in each patient. The facial asymmetry index was calculated by putting the absolute differences in relation with the coordinates of the nonaffected side.

RESULTS

Present results indicate that positional plagiocephaly results in a distinct facial asymmetry (range, -3.8 to 9.6 mm) in nearly all spatial directions and facial regions. Helmet therapy led to a significant reduction (p < 0.05) of intraindividual facial asymmetry (median change in facial asymmetry index, -1.9 to 3.1 percent). However, no correlation of the Cranial Vault Asymmetry Index and facial asymmetry (Spearman rank correlation coefficient, ρ = -0.09 to 0.47) has been seen. According to these results, severe occipital deformation does not necessarily provoke distinct facial asymmetry.

CONCLUSIONS

Present three-dimensional photogrammetry method allows the longitudinal quantification of facial involvement in positional plagiocephaly. Asymmetry has been determined in all facial regions. The facial asymmetry decreased through helmet therapy but was not eliminated completely.

Standardized Three-Dimensional Lateral Distraction Test: Its Reliability to Assess Medial Canthal Tendon Laxity

Background

Assessment of MCT laxity is critical to the surgery options. Our study aimed to analyze the reliability of measuring medial canthal tendon (MCT) laxity by using a novel standardized three-dimensional lateral distraction test (3D-LDT).

Methods

Forty-eight Caucasian volunteers (25 males and 23 females, 96 eyes) between 22 and 84 years of age (55.6 ± 18.6 years old) were included in our study. From a neutral position, the lower eyelid was gently pulled laterally along a horizontal line to define the most distracted position of the lower punctum. Both in the neutral and distracted position, standardized 3D images were acquired for each subject by two observers, and each image were measured twice by two raters. Four landmarks and six corresponding linear measurements were evaluated for intra-rater, inter-rater, and inter-method reliability.

Results

Intra-rater, inter-rater and inter-method reliability analyses of 3D-LDT revealed an intraclass correlation of more than 95%, a mean absolute difference of less than 1 mm, and a technical error of measurement of less than 1 mm. Measurements of relative error (2.59–12.04%) and relative technical error (1.83–16.05%) for the inter-landmarks distance from pupil center to the lower punctum were higher than those from limbus nasal center to the lower punctum (6.13–30.39 and 4.34–26.85%, respectively).

Conclusions

This study provided high reliability of the three-dimensional lateral distraction test (3D-LDT) for assessing medial canthal tendon (MCT) laxity, which were never evaluated by digital imaging system.

Level of Evidence IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Validation of a low-cost portable 3-dimensional face scanner

Purpose

The goal of this study was to assess the accuracy and reliability of a low-cost portable scanner (Scanify) for imaging facial casts compared to a previously validated portable digital stereophotogrammetry device (Vectra H1). This in vitro study was performed using 2 facial casts obtained by recording impressions of the authors, at King's College London Academic Centre of Reconstructive Science.

Materials and Methods

The casts were marked with anthropometric landmarks, then digitised using Scanify and Vectra H1. Computed tomography (CT) scans of the same casts were performed to verify the validation of Vectra H1. The 3-dimensional (3D) images acquired with each device were compared using linear measurements and 3D surface analysis software.

Results

Overall, 91% of the linear Scanify measurements were within 1 mm of the corresponding reference values. The mean overall surface difference between the Scanify and Vectra images was <0.3 mm. Significant differences were detected in depth measurements. Merging multiple Scanify images produced significantly greater registration error.

Conclusion

Scanify is a very low-cost device that could have clinical applications for facial imaging if imaging errors could be corrected by a future software update or hardware revision.

Development of a Three-Dimensional Hand Model Using Three-Dimensional Stereophotogrammetry: Assessment of Image Reproducibility

Purpose

Using three-dimensional (3D) stereophotogrammetry precise images and reconstructions of the human body can be produced. Over the last few years, this technique is mainly being developed in the field of maxillofacial reconstructive surgery, creating fusion images with computed tomography (CT) data for precise planning and prediction of treatment outcome. Though, in hand surgery 3D stereophotogrammetry is not yet being used in clinical settings.

Methods

A total of 34 three-dimensional hand photographs were analyzed to investigate the reproducibility. For every individual, 3D photographs were captured at two different time points (baseline T0 and one week later T1). Using two different registration methods, the reproducibility of the methods was analyzed. Furthermore, the differences between 3D photos of men and women were compared in a distance map as a first clinical pilot testing our registration method.

Results

The absolute mean registration error for the complete hand was 1.46 mm. This reduced to an error of 0.56 mm isolating the region to the palm of the hand. When comparing hands of both sexes, it was seen that the male hand was larger (broader base and longer fingers) than the female hand.

Conclusions

This study shows that 3D stereophotogrammetry can produce reproducible images of the hand without harmful side effects for the patient, so proving to be a reliable method for soft tissue analysis. Its potential use in everyday practice of hand surgery needs to be further explored.

A Pilot Study on the Influence of Facial Expression on Measurements in Three-Dimensional Digital Surfaces of the Face in Infants With Cleft Lip and Palate

OBJECTIVE

Three-dimensional surface imaging is an increasingly popular modality for face measurements in infants with cleft lip and palate. Infants are noncompliant toward producing specific facial expressions, and selecting the appropriate moment of acquisition is challenging. The objective was to estimate amount and spatial distribution of deformation of the face due to facial expression in infants with cleft lip and palate and provide recommendations for an improved acquisition protocol, including a method of quality control in terms of obtaining images with true neutral expression.

MATERIAL AND METHODS

Three-dimensional surface images of ten 4-month-old infants with unrepaired cleft lip and palate were obtained using a 3dMDface stereophotogrammetric system. For each subject, five surface images judged as representing a neutral expression were obtained during the same photo session. Mean and maximum deformations were calculated. A formalized review was performed, allowing the image exhibiting the "best" neutral expression to be selected, thus decreasing errors due to residual facial expression.

RESULTS

Deformation due to facial expression generally increased from forehead to chin. The amount of deformation in three selected regions were determined: nose (mean, 1 mm; maximum = 3 mm); cleft region (mean, 2 mm; maximum = 5 mm); chin region (mean, 5 mm; maximum = 12 mm). Analysis indicated that introduction of a formalized review of images could reduce these errors by a factor of 2.

CONCLUSIONS

The continuous change of facial expression in infants represents a substantial source of error; however, this may be reduced by incorporating a formalized review into the acquisition protocol.

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.

Facial surface changes after cleft alveolar bone grafting

PURPOSE

The aim of this study was to assess the 3-dimensional facial surface changes after cleft alveolar bone grafting with digital surface photogrammetry.

PATIENTS AND METHODS

In a prospective study, 22 patients with cleft lip and palate underwent alveolar bone grafting. Before the procedure and 6 weeks postoperatively and before the continuation of orthodontic treatment, 3-dimensional images were taken with digital surface photogrammetry. Seven standard craniofacial landmarks on the nose and the upper lip were identified. Their spatial change because of bone grafting was assessed. Statistical analysis was performed with analysis of variance and t test.

RESULTS

A significant increase in anterior projection on the operative side (P < .05) was found for the labial insertion points of the alar base (subalare). No significant changes were detected for the position of the labial landmarks.

CONCLUSION

Our results show 3-dimensionally that there is a positive influence of the alveolar bone graft on the projection of the alar base on the cleft side.

Registration of 3-dimensional facial photographs for clinical use

PURPOSE

To objectively evaluate treatment outcomes in oral and maxillofacial surgery, pre- and post-treatment 3-dimensional (3D) photographs of the patient's face can be registered. For clinical use, it is of great importance that this registration process is accurate (< 1 mm). The purpose of this study was to determine the accuracy of different registration procedures.

MATERIALS AND METHODS

Fifteen volunteers (7 males, 8 females; mean age, 23.6 years; range, 21 to 26 years) were invited to participate in this study. Three-dimensional photographs were captured at 3 different times: baseline (T(0)), after 1 minute (T(1)), and 3 weeks later (T(2)). Furthermore, a 3D photograph of the volunteer laughing (T(L)) was acquired to investigate the effect of facial expression. Two different registration methods were used to register the photographs acquired at all different times: surface-based registration and reference-based registration. Within the surface-based registration, 2 different software packages (Maxilim [Medicim NV, Mechelen, Belgium] and 3dMD Patient [3dMD LLC, Atlanta, GA]) were used to register the 3D photographs acquired at the various times. The surface-based registration process was repeated with the preprocessed photographs. Reference-based registration (Maxilim) was performed twice by 2 observers investigating the inter- and intraobserver error.

RESULTS

The mean registration errors are small for the 3D photographs at rest (0.39 mm for T(0)-T(1) and 0.52 mm for T(0)-T(2)). The mean registration error increased to 1.2 mm for the registration between the 3D photographs acquired at T(0) and T(L). The mean registration error for the reference-based method was 1.0 mm for T(0)-T(1), 1.1 mm for T(0)-T(2), and 1.5 mm for T(0) and T(L). The mean registration errors for the preprocessed photographs were even smaller (0.30 mm for T(0)-T(1), 0.42 mm for T(0)-T(2), and 1.2 mm for T(0) and T(L)). Furthermore, a strong correlation between the results of both software packages used for surface-based registration was found. The intra- and interobserver error for the reference-based registration method was found to be 1.2 and 1.0 mm, respectively.

CONCLUSION

Surface-based registration is an accurate method to compare 3D photographs of the same individual at different times. When performing the registration procedure with the preprocessed photographs, the registration error decreases. No significant difference could be found between both software packages that were used to perform surface-based registration.

Implementing a superimposition and measurement model for 3D sagittal analysis of therapy-induced changes in facial soft tissue: a pilot study

AIM

3D digital surface photogrammetry is an objective means of documenting the quantitative evaluation of facial morphology. However, there are no standardized superimposition and measurement systems for surveying soft tissue changes. The aim of this study was to present a superimposition and measurement model for three-dimensional analysis of therapy-induced sagittal changes in facial soft tissue and to ascertain its applicability based on the reproducibility of 3D landmark positions.

PATIENTS AND METHOD

Twenty-nine children were examined (eight with cleft lip and palate, six with cleft palate, eight with Class III malocclusion and seven healthy controls, between 4.1 and 6.4 years). The mean time between examinations was 8.2 months for the patients and 8 months for the control group. Data was acquired with the DSP 400((c))imaging system. A mathematical model with seven superimposition points was developed. Two 3D images, one at the beginning and the other at the end of the examination, were generated. Both images were superimposed ten times. Ten landmarks for evaluating the soft tissue changes were geometrically defined on the superimposition image, put in place ten times, and measured. The landmarks' reproducibility was calculated via statistical intraoperator analysis. Measurement error was identified using the root mean square error (RMSE).

RESULTS

The superimposition points were easy to locate and the landmarks well definable. All midface landmarks proved to be highly reproducible with an RMSE under 0.50 mm. The lower face landmarks demonstrated good reproducibility with an RMSE under 1 mm. The midface landmarks' precision fell below the range of accuracy, while the lower face landmarks' precision fell within the optoelectronic scanner device's range of accuracy (0.50-1 mm).

CONCLUSIONS

As an accurate, non-invasive, millisecond-fast, non-ionizing and ad infinitum repeatable procedure, 3D digital surface photogrammetry is very well suited for clinical and scientific application in orthodontics. We developed a reliable superimposition and measurement model with 3D digital surface photogrammetry. This new capturing and measurement system provides a simple means of determining 3D changes in facial soft tissue. Our landmarks proved to be highly reproducible for the midface while revealing good reproducibility for the lower face.

3D soft tissue changes in facial morphology in patients with cleft lip and palate and class III mal occlusion under therapy with rapid maxillary expansion and delaire facemask

AIM

Rapid Maxillary Expansion (RME) and Delaire facemask are a well-established treatment method for patients with cleft lip and palate and Class III malocclusion. Several roentgenocephalometric studies on skeletal effects of this therapy are known. However, there are no systematic studies on soft tissue changes. The aim of this study was to analyze three-dimensionally the soft tissue changes in facial morphology of children with cleft lip and palate and Class III malocclusion under therapy with RME and Delaire facemask.

PATIENTS AND METHOD

A prospective longitudinal clinical trial was undertaken. 29 children between 4.1 and 6.4 years were divided into four groups: eight patients with unilateral cleft lip and palate (group 1), six patients with isolated cleft palate (group 2), eight patients with Class III malocclusion (group 3). The mean treatment period with RME and Delaire mask was 8.2 months. Seven untreated children with no need of orthodontic treatment were chosen as the control (group 4). Two 3D images, one at the beginning and one at the end of the study, were generated with the DSP 400((c)) imaging system. Both images were superimposed ten times and measured ten times.

RESULTS

We detected significant forward rotation and forward displacement of the soft tissue in the lower midface with the dentoalveolar areas in all patient groups. No significant asymmetric forward displacement of the soft tissue in the maxilla could be verified in the lower or upper midface, not even in the unilateral cleft lip and palate patients. Among the groups, the Class III malocclusion patients showed greater maxillary soft tissue changes.

CONCLUSION

The RME and the Delaire facemask demonstrated the greatest effectiveness in the lower midface soft tissue in terms of forward displacement and forward rotation in the cleft lip and palate patients, particularly in the Class III patients. The 3D data allowed us to discriminatively interpret the effects of the orthopedic mask on the entire maxillary complex and maxillary alveolar process. In the unilateral cleft lip and palate patients, there was descriptively both symmetric and asymmetric advancement of the midface soft tissue.

Three-dimensional assessment of facial development in children with Pierre Robin sequence

Newborns with Pierre Robin sequence (PRS) have mandibular hypoplasia, glossoptosis, and possibly cleft palate. Their facial appearance is characteristic. The further facial development is controversial. The aim of this study was to analyze the facial development of children with PRS.In a prospective, cross-sectional study, 344 healthy children and 37 children with PRS and cleft palate younger than 8 years were scanned three-dimensionally. Twenty-one standard anthropometric landmarks were identified, and the images were superimposed. Growth curves for normal facial development were calculated. The facial morphology of children with PRS was compared with that of healthy children.The facial growth of children with PRS in the transversal and vertical direction was normal. In the sagittal direction, the mandibular deficit was confirmed. Except for the orbital landmarks and nasion, all landmarks of the midface demonstrated a significant sagittal deficit. This difference to healthy children remained constant for all ages.Our study cannot support the theory of mandibular catch-up growth. The sagittal deficit of the midface could be observed in all ages. This indicates that children with PRS have a very early, severe, and persistent underdevelopment of this part of the face. We conclude that this disturbance must be addressed in early childhood with orthodontic and speech therapy.

Digital surface photogrammetry for anthropometric analysis of the cleft infant face

OBJECTIVE

To analyze the three-dimensional morphology of the cleft infant face with digital surface photogrammetry.

DESIGN

Fifty plaster casts of unoperated infants with cleft lip and palate were imaged three-dimensionally with digital surface photogrammetry. Twenty-one standard craniofacial measurements were taken. The plaster casts were divided into 4 groups with unilateral, bilateral, complete, and incomplete clefts of the lip and palate. The measurements were compared with standard values for healthy infants.

RESULTS

Significant differences (p < .0025) were found for the alar base width (33% to 55%), the alar base root width (59% to 103%), the width of the nose (7% to 25%), the length of the alar wing (18% to 25%), and the intercanthal (6% to 17%) and biocular (4% to 12%) width, depending on the cleft type. The vertical dimensions of the nose and the upper lip did not differ significantly from the controls.

CONCLUSION

This study describes preliminary data on the cleft infant facial deformity. The obtained results were mainly in agreement with data in the limited literature. Three-dimensional photogrammetry has proven to be reliable and can be applied more readily to potentially uncooperative patients.