Three-dimensional Stereophotogrammetry Research Articles

Periocular Asymmetry Index in Caucasian Populations Using Three-dimensional Photogrammetry Assessment.

To quantitatively assess the periocular asymmetry and investigate its sex and age-related differences in a Caucasian population using three-dimensional (3D) stereophotogrammetry. Standardized 3D photos of the periocular region of 301 Caucasians were taken using the VECTRA M3 3D Imaging System. Standardized landmarks were positioned, and data measurements in the periocular region were obtained from these images using VAM software and assessed using intraclass correlation coefficients (ICC) for reliability. Absolute differences and asymmetry index between the right and the left periocular region were calculated with a focus on gender and age-related differences. Fissure height asymmetry was positively correlated with age (p < 0.01). Furthermore, reflex distance asymmetry was positively correlated with age in the elderly group (p < 0.05). Absolute differences of upper eyelid crease were 0.65 ± 0.79 mm for females and 0.90 ± 0.94 mm for males (p < 0.05). In the elderly group, the absolute differences of reflex distance were 0.664 ± 0.471 mm for males and 0.470 ± 0.408 mm for females (p < 0.05), while the absolute differences of fissure height were 0.619 ± 0.469 mm and 0.436 ± 0.372 mm, respectively (p < 0.05). All measurements had an inter-rater ICC and intra-rater ICC between 0.761 and 0.957. Periocular asymmetry is more prominent in older and male people. 3D photogrammetry is a reliable tool to detect periocular asymmetry and might provide an accurate and effective reference for periocular cosmetic, plastic, and reconstructive surgery in the clinical routine. 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 .

Impact of Unilateral Alveolar Bone Grafting on Nasal Volume and Nasolabial Surface: A 3D Analysis.

To determine possible effects of unilateral alveolar cleft closure on internal nasal volume and external nasolabial surface. Retrospective, single-arm, cohort study. Institutional, tertiary care. Patients with complete unilateral cleft lip, alveolus, and palate (CUCLAP), who underwent closure of the alveolar cleft with autologous bone graft (ABG) at the age of 9-11 years, with cone beam computed tomography (CBCT) and/or three-dimensional (3D) stereophotogrammetry images taken before and one year after the ABG procedure. ABG-pocedure in patients with CUCLAP. The influence of ABG on the internal and external nasal morphology. A total of 28 patients (21M/7F, 14R/14L) were divided into internal (CBCT) and external (3D-stereophotogrammetry) measurement subgroups. The external nasolabial surface showed a significant decrease of the angle alar curvature right-subnasale-alar curvature left (-1.99°; P = .02; 95% CI -2.61, -0.36) and an increase of the linear measurement between these points (+1.01 mm; P = .03; 95% CI: 0.11, 1.91). No significant differences were found when comparing the distance maps of the affected side with the non-affected side (P = .50, 95% CI: -0.20, 0.29). Closure of the alveolar cleft in CUCLAP patients with ABG did not affect the internal nasal volume, but significantly affected the external nasal surface. The procedure resulted in the nose becoming wider because both alar curvatures moved caudally and laterally relative to the subnasale.

Protocol Establishment and Reliability Verification of Three-Dimensional Digital Stereophotogrammetry in Lower Eyelid Anthropometry.

Three-dimensional (3D) stereophotogrammetry has been widely used in anthropometry for both medical and esthetic purposes. However, no studies have assessed its reliability on measuring the lower eyelid by 3D imaging. This study aimed to establish a standardized 3D anthropometric protocol for lower eyelid region and validate its reliability. Fifty-eight participants (116 eyes) were recruited with mean age of 39.14 ± 11.25 years. Two sets of VECTRA 3D images were taken for each subject, and each set of images was individually measured twice by two raters. Twenty-seven landmarks were identified in the lower eyelid region, and then 19 linear, 4 curvilinear, 7 angular and 2 areal metrics were assessed for intrarater, interrater and intramethod reliability. High reliability was found in this 3D imaging-based lower eyelid anthropometry. The mean absolute difference within 2 intrarater measurement were 0.22 and 0.08 units, the technical errors measurement were 0.31 and 0.15 units, the relative errors of measurement were 0.90% and 0.31%, the relative technical errors of measurement were 1.53% and 0.64%, and the intra-group correlation coefficient was 0.99 and 0.99. The results for interrater measurement were 0.53 units, 0.59 units, 2.94%, 3.41% and 0.96, and for intramethod measurement were 0.71 units, 0.77 units, 4.12%, 4.05% and 0.95 units, respectively. 3D stereophotogrammetry is reliable for lower eyelid anthropometry. The standardized protocol can be further applied for many purposes such as lower eyelid aging evaluation, surgical related assessment and periocular rejuvenation plan. 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 .

Estimating the Change in Facial Subunits During Positive and Negative Facial Expression Using Three-Dimensional Stereophotogrammetry Facial Analysis.

Background: A more refined and clinically related facial expression analysis is required for patients who wish to be perceived more emotionally positive. Objective: To measure the change in skin vector and volume in facial subunits when expressing positive expression (happiness) compared with negative expressions (sadness, fear, disgust, and anger), using three-dimensional (3D) stereophotogrammetry analysis. Methods: This study took 3D photographs of 20 volunteers' face at rest and during positive and negative expression. The directions of skin vector and volume changes in each facial subregion were recorded and calculated. Results: In the positive expression, 78.3% (95% confidence interval [CI] 66.8-89.9) of the medial midfacial subregions presented superolateral vector and volume increase, whereas volume decrease in 82.5% (95% CI 78.5-86.5) of the lip subregions could be observed. In the negative expression, the vector changes were predominantly inferomedial in 26.0% (95% CI 15.4-36.5) of the forehead and 36.8% (95% CI 33.2-40.3) of the upper eyelid subregions, whereas volume increases in 34.0% (95% CI 30.4-37.7) of the upper eyelid subregions were observed. Conclusions: This 3D stereophotogrammetry analysis presents the morphological difference between the positive and negative expression.

What is the impact of miniscrew-assisted rapid palatal expansion on the midfacial soft tissues? A prospective three-dimensional stereophotogrammetry study

ObjectivesTo evaluate the midfacial soft tissue changes of the face in patients treated with miniscrew-assisted rapid palatal expansion (MARPE).Materials and methods3D facial images and intra-oral scans (IOS) were obtained before expansion (T0), immediately after completion of expansion (T1), and 1 year after expansion (T2). The 3D images were superimposed and two 3D distance maps were generated to measure the midfacial soft tissue changes: immediate effects between timepoints T0 and T1 and overall effects between T0 and T2. Changes of the alar width were also measured and dental expansion was measured as the interpremolar width (IPW) on IOS.ResultsTwenty-nine patients (22 women, 7 men, mean age 25.9 years) were enrolled. The soft tissue in the regions of the nose, left of philtrum, right of philtrum, and upper lip tubercle demonstrated a statistically significant anterior movement of 0.30 mm, 0.93 mm, 0.74 mm, and 0.81 mm, respectively (p < 0.01) immediately after expansion (T0–T1). These changes persisted as an overall effect (T0–T2). The alar width initially increased by 1.59 mm, and then decreased by 0.08 mm after 1 year, but this effect was not significant. The IPW increased by 4.58 mm and remained stable 1 year later. There was no significant correlation between the increase in IPW and alar width (r = 0.35, p = 0.06).ConclusionsOur findings indicate that MARPE results in significant but small changes of the soft tissue in the peri-oral and nasal regions. However, the clinical importance of these findings is limited.Clinical relevanceMARPE is an effective treatment modality to expand the maxilla, incurring only minimal and clinically insignificant changes to the midfacial soft tissues.

A Quantitative Three-Dimensional Tear Trough Deformity Assessment and Its Application in Orbital Septum Fat Transposition.

Existing evaluation tools of tear trough deformity are based on subjective impression of clinicians. More accurate quantitative assessment methods are needed. This study aimed to propose a quantitative three-dimensional assessment method for the tear trough deformity in comparison with the Barton's grading system and apply it to the efficacy evaluation of orbital septum fat transposition. 117 healthy Chinese adults (234 eyes) were enrolled and divided into four groups according to the Barton's grading system. Three-dimensional facial images were captured using Vectra H1 handheld camera. 6 anthropometric landmarks were identified on each eye and 8 linear measurements were generated accordingly. Intra-observer reliability was determined and measurements were compared between groups. Pre- and post-operative three-dimensional measurements were compared in 19 patients who received lower blepharoplasty with orbital septum fat transposition. The severity of tear trough was positively correlated with age (P < 0.001) but not BMI (P = 0.145) or gender (P = 0.280). Intra-rater reliability of the 8 linear measurements was excellent except for the vertical distance between the palpebrale inferioris margin and the tear trough below the pupillary center. Intergroup comparison showed that the horizontal distance between the lateral end of tear trough (P < 0.001) and medial canthus and the sagittal vector from tear trough point toward eyelid bag point (P = 0.009) increased with grade, while the vertical distance from mid-pupil to palpebrale inferioris margin decreased gradually (P = 0.001). Orbital septum fat transposition significantly improved the tear trough deformity as assessed by these three-dimensional measurements. We demonstrated a novel quantitative evaluation method of the tear trough deformity using three-dimensional stereophotogrammetry and proved it to be valid and reliable. It showed good value of clinical application and might help with periorbital rejuvenation planning and outcome assessment. 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 .

Development and Validation of a Comprehensive Perioral Evaluation Method Using Three-Dimensional Stereophotogrammetry.

The non-invasive three-dimensional (3D) stereophotogrammetry is widely used in anthropometry for medical purpose. Yet, few studies have assessed its reliability on measuring the perioral region. This study aimed to provide a standardized 3D anthropometric protocol for the perioral region. 38 female and 12 male Asians were recruited (mean age 31.6±9.6 years). Two sets of 3D images using the VECTRA 3D imaging system were acquired for each subject, and two measurement sessions for each image were performed independently by two raters. 25 landmarks were identified, and 28 linear, 2 curvilinear, 9 angular and 4 areal measurements were evaluated for intrarater, interrater, and intramethod reliability. Our results showed high reliability of 3D imaging-based perioral anthropometry by mean absolute difference (0.57 and 0.57 unit), technical error measurement (0.51 and 0.55 unit), relative error of measurement (2.18% and 2.44%), relative technical error of measurement (2.02% and 2.34%), and intraclass correlation coefficient (0.98 and 0.98) for intrarater 1 and intrarater 2 reliability; respectively 0.78 unit, 0.74 unit, 3.26%, 3.06% and 0.97 for interrater reliability; and respectively 1.01 unit, 0.97 unit, 4.74%, 4.57% and 0.95 for intramethod reliability. This standardized protocol utilizing 3D surface imaging technologies are feasible and highly reliable in perioral assessment. It could be further applied for diagnostic purpose, surgical planning and therapeutic effect evaluation in clinical practice in relation to perioral morphologies. 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 .

Facial morphology differences in monozygotic twins: a retrospective stereophotogrammetric study.

To assess soft tissue differences between monozygotic twins (MZ) for the total face and between facial regions using three-dimensional (3D) stereophotogrammetry and quantitative surface-based 3D deviation analyses. The study sample consisted of 14 untreated MZ twins (6 males, 8 females, mean age: 14.75 years) from the archive of Marmara University, Department of Orthodontics. The images were taken by the 3dMDface system, and 3dMDvultus software was used for removal of undesired areas and approximation of the images. Then, stereolithography (.stl) format images were superimposed using the best-fit algorithm using 3-matic software. The face was divided into facial thirds, and upper lip and lower lip + chin regions were created. For the comparison, 3D deviation analyses were performed, and a color map and histogram were created. The data were presented as mean deviation, root mean square (RMS), median, and interquartile range. Between the facial thirds, there was no significant difference in soft tissue differences for mean deviation. A statistically significant difference was found between the upper and lower face for the RMS value. For the comparison of upper lip and lower lip + chin region, the only significant difference was for the RMS. When the data were presented as median and interquartile range, there were no statistically significant differences between any facial regions. Lower facial third and lower lip + chin regions had the greatest differences within MZ twin pairs. The genetic and environmental influences might not be the same for different parts of the face.

Estimation of Spatiotemporal Gait Parameters in Walking on a Photoelectric System: Validation on Healthy Children by Standard Gait Analysis.

The use of stereophotogrammetry systems is challenging when targeting children's gait analysis due to the time required and the need to keep physical markers in place. For this reason, marker-less photoelectric systems appear to be a solution for accurate and fast gait analysis in youth. The aim of this study is to validate a photoelectric system and its configurations (LED filter setting) on healthy children, comparing the kinematic gait parameters with those obtained from a three-dimensional stereophotogrammetry system. Twenty-seven healthy children were enrolled. Three LED filter settings for the OptoGait were compared to the BTS P6000. The analysis included the non-parametric 80% limits of agreement and the intraclass correlation coefficient (ICC). Additionally, normalised limits of agreement and bias (NLoAs and Nbias) were compared to the clinical experience of physical therapists (i.e., assuming an error lower than 5% is acceptable). ICCs showed excellent consistency for most of the parameters and filter settings; NLoAs varied between 1.39% and 12.62%. An inverse association between the number of LEDs for filter setting and the bias values was also observed. Observations confirm the validity of the OptoGait system for the evaluation of spatiotemporal gait parameters in children.

Three-Dimensional Analysis of Tear Trough Volume After Lower Blepharoplasty with Midface Lift.

Background: This study aims to evaluate three-dimensional stereophotogrammetry measured volume changes in the tear trough area after lower blepharoplasty with midface lift with or without orbital fat manipulation. Objective: Among patients undergoing midface lift surgery, volume change by three-dimensional photography in the tear trough region was compared between those having no orbital fat manipulation, fat transposition, or fat resection. Methods: This is a prospective study of 260 eyelids of 130 patients who underwent cosmetic midface surgery. All patients had an external skin muscle flap midface lift. During the procedure, medial inferior orbital fat was resected, repositioned to a preperiosteal dissection pocket, or not manipulated. Forty-six patients (35.4%) had no fat manipulation, 42 patients (32.3%) had fat preservation with repositioning to the preperiosteal pockets on the medial inferior orbital rim, and 42 patients (32.3%) had fat resection without repositioning. Results: All patients had volume gain in tear trough volume. The amount was not statistically significantly different between fat treatment groups. Mean follow-up time was 12 months (range 6-20 months). Conclusions: Midface lifting improved tear trough volume irrespective of how fat was manipulated.

Three-Dimensional Analyses of Postoperative Effects of Surgically Assisted Rapid Palatal Expansion (SARPE) on the Soft Tissue of the Midface Region and the Upper Airway Space Using Stereophotogrammetry and Cone Beam Computed Tomography (CBCT).

Surgically assisted rapid palatal expansion (SARPE) is an established method to treat transverse maxillary hypoplasia in skeletally mature adult patients. SARPE affects the surrounding soft tissue. In addition, effects on the airway and breathing have been described. Aim of this study was to assess the effects of SARPE on the nasal soft tissue and the upper airway by means of three-dimensional stereophotogrammetry and cone beam computed tomography (CBCT). This retrospective study used preoperative and postoperative cone beam computed tomography (CBCT) scans and three-dimensional stereophotogrammetry. Ten skeletally adult patients (4 male, 6 female; mean age 27.68 years) with transverse maxillary hypoplasia were included. Patients had undergone SARPE procedure, performed by the same surgical team using the same technique. Nasal soft tissue changes were analyzed, using three-dimensional stereophotogrammetry records taken preoperatively (t0) and at the postoperative checkup appointment (t1). The upper airway was assessed using CBCT scans for surgical planning (t0) and the first scan taken after SARPE (t1). In stereophotogrammetry, it was shown that only a few soft tissue nasal parameters increased significantly and SARPE leads to mainly clinically irrelevant changes in nasal soft tissue. In CBCT, only a significant increase in nasopharyngeal airway volume was found. Results were in alignment with literature. The effects of SARPE on the nasal soft tissue are mostly statistically insignificant and clinically irrelevant. Airway volume significantly increased in the nasopharyngeal area. Further research on SARPE effects should be conducted to reinforce SARPE as a treatment option for sleep apnea patients.

Reliability of 3D Stereophotogrammetry for Measuring Postoperative Facial Swelling.

This study aimed to determine the reliability of three-dimensional (3D) stereophotogrammetry as a measurement instrument for evaluating soft tissue changes in the head and neck area. Twelve patients received a bilateral sagittal split osteotomy (BSSO). Test and retest 3D photographs were captured within the first three postoperative weeks, and a reference 3D photograph was capture at three months postoperatively. Distance measurements, mean and root mean square of the distance map, and volume differences were obtained. Reliability of these parameters was assessed by intraclass correlation coefficients (ICCs), standard error of measurement (SEM), and smallest detectable change (SDC). All distance measurements had an ICC > 0.91, and the distance map parameters and volume differences showed ICCs > 0.89. The neck region presented the largest SEMs (5.09 mL) and SDC (14.1 mL) for the volume difference. In conclusion, 3D stereophotogrammetry is reliable for distance and volume measurements of soft tissues in patients after a BSSO advancement.

Reproducibility of Three-Dimensional Volumetric Measurement of Periocular Tumor Models.

In this study, we measured the volume of customized tumor models in the periocular area using three-dimensional (3D) stereophotogrammetry and evaluated the reproducibility of these measurements. Five tumor models of different colors and sizes were placed in different periocular positions, and 3D facial images were obtained from 68 healthy adult volunteers. Subsequently, the volumes of the tumor models were measured, and the intra- and interrater reproducibility was assessed. The gray 6mm model revealed the highest reliable measurements in both Caucasians (intra- and interrater intraclass correlation coefficients of 0.981 and 0.899, mean absolute difference of 1.446 and 3.327mm3, relative error measurement of 3.497% and 8.120%, technical error of measurement of 1.450 and 3.105mm3, and relative technical error of measurement of 3.506% and 7.580%) and Asians (0.968 and 0.844, 1.974 and 4.067mm3, 4.772% and 9.526%, 2.100 and 4.302mm3, and 5.076% and 10.076%, respectively). The highest reliability of measurements in the lateral upper eyelid (0.88 and 0.95, 4.042 and 3.626mm3, 9.730% and 9.020%, 5.714 and 3.358mm3, and 9.730% and 8.350%, respectively) and medial upper eyelid (0.81 and 0.89, 4.313 and 4.226mm3, 9.730% and 9.020%, 6.098 and 4.069mm3, and 9.730% and 8.350%, respectively) with eyes closed was evident in Caucasians, while the same trend (0.841 and 0.815, 2.828 and 3.757mm3, 9.860% and 9.840%, 4.052 and 4.308mm3, and 9.860% and 9.740%, respectively) was observed in Asians in the medial canthus with eyes closed. This study confirms, for the first time, the high reliability of periocular tumor volume measurements using 3D stereophotogrammetry, suggesting its feasibility for eyelid tumor measurement. Further trials are required to investigate its clinical use for documentation and follow-up of different eyelid tumors.

3-Dimensional Morphometric Outcomes After Endoscopic Strip Craniectomy for Unicoronal Synostosis.

Endoscopic strip craniectomy with postoperative helmeting (ESCH) for unicoronal synostosis has shown to be a less morbid procedure when compared with fronto-orbital remodeling (FOR). We aim in this pilot study to report objective methods and quantitative morphologic outcomes of endoscopically treated unicoronal synostosis using 3-dimensional surface scans. Our electronic records were reviewed for ophthalmological, neurodevelopmental outcomes, and helmet-related complications. For morphologic outcomes, the following parameters were used: Cranial Index, Cranial Vault Asymmetry Index, Anterior Symmetry Ratio (ASR), and Root Mean Square between the normal and synostotic sides of the head. Three-dimensional stereophotogrammetry scans were evaluated at 3 time points preoperative, 6 months post-op, and at the end of the treatment, which was compared with age-matched scans of normal controls and FOR patients. Nonparametric tests were used for statistical analysis. None of the ESCH cases developed strabismus, major neurodevelopmental delay, or helmet complications. All morphologic parameters improved significantly at 6 months post-op except for the Cranial Vault Asymmetry Index. The ASR was the only parameter to change significantly between 6 months post-op and final scans. At end of helmet treatment, ASR and Root Mean Square differed significantly between the ESCH and both FOR and control groups. Endoscopic strip craniectomy with postoperative helmeting for single unicoronal synostosis had excellent clinical outcomes. Most of the improvement in head morphology occurred in the first 6 months of treatment. Despite the normalization of the overall head shape, there was residual asymmetry in the frontal and temporal regions of the head.

Soft tissue evaluation after maxillary protraction with RPE or with the ALT-RAMEC protocol : Acontrolled 3D study.

To evaluate soft tissue changes following maxillary protraction with different expansion protocols using three-dimensional (3D) stereophotogrammetry. Pretreatment (T0) and postprotraction (T1) stereophotogrammetry and lateral cephalometric images of skeletal classIII patients were included in this retrospective study. In all, 32patients were treated either with acombination of rapid palatal expansion and facemask (RPE/FM; n = 16; mean age: 9.94 ± 0.68years) or with alternate rapid maxillary expansion and constriction together with afacemask (Alt-RAMEC/FM; n = 16; mean age: 9.74 ± 1.35years). As acontrol group16 untreated patients were recruited (mean age: 9.46 ± 0.8years). For superimpositioning of the 3D images taken at T0 and T1, the face was divided into defined regions and 3D and differences between the groups were evaluated using 3‑matic software (Materialise Europe, Leuven, Belgium). Cephalometric analyses were also performed. While the increases in the cephalometric parameters SNA and ANB were significantly greater in the treatment groups, the value for SNB also increased in the control group (p < 0.05). The results of the stereophotogrammetry analyses demonstrated that the mean changes in the RPE/FM and in the Alt-RAMEC/FM groups were significantly different for the midface compared to the control group (0.33 ± 0.26 mm, 0.3 ± 0.31 mm, 0.1 ± 0.18 mm). The maximum positive, negative, and mean changes were also significantly different between the treatment and control groups for the upper lip (p < 0.05). For the lower lip and the chin significant backward movements in the RPE/FM as well as in the Alt-RAMEC/FM group (-1.06 ± 1.26 mm, -0.68 ± 0.45 mm) were observed, while the control group (0.09 ± 0.53 mm) presented changes in the opposite direction. Regarding soft tissue changes, no significant differences were found between the RPE/FM and Alt-RAMEC/FM groups. Both treatment protocols improved the soft tissue profile due to aforward movement of the midface and the upper lip, and abackward movement of the lower lip and chin, compared to the control group.

Evaluation of facial soft tissue asymmetric changes in Class III patients after orthognathic surgery using three-dimensional stereophotogrammetry

The aim of this study was to investigate changes in facial soft tissue asymmetry over time after orthognathic surgery in Class III patients using three-dimensional stereophotogrammetry. The study included 101 patients with a skeletal Class III malocclusion (72 female, 29 male; age range 19–53 years, mean age 28.6 years) who underwent orthognathic surgery. The minimum follow-up was 12 months. Three-dimensional photographs were acquired using the 3dMDtrio stereophotogrammetry system, and 21 anthropometric landmark positions were evaluated at three time points: before surgery (T0), 6 months (T1) and 12 months (T2) after surgery. Facial asymmetry was assessed and classified as follows: 0–2 mm, mild; 2–5 mm, moderate;> 5 mm, severe. The average distance for whole face asymmetry differed between T0 (median 0.76 mm) and T1 (median 0.70 mm); however, there was no statistically significant difference at any time point. The chin volume asymmetry score differed significantly between T0 (median 1.11 mm) and T1 and T2 (median 1.08 mm for both; P < 0.001 and P = 0.001, respectively), but not between T1 and T2 (P = 0.061). The study findings indicate that the asymmetry of the facial soft tissues has the potential to return after 6 months, without reaching the baseline.

Measurement method and recent progress of vision-based deflection measurement of bridges: a technical review

The deflection that can reflect the vertical stiffness of a bridge plays an important role in the structural evaluation and health monitoring of bridges. In the past 20 years, the bridge deflection measurement methods based on computer vision and photogrammetry have been gradually applied to the field measurement due to the advantages of noncontact measurement, simple experimental setup, and easy installation. The technical research progress of vision-based bridge deflection measurement is reported from four aspects: basic principles, measurement methods, influencing factors, and applications. Basic principles mainly include camera calibration, three-dimensional (3D) stereo vision, photogrammetry, feature detection, and matching. For measurement methods, the single-camera two-dimensional measurement, the dual-camera 3D measurement, the quasistatic measurement based on photogrammetry, the multipoint dynamic measurement based on the displacement-relay videometrics and the deflection measurement based on UAV platform are introduced, respectively. In the section of influencing factors, this part summarizes the work of many researchers on the effects of camera imaging factors, calibration factors, algorithm factors, and environmental factors on measurement results. The field measurement results at different measurement distances and measurement accuracy based on these are presented in terms of applications. Finally, the future development trends of vision-based bridge deflection measurement are expected.

Measuring vertical displacement using laser lines and cameras

Measuring displacements in model tests typically involves contact-based sensors such as linear potentiometers, where contact between two moving parts occurs at the sensing point. The sensor's finite mass, the limited stiffness of the beams and the clamping mechanism, and the slippage and hinging of the sensor body could affect the object's response and lead to measurement errors. Also, the physical mounting rack required to hold these sensors often obstructs the view and makes significant areas unavailable for conducting some other essential investigations. The advancement in high-speed, high-resolution and reasonably priced rugged cameras makes it feasible to obtain better displacement measurements by image analysis. This paper introduces a non-contact method that works by video recording the projection of laser lines on a test object to measure static and dynamic vertical displacements. The technique produces a continuous settlement distribution along the laser line passing through multiple objects of interest. This paper presents the theory for converting laser line images to displacements. The new method's validity is demonstrated by comparing the results from other measurement techniques: hand measurements, linear potentiometers and three-dimensional stereophotogrammetry.

Muscle Flap Reconstruction Based on Muscle Tension Line Groups to Repair the Philtrum of Patients With Microform Cleft Lip or Secondary Cleft Lip.

The muscle flap reconstruction technique was developed based on the concept of muscle tension line groups, which elucidates how nasolabial muscle tension helps maintain the shape of the philtrum. To investigate the operative effect, we reviewed 43 patients with microform cleft lip and 102 patients with secondary cleft lip treated with muscle flap reconstruction between January 2018 and June 2020. The patients were scanned using the digital three-dimensional stereophotogrammetry face system pre- and post-operatively, and comparative analysis of three-dimensional (3D) images was used to highlight variations of the philtrum. Visual analog scales were used to assess surgical outcomes. More than 6 months after the surgery, comparative 3D images of 37 patients (86.04%) with microform cleft lip and 86 patients (84.31%) with secondary cleft lip showed visible improvement in the prominence of the affected column. In addition, visual analog scale scores showed that 38 microform cleft lip patients (88.37%) and 89 secondary cleft lip patients (87.25%) had a good appearance. The postoperative prominence of the philtral column in both groups improved significantly compared to before surgery (P < 0.001 and P < 0.001, respectively). There was no significant difference in scores for philtrum prominence pre- and post-operatively between the 2 groups (P > 0.05). Muscle flap reconstruction is an effective means to create the 3D configuration of the philtrum. The biomechanical properties of muscles play a vital role in the morphological maintenance of the philtrum.

The effect of subspinal Le Fort 1 corticotomy on nasal morphology in surgically assisted rapid palatal expansion

The purpose of this retrospective study was to evaluate the influence of subspinal Le Fort 1 corticotomy (SLF1C) on nasal morphology in patients treated with surgically assisted rapid palatal expansion (SARPE) using three-dimensional (3D) stereophotogrammetry images. A total of 64 patients were enrolled in the study and divided into two groups according to the surgical approach that was used: in group 1 (n = 32) SARPE was performed using a conventional Le Fort 1 corticotomy (CLF1C), and in group 2 (n = 32) SARPE was performed using a subspinal Le Fort 1 corticotomy (SLF1C). Measurements of alar and columellar width, and nasolabial angle were taken on 3D stereophotogrammetry images before and after SARPE using Vectra 3D camera system. Both surgical groups showed a statistically significant increase in alar and columellar width, and nasolabial angle postoperatively (p<0.05). SLF1C resulted in significantly smaller changes of the columellar base postoperatively (p=0.0456). The data suggests that SARPE with an osteotomy of the anterior nasal spine as an additional step to the conventional Le Fort 1 corticotomy results in a smaller increase of the columellar base.