Exploring reliable photogrammetry techniques for 3D modeling in anatomical research and education.

In anatomical research and education, three-dimensional visualization of anatomical structures is crucial for understanding spatial relationships in diagnostics, surgical planning, and teaching. While computed tomography (CT) and magnetic resonance imaging (MRI) offer valuable insights, they are often expensive and require specialized resources. This study explores photogrammetry as an affordable and accessible approach for 3D modeling in anatomical contexts. Two photogrammetry methods were compared: conventional open-source software (Colmap) and Apple's RealityKit Object Capture. Human C3 vertebrae were imaged with a 24 MP camera, with and without a cross-polarization filter. Reconstruction times, vertex distances, surface area, and volume measurements were compared to CT scans. Results revealed that the Object Capture method surpassed the conventional approach in reconstruction speed and user-friendliness. Both methods exhibited similar vertex distance from reference mesh and volume measurements, although the conventional approach produced larger surface areas compared to CT-based models. Cross-polarization filters eliminated the need for pre-processing and improved outcomes in challenging lighting conditions. This study demonstrates that photogrammetry, especially Object Capture, as a reliable and time-efficient tool for 3D modeling in anatomical research and education. It offers accessible alternatives to traditional techniques with advantages in texture mapping. While further validation of various anatomical structures is required, the accessibility and cost-effectiveness of photogrammetry make it a valuable asset for the field. In summary, photogrammetry would have the potential to revolutionize anatomical research and education by providing cost-effective, accessible, and accurate 3D modeling. The study underscores the promise of advancing anatomical research and education through the integration of photogrammetry with ongoing improvements in user-friendliness and accessibility.

Quantitate evaluation of photogrammetry with CT scanning for orbital defect.

Facial deformities can be caused by cancer, tumours, trauma, infections, congenital or acquired defects and may lead to alteration in basic functions such as communication, breathing, and mastication and aesthetic thereby affecting quality of life. Traditional processes for manufacturing maxillofacial prostheses involve complicated, time-consuming and tedious processes for the patient and the operator. Impression of the defect area, which is the one of the crucial step in fabrication of prosthesis, is the longest and most difficult process as it requires a long contact with the patient. The digital revolution is now changing the landscape of prosthetic production and making the impression making procedure simpler. Digital technology reduces patient chair side time by providing more accurate display data in less time (3-5 min) than traditional methods. Digital impressions eliminate the need for bulky impression materials and provide a more comfortable patient experience.

Surface Reconstruction of the Pediatric Larynx via Structure from Motion Photogrammetry: A Pilot Study.

Endoscopy is the gold standard for characterizing pediatric airway disorders, however, it is limited for quantitative analysis due to lack of three-dimensional (3D) vision and poor stereotactic depth perception. We utilize structure from motion (SfM) photogrammetry, to reconstruct 3D surfaces of pathologic and healthy pediatric larynges from monocular two-dimensional (2D) endoscopy. Models of pediatric subglottic stenosis were 3D printed and airway endoscopies were simulated. 3D surfaces were successfully reconstructed from endoscopic videos of all models using an SfM analysis toolkit. Average subglottic surface error between SfM reconstructed surfaces and 3D printed models was 0.65 mm as measured by Modified Hausdorff Distance. Average volumetric similarity between SfM surfaces and printed models was 0.82 as measured by Jaccard Index. SfM can be used to accurately reconstruct 3D surface renderings of the larynx from 2D endoscopy video. This technique has immense potential for use in quantitative analysis of airway geometry and virtual surgical planning.

Three-dimensional evaluation of symmetry in facial palsy reanimation using stereophotogrammetric devices: A series of 15 cases.

Facial palsy can severely compromise quality of life, significantly altering the harmony and symmetry of the face, which can be restored by surgical rehabilitation. The aim of the study was the quantification of facial symmetry following facial reanimation. Fifteen consecutive adult patients were surgically treated through triple innervation for reanimation of flaccid unilateral facial paralysis (contralateral facial nerve, masseteric nerve, and hypoglossal nerve) and fascia lata graft for definition of the nasolabial sulcus. In the preoperative stage and at least 11 months after the surgical treatment, three-dimensional facial images were recorded through stereophotogrammetry in a neutral (rest) position, and with Mona Lisa and full-denture (maximum) smiles. Labial commissure inclination relative to the interpupillary axis, and a surface assessment of local facial asymmetry at rest and while smiling were obtained for the upper, middle, and lower facial thirds. The angle between the interpupillary axis and the labial commissure significantly improved in post-surgical acquisitions, regaining symmetry at rest (t-test; p < 0.001). Facial symmetry increased significantly when passing from pre-to postsurgical facial scans, from the lower to the upper facial third, and from the full smile to the rest position (ANOVA; p < 0.001). After treatment, the full smile recovered more symmetry than the other two expressions. In summary, surgical treatment significantly reduced facial asymmetry, but this reduction differed significantly among the various animations and facial thirds. The results of this study confirmed clinical findings of significant static and dynamic improvements in facial symmetry after triple innervation reanimation surgery.

Three-dimensional evaluation of social smile asymmetry in patients with unilateral impacted maxillary canine: a 3D stereophotogrammetry study.

OBJECTIVE: This study aimed to evaluate social smile asymmetry in patients with unilateral impacted maxillary canine on 3D stereophotogrammetric images. MATERIAL AND METHODS: The 3D social smile images of participants with unilateral impacted maxillary canine (n:20) and without impaction as a control group (n:20) were included. The images were recorded with a hand-held 3D stereophotogrammetry device (Fuel3D® Scanify®) and Geomagic Essentials 2 reverse engineering software were used for analyses. After the orientation process of the 3D records, the tissues around the smile area were divided into five morphological regions: cheek, upper lip lateral and medial, and lower lip lateral and medial. The deviation margins in the negative and positive directions for the 95% mesh rate and the total percentages of meshes between - 0.5- and + 0.5-mm deviations were calculated. ICC, paired samples t test, independent samples t test, and the Mann-Whitney U test were used for statistical analyses. RESULTS: In individuals with impacted canine, the amount of maximum positive deviation in the upper lip medial was 5.64 mm ± 1.46 and maximum negative deviation was - 4.6 mm ± 1.17. In the control group, mean of deviation limits for all parameters was less than 1.19 mm ± 2.62, while in individuals with unilateral impacted maxillary canine, the maximum value was 8.34 mm ± 2.23. The mesh percentage between - 0.5 and 0.5-mm deviations was over 95% in all morphological areas in the control group, while in the impacted canine group, the number of meshes within the specified deviation limits was less than 95%. CONCLUSION: Individuals with unilateral impacted maxillary canine exhibit greater asymmetry in social smile compared to the control group, with the asymmetry being most prominent near the corners of the mouth and cheeks. CLINICAL RELEVANCE: Amount of asymmetry was higher in impaction group compared to the control group in social smile. The quantification of a possible smile asymmetry due to the impacted canine is crucial for the diagnosis and treatment planning of orthodontic and/or orthognathic cases for ideal aesthetic results. Hence, smile asymmetry should not be overlooked and should be considered in diagnosis and treatment planning.

Use of 3-Dimensional Stereophotogrammetry to Detect Disease Progression in Craniofacial Morphea.

Importance: Objectively determining disease progression in craniofacial morphea (CM) is challenging, as clinical findings of disease activity are often lacking. Objective: To evaluate the utility of 3-dimensional (3D) stereophotogrammetry in detecting disease progression in CM over time. Design, Setting, and Participants: This prospective cohort study included 27 pediatric and adult patients with CM from 2 hospitals in Boston (Boston Children's Hospital and Brigham & Women's Hospital) consecutively enrolled from April 1, 2019, to March 1, 2023. Review of 3D stereophotogrammetry images and data analysis occurred from March 1 to April 1, 2023. Main Outcomes and Measures: Clinical and 3D stereophotogrammetry assessments were performed at 2- to 12-month intervals, depending on the clinical context. The 3D stereophotogrammetry images were then qualitatively rated as demonstrating no progression or definitive progression by an expert (board-certified plastic craniofacial surgeon) and nonexpert (board-certified dermatologist) in 3D stereophotogrammetry. In addition, κ coefficients were calculated for interrater reliability. Results: Of 27 patients with CM (19 female; median age, 14 [range, 5-40] years) and 3D stereophotogrammetry images obtained from a minimum of 2 time points (median, 4 [range, 2-10] images) spaced a median of 3 (range, 2-12) months apart, 10 experienced progression of their disease based on clinical assessments performed during the study period. In all cases in which clinical progression was favored, blinded qualitative assessment of 3D stereophotogrammetry images also favored progression with substantial interrater reliability (κ = 0.80 [95% CI, 0.61-0.99]). Furthermore, review of 3D stereophotogrammetry detected occult progression of asymmetry not noted on clinical examination in 3 additional patients. Conclusions and Relevance: In this prospective cohort study, blinded assessment of sequential 3D stereophotogrammetry images in patients with CM not only corroborated clinical assessment of disease progression but also detected occult progression of facial asymmetry not appreciable on clinical examination alone. Therefore, 3D stereophotogrammetry may serve as a useful adjunct to clinical examination of patients with CM over time. Future investigations are warranted to validate 3D stereophotogrammetry as an outcome measure in CM.

Geometric learning and statistical modeling for surgical outcomes evaluation in craniosynostosis using 3D photogrammetry.

BACKGROUND AND OBJECTIVE: Accurate and repeatable detection of craniofacial landmarks is crucial for automated quantitative evaluation of head development anomalies. Since traditional imaging modalities are discouraged in pediatric patients, 3D photogrammetry has emerged as a popular and safe imaging alternative to evaluate craniofacial anomalies. However, traditional image analysis methods are not designed to operate on unstructured image data representations such as 3D photogrammetry. METHODS: We present a fully automated pipeline to identify craniofacial landmarks in real time, and we use it to assess the head shape of patients with craniosynostosis using 3D photogrammetry. To detect craniofacial landmarks, we propose a novel geometric convolutional neural network based on Chebyshev polynomials to exploit the point connectivity information in 3D photogrammetry and quantify multi-resolution spatial features. We propose a landmark-specific trainable scheme that aggregates the multi-resolution geometric and texture features quantified at every vertex of a 3D photogram. Then, we embed a new probabilistic distance regressor module that leverages the integrated features at every point to predict landmark locations without assuming correspondences with specific vertices in the original 3D photogram. Finally, we use the detected landmarks to segment the calvaria from the 3D photograms of children with craniosynostosis, and we derive a new statistical index of head shape anomaly to quantify head shape improvements after surgical treatment. RESULTS: We achieved an average error of 2.74 ± 2.70 mm identifying Bookstein Type I craniofacial landmarks, which is a significant improvement compared to other state-of-the-art methods. Our experiments also demonstrated a high robustness to spatial resolution variability in the 3D photograms. Finally, our head shape anomaly index quantified a significant reduction of head shape anomalies as a consequence of surgical treatment. CONCLUSION: Our fully automated framework provides real-time craniofacial landmark detection from 3D photogrammetry with state-of-the-art accuracy. In addition, our new head shape anomaly index can quantify significant head phenotype changes and can be used to quantitatively evaluate surgical treatment in patients with craniosynostosis.

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

OBJECTIVE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Mechatronic Design and Experimental Research of an Automated Photogrammetry-Based Human Body Scanner.

The article concerns the mechatronic design and experimental investigations of the HUBO automated human body scanning system. Functional problems that should be solved by using the developed scanning system are defined. These include reducing the number of sensors used while eliminating the need to rotate a human and ensuring the automation of the scanning process. Research problems that should be the subject of experimental research are defined. The current state of the art in the field of systems and techniques for scanning the human figure is described. The functional and technical assumptions for the HUBO scanning system are formulated. The mechanical design of the scanner, the hardware and information system architectures as well as the user's mobile application are presented. The method of operation of the scanning system and its innovative features are discussed. It is demonstrated that the developed solution of the scanning system allows the identified problems to be overcome. The methodology of the experimental research of the scanning system based on the photogrammetry technique is described. The results of laboratory studies with the use of dummies and experimental research with human participation are presented. The scope of the research carried out allows answers to the identified research problems related to the scanning of the human figure using the photogrammetry technique to be obtained. As part of laboratory tests using a measuring dummy, a mean error of 0.65 mm and standard deviation of the mean of 0.65 mm were obtained for the best scanner configuration. Research with human participation was carried out for the scanner version, in which the scanning time was 30 s, with the possibility of its reduction to 15 s. The results of studies using realistic dummies and with human participation were compared using the root mean square error parameter (RMSE) provided by the AliceVision framework, which was available for all analyzed objects. As a result, it was observed that these results are comparable, i.e., the RMSE parameter is equal to about 1 px.

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

OBJECTIVES: To evaluate the midfacial soft tissue changes of the face in patients treated with miniscrew-assisted rapid palatal expansion (MARPE). MATERIALS AND METHODS: 3D 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. RESULTS: Twenty-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). CONCLUSIONS: Our 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 RELEVANCE: MARPE is an effective treatment modality to expand the maxilla, incurring only minimal and clinically insignificant changes to the midfacial soft tissues.

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

BACKGROUND: 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. OBJECTIVES: This study aimed to provide a standardized 3D anthropometric protocol for the perioral region. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. 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 .

Protocol for capturing 3D facial meshes for rhinoseptoplasty planning.

OBJECTIVES: To present and execute a protocol for the capture of 3D facial images using photogrammetry through the open access software Blender and its add-on OrtogOnBlender (OOB) and to evaluate the compatibility of the 3D meshes generated with Computed tomography (CT) of the sinuses. METHODS: Individuals >18 years old, candidates for Rhinoseptoplasty in a tertiary hospital, were submitted to a photographic session to perform the standardized protocol. In the session, divided into 3 phases, sequential photos were taken for processing the photogrammetry in the OOB and producing 3D meshes of the face. The photogrammetry reconstructions were compared with the reference mesh of the soft tissue surface of the Sinus CT scan to assess compatibility between them. RESULTS: 21 patients were included, 67% female. 3 photogrammetry meshes and 1 CT reference mesh were generated, which demonstrated matching compatibility, as most of the mean distances between cloud points were <1.48 mm. Phase 3 of the session with the highest number of photos (54.36 ±â€¯15.05) generated the most satisfactory mesh with the best resolution. CONCLUSIONS: The proposed protocol is reproducible and feasible in clinical practice, generated satisfactory 3D meshes of the face, being a potential tool for surgical planning and comparison of results. For the implementation of photogrammetry for use in 3D anthropometry, it is necessary to validate this method. LEVEL OF EVIDENCE: 3: OCEBM Levels of Evidence Working Group.1 "The Oxford 2011 Levels of Evidence". Oxford Centre for Evidence-Based Medicine. http://www.cebm.net/index.aspx?o=5653.

Simplified Easy-Accessible Smartphone-Based Photogrammetry for 3-Dimensional Anatomy Presentation Exemplified With a Photorealistic Cadaver-Based Model of the Intracranial and Extracranial Course of the Facial Nerve.

BACKGROUND AND OBJECTIVES: Smartphone-based photogrammetry (SMPhP) was recently presented as a practical and simple algorithm to create photorealistic 3-dimensional (3D) models that benefit from volumetric presentation of real anatomic dissections. Subsequently, there is a need to adapt the techniques for realistic depiction of layered anatomic structures, such as the course of cranial nerves and deep intracranial structures; the feasibility must be tested empirically. This study sought to adapt and test the technique for visualization of the combined intracranial and extracranial course of the facial nerve's complex anatomy and analyze feasibility and limitations. METHODS: We dissected 1 latex-injected cadaver head to depict the facial nerve from the meatal to the extracranial portion. A smartphone camera alone was used to photograph the specimen, and dynamic lighting was applied to improve presentation of deep anatomic structures. Three-dimensional models were created with a cloud-based photogrammetry application. RESULTS: Four 3D models were generated. Two models showed the extracranial portions of the facial nerve before and after removal of the parotid gland; 1 model showed the facial nerve in the fallopian canal after mastoidectomy, and 1 model showed the intratemporal segments. Relevant anatomic structures were annotated through a web-viewer platform. The photographic quality of the 3D models provided sufficient resolution for imaging of the extracranial and mastoid portions of the facial nerve, whereas imaging of the meatal segment only lacked sufficient precision and resolution. CONCLUSION: A simple and accessible SMPhP algorithm allows 3D visualization of complex intracranial and extracranial neuroanatomy with sufficient detail to realistically depict superficial and deeper anatomic structures.

Reliability and Agreement of Automated Head Measurements From 3-Dimensional Photogrammetry in Young Children.

This study aimed to assess the reliability and agreement of automated head measurements using 3-dimensional (3D) photogrammetry in young children. Specifically, the study evaluated the agreement between manual and automated occipitofrontal circumference (OFC) measurements (n = 264) obtained from 3D images of 188 patients diagnosed with sagittal synostosis using a novel automated method proposed in this study. In addition, the study aimed to determine the interrater and intrarater reliability of the automatically extracted OFC, cephalic index, and volume. The results of the study showed that the automated OFC measurements had an excellent agreement with manual measurements, with a very strong regression score ( R2 = 0.969) and a small mean difference of -0.1 cm (-0.2%). The limits of agreement ranged from -0.93 to 0.74 cm, falling within the reported limits of agreement for manual OFC measurements. High interrater and intrarater reliability of OFC, cephalic index, and volume measurements were also demonstrated. The proposed method for automated OFC measurements was found to be a reliable alternative to manual measurements, which may be particularly beneficial in young children who undergo 3D imaging in craniofacial centers as part of their treatment protocol and in research settings that require a reproducible and transparent pipeline for anthropometric measurements. The method has been incorporated into CraniumPy, an open-source tool for 3D image visualization, registration, and optimization, which is publicly available on GitHub ( https://github.com/T-AbdelAlim/CraniumPy ).

How Do the Faces of Kyrgyz Beauties Look? A Photogrammetric Analysis of Beauty Pageant Winners.

The aim of this study was to assess how the eyes of Kyrgyz beauties look through an anthropometric analysis of beauty pageant winners. Eleven winners of the Miss Kyrgyzstan contest (2011-2021) were included. Ten other beauty contest winners were added, resulting in a total of 21 beauties who were included. The horizontal corneal diameter, which is 11.75 mm, was used as a standard distance. Other distances were calculated in millimeters based on the proportions of the pixels measured. Twenty-six distances (face: 10, eyebrows: 2, eyes: 4, nose: 4, lips: 4, and chin: 2) and 9 angles (forehead-brow, cantal tilt, 5 face angles, the mandible angle, and the chin angle) were measured. Thereafter, 16 indices (forehead: 1, eyes: 5, nose: 4, lips and chin: 3, and contours 3) were calculated. The forehead-brow angle was 82.2±7.2 degrees. The canthal tilt was 9.0±2.0 degrees. The overall face angles 1 and 2 were 108.6±4.1 degrees and 69.6±2.3 degrees, respectively. The midface angles 1 and 2 were 129.9±3.8 degrees and 125.1±3.9 degrees, respectively. The lower face angle was 139.6±4.1 degrees. The mandible angle and chin angle were 136.9±4.0 degrees and 106.0±4.0 degrees, respectively. The ratio of forehead height to total face height was 0.33±0.03. The ratio of nose height to total face height was 0.25±0.02. The lower face width/face width ratio was 0.82±0.05. The ratio of face width to total face height was 0.72±0.03. The ratio of midface height to total face height was 0.34±0.02. The data from this study might serve as the recommended esthetic proportions for performing plastic surgical procedures.

Sagittal Craniosynostosis: Comparing Surgical Techniques Using 3D Photogrammetry.

BACKGROUND: The aim of this study was to compare three surgical interventions for correction of sagittal synostosis-frontobiparietal remodeling (FBR), extended strip craniotomy (ESC), and spring-assisted correction (SAC)-based on three-dimensional (3D) photogrammetry and operation characteristics. METHODS: Patients who were born between 1991 and 2019 and diagnosed with nonsyndromic sagittal synostosis who underwent FBR, ESC, or SAC and had at least one postoperative 3D photogrammetry image taken during one of six follow-up appointments until age 6 were considered for this study. Operative characteristics, postoperative complications, reinterventions, and presence of intracranial hypertension were collected. To assess cranial growth, orthogonal cranial slices and 3D photocephalometric measurements were extracted automatically and evaluated from 3D photogrammetry images. RESULTS: A total of 322 postoperative 3D images from 218 patients were included. After correcting for age and sex, no significant differences were observed in 3D photocephalometric measurements. Mean cranial shapes suggested that postoperative growth and shape gradually normalized with higher occipitofrontal head circumference and intracranial volume values compared with normal values, regardless of type of surgery. Flattening of the vertex seems to persist after surgical correction. The authors' cranial 3D mesh processing tool has been made publicly available as a part of this study. CONCLUSIONS: The findings suggest that until age 6, there are no significant differences among the FBR, ESC, and SAC in their ability to correct sagittal synostosis with regard to 3D photocephalometric measurements. Therefore, efforts should be made to ensure early diagnosis so that minimally invasive surgery is a viable treatment option. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

An in vitro study of digital impressions and three-dimensional printed models of orbital defects using mobile devices and monoscopic photogrammetry.

PURPOSE: The purpose of this study was to perform an in vitro evaluation of digital impressions using a mobile device and monoscopic photogrammetry in cases of orbital defects with undercuts. METHODS: Three 10-mm-square cubes were attached to a diagnostic cast of a patient with a right orbital defect. Still images acquired with a mobile device were used to generate facial three-dimensional (3D) data. Two types of still images were used: one was a whole face image, and the other was a defect site-focused image. For comparison, an extraoral scanner was used to obtain facial 3D data. Five dental technicians fabricated 3D printed models using additive manufacturing and measured the distances between the measurement points using a digital caliper. The discrepancy between the distances measured on the diagnostic cast of the patient and the 3D printed model was calculated. Friedman test was used to analyze the discrepancy, and the Bonferroni test was used to verify the differences between the pairs. RESULTS: Statistical significance was found with respect to the type of 3D model fabrication method. CONCLUSION: Within the limitations of this in vitro study, the results suggested that the workflow can be applied to digital impressions of the maxillofacial region.

Foundations and guidelines for high-quality three-dimensional models using photogrammetry: A technical note on the future of neuroanatomy education.

Hands-on dissections using cadaveric tissues for neuroanatomical education are not easily available in many educational institutions due to financial, safety, and ethical factors. Supplementary pedagogical tools, for instance, 3D models of anatomical specimens acquired with photogrammetry are an efficient alternative to democratize the 3D anatomical data. The aim of this study was to describe a technical guideline for acquiring realistic 3D anatomic models with photogrammetry and to improve the teaching and learning process in neuroanatomy. Seven specimens with different sizes, cadaveric tissues, and textures were used to demonstrate the step-by-step instructions for specimen preparation, photogrammetry setup, post-processing, and display of the 3D model. The photogrammetry scanning consists of three cameras arranged vertically facing the specimen to be scanned. In order to optimize the scanning process and the acquisition of optimal images, high-quality 3D models require complex and challenging adjustments in the positioning of the specimens within the scanner, as well as adjustments of the turntable, custom specimen holders, cameras, lighting, computer hardware, and its software. MeshLab® software was used for editing the 3D model before exporting it to MedReality® (Thyng, Chicago, IL) and SketchFab® (Epic, Cary, NC) platforms. Both allow manipulation of the models using various angles and magnifications and are easily accessed using mobile, immersive, and personal computer devices free of charge for viewers. Photogrammetry scans offer a 360° view of the 3D models ubiquitously accessible on any device independent of operating system and should be considered as a tool to optimize and democratize the teaching of neuroanatomy.

An Overview on Image-Based and Scanner-Based 3D Modeling Technologies.

Advances in the scientific fields of photogrammetry and computer vision have led to the development of automated multi-image methods that solve the problem of 3D reconstruction. Simultaneously, 3D scanners have become a common source of data acquisition for 3D modeling of real objects/scenes/human bodies. This article presents a comprehensive overview of different 3D modeling technologies that may be used to generate 3D reconstructions of outer or inner surfaces of different kinds of targets. In this context, it covers the topics of 3D modeling using images via different methods, it provides a detailed classification of 3D scanners by additionally presenting the basic operating principles of each type of scanner, and it discusses the problem of generating 3D models from scans. Finally, it outlines some applications of 3D modeling, beyond well-established topographic ones.