Laser Surface Scanning Research Articles

The prevalence of lip vermilion morphological traits in a 15‐year‐old population

The aim of this study is to describe and categorize the various lip vermilion morphological traits, prevalence, and associations present in a 15-year-old population The instrument we developed was checked for the reliability of assessment. The study is a cross-sectional study of lip vermilion morphology in 2,246 fifteen-year-old children. Three-dimensional surface laser scans were taken of the children, and a classification scale was derived and assessed for intra- and inter-reliability. The prevalence of lip vermilion morphological traits and associations was identified. Certain features are found to be likely to be associated with each other: thin philtrum and smooth/deep indentation of the philtrum; wide philtrum and smooth/normal gradient, flat/absent Cupid's bow and smooth/normal/indentation near nose, V-shaped Cupid's bow and indentation in middle/deep groove; thin upper lip vermilion and deep groove; thick upper lip vermilion and smooth philtrum; acute nasolabial angle and upper lip double border and thick upper lip vermilion; obtuse nasolabial angle and thin upper lip vermilion. In conclusion, we present a new method to identify the various morphological features of the vermilion of the lips. The prevalence of morphological traits has been identified in this 15-year-old population. In addition, the association of lip traits has been reported. This classification scale may be utilized to ascertain prevalence of features amongst other ethnic groups, to gain knowledge of what is considered to be attractive features, and to determine genotype/phenotype associations.

Facial variation: from visual assessment to three-dimensional quantification

The extensive study presented by Toma and coworkers is one of the first presenting normative three-dimensional soft tissue face data derived from a large group of 15-year-old Caucasians using laser surface scanning. This data is not only important to quantify facial variation in a normal population but can help to analyse facial dysmorphology. The study methodology and statistical handling of the data provide a good basis for future studies into facial variation.

Investigation of Thermal Damage and the Consequent Fatigue Property of Laser Surface Heat Treated Component

In order to signify the thermal damage and the influence it has on the fatigue property, a 3D finite element method, as well as experiment investigation, was employed for this research. By the study, it suggests that laser surface scanning can bring about some tensile residual stress and a heat affected zone in the workpiece, so as to lead a fall in fatigue life cycles. Since the fatigue character is affected by the residual stress and the microstructure change, which relate to the laser process parameters, it is expected to draw a scalar variable from stress feature and microstructure parameter to stand the level of thermal damage influence.

Treatment Efficacy of Deformational Plagiocephaly and Brachiocephaly

INTRODUCTION: Although various treatments for deformational plagiocephaly (DP) and brachiocephaly (DB) have been well described, previous studies evaluating their efficacy are limited by small cohorts, inadequate follow-up, lack of reliable objective outcomes measures, and influence of commercial interests.1–3 This study analyzed the efficacy of repositioning, physical therapy (PT) and cranial molding in the treatment of DP/DB in a large, prospective cohort utilizing objective outcome measures. METHODS: All patients undergoing treatment of DP/DB between 2004 and 2010 were followed until cure or 18 months of age. Patients underwent either regimented conservative treatment (repositioning and/or PT) and/or cranial orthotic molding. Outcomes where measured objectively using a 3D laser surface scanner. Complete correction was defined as a cranial ratio (CR)<0.85 and diagonal difference (DD)<5mm. Independent risk factors for treatment failure were identified for each group by multivariate analysis. RESULTS: The study included 4,378 patients with DP/DB. Conservative treatment (repositioning and/or PT) was initiated in 3,381 infants, and cranial orthotic molding in 997 infants. Of patients initially treated conservatively, 22.9% failed management (15.8% required cranial molding, 7.1% had incomplete correction). Independent risk factors for conservative treatment failure included DP/DB severity (RR 1.31-1.64), advanced age (RR 1.20-2.08), torticollis (RR 1.12-1.74), developmental delay (RR 1.44) and poor treatment compliance (RR 2.4). Prematurity and male gender were non-risk factors; multiparity and vaginal delivery were protective. Ultimately, 1,531 patients underwent cranial orthotic molding (997 initially assigned, 534 failed conservative management), and 95.0% achieved complete correction. Independent risk factors for cranial orthotic molding failure included advanced age (RR 1.13-3.08) and poor treatment compliance (RR 3.01). CONCLUSION: Repositioning, PT, and cranial orthotic molding are effective treatments for DP/DB. Appropriate selection of a treatment modality requires evaluation of patient-specific risk factors. Cranial orthotic molding appears to isolate out intrinsic and environmental factors that increase the risk of conservative treatment failure.

Comparative Assessment of 3D Surface Scanning Systems in Breast Plastic and Reconstructive Surgery

In this work, we compared accuracy, repeatability, and usability in breast surface imaging of 2 commercial surface scanning systems and a hand-held laser surface scanner prototype coupled with a patient's motion acquisition and compensation methodology. The accuracy of the scanners was assessed on an anthropomorphic phantom, and to evaluate the usability of the scanners on humans, thorax surface images of 3 volunteers were acquired. Both the intrascanner repeatability and the interscanner comparative accuracy were assessed. The results showed surface-to-surface distance errors inferior to 1 mm and to 2 mm, respectively, for the 2 commercial scanners and for the prototypical one. Moreover, comparable performances of the 3 scanners were found when used for acquiring the breast surface. On the whole, this study demonstrated that handheld laser surface scanners coupled with subject motion compensation methods lend themselves as competitive technologies for human body surface modeling.

Soft Tissue Changes After Orthodontic Surgical Correction of Jaws Asymmetry Evaluated by Three-Dimensional Surface Laser Scanner

Aesthetic improvement is an essential goal of treatment of facial asymmetry, and it is often difficult to achieve. Reliable three-dimensional measurements are required to support outcome studies. In this study, 15 white adult subjects, 9 females and 6 males, with maxillomandibular asymmetry and malocclusion were studied. The patients were treated with orthodontics and different surgical procedures in single or multiple steps. All patients received double-jaw surgery, except 1 patient who underwent only maxillary osteotomy. Nine of the 15 patients received additional procedures (genioplasty and rhinoplasty) to achieve better symmetry. Posterior-anterior and lateral cephalometry and three-dimensional facial surface data were obtained before (T0) and 1 year (T1) after surgery. Scan data at T0 and T1 were pooled by electronic surface averaging to obtain the mean pretreatment and posttreatment facial model. A symmetric model was constructed by averaging the actual T0 scans and their mirrored models to obtain the virtual optimal symmetric face. Different linear and angular measurements were then calculated for comparison of the mean T0 and T1 models. The normalization of facial proportion and a high increase in symmetry were evident. Residual defects were documented in the postoperative symmetry of the chin. Treatment of facial asymmetry, combined with dental occlusion problems, is still a challenge for maxillofacial surgeons. Orthognathic surgery provides an important improvement of symmetry, but further refinements of technique are still required. Three-dimensional evaluation results in an effective method to support outcome studies on the surgical correction of complex facial deformities.

A test of a new method and software for the rapid estimation of cross-sectional geometric properties of long bone diaphyses from 3D laser surface scans

This paper introduces a new methodological approach to the quantification of cross-sectional geometric properties based on 3D laser scan data. A variety of methods have been used to calculate estimates of rigidity in the diaphyses of long bones. CT scan, biplanar radiograph, and periosteal mould techniques have all been applied to collect image data of bone sections to assess biomechanical properties (cross-sectional area and second moments of area). Whilst direct quantification of both endosteal and periosteal contours allows the greatest accuracy, such data correlate highly with a periosteal-only approach that is of greater practical application in many contexts. The advent of non-invasive 3D laser scan technologies presents a method to capture bone surface morphology that can be applied to the study of variation in the cross-sectional properties of human bones. This study tests the correspondence between cross-sectional geometric properties derived from laser scans to those obtained through traditional approaches (periosteal moulding and biplanar radiography). A custom-built program, AsciiSection, is introduced for the automated analysis of biomechanical properties direct from 3D coordinate data. The results indicate that the AsciiSection method is of comparable if not greater accuracy than traditional moulding techniques. The study suggests that there is a strong correlation between mid-diaphyseal cortical bone distribution and cross-sectional geometry calculated using laser scans. The approach provides a viable alternative to traditional techniques for the estimation of biomechanical properties and also allows the collection of rich data and descriptions of morphological variation along the diaphysis.

Methods to Quantify Soft-Tissue Based Facial Growth and Treatment Outcomes in Children: A Systematic Review

ContextTechnological advancements have led craniofacial researchers and clinicians into the era of three-dimensional digital imaging for quantitative evaluation of craniofacial growth and treatment outcomes.ObjectiveTo give an overview of soft-tissue based methods for quantitative longitudinal assessment of facial dimensions in children until six years of age and to assess the reliability of these methods in studies with good methodological quality.Data SourcePubMed, EMBASE, Cochrane Library, Web of Science, Scopus and CINAHL were searched. A hand search was performed to check for additional relevant studies.Study SelectionPrimary publications on facial growth and treatment outcomes in children younger than six years of age were included.Data ExtractionIndependent data extraction by two observers. A quality assessment instrument was used to determine the methodological quality. Methods, used in studies with good methodological quality, were assessed for reliability expressed as the magnitude of the measurement error and the correlation coefficient between repeated measurements.ResultsIn total, 47 studies were included describing 4 methods: 2D x-ray cephalometry; 2D photography; anthropometry; 3D imaging techniques (surface laser scanning, stereophotogrammetry and cone beam computed tomography). In general the measurement error was below 1 mm and 1° and correlation coefficients range from 0.65 to 1.0.ConclusionVarious methods have shown to be reliable. However, at present stereophotogrammetry seems to be the best 3D method for quantitative longitudinal assessment of facial dimensions in children until six years of age due to its millisecond fast image capture, archival capabilities, high resolution and no exposure to ionizing radiation.

Accuracy and reproducibility of 3-dimensional digital model measurements

The purpose of this study was to evaluate the reliability of measurements made on 3-dimensional digital models obtained with a surface laser scanner (D-250; 3Shape, Copenhagen, Denmark). Twenty orthodontic dental casts of permanent dentitions were selected. Three-dimensional images were obtained on this scanner and analyzed by using the Geomagic Studio 5 software (Raindrop Geomagic, Inc, Morrisville, NC). Measurements were made with a digital caliper directly on the dental casts and also digitally on the digital models. Fifteen anatomic dental points were identified, and a total of 11 linear measurements were taken from each cast, including arch length and width. Dependent t tests were used to evaluate intraexaminer reproducibility and measurement accuracy on the digital models. No statistically significant differences were found between the measurements made directly on the dental casts and on the digital models. Linear measurements on digital models are accurate and reproducible. Digital models obtained with the surface laser scanner are reliable for measurements of arch width and length.

A study on the theoretical and practical accuracy of conoscopic holography-based surface measurements: toward image registration in minimally invasive surgery.

Registered medical images can assist with surgical navigation and enable image-guided therapy delivery. In soft tissues, surface-based registration is often used and can be facilitated by laser surface scanning. Tracked conoscopic holography (which provides distance measurements) has been recently proposed as a minimally invasive way to obtain surface scans. Moving this technique from concept to clinical use requires a rigorous accuracy evaluation, which is the purpose of our paper. We adapt recent non-homogeneous and anisotropic point-based registration results to provide a theoretical framework for predicting the accuracy of tracked distance measurement systems. Experiments are conducted a complex objects of defined geometry, an anthropomorphic kidney phantom and a human cadaver kidney. Experiments agree with model predictions, producing point RMS errors consistently < 1 mm, surface-based registration with mean closest point error < 1 mm in the phantom and a RMS target registration error of 0.8 mm in the human cadaver kidney. Tracked conoscopic holography is clinically viable; it enables minimally invasive surface scan accuracy comparable to current clinical methods that require open surgery.

Clinical Evaluation of a Laser Surface Scanning System in 120 Patients for Improving Daily Setup Accuracy in Fractionated Radiation Therapy

To evaluate the clinical suitability of a specific optical surface imaging system to detect setup errors in fractionated radiation therapy. The setup correction accuracy of a 3-dimensional laser imaging system was analyzed for 6 different tumor locations with 20 patients each. For each patient, the setup corrections of the megavoltage computed tomography (MVCT) images of a TomoTherapy unit (TomoTherapy, Madison, WI) were compared with those of the laser system for the first 10 fractions. For the laser system, the reference surface either was obtained from the DICOM (Digital Imaging and Communications in Medicine) surface structure delineated on the planning computed tomography images or was acquired with the system itself at the first fraction after the MVCT-based setup correction. Data analysis was performed for both reference types. By use of the DICOM reference image, systematic shifts between 3 and 9 mm were found, depending on the tumor location. For the optical reference, no clinically relevant systematic shifts were found. MVCT-based setup corrections were detected with high accuracy, and only small movements were observed during treatment. Using a reference image acquired with the laser system itself after MVCT-based setup correction appears more reliable than importing the DICOM reference surface. After generation of the optical reference, the laser system may be used to derive setup corrections over a certain number of fractions, but additional radiologic imaging may still be necessary on a regular basis (eg, weekly) or if the corrections of the optical system appear implausibly large. Nevertheless, such a combined application may help to reduce the imaging dose for the patient.

Humeral head arthroplasty and its ability to restore original humeral head geometry

Modern prosthetic components are designed to enable restoration of proximal humeral morphology, provided that a precise osteotomy of the humeral head at the level of the anatomic neck is performed. To determine whether a simulated osteotomy and replacement arthroplasty with an idealized implant were able to restore original head geometry. A handheld digitizer and surface laser scanner were used to digitize 24 humeri. Computer models were used to simulate an osteotomy, performed at the anterior cartilage-metaphyseal interface, and reconstruct the head with a spherical prosthetic head. The head diameter, radius of curvature, and inclination and retroversion angles were calculated for each specimen and compared with the original humeral head. The simulated osteotomy resulted in a 4.8° decrease in inclination (P<.01) and 11.3° increase in retroversion (P<.001). The radius of curvature in the coronal plane was not significantly different (P=.284). However, in the axial plane, the prosthesis was significantly larger than the original head for both head diameter (P<.001) and radius of curvature (P<.05). The study suggests that the humeral head is not a perfect segment of a sphere and an osteotomy along the anterior cartilage-metaphyseal interface does not remove only the proximal humeral articular surface. Even with a fully adaptable prosthetic implant, replacement arthroplasty is not able to restore original head geometry. Alterations to head geometry with the osteotomy described may alter the line of force through the prosthetic joint, producing eccentric loading at the glenoid, and contribute to early failure.

Is there an equivalence of non-invasive to invasive referenciation in computer-aided surgery?

Various navigation systems with non-invasive patient referenciation and registration methods have been developed in times of minimal-invasive and computer-aided surgery. However, hard data proving the equivalence of different referenciation systems are missing. The present study investigated invasive and non-invasive referenciation systems with regard to overall navigation accuracy as well as navigation accuracy at specific anatomic locations. Four skull models were individually fabricated with a 3D printer based on patient's CT data sets and fitted with an individual customized silicone skin. 26 titanium screws on defined anatomic locations served as target fiducials. Two non-invasive referenciation systems (headband and headset) were compared with the invasive skull fixed reference array. Registration was done with laser surface scan. The mean accuracy was calculated and the target registration error for eight anatomical locations was measured. Mean accuracy was 1.3 ± 0.12 mm for the skull fixed reference array, 1.44 ± 0.24 mm for the headset and 1.46 ± 0.15 mm for the headband referenciation (non-significant). Navigation accuracy of the invasive referenciation system was significantly superior to the accuracy of both non-invasive systems on the ethmoid sinus with respect to the selected anatomic locations. In the midface headband referenciation was statistically significantly worse than the invasive system. Invasive and non-invasive referenciation systems seem to be on par in terms of overall navigation accuracy, but not regarding specific anatomic locations. Therefore, invasive referenciation systems should be preferred in high precision surgery.

Non‐orthogonal tool/flange and robot/world calibration

For many robot-assisted medical applications, it is necessary to accurately compute the relation between the robot's coordinate system and the coordinate system of a localisation or tracking device. Today, this is typically carried out using hand-eye calibration methods like those proposed by Tsai/Lenz or Daniilidis. We present a new method for simultaneous tool/flange and robot/world calibration by estimating a solution to the matrix equation AX = YB. It is computed using a least-squares approach. Because real robots and localisation are all afflicted by errors, our approach allows for non-orthogonal matrices, partially compensating for imperfect calibration of the robot or localisation device. We also introduce a new method where full robot/world and partial tool/flange calibration is possible by using localisation devices providing less than six degrees of freedom (DOFs). The methods are evaluated on simulation data and on real-world measurements from optical and magnetical tracking devices, volumetric ultrasound providing 3-DOF data, and a surface laser scanning device. We compare our methods with two classical approaches: the method by Tsai/Lenz and the method by Daniilidis. In all experiments, the new algorithms outperform the classical methods in terms of translational accuracy by up to 80% and perform similarly in terms of rotational accuracy. Additionally, the methods are shown to be stable: the number of calibration stations used has far less influence on calibration quality than for the classical methods. Our work shows that the new method can be used for estimating the relationship between the robot's and the localisation device's coordinate systems. The new method can also be used for deficient systems providing only 3-DOF data, and it can be employed in real-time scenarios because of its speed.

Sexual dimorphism in skeletal browridge and chin morphologies determined using a new quantitative method.

Qualitative methods of describing sexual dimorphism in discrete cranial traits have been criticized for their subjectivity and statistical limitations. However, researchers have yet to be able to accurately capture the morphology of these individual traits using traditional metric techniques. This article presents a method to quantify morphological variation in the skeletal browridge and chin using 3D surface laser scans. Browridge and chin regions are isolated from the skull using objectively defined landmarks and planes. Region areas and volumes are used to quantify absolute and relative size, while semilandmarks along transects are used for more detailed morphometric analyses. An intraobserver error study indicates high repeatability of the method. Application of the method is demonstrated on a sample of US males and females of black and white ancestries. Results suggest significant effects of both sex and ancestry on brow and chin morphologies and are consistent with traditional qualitative descriptions. Our results indicate that the method can accurately and reliably quantify browridge and chin morphologies, providing a tool to objectively describe and statistically analyze these traditionally qualitative discrete cranial traits.

Development and Implementation of a Web-Enabled 3D Consultation Tool for Breast Augmentation Surgery Based on 3D-Image Reconstruction of 2D Pictures

BackgroundProducing a rich, personalized Web-based consultation tool for plastic surgeons and patients is challenging.Objective(1) To develop a computer tool that allows individual reconstruction and simulation of 3-dimensional (3D) soft tissue from ordinary digital photos of breasts, (2) to implement a Web-based, worldwide-accessible preoperative surgical planning platform for plastic surgeons, and (3) to validate this tool through a quality control analysis by comparing 3D laser scans of the patients with the 3D reconstructions with this tool from original 2-dimensional (2D) pictures of the same patients.MethodsThe proposed system uses well-established 2D digital photos for reconstruction into a 3D torso, which is then available to the user for interactive planning. The simulation is performed on dedicated servers, accessible via Internet. It allows the surgeon, together with the patient, to previsualize the impact of the proposed breast augmentation directly during the consultation before a surgery is decided upon. We retrospectively conduced a quality control assessment of available anonymized pre- and postoperative 2D digital photographs of patients undergoing breast augmentation procedures. The method presented above was used to reconstruct 3D pictures from 2D digital pictures. We used a laser scanner capable of generating a highly accurate surface model of the patient’s anatomy to acquire ground truth data. The quality of the computed 3D reconstructions was compared with the ground truth data used to perform both qualitative and quantitative evaluations.ResultsWe evaluated the system on 11 clinical cases for surface reconstructions and 4 clinical cases of postoperative simulations, using laser surface scan technologies showing a mean reconstruction error between 2 and 4 mm and a maximum outlier error of 16 mm. Qualitative and quantitative analyses from plastic surgeons demonstrate the potential of these new emerging technologies.ConclusionsWe tested our tool for 3D, Web-based, patient-specific consultation in the clinical scenario of breast augmentation. This example shows that the current state of development allows for creation of responsive and effective Web-based, 3D medical tools, even with highly complex and time-consuming computation, by off-loading them to a dedicated high-performance data center. The efficient combination of advanced technologies, based on analysis and understanding of human anatomy and physiology, will allow the development of further Web-based reconstruction and predictive interfaces at different scales of the human body. The consultation tool presented herein exemplifies the potential of combining advancements in the core areas of computer science and biomedical engineering with the evolving areas of Web technologies. We are confident that future developments based on a multidisciplinary approach will further pave the way toward personalized Web-enabled medicine.

Functionally graded NiTi strips prepared by laser surface anneal

In this study, two-dimensional functionally graded NiTi thin plates were created by laser surface scanning anneal. Owing to the natural degradation of heat penetrating into the material, a temperature gradient within the thickness was created by laser surface interaction and heat conduction. A microstructural gradient was created due to partial annealing within the temperature field. The microstructural variation through the thickness was characterized by hardness measurement and layered differential scanning calorimetry analysis. The microstructural gradient led to a unique shape memory effect, involving shape change in two opposite directions upon one heating, analogous to stingray motion. Such behaviour also experiences enlarged temperature windows for both the forward and reverse martensitic transformations, rendering high controllability of actuation.

Comparison of a Novel Surface Laser Scanning Anthropometric Technique to Traditional Methods for Facial Parameter Measurements

This study was designed to determine if three-dimensional (3D) laser scanning techniques could be used to collect accurate anthropometric measurements, compared with traditional methods. The use of an alternative 3D method would allow for quick collection of data that could be used to change the parameters used for facepiece design, improving fit and protection for a wider variety of faces. In our study, 10 facial dimensions were collected using both the traditional calipers and tape method and a Konica-Minolta Vivid9i laser scanner. Scans were combined using RapidForm XOR software to create a single complete facial geometry of the subject as a triangulated surface with an associated texture image from which to obtain measurements. A paired t-test was performed on subject means in each measurement by method. Nine subjects were used in this study: five males (one African-American and four Caucasian females) and four females displaying a range of facial dimensions. Five measurements showed significant differences (p < 0.05), with most accounted for by subject movements or amended by scanning technique modifications. Laser scanning measurements showed high precision and accuracy when compared with traditional methods. Significant differences found can be very small changes in measurements and are unlikely to present a practical difference. The laser scanning technique demonstrated reliable and quick anthropometric data collection for use in future projects in redesigning respirators.

Maxillary posterior intrusion mechanics with mini-implant anchorage evaluated with the finite element method

The goal of this study was to evaluate the effects of 3 maxillary posterior intrusion mechanics with mini-implant anchorage by using the finite element method. Finite element models were generated by assembling the images obtained by computed tomography and a laser surface scanner. For each posterior dental segment, a 300-g force was applied and distributed to the mini-implants in proportion to their calculated root surface areas. The most balanced intrusion and the most uniform stress distribution were obtained by concurrent force applications from the vestibular and palatinal sides. In the models with transpalatal arches and buccal force application, vestibular tipping movement and overall stress values were prominent. In all models, increased stress values were identified at the apical region of the first premolar roots and at the apical region of the first molar mesial root. The results of this study suggest that the apical region of the first premolar roots and the apical region of the first molar mesial root should be considered to be prone to resorption during posterior intrusion treatment. Posterior intrusion systems with force application from counterbalancing sites lead to a more uniform stress distribution and balanced intrusion than the mechanics with a transpalatal arch. For a balanced intrusion, root surface areas should be considered when determining the appropriate forces.

Impact load-induced micro-structural damage and micro-structure associated mechanical response of concrete made with different surface roughness and porosity aggregates

The relationship between the nature of micro damage under impact loading and changes in mechanical behavior associated with different microstructures is studied for concretes made with two different coarse aggregates having significant differences mainly in roughness and porosity — sintered fly ash and uncrushed gravel. A range of techniques including X-ray diffraction, digital image analysis, mercury porosimetry, X-ray computed tomography, laser surface profilometry and scanning electron microscopy were used to characterize the aggregates and micro-structures. The concrete prepared with lightweight aggregates was stronger in compression than the gravel aggregate concrete due to enhanced hydration as a result of internal curing. In the lightweight concrete, it was deduced that an inhomogeneous micro-structure led to strain incompatibilities and consequent localized stress concentrations in the mix, leading to accelerated failure. The pore structure, compressibility, and surface texture of the aggregates are of paramount importance for the micro-cracking growth.