A Novel Approach for Dynamic (4d) Multi-View Stereo System Camera Network Design.

Image network design is a critical factor in image-based 3D shape reconstruction and data processing (especially in the application of combined SfM/MVS methods). This paper aims to present a new approach to designing and planning multi-view imaging networks for dynamic 3D scene reconstruction without preliminary information about object geometry or location. The only constraints are the size of defined measurement volume, the required resolution, and the accuracy of geometric reconstruction. The proposed automatic camera network design method is based on the Monte Carlo algorithm and a set of prediction functions (considering accuracy, density, and completeness of shape reconstruction). This is used to determine the camera positions and orientations and makes it possible to achieve the required completeness of shape, accuracy, and resolution of the final 3D reconstruction. To assess the accuracy and efficiency of the proposed method, tests were carried out on synthetic and real data. For a set of 20 virtual images of rendered spheres, completeness of shape reconstruction was up by 92.3% while maintaining accuracy and resolution at the user-specified level. In the case of the real data, the differences between predictions and evaluations for average density were in the range between 33.8% to 45.0%.

sSfS: Segmented Shape from Silhouette Reconstruction of the Human Body.

Three-dimensional (3D) shape estimation of the human body has a growing number of applications in medicine, anthropometry, special effects, and many other fields. Therefore, the demand for the high-quality acquisition of a complete and accurate body model is increasing. In this paper, a short survey of current state-of-the-art solutions is provided. One of the most commonly used approaches is the Shape-from-Silhouette (SfS) method. It is capable of the reconstruction of dynamic and challenging-to-capture objects. This paper proposes a novel approach that extends the conventional voxel-based SfS method with silhouette segmentation-segmented Shape from Silhouette (sSfS). It allows the 3D reconstruction of body segments separately, which provides significantly better human body shape estimation results, especially in concave areas. For validation, a dataset representing the human body in 20 complex poses was created and assessed based on the quality metrics in reference to the ground-truth photogrammetric reconstruction. It appeared that the number of invalid reconstruction voxels for the sSfS method was 1.7 times lower than for the state-of-the-art SfS approach. The root-mean-square (RMS) error of the distance to the reference surface was also 1.22 times lower.

Segmentation of Change in Surface Geometry Analysis for Cultural Heritage Applications.

This work proposes a change-based segmentation method for applications to cultural heritage (CH) imaging to perform monitoring and assess changes at each surface point. It can be used as a support or component of the 3D sensors to analyze surface geometry changes. In this research, we proposed a new method to identify surface changes employing segmentation based on 3D geometrical data acquired at different time intervals. The geometrical comparison was performed by calculating point-to-point Euclidean distances for each pair of surface points between the target and source geometry models. Four other methods for local distance measurement were proposed and tested. In the segmentation method, we analyze the local histograms of the distances between the measuring points of the source and target models. Then the parameters of these histograms are determined, and predefined classes are assigned to target surface points. The proposed methodology was evaluated by considering two different case studies of restoration issues on CH surfaces and monitoring them over time. The results were presented with a colormap visualization for each category of the detected change in the analysis. The proposed segmentation method will help in the field of conservation and restoration for the documentation and quantification of geometrical surface change information. This analysis can help in decision-making for the assessment of damage and potential prevention of further damage, and the interpretation of measurement results.

Applicability of Augmented Reality in an Organ Transplantation.

Augmented reality (AR) delivers virtual information or some of its elements to the real world. This technology, which has been used primarily for entertainment and military applications, has vigorously entered medicine, especially in radiology and surgery, yet has never been used in organ transplantation. AR could be useful in training transplant surgeons, promoting organ donations, graft retrieval and allocation, and microscopic diagnosis of rejection, treatment of complications, and post-transplantation neoplasms. The availability of AR display tools such as Smartphone screens and head-mounted goggles, accessibility of software for automated image segmentation and 3-dimensional reconstruction, and algorithms allowing registration, make augmented reality an attractive tool for surgery including transplantation. The shortage of hospital IT specialists and insufficient investments from medical equipment manufacturers into the development of AR technology remain the most significant obstacles in its broader application.

Monitoring Improvement in Infantile Cerebral Palsy Patients Using the 4DBODY System-A Preliminary Study.

Monitoring the patient's condition during rehabilitation is the key to success in this form of treatment. This is especially important in patients with infantile cerebral palsy (ICP). Objective assessment can be achieved through modern optical measurement techniques. The 4DBODY system allows to capture dynamic movement with high accuracy. Eight patients with ICP participated in the study. The group underwent therapy lasting seven days using neurodevelopmental treatment (NDT) and functional training (FT). The patients' condition was monitored by the 4DBODY system. The measurements were taken three times: before the therapy, after, and then again after one week. We have developed the Trunk Mobility in the Frontal Plane Index (TMFPI) for its assessment. The results were compared with a score obtained using the Gross Motor Function Measure scale (GMFM 88). An improvement of the TMFPI parameter was observed in five patients, inconsistent results in two and deterioration in one. The reference GMFM score was higher in all patients relative to pre-treatment values. We found that surface scanning with the 4DBODY system allows to precisely track body movement in ICP patients. The decrease in the TMFPI parameter reflects the improvement in the dysfunction of body alignment, balance and symmetry of movement on the L and R body side.

Temperature Compensation Method for Mechanical Base of 3D-Structured Light Scanners.

The effect of temperature on three-dimensional (3D) structured light scanners is a very complex issue that, under some conditions, can lead to significant deterioration of performed measurements. In this paper, we present the results of several studies concerning the effect of temperature on the mechanical base of 3D-structured light scanners. We also propose a software compensation method suitable for implementation in any existing scanner. The most significant advantage of the described method is the fact that it does not require any specialized artifact or any additional equipment, nor access to the thermal chamber. It uses a simulation of mechanical base thermal deformations and a virtual 3D measurement environment that allows for conducting virtual measurements. The results from the verification experiments show that the developed method can extend the range of temperatures in which 3D-structured light scanners can perform valid measurements by more than six-fold.

Decreased Vertical Trunk Inclination Angle and Pelvic Inclination as the Result of Mid-High-Heeled Footwear on Static Posture Parameters in Asymptomatic Young Adult Women.

The influence of high-heel footwear on the lumbar lordosis angle, anterior pelvic tilt, and sacral tilt are inconsistently described in the literature. This study aimed to investigate the impact of medium-height heeled footwear on the static posture parameters of homogeneous young adult standing women. Heel geometry, data acquisition process, as well as data analysis and parameter extraction stage, were controlled. Seventy-six healthy young adult women with experience in wearing high-heeled shoes were enrolled. Data of fifty-three subjects were used for analysis due to exclusion criteria (scoliotic posture or missing measurement data). A custom structured light surface topography measurement system was used for posture parameters assessment. Three barefoot measurements were taken as a reference and tested for the reliability of the posture parameters. Two 30-degree wedges were used to imitate high-heel shoes to achieve a repeatable foot position. Our study confirmed the significant (p < 0.001) reduced vertical balance angle and pelvis inclination angle with large and medium-to-large effects, respectively, due to high-heel shoes. No significant differences were found in the kyphosis or lordosis angles. High-heeled shoes of medium height in young asymptomatic women can lead to a straightening effect associated with a reduced vertical balance angle and decreased pelvic inclination.

Temperature Compensation Method for Digital Cameras in 2D and 3D Measurement Applications.

This paper presents the results of several studies concerning the effect of temperature on digital cameras. Experiments were performed using three different camera models. The presented results conclusively demonstrate that the typical camera design does not adequately take into account the effect of temperature variation on the device's performance. In this regard, a modified camera design is proposed that exhibits a highly predictable behavior under varying ambient temperature and facilitates thermal compensation. A novel temperature compensation method is also proposed. This compensation model can be applied in almost every existing camera application, as it is compatible with every camera calibration model. A two-dimensional (2D) and three-dimensional (3D) application of the proposed compensation model is also described. The results of the application of the proposed compensation approach are presented herein.

Structured-Light-Based System for Shape Measurement of the Human Body in Motion.

The existing methods for measuring the shape of the human body in motion are limited in their practical application owing to immaturity, complexity, and/or high price. Therefore, we propose a method based on structured light supported by multispectral separation to achieve multidirectional and parallel acquisition. Single-frame fringe projection is employed in this method for detailed geometry reconstruction. An extended phase unwrapping method adapted for measurement of the human body is also proposed. This method utilizes local fringe parameter information to identify the optimal unwrapping path for reconstruction. Subsequently, we present a prototype 4DBODY system with a working volume of 2.0 × 1.5 × 1.5 m³, a measurement uncertainty less than 0.5 mm and an average spatial resolution of 1.0 mm for three-dimensional (3D) points. The system consists of eight directional 3D scanners functioning synchronously with an acquisition frequency of 120 Hz. The efficacy of the proposed system is demonstrated by presenting the measurement results obtained for known geometrical objects moving at various speeds as well actual human movements.

Monitoring of spine curvatures and posture during pregnancy using surface topography - case study and suggestion of method.

BACKGROUND: Low back and pelvic pain is one of the most frequently reported disorders in pregnancy, however etiology and pathology of this problem have not been fully determined. The relationship between back pain experienced during pregnancy and posture remains unclear. It is challenging to measure reliably postural and spinal changes at the time of pregnancy, since most imaging studies cannot be used due to the radiation burden. 3D shape measurement, or surface topography (ST), systems designed for posture evaluation could potentially fill this void. A pilot study was conducted to test the potential of monitoring the change of spine curvatures and posture during pregnancy using surface topography. A single case was studied to test the methodology and preliminarily assess the usefulness of the procedure before performing a randomized trial. The apparatus used in this study was metrologically tested and utilized earlier in scoliosis screening. CASE PRESENTATION: The subject was measured using a custom-made structured light illumination scanner with accuracy of 0.2 mm. Measurement was taken every 2 weeks, between 17th and 37th week of pregnancy, 11 measurements in total. From the measurement the thoracic kyphosis and lumbar lordosis angles, and vertical balance angle were extracted automatically. Custom-written software was used for analysis. Oswestry Low Back Pain Disability Questionnaire (ODI) was done with every measurement. The values were correctly extracted from the measurement. The results were: 50.9 ± 2.4° for kyphosis angle, 58.1 ± 2.1° for lordosis angle and 4.7 ± 1.7° for vertical balance angle. The registered change was 7.4° in kyphosis angle, 8.4° in lordosis angle and 5.5° in vertical balance angle. The calculated ODI values were between moderate disability and severe disability (22 to 58 %). CONCLUSIONS: This case study presents that surface topography may be suitable for monitoring of spinal curvature and posture change in pregnant women. The ionizing radiation studies are contraindicated during pregnancy. Surface topography data connected with information from pain level questionnaires allows to investigate the connection between changes in posture and back pain.

Posture and low back pain during pregnancy - 3D study.

OBJECTIVES: Back pain is a common complaint of pregnant women. The posture, curvatures of the spine and the center of gravity changes are considered as the mechanisms leading to pain. The study aimed to assess spinal curvatures and static postural characteristics with three-dimensional surface topography and search for relationships with the occurrence of back pain complaints among pregnant women. MATERIAL AND METHODS: The study was conducted from December 2012 to February 2014. Patients referred from University Clinic of Gynecology and Obstetrics were examined outpatient at the Posture Study Unit of Department of Orthopaedics and Traumatology. Sixty-five women at 4-39 weeks of pregnancy were assessed and surveyed with Oswestry Disability Index; posture was evaluated using surface topography. RESULTS: The study confirmed that difficulties in sitting and standing are significant in the third trimester of the pregnancy. The overall tendency for significant lumbar curvature changes in pregnant women was not confirmed. Major changes in sagittal trunk inclination in relation to the plumb line were not observed in the study group. CONCLUSIONS: The issue regarding how the pregnancy causes changes in spinal curvature and posture remains open for further studies. Presented method of 3D surface topography can reveal postural changes, but that requires several exams of each subject and strict follow-up of the series of cases.

Application of multi-resolution 3D techniques in crime scene documentation with bloodstain pattern analysis.

In forensic documentation with bloodstain pattern analysis (BPA) it is highly desirable to obtain non-invasively overall documentation of a crime scene, but also register in high resolution single evidence objects, like bloodstains. In this study, we propose a hierarchical 3D scanning platform designed according to the top-down approach known from the traditional forensic photography. The overall 3D model of a scene is obtained via integration of laser scans registered from different positions. Some parts of a scene being particularly interesting are documented using midrange scanner, and the smallest details are added in the highest resolution as close-up scans. The scanning devices are controlled using developed software equipped with advanced algorithms for point cloud processing. To verify the feasibility and effectiveness of multi-resolution 3D scanning in crime scene documentation, our platform was applied to document a murder scene simulated by the BPA experts from the Central Forensic Laboratory of the Police R&D, Warsaw, Poland. Applying the 3D scanning platform proved beneficial in the documentation of a crime scene combined with BPA. The multi-resolution 3D model enables virtual exploration of a scene in a three-dimensional environment, distance measurement, and gives a more realistic preservation of the evidences together with their surroundings. Moreover, high-resolution close-up scans aligned in a 3D model can be used to analyze bloodstains revealed at the crime scene. The result of BPA such as trajectories, and the area of origin are visualized and analyzed in an accurate model of a scene. At this stage, a simplified approach considering the trajectory of blood drop as a straight line is applied. Although the 3D scanning platform offers a new quality of crime scene documentation with BPA, some of the limitations of the technique are also mentioned.

The time effectiveness of three-dimensional telediagnostic postural screening of back curvatures and scoliosis.

BACKGROUND: Postural screening remains a powerful tool that can be used to identify children and adolescents with scoliosis or sagittal plane deformities. The aim of this study was to assess the time effectiveness of implemented telediagnostic screening procedures. MATERIALS AND METHODS: Medical images (virtual objects) of acquired clouds of points of 100 subjects of both sexes were chosen at random from the database and used for parametric evaluation for this study. This study was performed using a newly developed three-dimensional (3D) back surface topography measurement system for posture and scoliosis using a structured light method. The duration of each step of therapist/nurse/physician-assisted 3D assessment was measured independently with a stopwatch. Two configurations of PC computers and Internet connections were used to test the time effectiveness. Scoliotic postures were detected using cutoff values of angle of trunk rotation, Posterior Trunk Symmetry Index, and Deformity in the Axial Plane Index indices. RESULTS: The overall assessment of all subjects consumed from 2 h 55 min 55 s to 3 h 18 min 59 s dependent on PC and Internet connection configuration. Average examination time per subject ranged from 2 min 43 s to 4 min 51 s, respectively. The virtual landmarking and report generation times were dependent on the PC configuration (p<0.001). Our study confirmed satisfactory time effectiveness of the implemented telediagnostic postural screening procedure. We assume that it may influence the cost-effectiveness of the screening, which is usually mentioned as an important factor for recommendations against postural school screening. Relatively fast Internet connection and a medium-level PC configuration are sufficient for achieving a reasonably short time of 3D posture assessment of a virtual object representing a real subject's back surface. CONCLUSIONS: The efficiency of remote assessment of exact 3D surface topography can be used in large-scale studies for posture and scoliosis epidemiology.

Lower body kinematics evaluation based on a multidirectional four-dimensional structured light measurement.

We report on a structured light-scanning system, the OGX|4DSCANNER, capable of capturing the surface of a human body with 2 mm spatial resolution at a 60 Hz frame-rate. The performance of modeling the human lower body dynamics is evaluated by comparing the system with the current gold standard, i.e., the VICON system. The VICON system relies on the application of reflective markers on a person's body and tracking their positions in three-dimensional space using multiple cameras [optical motion capture (OMC)]. For the purpose of validation of the 4DSCANNER, a set of "virtual" markers was extracted from the measured surface. A set of musculoskeletal models was built for three subjects based on the trajectories of real and virtual markers. Next, the corresponding models were compared in terms of joint angles, joint moments, and activity of a number of major lower body muscles. Analyses showed a good overall agreement of the modeling outcome. We conclude that the 4DSCANNER within its limitations has the potential to be used in clinical gait analysis instead of optical marker-based systems. The advantage of the 4DSCANNER over OMC solutions is that it does not burden patients with time-consuming marker application. This study demonstrates the versatility of this measurement technique.

Telediagnostic 3D school screening of back curvatures and posture using structured light method - pilot study.

BACKGROUND: Several studies consider the school scoliosis screening as controversial. Many authors postulate to improve its clinical effectiveness. AIM: Authors assumed that three dimensional telediagnostic surface topography measurements allowing measuring several postural deformity indexes and angles of curvatures in sagittal plane may enhance current practice. The study was designed to determine usefulness of school screening back evaluation performed utilizing the three dimensional telediagnostic measurement system. METHODS: The measurement module is based on structured light method using "3D Orthoscreen" system. The technique for 3D image acquisition of back shape is based on temporal phase shifting and Gray codes. Measurement data was securely archived for remote access by investigator over the secure Internet connection. Acquired "images" were transferred to Telediagnostic Center for clinical evaluation. Spine parameters and deformation indexes like Posterior Trunk Symmetry Index (POTSI), Deformity in the Axial Plane Index (DAPI), kyphosis and lordosis angle were measured. The preliminary study was performed in 2 selected schools (basic and middle schools). The study was approved by Bioethical Committee. Clouds of points representing back topography of assessed subjects were acquired at schools in March and May 2011 and stored for remote evaluation and analysis. RESULTS: 758 children averagely aged 11.1 years (from 5 to 16), 387 females and 371 males, were examined. Their average body mass was 45.13 kg [16-105; STD 16.4] and average height was 151.43 cm, [110-192; STD 18.3]. The average values of back assessment parameters were as follows: POTSI 15.97% [0-73.4; STD 10.3]; DAPI 0.88% [0-5.9; STD 0.76]; kyphosis angle 10.19° [0-32; STD 5.82]; and lordosis angle 32,82° [0-56; STD 9.86]. CONCLUSION: Technical and clinical issues of the practical implementation allowed to elaborate preliminary protocol for cohort studies addressed to subject (i.e. parents acceptance of examination of undressed back) and technical issues (i.e. upload data and retrieval, network transfer velocity). Postural telediagnostics was found sufficiently feasible for further implementation of remote, cohort 3D back shape evaluations including school screening. Permanently saved 3D data allow monitoring back surface of the individual subjects.

Automatic recognition of surface landmarks of anatomical structures of back and posture.

Faulty postures, scoliosis and sagittal plane deformities should be detected as early as possible to apply preventive and treatment measures against major clinical consequences. To support documentation of the severity of deformity and diminish x-ray exposures, several solutions utilizing analysis of back surface topography data were introduced. A novel approach to automatic recognition and localization of anatomical landmarks of the human back is presented that may provide more repeatable results and speed up the whole procedure. The algorithm was designed as a two-step process involving a statistical model built upon expert knowledge and analysis of three-dimensional back surface shape data. Voronoi diagram is used to connect mean geometric relations, which provide a first approximation of the positions, with surface curvature distribution, which further guides the recognition process and gives final locations of landmarks. Positions obtained using the developed algorithms are validated with respect to accuracy of manual landmark indication by experts. Preliminary validation proved that the landmarks were localized correctly, with accuracy depending mostly on the characteristics of a given structure. It was concluded that recognition should mainly take into account the shape of the back surface, putting as little emphasis on the statistical approximation as possible.

Integrated three-dimensional shape and reflection properties measurement system.

Creating accurate three-dimensional (3D) digitalized models of cultural heritage objects requires that information about surface geometry be integrated with measurements of other material properties like color and reflectance. Up until now, these measurements have been performed in laboratories using manually integrated (subjective) data analyses. We describe an out-of-laboratory bidirectional reflectance distribution function (BRDF) and 3D shape measurement system that implements shape and BRDF measurement in a single setup with BRDF uncertainty evaluation. The setup aligns spatial data with the angular reflectance distribution, yielding a better estimation of the surface's reflective properties by integrating these two modality measurements into one setup using a single detector. This approach provides a better picture of an object's intrinsic material features, which in turn produces a higher-quality digitalized model reconstruction. Furthermore, this system simplifies the data processing by combining structured light projection and photometric stereo. The results of our method of data analysis describe the diffusive and specular attributes corresponding to every measured geometric point and can be used to render intricate 3D models in an arbitrarily illuminated scene.

Method of pectus excavatum measurement based on structured light technique.

We present an automatic method for assessment of pectus excavatum severity based on an optical 3-D markerless shape measurement. A four-directional measurement system based on a structured light projection method is built to capture the shape of the body surface of the patients. The system setup is described and typical measurement parameters are given. The automated data analysis path is explained. Their main steps are: normalization of trunk model orientation, cutting the model into slices, analysis of each slice shape, selecting the proper slice for the assessment of pectus excavatum of the patient, and calculating its shape parameter. We develop a new shape parameter (I(3ds)) that shows high correlation with the computed tomography (CT) Haller index widely used for assessment of pectus excavatum. Clinical results and the evaluation of developed indexes are presented.

Four-dimensional measurement by a single-frame structured light method.

A four-dimensional [4D--three-dimensional (3D) shape varying in time] shape measurement system is described. A single 3D shape of an object is calculated from only one frame. The projected pattern is composed of sinusoidal intensity fringes and one color-encoded stripe, the analysis of which allows us to find the absolute coordinates of the measured object. During measurement, the position of the stripe changes due to the improvement of the quality of spatiotemporal unwrapping. The fringes deformed by the shape of the object are captured by a CCD camera and processed by an adaptive spatial carrier phase-shifting algorithm. The use of an algorithm based on fast Fourier transformation is proposed to approximate the local period of fringes. A new phase-unwrapping routine based on the spatiotemporal information is presented as well. All these features make the 3D shape measurement of an object in motion possible with the additional advantage of using a low-cost system. Experimental results of the developed method together with a preliminary assessment of measurement uncertainty are presented to show the validity of the method.

Locating and tracing of anatomical landmarks based on full-field four-dimensional measurement of human body surface.

Four-dimensional (4D) (3D+time) measurement systems make it possible today to measure objects while moving and deforming. One of the fields where 4D systems prove themselves useful is medicine--particularly orthopedics and neural sciences--where measurement results may be used to estimate dynamic parameters of a patient's movement. Relatively new in 4D, optical full-field shape measurement systems capture more data than standard marker-based systems and open new ways for clinical diagnosis. However, before this is possible, the appropriate 4D data processing and analysis methods need to be developed. We present a new data analysis path for 4D data input as well as new shape parameters describing local features of a surface. The developed shape parameters are easier and quicker to calculate than standard surface parameters, such as curvatures, but they give results that are very similar to the latter. The presented 4D data analysis path allows characteristic areas on the body, so-called anatomical landmarks, to be located and traces them in time along the measurement sequence. We also present the general concepts and describe selected steps of the developed 4D data analysis path. The algorithms were implemented and tested on real and computer-generated data representing the surface of lower limbs. Finally, we give sample processing and analysis results.