Three-dimensional Shape Model Research Articles

Stochastic PCA-Based Bone Models from Inverse Transform Sampling: Proof of Concept for Mandibles and Proximal Femurs

Principal components analysis is a powerful technique which can be used to reduce data dimensionality. With reference to three-dimensional bone shape models, it can be used to generate an unlimited number of models, defined by thousands of nodes, from a limited (less than twenty) number of scalars. The full procedure has been here described in detail and tested. Two databases were used as input data: the first database comprised 40 mandibles, while the second one comprised 98 proximal femurs. The “average shape” and principal components that were required to cover at least 90% of the whole variance were identified for both bones, as well as the statistical distributions of the respective principal components weights. Fifteen principal components sufficed to describe the mandibular shape, while nine components sufficed to describe the proximal femur morphology. A routine has been set up to generate any number of mandible or proximal femur geometries, according to the actual statistical shape distributions. The set-up procedure can be generalized to any bone shape given a sufficiently large database of the respective 3D shapes.

Computer-Aided Assessment of Displacement and Reduction of Distal Radius Fractures.

This study aims to investigate displacements and reductions of distal radius fractures using measurement indices based on the computer-aided three-dimensional (3D) radius shape model. Fifty-two distal radius fracture patients who underwent osteosynthesis were evaluated with pre- and post-operative distal radius 3D images. In the 3D images, three reference points, i.e., the radial styloid process (1), sigmoid notch volar, and dorsal edge (2) (3) were marked. The three-dimensional coordinates of each reference point and the barycentric coordinates of the plane connecting the three reference points were evaluated. The distance and direction moved, due to the reductions for each reference point, were (1) 12.1 ± 8.1 mm in the ulnar-palmar-distal direction, (2) 7.5 ± 4.1 mm in the ulnar-palmar-proximal direction, and (3) 8.2 ± 4.7 mm in the ulnar-palmar-distal direction relative to the preoperative position. The barycentric coordinate moved 8.4 ± 5.3 mm in the ulnar-palmar-distal direction compared to the preoperative position. This analyzing method will be helpful to understand the three-dimensional direction and the extent of displacements in distal radius fractures.

Evaluation of Statistical Shape Modeling in Quantifying Femoral Morphologic Differences Between Symptomatic and Nonsymptomatic Hips in Patients with Unilateral Femoroacetabular Impingement Syndrome

PurposeTo determine whether statistical shape modeling can detect subtle morphologic differences in the shape of the proximal femur that correlate with clinical findings of unilateral femoroacetabular impingement syndrome.MethodsPatients who had diagnoses of unilateral femoroacetabular impingement syndrome and who had existing computed tomography scans of their pelvises were included. Three-dimensional shape models in the form of triangle meshes were generated from the computed tomography images. Statistical shapes of cam-type and normal hips were compared to identify structural differences.ResultsThe study included 33 hips in 17 subjects. Of the subjects, 7 (41.1%) were male, and 10 (58.9%) were female. The subjects ranged in age from 17-60 years of age (mean 36.3 ± 11.0 years old). The statistical shape modeling found mean shapes and modes after optimizing the groupwise correspondence. Symptomatic hips demonstrated 1 mm of thickening as compared to the femoral necks of asymptomatic hips, corresponding to cam lesions.ConclusionsSymptomatic cam deformities were an average of 1 mm more prominent in the femoral neck region as compared to the asymptomatic hips when using statistical shape modeling. The present study provides a proof of the concept that statistical shape modeling can be used to examine and help define cam morphology and that subtle morphologic differences may account for developing femoroacetabular impingement syndrome.Clinical RelevanceUsing the methods presented in this study, it would be possible to define cam and pincer morphologies by creating statistical shape models, and this work could potentially lead to the development of a new classification system for femoroacetabular impingement syndrome lesions.

Three-Dimensional Shape Modeling and Analysis of Brain Structures.

Statistical shape analysis of brain structures has been used to investigate the association between their structural changes and pathological processes. We have developed a software package for accurate and robust shape modeling and group-wise analysis. Here, we introduce an pipeline for the shape analysis, from individual 3D shape modeling to quantitative group shape analysis. We also describe the pre-processing and segmentation steps using open software packages. This practical guide would help researchers save time and effort in 3D shape analysis on brain structures.

Three-Dimensional Shape Modeling and Analysis of Brain Structures

Three-Dimensional Shape Modeling and Analysis of Brain Structures

Three-dimensional computer modeling of standard orbital mean shape in Asians

Although some data for western norms in orbit shape were reported, the standard norms for Asian orbits were not established yet. The data would be very valuable for the various surgical procedures as well as the production of the appropriate instruments and implants. Therefore, we suggest a Korean orbit mean shape model based on the three-dimensional computer modeling, which includes the analysis of the various parameters with the calculated average value, thereby providing a standard mean shape orbital model that could be used for the Asian patients' orbital surgeries. This paper would be the first literature that provides the standard orbit model for Asians. We developed orbit-specific computer software (AMC-SWUⓇ) for the production of an orbit mean shape model. The production steps included semi-automatic segmentation, shape reconstruction, statistical shape model generation, and mean shape and variance model production. The study included records of 48 male and 48 female patients who met the inclusion criteria. Three-dimensional facial bone computed tomography (CT) images of 96 patients were obtained, and these images were used to produce a representative mean shape model. The mean models had vertical dimensions of 36.93 and 35.11 mm, horizontal dimensions of 38.49 and 36.79 mm, and rim dimensions of 45.76 and 42.90 mm for males and females, respectively. We developed a realistic, visualized three-dimensional Korean orbit mean shape model and compared its parameters with calculated values. There is a variance in orbital dimensions between the sexes and the orbital changes with age. We also demonstrated orbital anatomic differences between ethnic groups.

Interactive foreground segmentation and shape reconstruction from RGBD images

Three dimensional shape reconstruction of objects in complex scenes has important applications in intelligent transportation systems and medical image processing. This paper aims to segment and locate the foreground object through the interactive segmentation with multiple cues including saliency, depth and color. The desired foreground object is obtained by using the foreground and background information provided by saliency map and heatmap. Then, the multi-view point cloud information of the foreground object is recovered by depth information, and a multi-view point cloud registration algorithm based on color information is proposed. The three-dimensional shape model of the object is reconstructed through a multi-view point cloud registration algorithm combined with motion averaging and low-rank sparse matrix decomposition. The validity of the framework is empirically assessed with comparative experiments.

Development of a three-dimensional body shape model of young children for child restraint design

The design of child restraints is guided in part by anthropometric data describing the distributions of body dimensions of children. However, three-dimensional body shape data have not been available for children younger than three years of age. This study presents body shape models for children weighing 9–23 kg in a seated posture relevant to child restraint design. A laboratory study collected surface geometry data of 67 children, ages 12–58 months. Novel template fitting methods were employed to obtain homologous meshes and to standardize the posture. Principal component analysis and regression were used to develop a statistical body shape model (SBSM). The SBSM was exercised to create 18 manikins representing children aged 1–3 years, with varying size and shape. These manikins will be useful for assessing child accommodation in restraints. The SBSM can also provide guidance for the development of anthropomorphic test devices and computational models of child occupants.

Origin of Phobos grooves: Testing the Stickney Crater ejecta model

The model of Wilson and Head (1989, 2005, 2015) interprets the grooves of Phobos as the product of sliding, rolling, and bouncing ejecta boulders from the Stickney Crater impact. To test the model of Wilson and Head (1989, 2005, 2015) we apply a dynamical physics simulation to a three-dimensional shape model of Phobos and systematically assess six specific objections to the rolling boulder model. Our simulation calculates the motions of Stickney Crater ejecta boulders under the influence of Mars gravitation, the post-Stickney-impact desynchronized rotation of Phobos and altered orbit of Phobos, a spherically symmetrical gravity field of Phobos, and a collision system that simulates the effects of surface friction. We also take the orbital history of Phobos into account and test the rolling boulder model at three semimajor axes greater than the present day (10,000 km, 12,000 km, and 14,000 km). At a Phobos semimajor axis of 12,000 km, we find that boulder motions are generally consistent with observed grooves – specifically 1) Test boulders travel in linear/parallel patterns that are consistent with observed grooves, including grooves that are not radially aligned with Stickney Crater; 2) test boulders drift into suborbital flights over the trailing hemisphere of Phobos and do not travel on the surface of Phobos in this region; 3) grooves inside Stickney Crater are produced by Stickney ejecta boulders that return to Stickney Crater; 4) boulders that travel around Phobos >180° from Stickney Crater crosscut the motions of other boulders that travel >180° from Stickney; 5) at boulder ejection velocities ≲6 m/s, test boulders moving in contact with Phobos typically follow the contours of local terrain. We also find that 6) a spike of Stickney secondary impacts likely destroyed missing groove-producing boulders and removed grooves with widths ≲80 m; 7) with respect to the motion of test boulders, the two possible pre-Stickney-impact tidal-lock orientations of Phobos produce the same boulder motion effects; and 8) where our 12,000 km semimajor axis testing model is consistent with observed grooves, this supports a ∼150 Ma prediction for the age of Phobos grooves and Stickney Crater.

(16) Psyche: A mesosiderite-like asteroid?

Context. Asteroid (16) Psyche is the target of the NASA Psyche mission. It is considered one of the few main-belt bodies that could be an exposed proto-planetary metallic core and that would thus be related to iron meteorites. Such an association is however challenged by both its near- and mid-infrared spectral properties and the reported estimates of its density. Aims. Here, we aim to refine the density of (16) Psyche to set further constraints on its bulk composition and determine its potential meteoritic analog. Methods. We observed (16) Psyche with ESO VLT/SPHERE/ZIMPOL as part of our large program (ID 199.C-0074). We used the high angular resolution of these observations to refine Psyche’s three-dimensional (3D) shape model and subsequently its density when combined with the most recent mass estimates. In addition, we searched for potential companions around the asteroid. Results. We derived a bulk density of 3.99 ± 0.26 g cm−3 for Psyche. While such density is incompatible at the 3-sigma level with any iron meteorites (∼7.8 g cm−3), it appears fully consistent with that of stony-iron meteorites such as mesosiderites (density ∼4.25 g cm−3). In addition, we found no satellite in our images and set an upper limit on the diameter of any non-detected satellite of 1460 ± 200 m at 150 km from Psyche (0.2% × RHill, the Hill radius) and 800 ± 200 m at 2000 km (3% × RHill). Conclusions. Considering that the visible and near-infrared spectral properties of mesosiderites are similar to those of Psyche, there is merit to a long-published initial hypothesis that Psyche could be a plausible candidate parent body for mesosiderites.

A revised shape model of asteroid (216) Kleopatra

We used three different sets of Arecibo delay-Doppler radar images and five well-covered occultations to generate a revised three-dimensional shape model of asteroid (216) Kleopatra with a spatial resolution of ∼10 km. We find Kleopatra to be a bi-lobate contact binary of overall dimensions 276 × 94 × 78 km ± 15% and equivalent diameter Deq = 122 ± 30 km; our uncertainties are upper and lower bounds. Separated binary models are ruled out by multi-chord occultations. Our model is 27% longer than the “dog-bone” model originally published by Ostro et al. (2000) but is similar to their model in the minor and intermediate axes extents. Our model's dimensions are also consistent with more recent ones based on lightcurves, adaptive-optics, and interferometric imaging. We confirm a rotational period of P = 5.385280 h ± 0.000001 h and a rotation pole at ecliptic longitude and latitude (λ, β) = (74°, + 20°) ± 5°. Over its southern hemisphere (the one most frequently observed on Earth), Kleopatra's radar albedo is 0.43 ± 0.10, consistent with a high near-surface bulk density and, by inference, the high metal content expected for M-class asteroids. However, the radar albedo for equatorial observations is considerably lower and more typical of a dominantly silicate composition. This observation could readily be explained by a relatively thin (1–2 m) silicate mantle over equatorial latitudes. Kleopatra's surface is relatively smooth with a mean slope of 12° at the ∼10 km baseline scale. Analysis of its geopotential surface suggests loose material will preferentially migrate to the neck, and this is supported by our radar observations.

Where does meniscal damage progress most rapidly? An analysis using three-dimensional shape models on data from the Osteoarthritis Initiative.

Meniscal pathology is integral to knee osteoarthritis (OA) and its progression; it provides a progression biomarker and a potential treatment target. Magnetic resonance imaging (MRI) demonstrates large heterogeneity in meniscal damage; this structural complexity means measurement is difficult. The aim of this study was to apply novel 3D image analysis to determine which meniscal pathologies demonstrated most change during OA progression. Knee images were selected from the progression cohort of the Osteoarthritis Initiative choosing participants with risk factors for medial OA progression. Medial and lateral menisci were manually segmented then analysed using a statistical shape model of the tibia as a reference surface. Responsiveness was assessed at 1 year using standardised response means (SRMs) for four constructs: meniscal volume, extrusion volume, thickness and tibial coverage; anatomical sub-regions of these constructs were also explored. Paired images from 86 participants (median age 61.5, 49% female, 56% obese) were included. Reliability of the novel meniscal measurements was very good intraclass correlation coefficients (ICCs all>0.98). Meniscal volume and extrusion demonstrated no significant change. Moderate responsiveness was observed for medial meniscus thickness (SRM-0.35) and medial tibial coverage (SRM-0.36). No substantial change was seen for the lateral meniscus measures. Sub-region analysis did not improve responsiveness; while greater change was seen in the posterior medial compartment, it was associated with increased variance of the change. The location of meniscal damage was consistently in the posterior medial region, and two measurements (thickness and tibial coverage) were most responsive. Meniscal measures should add to discriminatory power in OA progression assessment.

Morphometry of the sacrum and its implication on trans-sacral corridors using a computed tomography data-based three-dimensional statistical model

Background ContextTrans-sacral implants are increasingly used to treat fractures of the sacrum, especially for osteoporosis-associated fragility fractures. However, the complex and highly variable sacral anatomy limits their use. It is still not clear which morphologic characteristics are critical to determine the availability and dimensions of trans-sacral corridors. PurposeThis study aims to assess sacral anatomy and its influence on trans-sacral corridors. Study DesignThis study used a computed tomography (CT)-based three-dimensional (3D) statistical size and shape model of the sacrum with multiple morphometric measurements. Materials and MethodsA 3D statistical model was computed using clinical CT data of 92 intact pelvises (mean age 61.5 years). Multiple measurements of the sacrum and the trans-sacral corridors were taken. Descriptive statistics and linear regression were calculated. Shape and size were analyzed using principal component analysis. ResultsThe limiting craniocaudal diameter of the trans-sacral corridor was 13.1 mm (±5 mm) in S1 and 13.8 mm (±2.4 mm) in S2. In S1, the craniocaudal diameter correlated with larger sacral curvature (SC), pelvic incidence (PI), and cranially located auricular surfaces. The presence of an accessory articulation with L5 was associated with a larger trans-sacral corridor S1. In contrast, the craniocaudal diameter of the S2 corridor correlated with more caudally situated auricular surfaces and lower PI. The sacral shape, as demonstrated by the statistical model, was highly variable, which affected the size and availability of trans-sacral corridor S1. Important determinants of trans-sacral corridor S1 were the craniocaudal position of the auricular surfaces and the shape of the sacral ala, which were influenced by SC, sacral height, and PI. ConclusionsThe human sacrum is highly variable in size and shape. The dimensions of trans-sacral corridors depend on the sacral shape and specific morphologic characteristics. Understanding of morphologic variants helps with preoperative assessments of the trans-sacral corridors. When planning to use trans-sacral implants, because of variable sacral anatomy and dimensions of the trans-sacral corridors, thorough preoperative planning is mandatory.

Numerical simulation for injection of blood-contrast medium using a three-dimensional real shape model

Numerical simulation for injection of blood-contrast medium using a three-dimensional real shape model

Remember like humans

Visual tracking is a challenging computer vision task due to the significant observation changes of the target. By contrast, the tracking task is relatively easy for humans. In this article, we propose a tracker inspired by the cognitive psychological memory mechanism, which decomposes the tracking task into sensory memory register, short-term memory tracker, and long-term memory tracker like humans. The sensory memory register captures information with three-dimensional perception; the short-term memory tracker builds the highly plastic observation model via memory rehearsal; the long-term memory tracker builds the highly stable observation model via memory encoding and retrieval. With the cooperative models, the tracker can easily handle various tracking scenarios. In addition, an appearance-shape learning method is proposed to update the two-dimensional appearance model and three-dimensional shape model appropriately. Extensive experimental results on a large-scale benchmark data set demonstrate that the proposed method outperforms the state-of-the-art two-dimensional and three-dimensional trackers in terms of efficiency, accuracy, and robustness.

Radar observations and shape model of asteroid 16 Psyche

Using the S-band radar at Arecibo Observatory, we observed 16 Psyche, the largest M-class asteroid in the main belt. We obtained 18 radar imaging and 6 continuous wave runs in November and December 2015, and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images (Drummond et al., 2016) to generate a three-dimensional shape model of Psyche. Our model is consistent with a previously published AO image (Hanus et al., 2013) and three multi-chord occultations. Our shape model has dimensions 279 × 232 × 189km (± 10%), Deff= 226 ± 23km, and is 6% larger than, but within the uncertainties of, the most recently published size and shape model generated from the inversion of lightcurves (Hanus et al., 2013). Psyche is roughly ellipsoidal but displays a mass-deficit over a region spanning 90° of longitude. There is also evidence for two ∼50–70km wide depressions near its south pole. Our size and published masses lead to an overall bulk density estimate of 4500 ± 1400kgm−3. Psyche's mean radar albedo of 0.37 ± 0.09 is consistent with a near-surface regolith composed largely of iron-nickel and ∼40% porosity. Its radar reflectivity varies by a factor of 1.6 as the asteroid rotates, suggesting global variations in metal abundance or bulk density in the near surface. The variations in radar albedo appear to correlate with large and small-scale shape features. Our size and Psyche's published absolute magnitude lead to an optical albedo of pv= 0.15 ± 0.03, and there is evidence for albedo variegations that correlate with shape features.

A new ASM framework for left ventricle segmentation exploring slice variability in cardiac MRI volumes

Three-dimensional active shape models use a set of annotated volumes to learn a shape model. Using unique landmarks to define the surface models in the training set, the shape model is able to learn the expected shape and variation modes of the segmentation. This information is then used during the segmentation process to impose shape constraints. A relevant problem in which these models are used is the segmentation of the left ventricle in 3D MRI volumes. In this problem, the annotations correspond to a set of contours that define the LV border at each volume slice. However, each volume has a different number of slices (thus, a different number of landmarks), which makes model learning difficult. Furthermore, motion artifacts and the large distance between slices make interpolation of voxel intensities a bad choice when applying the learned model to a test volume. These two problems raise the following questions: (1) how can we learn a shape model from volumes with a variable number of slices? and (2) how can we segment a test volume without interpolating voxel intensities between slices? This paper provides an answer to these questions by proposing a framework to deal with the variable number of slices in the training set and a resampling strategy for the test phase to segment the left ventricle in cardiac MRI volumes with any number of slices. The proposed method was evaluated on a public database with 660 volumes of both healthy and diseased patients, with promising results.

Ventricular structure in ARVC: going beyond volumes as a measure of risk

BackgroundAltered right ventricular structure is an important feature of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), but is challenging to quantify objectively. The aim of this study was to go beyond ventricular volumes and diameters and to explore if the shape of the right and left ventricles could be assessed and related to clinical measures. We used quantifiable computational methods to automatically identify and analyse malformations in ARVC patients from Cardiovascular Magnetic Resonance (CMR) images. Furthermore, we investigated how automatically extracted structural features were related to arrhythmic events.MethodsA retrospective cross-sectional feasibility study was performed on CMR short axis cine images of 27 ARVC patients and 21 ageing asymptomatic control subjects. All images were segmented at the end-diastolic (ED) and end-systolic (ES) phases of the cardiac cycle to create three-dimensional (3D) bi-ventricle shape models for each subject. The most common components to single- and bi-ventricular shape in the ARVC population were identified and compared to those obtained from the control group. The correlations were calculated between identified ARVC shapes and parameters from the 2010 Task Force Criteria, in addition to clinical outcomes such as ventricular arrhythmias.ResultsBi-ventricle shape for the ARVC population showed, as ordered by prevalence with the percent of total variance in the population explained by each shape: global dilation/shrinking of both ventricles (44 %), elongation/shortening at the right ventricle (RV) outflow tract (15 %), tilting at the septum (10 %), shortening/lengthening of both ventricles (7 %), and bulging/shortening at both the RV inflow and outflow (5 %). Bi-ventricle shapes were significantly correlated to several clinical diagnostic parameters and outcomes, including (but not limited to) correlations between global dilation and electrocardiography (ECG) major criteria (p = 0.002), and base-to-apex lengthening and history of arrhythmias (p = 0.003). Classification of ARVC vs. control using shape modes yielded high sensitivity (96 %) and moderate specificity (81 %).ConclusionWe presented for the first time an automatic method for quantifying and analysing ventricular shapes in ARVC patients from CMR images. Specific ventricular shape features were highly correlated with diagnostic indices in ARVC patients and yielded high classification sensitivity. Ventricular shape analysis may be a novel approach to classify ARVC disease, and may be used in diagnosis and in risk stratification for ventricular arrhythmias.

Three-dimensional MRI-based statistical shape model and application to a cohort of knees with acute ACL injury

The aim of this study is to develop a novel 3D magnetic resonance imaging (MRI)-based Statistical Shape Modeling (SSM) and apply it in knee MRIs in order to extract and compare relevant shapes of the tibia and femur in patients with and without acute Anterior cruciate ligament (ACL) injuries. Bilateral MR images were acquired and analyzed for 50 patients with acute ACL injuries and for 19 control subjects. A shape model was extracted for the tibia and femur using an SSM algorithm based on a set of matched landmarks that are computed in a fully automatic manner. Shape differences were detected between the knees in the ACL-injury group and control group, suggesting a common shape feature that may predispose these knees to injury. Some of the detected shape features that discriminate between injured and control knees are related to intercondylar width and posterior tibia slope, features that have been suggested in previous studies as ACL morphological risk factors. However, shape modeling has the great potential to quantify these characteristics with a comprehensive description of the surfaces describing complex 3D deformation that cannot be represented with simple geometric indexes. 3D MRI-based bone shape quantification has the ability to identify specific anatomic risk factors for ACL injury. A better understanding of the role in bony shape on ligamentous injuries could help in the identification of subjects with an increased risk for an ACL tear and to develop targeted prevention strategies, including education and training.

The developement of red mud flood environmental information system and the methodology for the spatial analysis of the degraded area

The red mud disaster occurred on 4th October 2010 in Hungary has raised the necessity of rapid intervention and drew attention to the long-term monitoring of such threat. Both the condition assessment and the change monitoring indispensably required the prompt and detailed spatial survey of the impact area. It was conducted by several research groups - independently - with different recent surveying methods. The high spatial resolution multispectral aerial photogrammetry is the spatially detailed (high resolution) and accurate type of remote sensing. The hyperspectral remote sensing provides more information about material quality of pollutants, with less spatial details and lower spatial accuracy, while LIDAR ensures the three-dimensional shape and terrain models. The article focuses on the high spatial resolution, multispectral electrooptical method and the evaluation methodology of the deriving high spatial resolution ortho image map, presenting the derived environmental information database