Rigid Deformation Research Articles

An Open Benchmark Challenge for Motion Correction of Myocardial Perfusion MRI.

Cardiac magnetic resonance perfusion examinations enable noninvasive quantification of myocardial blood flow. However, motion between frames due to breathing must be corrected for quantitative analysis. Although several methods have been proposed, there is a lack of widely available benchmarks to compare different algorithms. We sought to compare many algorithms from several groups in an open benchmark challenge. Nine clinical studies from two different centers comprising normal and diseased myocardium at both rest and stress were made available for this study. The primary validation measure was regional myocardial blood flow based on the transfer coefficient (Ktrans), which was computed using a compartment model and the myocardial perfusion reserve (MPR) index. The ground truth was calculated using contours drawn manually on all frames by a single observer, and visually inspected by a second observer. Six groups participated and 19 different motion correction algorithms were compared. Each method used one of three different motion models: rigid, global affine, or local deformation. The similarity metric also varied with methods employing either sum-of-squared differences, mutual information, or cross correlation. There were no significant differences in Ktrans or MPR compared across different motion models or similarity metrics. Compared with the ground truth, only Ktrans for the sum-of-squared differences metric, and for local deformation motion models, had significant bias. In conclusion, the open benchmark enabled evaluation of clinical perfusion indices over a wide range of methods. In particular, there was no benefit of nonrigid registration techniques over the other methods evaluated in this study. The benchmark data and results are available from the Cardiac Atlas Project ( www.cardiacatlas.org).

Neo's Spoon and Newton's Apples: Prediction of rigid and non-rigid deformations of materials

Neo's Spoon and Newton's Apples: Prediction of rigid and non-rigid deformations of materials

Surface editing using swept surface 3D models

This paper presents a system for editing strip-like patches on the mesh using swept surface. The user first selects a rough cylinder-like region, the boundary of which is automatically refined. A swept surface approximation is automatically done, including extraction of the trajectory and the corresponding deforming 2D curves. The swept surface is described by a map from a real interval to both rigid body deformations and 2D curves. These 2D curves are analyzed and decomposed into many elements, which can be edited respectively, and a novel pattern analysis is also performed on these elements to extract curve patterns. These 2D curves serve as handles for controlling the geometry, and modifications to them can change the geometry directly. Thus, users can just edit the pattern or element curve to control the global geometry. We show the novelty and efficiency of our framework using varietal demonstrations.

Flow-induced deformation of unidirectional carbon fiber preform during the mold filling stage in liquid composite molding process

Liquid composite molding has been developed as a high-speed process for manufacturing automotive lightweight parts using new equipment that applies a high pressure for mixing and injection. One of the technical issues is the deformation of fiber preform during the process, which causes defects in the size, mechanical properties and appearance of the final products. In this study, two types of deformation in unidirectional fiber preform during the mold filling process are investigated, which are rigid body deformation and local deformation. Three important forces, namely friction, in-mold stiffness of fiber preform and resin flow, are measured to investigate the mechanism of the fiber deformation. The magnitude of the forces was compared at an instant, which influenced the types of fiber deformation. The effects of the orientation angle and the volume fraction of fiber preform and flow rate were investigated to identify controllable factors to prevent undesired deformation during the process.

Calculation of temperature distribution and rheological properties of the lithosphere along Profile 1 passing through Aswan

AbstractThe 2D integrated geophysical modelling approach has been used to determine the temperature distribution in the lithosphere along the profile passing through Aswan. Based on the temperature model and the rheological parameters, we have calculated strength distribution in the lithosphere for the studied profile. The strength envelopes have been calculated for both compressional and extensional regimes. Our results indicate that the strength is constant along the whole length of the profile passing through the Nubia plain. The largest strength can be observed within the upper crust which allows us to assume rigid deformation in this part of the lithosphere, with compressional processes predominant. Towards the lower crust and upper mantle, strength values rapidly decrease for both regimes, suggesting ductile deformations in the lower part of the lithosphere.

A Derivation of Linearized Griffith Energies from Nonlinear Models

We derive Griffith functionals in the framework of linearized elasticity from nonlinear and frame indifferent energies in a brittle fracture via {Gamma}-convergence. The convergence is given in terms of rescaled displacement fields measuring the distance of deformations from piecewise rigid motions. The configurations of the limiting model consist of partitions of the material, corresponding piecewise rigid deformations and displacement fields which are defined separately on each component of the cracked body. Apart from the linearized Griffith energy the limiting functional also comprises the segmentation energy, which is necessary to disconnect the parts of the specimen.

Fast Pixelwise Adaptive Visual Tracking of Non-Rigid Objects.

In this paper, we present a new algorithm for real-time single-object tracking in videos in unconstrained environments. The algorithm comprises two different components that are trained "in one shot" at the first video frame: a detector that makes use of the generalized Hough transform with color and gradient descriptors and a probabilistic segmentation method based on global models for foreground and background color distributions. Both components work at pixel level and are used for tracking in a combined way adapting each other in a co-training manner. Moreover, we propose an adaptive shape model as well as a new probabilistic method for updating the scale of the tracker. Through effective model adaptation and segmentation, the algorithm is able to track objects that undergo rigid and non-rigid deformations and considerable shape and appearance variations. The proposed tracking method has been thoroughly evaluated on challenging benchmarks, and outperforms the state-of-the-art tracking methods designed for the same task. Finally, a very efficient implementation of the proposed models allows for extremely fast tracking.

Obtenção de um elemento de viga unificado utilizando a formulação corrotacional e o princípio dos trabalhos virtuais complementares

In this work is described a shear flexible beam element model without shear locking and integrating Euler-Bernoulli’s and Timoshenko’s beam theories. The unified stiffness matrix of this beam is obtained by using the co-rotational formulation that is based on the separation of displacement fields into rigid body modes and deformation modes. The principle of complementary virtual work is also used for finding the unified stiffness matrix. The stiffness matrix is then implemented in a finite element software for linear analysis of plane frames. Some examples are presented and numerical results demonstrate that a shear flexible beam element do not show shear locking effects. Keywords: Co-rotational approach, Complementary virtual work, Shear flexible beam element.

Optimal point to point path planning of flexible manipulator under large deformation by using harmony search method

This paper aims at planning an optimal point to point path for a flexible manipulator under large deformation. For this purpose, the researchers use a direct method and meta-heuristic optimization process. In this paper, the maximum load carried by the manipulator and the minimum transmission time are taken as objective functions of the optimization process to get optimal path profiles. Kinematic constraints, the maximum velocity and acceleration, the dynamic constraint of the maximum torque applied to the arms and also the constraint of final point accuracy are discussed. For the optimization process, the Harmony Search (HS) method is used. To evaluate the effectiveness of the approach proposed, simulation studies are reviewed by considering a two-link flexible manipulator with the fixed base. The findings indicate that the proposed method is in power of dealing with nonlinear dynamics of the system. Furthermore, the results obtained by rigid, small and large deformation models are compared with each other.

Automated retina identification based on multiscale elastic registration

In this work we propose a novel method for identifying individuals based on retinal fundus image matching. The method is based on the image registration of retina blood vessels, since it is known that the retina vasculature of an individual is a signature, i.e., a distinctive pattern of the individual. The proposed image registration consists of a multiscale affine registration followed by a multiscale elastic registration. The major advantage of this particular two-step image registration procedure is that it is able to account for both rigid and non-rigid deformations either inherent to the retina tissues or as a result of the imaging process itself. Afterwards a decision identification measure, relying on a suitable normalized function, is defined to decide whether or not the pair of images belongs to the same individual. The method is tested on a data set of 21721 real pairs generated from a total of 946 retinal fundus images of 339 different individuals, consisting of patients followed in the context of different retinal diseases and also healthy patients. The evaluation of its performance reveals that it achieves a very low false rejection rate (FRR) at zero FAR (the false acceptance rate), equal to 0.084, as well as a low equal error rate (EER), equal to 0.053. Moreover, the tests performed by using only the multiscale affine registration, and discarding the multiscale elastic registration, clearly show the advantage of the proposed approach. The outcome of this study also indicates that the proposed method is reliable and competitive with other existing retinal identification methods, and forecasts its future appropriateness and applicability in real-life applications.

Deformable image registration for adaptive radiotherapy with guaranteed local rigidity constraints.

BackgroundDeformable image registration (DIR) is a key component in many radiotherapy applications. However, often resulting deformations are not satisfying, since varying deformation properties of different anatomical regions are not considered. To improve the plausibility of DIR in adaptive radiotherapy in the male pelvic area, this work integrates a local rigidity deformation model into a DIR algorithm.MethodsA DIR framework is extended by constraints, enforcing locally rigid deformation behavior for arbitrary delineated structures. The approach restricts those structures to rigid deformations, while surrounding tissue is still allowed to deform elastically. The algorithm is tested on ten CT/CBCT male pelvis datasets with active rigidity constraints on bones and prostate and compared to the Varian SmartAdapt deformable registration (VSA) on delineations of bladder, prostate and bones.ResultsThe approach with no rigid structures (REG0) obtains an average dice similarity coefficient (DSC) of 0.87 ± 0.06 and a Hausdorff-Distance (HD) of 8.74 ± 5.95 mm. The new approach with rigid bones (REG1) yields a DSC of 0.87 ± 0.07, HD 8.91 ± 5.89 mm. Rigid deformation of bones and prostate (REG2) obtains 0.87 ± 0.06, HD 8.73 ± 6.01 mm, while VSA yields a DSC of 0.86 ± 0.07, HD 10.22 ± 6.62 mm. No deformation grid foldings are observed for REG0 and REG1 in 7 of 10 cases; for REG2 in 8 of 10 cases, with no grid foldings in prostate, an average of 0.08 % in bladder (REG2: no foldings) and 0.01 % inside the body contour. VSA exhibits grid foldings in each case, with an average percentage of 1.81 % for prostate, 1.74 % for bladder and 0.12 % for the body contour. While REG1 and REG2 keep bones rigid, elastic bone deformations are observed with REG0 and VSA. An average runtime of 26.2 s was achieved with REG1; 31.1 s with REG2, compared to 10.5 s with REG0 and 10.7 s with VMS.ConclusionsWith accuracy in the range of VSA, the new approach with constraints delivers physically more plausible deformations in the pelvic area with guaranteed rigidity of arbitrary structures. Although the algorithm uses an advanced deformation model, clinically feasible runtimes are achieved.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-016-0697-4) contains supplementary material, which is available to authorized users.

Subspace Procrustes Analysis

Procrustes analysis (PA) has been a popular technique to align and build 2-D statistical models of shapes. Given a set of 2-D shapes PA is applied to remove rigid transformations. Later, a non-rigid 2-D model is computed by modeling the residual (e.g., PCA). Although PA has been widely used, it has several limitations for modeling 2-D shapes: occluded landmarks and missing data can result in local minima solutions, and there is no guarantee that the 2-D shapes provide a uniform sampling of the 3-D space of rotations for the object. To address previous issues, this paper proposes subspace PA (SPA). Given several instances of a 3-D object, SPA computes the mean and a 2-D subspace that can model rigid and non-rigid deformations of the 3-D object. We propose a discrete (DSPA) and continuous (CSPA) formulation for SPA, assuming that 3-D samples of an object are provided. DSPA extends the traditional PA, and produces unbiased 2-D models by uniformly sampling different views of the 3-D object. CSPA provides a continuous approach to uniformly sample the space of 3-D rotations, being more efficient in space and time. We illustrate the benefits of SPA in two different applications. First, SPA is used to learn 2-D face and body models from 3-D datasets. Experiments on the FaceWarehouse and CMU motion capture (MoCap) datasets show the benefits of our 2-D models against the state-of-the-art PA approaches and conventional 3-D models. Second, SPA learns an unbiased 2-D model from CMU MoCap dataset and it is used to estimate the human pose on the Leeds Sports dataset.

Sorted self-similarity for multi-modal image registration.

In medical image analysis, registration of multimodal images has been challenging due to the complex intensity relationship between images. Classical multi-modal registration approaches evaluate the degree of the alignment by measuring the statistical dependency of the intensity values between images to be aligned. Employing statistical similarity measures, such as mutual information, is not promising in those cases with complex and spatially dependent intensity relations. A new similarity measure is proposed based on the assessing the similarity of pixels within an image, based on the idea that similar structures in an image are more probable to undergo similar intensity transformations. The most significant pixel similarity values are considered to transmit the most significant self-similarity information. The proposed method is employed in a framework to register different modalities of real brain scans and the performance of the method is compared to the conventional multi-modal registration approach. Quantitative evaluation of the method demonstrates the better registration accuracy in both rigid and non-rigid deformations.

Increased rigidly triaxial deformations in neutron-rich Mo, Ru isotopes

Pairing-deformation-frequency self-consistent cranking Woods-Saxon model is employed to investigate the triaxiality in the ground states of the neutron-rich even-even Mo, Ru isotopes. Deformation evolutions and transition probabilities have been studied, giving the triaxial shapes in their ground states. The kinematic moments of inertia have been calculated to illustrate the gradually rigid deformation. To understand the origin of the asymmetry shape in this region, we analyze the evolution of single-particle orbits with changing $\gamma$ deformation. The present calculations reveal the importance of the triaxial deformation in describing not only static property, but also rotational behaviors in this mass region, providing significant probes into the shell structure around.

Postoperative Spine and Spinal Implants Instability as Complications of Treatment of the Rigid Scoliotical Deformation in Adult and Elderly Patients

Purpose The aim of this study was to assess the rate of complications of surgical treatment of rigid scoliotical deformation correction and stability of the fixation in adults and elderly. Material and Methods of Studies: A retrospective study of 60 patients (age 65 – 83 years) with rigid scoliotical deformation. Mean follow-up period was 5 years (2–8 years). Retrospectively we evaluated the deformation according to SRS-Schwab Based on HQROL Classification of Adult Deformity studying in all cases long cassette standing anteroposterior and lateral radiographs. Type L,A,L,P for 19 patients; type L,C,M,VP for 21 patients; type S,B,M,VP for 13 patients; type S,C,H,P and T,A,M,P for 7 patients equally. The main indications for surgery were static and biomechanical spinal disorders with pain (100%) and neurological syndrome (74.3%). All patients were divided into 2 groups based on the extent of surgical treatment and the severity of concomitant somatic pathology. The first group include 28 patients with high risk of cardiovascular complications who were undergone the correction of deformation by transpedicular screw fixation, multilevel SPO and TLIF. The second group include 32 patients with the correction of deformation by multilevel fixation, SPO, TLIF and PSO despite the possible risks of cardiovascular complications. Results and Discussion: In the first group in 13 cases we did not achieve a full postoperative restoration of the sagittal & coronal balance. In 6 patients the displacement of the screws was found in the postoperative period. In 5 cases the metal construction was broken. In 3 cases the terminal vertebras fractures with the displacement of the screws marked one year after the operation. These complications led to a loss of correction, which required a reoperation in all cases. In the second group a full restoration of the sagittal & coronal balance was achieved. In 1 case there was a screw migration due to osteoporosis. The rate of complications of the deformity correction in the first group was statistically significant higher than in the second group ( p < 0.01). Conclusions The study showed that the transpedicular fixation during the correction of a rigid deformation in patients requires the full restoration of sagittal balance. The surgical treatment of scoliotical deformation with PSO, TLIF and SPO showed an improvement of the long-term results. The aim of this study was to assess the rate of complications of surgical treatment of rigid scoliotical deformation correction and stability of the fixation in adults and elderly. A retrospective study of 60 patients (age 65 – 83 years) with rigid scoliotical deformation. The study showed that the transpedicular fixation during the correction of a rigid deformation in patients requires the full restoration of sagittal balance. The surgical treatment of scoliotical deformation with PSO, TLIF and SPO showed an improvement of the long-term results.

Study of Octupole Collectivity in $^{146}$Nd and $^{148}$Sm Using the New Coulomb Excitation Set-up at ALTO

For certain combinations of protons and neutrons in atomic nuclei, a rise of a reflection asymmetry is expected. Experimental E3 strengths, which as a function of the neutron number peak at around N approximate to 8 8 and N approximate to 1 3 4, indicate enhanced octupole correlations as predicted by theory. Low-energy Coulomb excitation is a highly successful method for establishing the evolution of nuclear shapes, through the measurement of cross sections, to populate excited states that can be directly related to the static and dynamic moments of the charge distribution of the nucleus. A Coulomb excitation experiment at the ALTO facility, Orsay was performed recently to study collective properties of Nd-146 and Sm-148. In particular, the strengths of the and matrix elements will provide a clear distinction between octupole vibration and rigid deformation.

Estimation method of rigid pavement deformation caused by a frost heave of subgrade

Estimation method of rigid pavement deformation caused by a frost heave of subgrade

Digital restoration of ancient color manuscripts from geometrically misaligned recto-verso pairs

Abstract We propose a fast automatic procedure for registration and restoration of images of recto-verso pairs of color manuscripts affected by bleed-through distortion. The registration algorithm assumes a rigid projective deformation of a side with respect to the other. The coefficients of the geometric transformation are computed from a large number of pairs of matching points, automatically detected by exploiting the estimates of local shifts between pairs of small patches. We validate the efficiency of the registration algorithm through the performance of a restoration method based on a model that relates each couple of corresponding pixels in the two images, and thus requiring a very accurate alignment of the two sides. The experiments show that this combined procedure of registration plus restoration can provide an excellent removal of the bleed-through pattern, while leaving unaltered the salient features of the original manuscript.

Phase transition in odd-N Pd-isotopes**Supported by Natural Science Foundation of Guangxi (2014jjBA10016, 2014jjDA10012) and National Natural Science Foundation of China (11465005)

Phase transition in odd-N isotopes 99,101,103Pd are investigated via the E-GOS (E-Gamma Over Spin) curves, which strongly suggest a structure evolution from vibration to rotation along the yrast lines with increasing spin. Theoretical calculations have been performed for the ground state bands of 99,101,103Pd in the framework of the cranked shell model (CSM) and the alignment properties observed experimentally are analyzed employing this model. The results show that the phase transition in the ground state bands of 99,101,103Pd can be interpreted as the valence nucleons start to occupy the g9/2 proton orbitals with increasing spin which would polarize the core to a small, but rigid quadrupole deformation.

Zdravljenje idiopatskega in kompleksnega prirojenega talipes ekvinovarusa z metodo po Ponsetiju

Abstract:Congenital idiopathic clubfoot is a deformity typically occurring in an otherwise healthy child which occurs in 11,4 in 10.000 live births. Approximately one-half of cases present with bilateral deformity and affects boys and girls equally. Clubfoot is characterized by adduction, supination and cavus deformity of the forefoot and midfoot, varus of the heel, and a fixed plantar flexion (equinus) of the ankle. Treatment od idiopathic type of clubfoot consists of corrective manipulation and casting by the Ponseti method, where usually four to six casts are needed. Equinus is corrected with tendo Achillis tenotomy followed by foot abduction brace application.Complex type of clubfoot, which has more severe rigid deformation, is present in 6,5% of all clubfeet and is refractory to the usual corrective manipulation and casting by the Ponsetti method. Clinically, complex clubfoot is characterized as short, stubby foot, having rigid equinus, severe adduction and plantar flexion of all metatarsals, a deep crease above the heel and a transverse crease in the sole of the foot. Modified Ponsetti method for treatment of complex clubfoot consists of simultaneus correction of adduction and heel varus and subsequent cavus and rigid equinus correction. After the Achillis tendon tenotomy, modified foot abduction brace is applied, where foot is in 40° outer rotation in contrast to 70° abduction used in less rigid congenital idiopathic clubfoot. Relapse occurs in 14% and is ussually related to problems with shoe fit and patient coplience.