Tilt Range Research Articles

Sampling limits for electron tomography with sparsity-exploiting reconstructions

Electron tomography (ET) has become a standard technique for 3D characterization of materials at the nano-scale. Traditional reconstruction algorithms such as weighted back projection suffer from disruptive artifacts with insufficient projections. Popularized by compressed sensing, sparsity-exploiting algorithms have been applied to experimental ET data and show promise for improving reconstruction quality or reducing the total beam dose applied to a specimen. Nevertheless, theoretical bounds for these methods have been less explored in the context of ET applications. Here, we perform numerical simulations to investigate performance of ℓ1-norm and total-variation (TV) minimization under various imaging conditions. From 36,100 different simulated structures, our results show specimens with more complex structures generally require more projections for exact reconstruction. However, once sufficient data is acquired, dividing the beam dose over more projections provides no improvements—analogous to the traditional dose-fraction theorem. Moreover, a limited tilt range of ±75° or less can result in distorting artifacts in sparsity-exploiting reconstructions. The influence of optimization parameters on reconstructions is also discussed.

Effect of Pelvic Tilt and Rotation on Cup Orientation in Both Supine and Standing Positions

BackgroundThe purpose of this study is to analyze the effect of pelvic tilt and rotation on radiographic measurement of cup orientation. MethodsA total of 68 patients (79 hips) were included in this study. The patients had a computed tomography study and approximately 3 months of postoperative standing anteroposterior pelvic radiographs in both supine and standing positions. We used 2-dimensional (2D)/3-dimensional (3D) matching to measure pelvic tilt and rotation, and cup orientation. ResultsThere was a wide range of pelvic tilt between individuals in both supine and standing positions. Supine pelvic tilt was different from standing pelvic tilt (P < .05). There were differences in cup anteversion before and after 2D/3D matching in both supine and standing positions (P < .05). Supine and standing pelvic tilt correlated with differences in cup anteversion before and after 2D/3D matching. When all 79 hips were separated into right and left side, pelvic rotation inversely correlated with the pelvic tilt-adjusted difference in anteversion before and after 2D/3D matching of the right side but directly correlated with that of the left side in both supine and standing positions. ConclusionThis study demonstrated that the measurement of cup anteversion on anteroposterior radiographs is significantly affected by both pelvic tilt and pelvic rotation (depending on the side). Improved understanding of pelvic orientation and improved ability to measure pelvic orientation may eventually allow for desired cup positioning to potentially protect against complications associated with malposition of the cup.

A Simple Preparation Method for Full-Range Electron Tomography of Nanoparticles and Fine Powders.

Electron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a "missing wedge" of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.

The Relationship between Prolonged Sitting Position and Adaptive Alterations in Lumbar Spine and Pelvic Range of Motion in Cyclists with Chronic Low Back Pain

Background: The majority of low back pain (LBP) problems in athletes are the result of stress induced by prolonged postures or repeated movements. Cycling is a sport that needs prolonged trunk flexion during the activity.& para;& para;Objective: To compare sagittal lumbar spine and sagittal pelvic tilt range of motion (ROM) between athletes with CLBP (chronic low back pain) who regularly ride bicycles and healthy controls without regular bicycle riding.& para;& para;Methods: Nineteen cyclists with CLBP and 20 asymptomatic non-cyclist athletes participated in the study, (mean age: 26.00 +/- 8.67 years). Sagittal lumbar spine and sagittal pelvic tilt range of motion (ROM) were measured during forward bending and backward return clinical tests using a three-dimensional motion capture system.& para;& para;Results: During forward bending. cyclists with CLBP demonstrated a limited anterior pelvic tilt angle (p = 0.03), compared to non-cyclists athletes. No significant differences were found in lumbar flexion angle between the groups during the test. During Backward return, cyclists with CLBP exhibited a limited posterior pelvic tilt angle (p = 0.02) and lumbar-extension range = 0.05). compared to non-cyclist athletes.& para;& para;Conclusions: A regular sitting position on the bicycle for a prolonged period may result in adaptations in sagittal lumbar and pelvic ROM which may contribute to the development of LBP.

The impact of core muscles training on the range of anterior pelvic tilt in subjects with increased stiffness of the hamstrings

The aim of this study is to verify the hypotheses that muscular coordination training of the core region in subjects showing increased hamstring stiffness results in an increase in anterior pelvic tilt and that there is a correlation between hamstring stiffness and anterior pelvic tilt. The two-group, non-blinded experimental controlled trial with three repeated measurements of the dependent variables. The experimental group received muscular coordination training during a period of two weeks, control group – no training. Thirty generally healthy subjects (9 women) were randomly assigned to the two equal groups. Passive knee extension test (hamstring stiffness); the range of anterior pelvic tilt (as measured in neutral standing position and during forward bending of the trunk). A significant decrease in the level of hamstring stiffness was recorded in the experimental group accompanied by an increase in anterior pelvic tilt. No significant changes were observed in the control group. There was a significant, negative, and moderate correlation between hamstring stiffness and anterior pelvic tilt with forward bending of the trunk).

A Three-Dimensional Study of Midfacial Changes Following Le Fort II Distraction With Zygomatic Repositioning in Syndromic Patients.

Le Fort II distraction with zygomatic repositioning introduced the ability to restore central midfacial height and convexity independent of changes in orbital morphology. This study analyzes midfacial and orbital morphology before and after Le Fort II distraction with zygomatic repositioning.All patients who underwent Le Fort II Distraction with zygomatic repositioning between 2013 and 2015 were included. Two- and 3-dimensional measurements were made using 3dMD Vultus software to assess canthal tilt, nasolabial angle, ratio of midfacial to lower facial height, and absolute change in nasal length. Presence of an open bite and Angle classification were assessed before and after surgery.Four patients underwent segmental midface advancement using Le Fort II distraction with zygomatic repositioning. Associated diagnoses included Apert syndrome, Goldenhar syndrome, and achondroplasia. Changes in facial dimensions included: 3.19° improvement in canthal tilt (range -4.7° to 8.4°), 9° change in nasolabial angle (range -1.0° to 19°), and 0.69 cm increase in absolute nasal length (range 0.2-0.94 cm). Mean ratio of midfacial to lower facial height was 0.79 preoperatively and 0.89 postoperatively. Preoperatively, all patients demonstrated Angle class III with 3 of 4 patients demonstrating anterior open bite. All achieved closure of open bite and demonstrated class I or II occlusion. No complications were observed.Le Fort II distraction with zygomatic repositioning resulted in normalization of midfacial soft tissue landmarks. This form of advancement demonstrates the ability to selectively improve midfacial height and canthal tilt while restoring normal occlusion.

The Effects of Coding Schemes on Vibrotactile Biofeedback for Dynamic Balance Training in Parkinson's Disease and Healthy Elderly Individuals.

Coding scheme for earlier versions of vibrotactile biofeedback systems for balance-related applications was primarily binary in nature, either on or off at a given threshold (range of postural tilt), making it unable to convey information about error magnitude. The purpose of this paper was to explore the effects of two coding schemes (binary versus continuous) for vibrotactile biofeedback during dynamic weight-shifting exercises that are common physical therapists' recommended balance exercises used in clinical settings. Nine individuals with idiopathic Parkinson's disease and nine healthy elderly individuals participated in this paper. All participants performed dynamic weight-shifting exercises assisted with either the binary or continuous vibrotactile biofeedback delivered using with vibrating actuators (tactors) in either the anterior-posterior or medial-lateral direction. Participants' limits of stability at pre and post exercises were compared to evaluate the effects of the exercises on their range of motion. The continuous coding scheme produced significantly better performance than the binary scheme when both groups were performing dynamic weight-shifting balance exercises with assistive vibrotactile biofeedback. The results have implications in terms of maximizing the effects of error-driven motor learning and increasing performance on balance rehabilitation training combined with vibrotactile biofeedback.

Effects of Slipper Features and Properties on Walking and Sit-to-Stand Tasks of Older Women.

Indoor slippers with a strap across the dorsal forefoot are popular with older women. However, their influence on the foot motion has not been reported. This study evaluated the range of movement in the knee and ankle joints during walking and changes in trunk displacement during sit-to-stand when 10 healthy older women wore two types of slippers and were barefoot. Compared to barefeet, walking in slippers results in significant increases in the knee flexion angle in the swing phase. However, there is nonsignificant differences in the ankle angle in any phase across all conditions. During the sit-stand transition when slippers are worn, there is a significant reduction in the peak trunk tilt angle and range, as well as the duration of the weight shift when motion is initiated. The findings therefore provide a better understanding of slipper features and designs associated with changes in foot kinematics in older women.

Stereo-vision three-dimensional reconstruction of curvilinear structures imaged with a TEM

Deriving accurate three-dimensional (3-D) structural information of materials at the nanometre level is often crucial for understanding their properties. Tomography in transmission electron microscopy (TEM) is a powerful technique that provides such information. It is however demanding and sometimes inapplicable, as it requires the acquisition of multiple images within a large tilt arc and hence prolonged exposure to electrons. In some cases, prior knowledge about the structure can tremendously simplify the 3-D reconstruction if incorporated adequately. Here, a novel algorithm is presented that is able to produce a full 3-D reconstruction of curvilinear structures from stereo pair of TEM images acquired within a small tilt range that spans from only a few to tens of degrees. Reliability of the algorithm is demonstrated through reconstruction of a model 3-D object from its simulated projections, and is compared with that of conventional tomography. This method is experimentally demonstrated for the 3-D visualization of dislocation arrangements in a deformed metallic micro-pillar.

Sagittal spino-pelvic alignment in rapidly destructive coxarthrosis.

To investigate the sagittal spino-pelvic alignment (SSPA) in patients with rapidly destructive coxarthrosis (RDC). SSPA was investigated in 44 patients with RDC and 70 patients with hip osteoarthritis (HOA). The study included only female patients over the age of 70years because epidemiological reports indicate that RDC most commonly occurs in this group of patients. The SSPA parameters that were analyzed included lumbar lordosis (LL), lumbar range of motion (ΔLL), sacral slope (SS), pelvic incidence (PI), and pelvic tilt (PT). The pelvic inclination angle (PIA) in the supine position and the change in the PIA from the supine to the standing position (ΔPIA) were measured using anteroposterior pelvic radiographs. The values of these parameters were compared between the two groups. The levels of the SRS-Schwab classification modifiers were used to investigate the degree of sagittal malalignment. The RDC group showed significant lower LL, ΔLL and SS values, and significantly higher PT and ΔPIA values than the HOA group (P<0.01). With regard to the sagittal modifiers in the SRS-Schwab classifications of the patients, the PI-LL and PT levels of the RDC group were significantly worse than those in the HOA group (P<0.01). The present study suggests that the static factors of a reduction in the lumbar lordotic angle and greater posterior pelvic tilt, the dynamic factors of small ΔLL values and large ΔPIA values and the complex interaction of these two types of factors, may play important roles in the development of RDC.

Comparison of 2 Dosages of Stretching Treatment in Infants with Congenital Muscular Torticollis: A Randomized Trial.

To compare the short-term efficacy of 2 dosages of stretching treatment on the clinical outcomes in infants with congenital muscular torticollis. This was a prospective randomized controlled study. Fifty infants with congenital muscular torticollis who were randomly assigned to 100-times stretching group and 50-times stretching group received stretching treatment for the affected sternocleidomastoid muscle. The outcomes including the head tilt, the cervical passive range of motion, and the muscle function of cervical lateral flexors determined by the muscle function scale were assessed at baseline and at 4 and 8 weeks after treatment. The sternocleidomastoid muscle growth analyzed by the thickness ratio of sternocleidomastoid muscles was measured using ultrasonography at baseline and 8 weeks after treatment. Except the ratio of muscle function scale scores, the postintervention outcomes were all significantly improved in both groups compared with baseline (P < 0.05). The 100-times stretching group showed greater improvement compared with 50-times stretching group in head tilt and cervical passive range of motion at 4 and 8 weeks after treatment (P < 0.05). Stretching treatment of 2 dosages may effectively improve head tilt, cervical passive range of motion, and sternocleidomastoid muscle growth in infants with congenital muscular torticollis. The stretching treatment of 100 times per day is likely to associate with greater improvement in head tilt and cervical passive range of motion.

Use of Acellular Dermal Matrix in Treatment of Congenital Muscular Torticollis in Patients Over Eight Years of Age.

Treatment for neglected or recurred congenital muscular torticollis should be differentiated from primary patients due to the long-standing adjacent tissue contracture. The aim of this study was to evaluate the effect of acellular dermal matrix (ADM) on surgery of recurred and neglected patients of congenital muscular torticollis. Forty-nine patients were included in the study. All patients underwent resection at the distal end of the sternocleidomastoid muscle. In the study group of 18 patients (ADM group), the defect caused by myectomy and scar tissue removal was covered with ADM. Passive range of neck motion, head tilt, cosmetic and functional satisfaction, and scar was evaluated and compared with the control group of 31 patients (non-ADM group) during follow-up. Logistic and linear regression analyses with adjustment by propensity score were performed to determine the association between ADM implantation and postoperative variables. The mean follow-up period was 18.8 months. No patient required further operation for recurrence during follow-up. The improvement of neck motion in ADM group was significantly superior to non-ADM group at the 1-year follow-up, and the overall assessment score was significantly higher in the ADM group. Acellular dermal matrix implantation was not associated with increased discharge of total drain. In patients over 8 years of age with recurred or neglected congenital muscular torticollis, use of dermal substitute to fill the defect caused by torticollis release is effective in achieving satisfactory neck motion. Surgical sectioning of the sternocleidomastoid muscle and ADM graft should be considered in recurred and neglected torticollis.

SURGICAL TREATMENT OF CONGENITAL TORTICOLLIS, AT THE SHRINERS HOSPITAL, MEXICO CITY

ABSTRACT Objective: This study aims to evaluate the outcome of surgical treatment of congenital torticollis in our hospital. Methods: We collected the medical records of all patients diagnosed with congenital torticollis in the last 3 years at Shriners Hospital, Mexico City. The cases of congenital torticollis treated with surgery were selected and we evaluated the type of surgical technique, bleeding, time of surgery and complications, as well as the associated diagnoses of hip dysplasia. Results: We found 11 patients, of whom 7 met the inclusion criteria. Three women and four men with mean age of 10.7 years, five of whom had right, and two left side affections. All were surgically treated, five with unipolar and two with bipolar release. The surgery time was similar in both techniques and no complications were found in any of the groups. In two cases there were associated diagnoses, Klippel-Feil syndrome and congenital talipes equinovarus (CTEV) in one and psychomotor retardation in another. No association was found with hip dysplasia. All patients had improved range of movement and head tilt. There were no complications related to the surgical procedure or need for reintervention in our patients. Conclusions: Surgical treatment of congenital torticollis by uni- or bipolar release is an effective and safe method for these patients, presenting aesthetic and functional benefits.

Automated discrete electron tomography – Towards routine high-fidelity reconstruction of nanomaterials

Electron tomography is an essential imaging technique for the investigation of morphology and 3D structure of nanomaterials. This method, however, suffers from well-known missing wedge artifacts due to a restricted tilt range, which limits the objectiveness, repeatability and efficiency of quantitative structural analysis. Discrete tomography represents one of the promising reconstruction techniques for materials science, potentially capable of delivering higher fidelity reconstructions by exploiting the prior knowledge of the limited number of material compositions in a specimen. However, the application of discrete tomography to practical datasets remains a difficult task due to the underlying challenging mathematical problem. In practice, it is often hard to obtain consistent reconstructions from experimental datasets. In addition, numerous parameters need to be tuned manually, which can lead to bias and non-repeatability. In this paper, we present the application of a new iterative reconstruction technique, named TVR-DART, for discrete electron tomography. The technique is capable of consistently delivering reconstructions with significantly reduced missing wedge artifacts for a variety of challenging data and imaging conditions, and can automatically estimate its key parameters. We describe the principles of the technique and apply it to datasets from three different types of samples acquired under diverse imaging modes. By further reducing the available tilt range and number of projections, we show that the proposed technique can still produce consistent reconstructions with minimized missing wedge artifacts. This new development promises to provide the electron microscopy community with an easy-to-use and robust tool for high-fidelity 3D characterization of nanomaterials.

Three-dimensional atomic models from a single projection using Z-contrast imaging: verification by electron tomography and opportunities.

In order to fully exploit structure-property relations of nanomaterials, three-dimensional (3D) characterization at the atomic scale is often required. In recent years, the resolution of electron tomography has reached the atomic scale. However, such tomography typically requires several projection images demanding substantial electron dose. A newly developed alternative circumvents this by counting the number of atoms across a single projection. These atom counts can be used to create an initial atomic model with which an energy minimization can be applied to obtain a relaxed 3D reconstruction of the nanoparticle. Here, we compare, at the atomic scale, this single projection reconstruction approach with tomography and find an excellent agreement. This new approach allows for the characterization of beam-sensitive materials or where the acquisition of a tilt series is impossible. As an example, the utility is illustrated by the 3D atomic scale characterization of a nanodumbbell on an in situ heating holder of limited tilt range.

How precise can atoms of a nanocluster be located in 3D using a tilt series of scanning transmission electron microscopy images?

In this paper, we investigate how precise atoms of a small nanocluster can ultimately be located in three dimensions (3D) from a tilt series of images acquired using annular dark field (ADF) scanning transmission electron microscopy (STEM). Therefore, we derive an expression for the statistical precision with which the 3D atomic position coordinates can be estimated in a quantitative analysis. Evaluating this statistical precision as a function of the microscope settings also allows us to derive the optimal experimental design. In this manner, the optimal angular tilt range, required electron dose, optimal detector angles, and number of projection images can be determined.

Effect of pelvic tilt exercise using pressure-based visual biofeedback training on the gait parameter in elderly patients with Alzheimer's disease

BackgroundGait and balance characteristics often appear altered in older adults with Alzheimer's disease (AD). However, no studies have examined the effects of pelvic tilt exercise on improvement in gait disturbances and pelvic tilt in older adults with AD. This study investigated the effect of pelvic tilt exercise using pressure-based visual biofeedback training (PVFT) on the gait and balance of older adults with AD. MethodsA total of 15 older adults with AD participated in the study. Subjects performed the pelvic tilt exercise using PVFT during the 4-week intervention that we had developed for training. At baseline and after the 4-week intervention, gait analysis was measured using the GAITRite system, and the pelvic tilt range was measured using a palpation meter (PALM). The Berg balance scale (BBS) was assessed at baseline and after the 4-week intervention program. The mean values of the gait parameters, the pelvic tilt range at baseline and after the 4-week intervention conditions were analyzed by paired t-test. ResultsSignificant differences (P<0.05) of mean values were found in the gait speed, stride length (left and right), pelvic tilt range and BBS scores after the 4-week intervention compared with baseline. ConclusionsOverall, the pelvic tilt exercise using PVFT improved gait speed, stride length, and pelvic tilt range after the intervention. These findings suggest that the pelvic tilt exercise with PVFT can be an effective training method with specific and simple techniques for improving gait disturbances in older adults with AD.

Movements Indicate Threat Response Phases in Children at Risk for Anxiety.

Temporal phases of threat response, including potential threat (anxiety), acute threat (startle, fear), and post-threat response modulation, have been identified as the underlying markers of anxiety disorders. Objective measures of response during these phases may help identify children at risk for anxiety; however, the complexity of current assessment techniques prevent their adoption in many research and clinical contexts. We propose an alternative technology, an inertial measurement unit (IMU), that enables noninvasive measurement of the movements associated with threat response, and test its ability to detect threat response phases in young children at a heightened risk for developing anxiety. We quantified the motion of 18 children (3-7 years old) during an anxiety-/fear-provoking behavioral task using an IMU. Specifically, measurements from a single IMU secured to the child's waist were used to extract root-mean-square acceleration and angular velocity in the horizontal and vertical directions, and tilt and yaw range of motion during each threat response phase. IMU measurements detected expected differences in child motion by threat phase. Additionally, potential threat motion was positively correlated to familial anxiety risk, startle range of motion was positively correlated with child internalizing symptoms, and response modulation motion was negatively correlated to familial anxiety risk. Results suggest differential theory-driven threat response phases and support previous literature connecting maternal child risk to anxiety with behavioral measures using more feasible objective methods. This is the first study demonstrating the utility of an IMU for characterizing the motion of young children to mark the phases of threat response modulation. The technique provides a novel and objective measure of threat response for mental health researchers.

Inversion of Dynamical Scattering from Large-Angle Rocking-Beam Electron Diffraction Patterns.

A method for abinitio structure factor retrieval from large-angle rocking-beam electron diffraction data of thin crystals is described and tested with experimental and simulated data. No additional information, such as atomicity or information about chemical composition, has been made use of. Our numerical experiments show that the inversion of dynamical scattering works best, if the beam tilt range is large and the specimen not too thick, because for moderate multiple scattering, the large tilt amplitude effectively removes local minima in this global optimization problem.

Hamstring muscle length and pelvic tilt range among individuals with and without low back pain

Hamstring tightness has been documented not to be related to the pelvic tilt position during static standing posture, but there is limited data on the relationship between hamstring muscle length (HML) and pelvic tilt range (PTR) during the dynamic movement of forward bending. This ex-post facto study was designed to compare each of HML and PTR in individuals with low back pain (LBP) and counterparts without LBP, and the relationship between HML and PTR in individuals with and without LBP. The study involved 30 purposively recruited individuals with LBP and 30 height and weight-matched individuals without LBP. Participants' PTR and HML were assessed using digital inclinometer and active knee extension test respectively. Data were analyzed using t-test and Pearson Correlation (r) at α=0.05. Participants without LBP had significantly longer (p=0.01) HML than those with LBP but the PTR of both groups were not significantly different. HML and PTR had indirect but not significant correlations in participants with and without LBP. Hamstring muscle length is significantly reduced in individuals with LBP but it has no significant correlation with pelvic tilt range. Pelvic tilt range reduces as hamstring muscle length increases.