RMS Distance Research Articles

An exclusionary screening method based on 3D morphometric features to sort commingled atlases and axes

In forensic commingled contexts, when the disarticulation occurs uniquely at the atlantoaxial joint, the correct match of atlas and axis may lead to the desirable assembly of the entire body. Notwithstanding the importance of this joint in such scenarios, no study has so far explored three-dimensional (3D) methodologies to match these two adjoining bones. In the present study, we investigated the potential of re-associating atlas and axis through 3D–3D superimposition by testing their articular surfaces congruency in terms of point-to-point distance (Root Mean Square, RMS). We analysed vertebrae either from the same individual (match) and from different individuals (mismatch). The RMS distance values were assessed for both groups (matches and mismatches) and a threshold value was determined to discriminate matches with a sensitivity of 100%. The atlas and the corresponding axis from 41 documented skeletons (18 males and 23 females), in addition to unpaired elements (the atlas or the axis) from 5 individuals, were superimposed, resulting in 41 matches and 1851 mismatches (joining and non-joining elements). No sex-related significant differences were found in matches and mismatches (p = 0.270 and p = 0.210, respectively), allowing to pool together the two sexes in each group. RMS values ranged between 0.41 to 0.77 mm for matches and between 0.37 and 2.18 mm for mismatches. Significant differences were found comparing the two groups (p < 0.001) and the highest RMS of matches (0.77 mm) was used as the discriminative value that provided a sensitivity of 100% and a specificity of 41%. In conclusion, the 3D–3D superimposition of the atlanto-axial articular facets cannot be considered as a re-association method per se, but rather as a screening one. However, further research on the validation of the 3D approach and on its application to other joints might provide clues to the complex topic of the reassociation of crucial adjoining bones.

What Is the Role of Sustained Visual Attention in the Maintenance of Postural Control in Young Adults?

Dual tasks requiring sustained visual attention and upright stance are common, yet their impact on standing balance is not well understood. We investigated the role of visual attention in the maintenance of postural control, using the multiple-object tracking (MOT) task. Healthy young adults (n = 12) performed the MOT task at three object movement speeds while seated or standing. MOT performance was assessed using tracking capacity (k). Metrics calculated to assess mediolateral (ML) and anterior-posterior (AP) postural control included: maximum difference between CoM and CoP position (CoM-CoP Max), root mean square distance for center of pressure and center of mass position (CoP and CoM RMS distance), and correlation between CoM and CoP time series signals (CoM/CoP correlation). As predicted, k decreased significantly as object movement speed increased for both standing and seated conditions. Object movement speed also significantly affected AP CoM-CoP Max in seated conditions (p = .021) and AP CoM/CoP correlation for standing conditions (p = .002). The results demonstrate utility of the MOT task in understanding the role of visual attention in postural control, even though healthy young adults were able to compensate for the addition of a sustained visual attention task, with minimal deficits to postural control.

Characterization of Regional Morphological Changes in Sagittal Craniosynostosis Following Endoscopic Strip Craniectomy With Post-operative Helmeting: Predictors for Success.

Sagittal craniosynostosis (SC) restricts craniofacial growth perpendicular to the sagittal plane resulting in scaphocephaly. The cranium grows in the anterior-posterior dimension causing disproportionate changes, which can be corrected with either cranial vault reconstruction (CVR) or endoscopic strip craniectomy (ESC) combined with post-operative helmet therapy. ESC is performed at an earlier age, and studies demonstrate benefits in risk profile and morbidity compared to CVR, with comparable results if the post-operative banding protocol is strictly upheld. We aim to identify predictors of successful outcome and, using three-dimensional (3D) imaging, assess cranial changes following ESC with post-banding therapy. A single institution retrospective review was performed from 2015-19 for patients with SC who underwent ESC. Patients received immediate post-operative 3D photogrammetry for helmet therapy planning and implementation as well as post-therapy 3D imaging. Using these 3D images, the cephalic index (CI) for study patients was calculated before and after helmet therapy. In addition, Deformetrica™ was used to measure volume and shape changes of pre-defined anatomic skull regions (frontal, parietal, temporal, & occipital) based on the pre- and post-therapy 3D imaging results. Fourteen institutional raters evaluated the pre- and post-therapy 3D imaging in order to determine the success of the helmeting therapy. Twenty-one SC patients met our inclusion criteria. Using 3D photogrammetry, 14 raters at our institution rated 16 of the 21 patients to have had successful helmet therapy. There was a significant difference in CI following helmet therapy with both groups, but there was no significant difference in CI between the "successful" and "unsuccessful" groups. Furthermore, the comparative analysis demonstrated that the parietal region had a significantly higher change in mean RMS distance when compared to the frontal or occipital regions. For patients with SC, 3D photogrammetry may be able to objectively recognize nuanced findings not readily detectable when using CI alone. The greatest changes in volume were observed in the parietal region, which falls in line with treatment goals for SC. Patients deemed to have unsuccessful outcomes were found to be older at time of surgery and initiation of helmet therapy. This suggests that early diagnosis and management for SC may increase the likelihood of success.

Roughening of two-dimensional interfaces in nonequilibrium phase-separated systems.

I show that nonequilibrium two-dimensional interfaces between three-dimensional phase separated fluids exhibit a peculiar "sublogarithmic" roughness. Specifically, an interface of lateral extent L will fluctuate vertically (i.e., normal to the mean surface orientation) a typical rms distance w≡sqrt[〈|h(r,t)|^{2}〉]∝[ln(L/a)]^{1/3} [where a is a microscopic length, and h(r,t) is the height of the interface at two-dimensional position r at time t]. In contrast, the roughness of equilibrium two-dimensional interfaces between three-dimensional fluids, obeys w∝[ln(L/a)]^{1/2}. The exponent 1/3 for the active case is exact. In addition, the characteristic timescales τ(L) in the active case scale according to τ(L)∝L^{3}[ln(L/a)]^{1/3}, in contrast to the simple τ(L)∝L^{3} scaling found in equilibrium systems with conserved densities and no fluid flow.

Polar Coordinate for Damage Imaging of Adhesively Bonded Plates Using Ultrasonic Guided Waves and Laser Doppler Vibrometer Measurements

Wavefield measurements by a scanning laser Doppler vibrometer are generally carried out in a cartesian coordinate. As a piezoelectric transducer generates Lamb waves following radial paths, the use of a polar coordinate can be a suitable alternative to the use of a cartesian coordinate. Therefore, in the proposed method, using a single transducer placed on the center of the specimen, the measured wavefields are transformed into polar coordinates, making several identical radial line inspections from the center in a direction of incident waves. Taking advantage of the properties of the polar coordinates, a signal processing technique is proposed through a frequency-wavenumber filtering process in these coordinates. In this technique, by using proper filters, unwanted wave modes of the incident wave along with all reflected waves are filtered out. In addition, the conventional features of RMS and Euclidean distance are adapted for the polar coordinate system to image the bonded plate. The proposed signal processing and damage imaging are first introduced through a numerical simulation. Then, the performance of the proposed technique is presented by experimental measurements of two specimens including adhesively bonded carbon fiber-reinforced plastic composite plates and bonded aluminum plates.

3D-3D Superimposition of Pubic Bones: Expanding the Anthropological Toolkit for the Pair-Matching of Commingled Skeletal Remains.

Virtual anthropology (VA) has recently produced an additional tool for the analysis of commingled remains and is based on the distance analysis between three-dimensional (3D) models of bones. To date, the pair-matching of the innominate bone through a 3D approach remains partially unexplored. Here, 44 abdominal CT scans (22 males and 22 females) were selected from a hospital database, and the pubic bones were segmented through ITK-SNAP software. The models were hollowed with Viewbox4 to minimize the amount of trabecular bone. The left pubic bones were mirrored and superimposed on the right ones, according to the smallest point-to-point difference between the two surfaces through VAM software. RMS distances between models were calculated through VAM, producing RMS values for 20 matches and 420 mismatches for each sex group. Differences in RMS distance values between matches and mismatches were investigated through Mann−Whitney tests (p < 0.05); the repeatability of the procedure was assessed through absolute and relative technical error measurement (TEM and rTEM). RMS distance values of matches and mismatches were significantly different (p < 0.01) in both groups. The method yielded optimal results with high sensitivity (100.0%) and specificity (99.8% in males, 98.8% in females) rates according to the chosen threshold. This project contributes to the research field of VA with a valuable adjunct that may bolster and strengthen the results of the current visual and osteometric methods through a multidisciplinary approach.

Can uncertainty estimation predict segmentation performance in ultrasound bone imaging?

Segmenting bone surfaces in ultrasound (US) is a fundamental step in US-based computer-assisted orthopaedic surgeries. Neural network-based segmentation techniques are a natural choice for this, given promising results in related tasks. However, to gain widespread use, we must be able to know how much to trust segmentation networks during clinical deployment when ground-truth data is unavailable. We investigated alternative ways to measure the uncertainty of trained networks by implementing a baseline U-Net trained on a large dataset, together with three uncertainty estimation modifications: Monte Carlo dropout, test time augmentation, and ensemble learning. We measured the segmentation performance, calibration quality, and the ability to predict segmentation performance on test data. We further investigated the effect of data quality on these measures. Overall, we found that ensemble learning with binary cross-entropy (BCE) loss achieved the best segmentation performance (mean Dice: 0.75-0.78 and RMS distance: 0.62-0.86mm) and the lowest calibration errors (mean: 0.22-0.28%). In contrast to previous studies of area or volumetric segmentation, we found that the resulting uncertainty measures are not reliable proxies for surface segmentation performance. Our experiments indicate that a significant performance and confidence calibration boost can be achieved with ensemble learning and BCE loss, as tested on 13,687 US images containing various anatomies and imaging parameters. However, these techniques do not allow us to reliably predict future segmentation performance. The results of this study can be used to improve the calibration and performance of US segmentation networks.

Validating 3D face morphing towards improving pre-operative planning in facial reconstruction surgery

ABSTRACT Pre-traumatic/pathologic 3D facial imaging is rarely available to guide craniofacial reconstruction. This study aims to independently validate the regional accuracy of a 3D morphable model to estimate face shapes from 2D photographs for craniofacial surgical planning. 3D shape estimates were generated using the Basel Face Model (BFM 2017) from 2D photographs of 100 multi-racial subjects in the Binghamton University 3D Facial Expression database. Accuracy was evaluated by the per-vertex Euclidean distance between the shape estimate and the true 3D scan within defined facial regions. The 3D estimates’ average RMS distance error across all facial regions was 2.68 ± 0.97 mm, based on photos analysed with 10,000 iterations. The eyes, cheek, chin, forehead and mouth regions fit within ~2.5 mm from the true face shape, representing only marginal perceptible error. The nose and temple regions had lower accuracy (~3.1 mm) for all subjects. Significant differences in the nose region were dependent on race (Caucasian: 2.4 mm, East-Asian: 4.8 mm) and sex (Male: 2.5 mm, Female: 3.6 mm). On average, 3D face shape estimates using the BFM yielded clinically acceptable accuracy sufficient for use in planning to guide several craniofacial reconstruction regions. However, in individual cases, considerable errors exceeded clinical limits.

Solving the Seismic Inverse Problem Using an Ensemble of Models: A Case Study of Inversion of Receiver Functions

This paper proposes a new method for determining the seismic parameters of the subsurface below a seismic station using the waveforms of converted waves. The subsurface below the seismic station is represented by a plane-layered model. In contrast to other methods, the new approach does not involve determining all the elastic parameters of each of the layers. Instead, it is proposed to use a combination of parameters related directly to the object under study. In our case, we estimate the depth dependencies of the seismic velocity and density. The quality of solutions is assessed based on the rms distance between the observed waveforms and the seismograms derived from the averaged depth dependences of the seismic parameters. The approach proposed is applicable to a wide range of inverse problems in geophysics.

Contribution to the classification of small catchments according to the drainage area

ABSTRACT The adoption of an area value to define large, medium or small river basins should take into account the hydrological processes involved in the basin. Changes in runoff are identified with greater sensitivity in small catchments, as in large catchments it is not possible to disregard factors such as infiltration and evaporation, which directly interfere with the rainfall-runoff conversion phenomenon. Thus, the objective of this study is to classify the small catchments of the Amazon Region by drainage area using a simple linear model (SLM). The SLM is based on a linear and time-invariant system that establishes a cause-and-effect relationship between the data. The model was applied to rainfall and runoff data from test catchments to verify the linearity between these variables. The performance of the model was evaluated through the Root Mean Square Error (RMS) and metric distance . The results indicated that in the catchments with drainage areas less than to 500 km², the adjustment between the observed and simulated flow was good, presenting RMS and metric distance values less than 3 m³/s and 2000, respectively. In basins of the dimensions above 500 km², the RMS and results began to show nonlinearity from 4 m³/s and 3000, respectively, showing that SLM should not be applied to medium and large river basins. Thus, the small catchments of the Amazon were classified as drainage areas less than 500 km².

Map segmentation, automated model-building and their application to the Cryo-EM Model Challenge.

A recently-developed method for identifying a compact, contiguous region representing the unique part of a density map was applied to 218 Cryo-EM maps with resolutions of 4.5 Å or better. The key elements of the segmentation procedure are (1) identification of all regions of density above a threshold and (2) choice of a unique set of these regions, taking symmetry into consideration, that maximize connectivity and compactness. This segmentation approach was then combined with tools for automated map sharpening and model-building to generate models for the 12 maps in the 2016 Cryo-EM Model Challenge in a fully automated manner. The resulting models have completeness from 24% to 82% and RMS distances from reference interpretations of 0.6 Å-2.1 Å.

Analysis of Ranging Precision in an FMCW Radar Measurement Using a Phase-Locked Loop

The standard deviation in a frequency modulated continuous wave radar distance measurement using a charge pump phase-locked loop (PLL) is calculated analytically. The phase noise of the PLL is modeled as an Ornstein-Uhlenbeck process resulting in a Lorentzian spectrum. We calculate the distance error as a function of the receiver noise bandwidth and the target distance. Depending on the frequency estimation algorithm and the target distance, the rms distance error due to PLL phase noise increases by about 6-9 dB with doubling the target distance. By contrast, the white noise in the radar receiver raises the distance error by about 12 dB in the far field with distance doubling, making this error contribution dominant for large target distances. These findings are verified by measurements on a scalable 61/122-GHz radar sensor platform.

Are Portable Stereophotogrammetric Devices Reliable in Facial Imaging? A Validation Study of VECTRA H1 Device

Modern 3-dimensional (3D) image acquisition systems represent a crucial technologic development in facial anatomy because of their accuracy and precision. The recently introduced portable devices can improve facial databases by increasing the number of applications. In the present study, the VECTRA H1 portable stereophotogrammetric device was validated to verify its applicability to 3D facial analysis. Fifty volunteers underwent 4 facial scans using portable VECTRA H1 and static VECTRA M3 devices (2 for each instrument). Repeatability of linear, angular, surface area, and volume measurements was verified within the device and between devices using the Bland-Altman test and the calculation of absolute and relative technical errors of measurement (TEM and rTEM, respectively). In addition, the 2 scans obtained by the same device and the 2 scans obtained by different devices were registered and superimposed to calculate the root mean square (RMS; point-to-point) distance between the 2 surfaces. Most linear, angular, and surface area measurements had high repeatability in M3 versus M3, H1 versus H1, and M3 versus H1 comparisons (range, 82.2 to 98.7%; TEM range, 0.3 to 2.0mm, 0.4° to 1.8°; rTEM range, 0.2 to 3.1%). In contrast, volumes and RMS distances showed evident differences in M3 versus M3 and H1 versus H1 comparisons and reached the maximum when scans from the 2 different devices were compared. The portable VECTRA H1 device proved reliable for assessing linear measurements, angles, and surface areas; conversely, the influence of involuntary facial movements on volumes and RMS distances was more important compared with the static device.

Partial-Matching RMS Distance Under Translation: Combinatorics and Algorithms

We consider the problem of minimizing the RMS distance (sum of squared distances between pairs of points) under translation between two point sets A and B, in the plane, with $$m=|B|\ll n=|A|$$ , in the partial-matching setup, in which each point in B is matched to a distinct point in A. Although the problem is not known to be polynomial, we establish several structural properties of the underlying subdivision $${\mathcal {D}}_{B,A}$$ of the plane and derive improved bounds on its complexity. Specifically, we show that this complexity is $$O(n^2m^{3.5} (e \ln m+e)^m)$$ , so it is only quadratic in |A|. These results lead to the best known algorithm for finding a translation for which the partial-matching RMS distance between the point sets is minimized. In addition, we show how to compute a local minimum of the partial-matching RMS distance under translation, in polynomial time.

2D/3D reconstruction of the distal femur using statistical shape models addressing personalized surgical instruments in knee arthroplasty: A feasibility analysis.

Personalized surgical instruments (PSI) have gained success in the domain of total knee replacement, demonstrating clinical outcomes similar or even superior to both traditional and navigated surgeries. The key requirement for prototyping PSI is the availability of the digital bony surface. In this paper, we aim at verifying whether the 2D/3D reconstruction of the distal femur, based on statistical shape models (SSM), grants sufficient accuracy, especially in the condylar regions, to support a PSI technique. Computed tomographic knee datasets acquired on 100 patients with severe cartilage damage were retrospectively considered in this work. All the patients underwent total knee replacement using the PSI-based surgical technique. Eighty out of 100 reconstructed distal femur surfaces were used to build the statistical model. The remaining 20 surfaces were used for testing. The 2D/3D reconstruction process was based on digital reconstructed radiographies (DRRs) obtained with a simulated X-ray projection process. An iterative optimization procedure, based on an evolutionary algorithm, systematically morphed the statistical model to decrease the difference between the DRR, obtained by the original CT dataset, and the DRR obtained from the morphed surface. Over the 80 variations, the first ten modes were found sufficient to reconstruct the distal femur surface with accuracy. Using three DRR, the maximum Hausdorff and RMS distance errors were lower than 1.50 and 0.75mm, respectively. As expected, the reconstruction quality improved by increasing the number of DRRs. Statistical difference (P<0.001) was found in the 2 vs 3, 2 vs 4 and 2 vs 5 DRR, thus proving that adding just a single displaced projection to the two traditional sagittal and coronal X-ray images improved significantly the reconstruction quality. The effect of the PSI contact area errors on the distal cut direction featured a maximum median error lower than 2° and 0.5° on the sagittal and frontal plane, respectively. Statistical difference was found (P<0.0001) in the reconstruction accuracy when comparing SSM built using pathologic with respect to non-pathologic shapes (cadavers), meaning that, to improve the patient-specific reconstruction, the morphologic anomalies, specific to the pathology, must be embedded into the SSM. We showed that the X-ray based reconstruction of the distal femur is reasonable also in presence of pathologic bony conditions, featuring accuracy results similar to earlier reports in the literature that reconstructed normal femurs. This finding discloses the chance of applying the proposed methodology to the reconstruction of bony surfaces used in the PSI surgical approach.

Image-based Registration for a Neurosurgical Robot: Comparison Using Iterative Closest Point and Coherent Point Drift Algorithms

Stereotactic neurosurgical robots allow quick, accurate location of small targets within the brain, relying on accurate registration of pre-operative MRI/CT images with patient and robot coordinate systems during surgery. Fiducial markers or a stereotactic frame are used as registration landmarks; the patient's head is fixed in position throughout surgery. An image-based system could be quicker and less invasive, allowing the head to be moved during surgery to give greater ease of access, but would be required to retain a surgical precision of ∼1mm at the target point.We compare two registration algorithms, iterative closest point (ICP) and coherent point drift (CPD), by registering ideal point clouds taken from MRI data with re-meshed, noisy and smoothed versions. We find that ICP generally gives better and more consistent registration accuracy for the region of interest than CPD, with a best RMS distance of 0.884±0.050mm between aligned point clouds, as compared to 0.995±0.170mm or worse for CPD.

Center-of-pressure based postural sway measures: Reliability and ability to distinguish between age, fear of falling and fall history

The purpose of this study was to compare the test-retest reliability of a wide variety of center-of-pressure (CoP) based postural sway measures and their ability to detect the differences between the young and older groups (age comparison), between the older low- and high-fear of falling groups (fear of falling comparison), and between the older non-faller and faller groups (fall history comparison). Forty healthy females (twenty each in both young and older groups) performed three trials of bipedal quiet standing on a force platform, in which eighteen reported CoP based measures were computed from recorded CoP trajectory. Intra-class correlation coefficient (ICC), standard error of measurement (SEM) and %SEM were used to quantify their relative and absolute reliability. Fear of falling and retrospective falls of the older group were recorded using falls efficacy scale-international (FES-I) and the history of falls questionnaire respectively. Experimental results showed that eight measures (RMS distance, RMS distance-AP, mean velocity, mean velocity-AP, mean frequency, mean frequency-AP, phase plane parameter and fractal dimension) had acceptable levels of relative and absolute reliability. Three measures (RMS distance-AP, mean velocity, and phase plane parameter) were sensitive to detect age-group difference and fear of falling under both visual conditions, but no single measure was capable to detect differences between the non-faller and faller groups. Relevance to industryThe results of this research provide useful information on the selection of appropriate center-of-pressure (CoP) based postural sway measures to assess individual's balance ability for preventing the occupational falls.

Powder diffraction and DFT studies of synthetic insect pheromones

Eight chiral monomethyl alkanes have been synthesized and their crystal structures solved from high resolution powder diffraction patterns collected using synchrotron radiation. Such compounds have been seen to act as recognition pheromones in social insects. Carbon chain lengths varied from C25to C31with the methyl group at various positions along the chain. One compound, (S)-7-methylnonacosane, also formed a low quality single crystal from which its structure was solved and refined. Although the powder diffraction patterns were good enough to solve the crystal structures, using the standard technique of real-space simulated annealing, with near-linear molecules, chemically unreasonable distortions occurred during Rietveld refinement unless many distance, angle and torsion restraints were imposed. From the results of the single-crystal structure it is evident that there is a gentle bend in the molecule close to the position of the methyl side chain. Thus imposing a near-linear molecule is incorrect, and giving sufficient freedom in the Rietveld refinement to allow the molecule to bend leads to an inaccurate structure. In short, the correct structure must be known to judge the strength of the restraints to apply, and this must vary at different parts of the chain. As an alternative to refining the structure from the powder diffraction data, the structures have been optimized via dispersion-corrected DFT calculations (Van der Streek and Neumann, 2010) starting from the powder structures. Agreement between the single-crystal and DFT-minimized structures is satisfactory, with an rms distance of 0.054 Å and a maximum distance of 0.132 Å when comparing carbon atoms positions. With this approach, a well defined structure optimization strategy is used for all the crystal structures. The molecules studied fall into two packing types, (both with monoclinic symmetry), depending on the position of the methyl group on the main carbon chain relative to the overall chain length.

Persons with lower-limb amputation have impaired trunk postural control while maintaining seated balance

Abnormal mechanics of movement resulting from lower-limb amputation (LLA) may increase stability demands on the spinal column and/or alter existing postural control mechanisms and neuromuscular responses. A seated balance task was used to investigate the effects of LLA on trunk postural control and stability, among eight males with unilateral LLA (4 transtibial, 4 transfemoral), and eight healthy, non-amputation controls (matched by age, stature, and body mass). Traditional measures derived from center of pressure (COP) time series, and measures obtained from non-linear stabilogram diffusion analyses, were used to characterize trunk postural control. All traditional measures of postural control (95% ellipse area, RMS distance, and mean velocity) were significantly larger among participants with LLA. Non-linear stabilogram diffusion analyses also revealed significant differences in postural control among persons with LLA, but only in the antero-posterior direction. Normalized trunk muscle activity was also larger among participants with LLA. Larger COP-based sway measures among participants with LLA during seated balance suggest an association between LLA and reduced trunk postural control. Reductions in postural control and spinal stability may be a result of adaptations in functional tissue properties and/or neuromuscular responses, and may potentially be caused by repetitive exposure to abnormal gait and movement. Such alterations could then lead to an increased risk for spinal instability, intervertebral motions beyond physiological limits, and pain.

Theoretical study on the removal function of computer controlled polishing SiC mirror with f ixed abrasive

A fixed abrasive technology combined with computer controlled optical surfacing is discussed, and a removal function model for multi-pellet polishing pad is established based on the removal function theory of planar motion. The parameters of the model, such as the movement eccentricity of the polishing pad and the distance between pellets, are optimized by introducing a approaching factor and a curve RMS distance in the simulation. The comparison of the theoretical model and the experimental results indicate that the error between the theoretical maximum removal rate and the experimental data is 0.0073 \mu m/min, and its error ratio is 5.58%; the RMS distance error between the theoretical removal function curve and the experimental curve is 0.0849 μm and its error ratio is 7.01%. The veracity of the theoretical model is verified by experimental results, which predicts the feasibility of the fixed abrasive polishing technology and establishes a promising basis for the SiC mirror precision fabrication field.