Diagnostic performance of MRI measurements to assess hindfoot malalignment. An assessment of four measurement techniques

Objective: To investigate the ability of coronal non-weight-bearing MR images to discriminate between normal and abnormal hindfoot alignment. Methods: Three different measurement techniques (calcaneal axis, medial/lateral calcaneal contour) based on weight-bearing hindfoot alignment radiographs were applied in 49 patients (mean, 48years; range 21-76years). Three groups of subjects were enrolled: (1) normal hindfoot alignment (0°-10° valgus); (2) abnormal valgus (>10°); (3) any degree of varus hindfoot alignment. Hindfoot alignment was then measured on coronal MR images using four different measurement techniques (calcaneal axis, medial/lateral calcaneal contour, sustentaculum tangent). ROC analysis was performed to find the MR measurement with the greatest sensitivity and specificity for discrimination between normal and abnormal hindfoot alignment. Results: The most accurate measurement on MR images to detect abnormal hindfoot valgus was the one using the medial calcaneal contour, reaching a sensitivity/specificity of 86%/75% using a cutoff value of >11° valgus. The most accurate measurement on MR images to detect abnormal hindfoot varus was the sustentaculum tangent, reaching a sensitivity/specificity of 91%/71% using a cutoff value of <12° valgus. Conclusion: It is possible to suspect abnormal hindfoot alignment on coronal non-weight-bearing MR images. Key Points : • Abnormal hindfoot alignment can be identified on coronal non-weight-bearing MR images. • The sustentaculum tangent was the best predictor of an abnormally varus hindfoot. • The medial calcaneal contour was the best predictor of a valgus hindfoo

Robust Performance Analysis: a Review of Techniques for Dealing with Infinite Dimensional LMIs

This paper compares three techniques for dealing with infinite dimensional linear matrix inequalities (LMIs) for robust performance analysis: the gridding based approximation, the polytopic relaxation and the linear fractional representation based relaxation. The latter draws on the Full Block S-Procedure with different types of multipliers. All three techniques are applied in two benchmark studies at the example of an aeroelastic system. The studies are backed up by results from the Robust Control Toolbox for Matlab

Experimental determination of frequency response function estimates for flexible joint industrial manipulators with serial kinematics

Abstract Two different approaches for the determination of frequency response functions (FRFs) are used for the non-parametric closed loop identification of a flexible joint industrial manipulator with serial kinematics. The two applied experiment designs are based on low power multisine and high power chirp excitations. The main challenge is to eliminate disturbances of the {FRF} estimates caused by the numerous nonlinearities of the robot. For the experiment design based on chirp excitations, a simple iterative procedure is proposed which allows exploiting the good crest factor of chirp signals in a closed loop setup. An interesting synergy of the two approaches, beyond validation purposes, is pointed out

LPV Gray Box Identification of Industrial Robots for Control

This paper treats the linear parameter-varying (LPV) model identification of an industrial robot. Since the model is supposed to be used to design an LPV controller, it must simultaneously feature low complexity and adequate accuracy. As for most systems, a simplified analytical model structure can be derived for the robot based on the laws of physics. Some physical model parameters however must be experimentally determined. Due to the model simplifications, these physical parameters vary over the workspace. In order to capture this variation in an LPV model, the physical parameters are scheduled. Based on an understanding of the system, three different scheduling laws are designed and the resulting LPV models are compared to experimentally determined frequency response functions

Design of Excitation Signals for the Closed Loop Identification of Industrial Robots

This paper focuses on closed loop experiment designs for the estimation of frequency response functions of industrial manipulators. It addresses the difficult choice of excitation signals w.r.t. a minimization of the disturbing impact of nonlinearities like Coulomb friction. The basis for the treatise are two widespread types of excitations, multisine and chirp signals. By superimposing the actual excitation with additional signals and by introducing a frequency dependent amplitude of the excitation signal, the disturbances due to the nonlinearities are purposefully detected and/or eliminated. Simulations of a simple academical example and experiments performed in a hardware testbed allow for a comparison of the proposed approaches and show their effectiveness and synergies

Linear Parameter-Varying Feedforward Control: A Missile Autopilot Design

The feedforward path of an autopilot is designed for the longitudinal dynamics of a tactical missile. A linear parameter-varying model is used to synthesize a self-scheduled control law based on a parameter-dependent Lyapunov function. The controller is evaluated on a nonlinear model of industrial complexity both under nominal conditions and parametric uncertainty. Tracking performance is significantly enhanced while leaving robustness properties of an existing feedback controller unaltered

Good correlation of goutallier rating of supraspinatus fatty changes on axial and reformatted parasagittal computed tomographic images

UNLABELLED Traumatic tendon tear of the rotator cuff occurs frequently and leads to fatty muscle infiltration. With regard to the outcome, fatty infiltration of the rotator cuff muscles constitutes a major negative predictive factor after rotator cuff surgery. In 1989, Goutallier et al established his classification system for assessment of fatty infiltration of the rotator cuff muscles. He used computed tomographic (CT) images in the axial plane. Today, the assessment of rotator cuff muscles on axial CT images has been widely replaced by assessment on parasagittal acquired magnetic resonance images. This change raised 2 important questions. First, there is a controversy whether the Goutallier classification can simply be adopted for magnetic resonance imaging. The second question is whether the muscle assessment in the axial plane is interchangeable with that in the parasagittal plane. We hypothesize that the assessment of fatty muscle infiltration is the same on reformatted parasagittal CT images as on axial CT images METHODS Three independent readers, 2 radiologists and one shoulder surgeon, rated fatty changes of the supraspinatus muscle on CT scans of 91 shoulders. Goutallier grades were assessed on axial and reformatted parasagittal CT images in 2 separate reading sessions. The paired t test was used to find differences between grading results on axial and reformatted parasagittal images. The Pearson correlation coefficient and weighted kappa statistics were used to quantify linear correlation, intrareader, and interreader agreement. RESULTS Mean (SD) Goutallier grading among all readers was 0.80 (1.16) (range, 0-4) on axial images and 0.89 (1.05) (range, 004) on parasagittal reconstructions. We detected a trend toward a slightly higher Goutallier grading on parasagittal reconstructions; however, this result was not significant (P = 0.07). The Pearson correlation coefficient was 0.702 (P < 0.001). Weighted kappa statistics indicated a moderately good to good intrareader (range of weighted kappa, 0.53-0.62) and interreader (weighted kappa, axial images, 0.55; reformatted parasagittal images, 0.65) agreement. CONCLUSION Grading of fatty infiltration of the supraspinatus muscle on parasagittal CT images is comparable with the standard Goutallier grading on axial images and is characterized by a moderately good to good intrareader and interreader agreement. Assessment of parasagittal images is characterized by a slightly higher interreader agreement and may therefore be the preferable modality

The network structure of posttraumatic stress symptoms in war-affected children and adolescents.

Scharpf F, Saupe L, Crombach A, et al. The network structure of posttraumatic stress symptoms in war-affected children and adolescents. JCPP Advances . 2023;3(1): e12124.Background: It is unclear whether findings from previous network analyses of posttraumatic stress disorder (PTSD) symptoms among children and adolescents are generalizable to youth living in war-torn settings and whether there are differences in the structure and connectivity of symptoms between children and adolescents. This study examined the network structure of PTSD symptoms in a sample of war-affected youth and compared the symptom networks of children and adolescents.; Methods: The overall sample comprised 2007 youth (6-18years old) living in Burundi, Democratic Republic of Congo, Iraq, Palestine, Tanzania, and Uganda amid or close to war and armed conflict. Youth reported their PTSD symptoms using a self-report questionnaire in Palestine and structured clinical interviews in all other countries. We computed the networks of the overall sample and of two sub-samples of 412 children (6-12years) and 473 adolescents (13-18years) and compared the structure and global connectivity of symptoms among children and adolescents.; Results: In both the overall sample and the sub-samples, re-experiencing and avoidance symptoms were most strongly connected. The adolescents' network had a higher global connectivity of symptoms than the children's network. Hyperarousal symptoms and intrusions were more strongly connected among adolescents compared to children.; Conclusion: The findings lend support to a universal concept of PTSD among youth characterized by core deficits in fear processing and emotion regulation. However, different symptoms may be particularly important in different developmental stages, with avoidance and dissociative symptoms dominating in childhood and intrusions and hypervigilance gaining importance in adolescence. Stronger symptom connections may render adolescents more vulnerable to the persistence of symptoms. © 2022 The Authors. JCPP Advances published by John Wiley & Sons Ltd on behalf of Association for Child and Adolescent Mental Health