A Probabilistic Higher-Order Fixpoint Logic

We introduce PHFL, a probabilistic extension of higher-order fixpoint logic, which can also be regarded as a higher-order extension of probabilistic temporal logics such as PCTL and the $\mu^p$-calculus. We show that PHFL is strictly more expressive than the $\mu^p$-calculus, and that the PHFL model-checking problem for finite Markov chains is undecidable even for the $\mu$-only, order-1 fragment of PHFL. Furthermore the full PHFL is far more expressive: we give a translation from Lubarsky's $\mu$-arithmetic to PHFL, which implies that PHFL model checking is $\Pi^1_1$-hard and $\Sigma^1_1$-hard. As a positive result, we characterize a decidable fragment of the PHFL model-checking problems using a novel type system

Survey on Current State-of-the-Art in Needle Insertion Robots: Open Challenges for Application in Real Surgery

AbstractMinimally invasive percutaneous treatment robots have become a popular area in medical robotics. Minimally invasive treatments are an important part of modern surgery; however percutaneous treatments are a difficult procedure for surgeons. They must carry out a procedure that has limited visibility, tool maneuverability and where the target and tissue surrounding it move because of the tool. Robot technology can overcome those limitations and increase the success of minimally invasive percutaneous treatment. In this paper we will present a review of the current state-of-the-art in robotic insertion needle for minimally invasive treatments, focusing on the limitations and challenges still open for their use in clinical application

Computational study of kinematics of the anterior cruciate ligament double-bundle structure during passive knee flexion–extension

The anterior cruciate ligament (ACL) comprises an anteromedial bundle (AMB) and posterolateral bundle (PLB). Cadaver studies showed that this double-bundle structure exhibits reciprocal function during passive knee flexion–extension, with the PLB taut in knee extension and the AMB taut in knee flexion. In vivo measurements indicated that straight-line lengths of both bundles decrease with increasing knee-flexion angle (KFA). To interpret these seemingly conflicting facts, we developed a computational ACL model simulating the kinematics of the double-bundle structure during passive knee flexion–extension. Tibial and femoral shapes were reconstructed from computed-tomography images of a cadaver knee and used to construct an idealized model of an ACL including its bundles at the tibiofemoral joint. The ACL deformations at various KFAs were computed by finite element analysis. Results showed that the PLB was stretched in knee extension (KFA = 0∘) and slackened with increasing KFA. The AMB was stretched in knee extension (KFA = 0∘) and remained stretched on the medial side when the knee flexed (KFA = 90∘), but its straight-line length decreased with increasing KFA. These findings are consistent with cadaver and in vivo experimental results and highlight the usefulness of a computational approach for understanding ACL functional anatomy.Otani T., Kobayashi Y., Tanaka M.. Computational study of kinematics of the anterior cruciate ligament double-bundle structure during passive knee flexion–extension. Medical Engineering and Physics, 83, 56-63. https://doi.org/10.1016/j.medengphy.2020.07.015

Computational modelling of ankle-foot orthosis to evaluate spatially asymmetric structural stiffness: Importance of geometric nonlinearity

An ankle-foot orthosis (AFO) constructed as a single piece of isotropic elastic material is a commonly used assistive device that provides stability to the ankle joint of patients with spastic diplegic cerebral palsy. The AFO has asymmetric stiffness that restricts plantarflexion during the swing phase while it is flexible to allow dorsiflexion during the stance phase with a large deflection, including buckling originating from geometric nonlinearity. However, its mechanical implications have not been sufficiently investigated. This study aims to develop a computational model of an AFO considering geometric nonlinearity and examine AFO stiffness asymmetry during plantarflexion and dorsiflexion using physical experiments. Three-dimensional AFO mechanics with geometric nonlinearities were expressed using corotational triangle-element formulations that obeyed Kirchhoff–Love plate theory. Computational load tests for plantarflexion and dorsiflexion, using idealised AFOs with two different ankle-region designs (covering or not covering the apexes of the malleoli), showed that plantarflexion moment–ankle angle relationships were linear and dorsiflexion moment–ankle angle relationships were nonlinear; increases in dorsiflexion led to negative apparent stiffness of the AFO. Both ankle-region designs resisted both plantarflexion and dorsiflexion, and out-of-plane elastic energy was locally concentrated on the lateral side, resulting in large deflections during dorsiflexion. These findings give insight into appropriate AFO design from a mechanical viewpoint by characterising three-dimensional structural asymmetry and geometric nonlinearity.Wataru Sumihira, Tomohiro Otani, Yo Kobayashi, Masao Tanaka, Computational modelling of ankle-foot orthosis to evaluate spatially asymmetric structural stiffness: Importance of geometric nonlinearity, Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. pp. 9544119221114199. Copyright © 2022 SAGE Publications. DOI: 10.1177/09544119221114199

Shape memory alloy actuated ankle foot orthosis for reduction of locomotion force

peer reviewedHumans can be considered inefficient at walking because they are unable to achieve the theoretically ideal 'zero energy cost' of steady-state locomotion that is possible for bipeds who have elastic tissues. This inefficiency is mainly due to part of the energy that is generated by the body to complete a single step being dissipated instead of being stored for use in the proceeding step. This suggests that we can improve locomotion efficiency and reduce the metabolic energy cost of walking by manipulating the elasticity of the lower limbs using exoskeletal devices [1]. However, most traditional designs use springs made from regular material that have a constant stiffness. These devices exert a linear force pattern that is not biocompatible because they do not mimic the forces of the muscles or the tendons of the human body. This paper presents an interdisciplinary study of the design of a passive-dynamic ankle foot orthosis mechanism that reduces the biological muscle force requirements during locomotion, thus reducing the metabolic energy cost of walking while maintaining biocompatibility. Shape memory alloy is used as a smart material for an actuator owing to its super-elasticity. This super-elasticity provides a nonlinear stiffness pattern that generates forces comparable to those of healthy muscles

Improving the Motion Performance for an Intelligent Walking Support Machine by RLS Algorithm

To make the old people and handicapped people move easily by themselves, an omni-directional walking support machine (WSM) has been developed. In our previous study, to improve the motion performance of the WSM, a digital acceleration control method has been developed to deal with the nonlinear friction. However, the design of the digital acceleration controller requires to know the exact plant parameters of the WSM which are variable due to center of gravity (COG) shift and load changes. The change of the plant parameters affects the motion performance of the digital acceleration control system. Therefore, in this paper, a discrete-time system identification method using recursive least squares (RLS) algorithm is proposed to online identify the WSM’s plant parameters for the digital acceleration controller. Simulations are executed and compared with the digital acceleration controller without using RLS algorithm, and the results demonstrate the feasibility and effectiveness of the proposed control method

Surgical assessment system reflexes and facilitates the developing the surgical skills of trainees for the Laparoscopic Distal Gastrectomy

Background: To assess laparoscopic distal gastrectomy (LDG) for gastric cancer (GC), the Japanese Operative Rating Scale (JORS) for LDG has been developed. This study evaluated the learning curve of the initial experience of LDG for GC using JORS-LDG.Methods: Thirty-one cases of LDG were performed by a trainee. The trainee and an instructor scored the surgical performance using JORS-LDG immediately after LDG. The 31 cases were evenly divided into early phase (EP), middle phase (MP), and late phase (LP).Results: The trainee successfully completed all cases of LDG without any complications. There were also no severe postoperative complications with Clavien–Dindo classification grade III or higher. The average JORS-LDG points were stable after 24 cases of experience in the CUSUM analysis. The median JORS-LDG points in EP were significantly lower than those in LP (EP: MP: LP = 43.5: 44.3: 45.5, P = 0.02). In operative data, procedure time, bleeding, and the drain fluid amylase level were correlated with the JORS-LDG points.Conclusion: The JORS-LDG scoring system is a practical tool to evaluate surgical performance in the initial LDG experience

Enhanced stability of hippocampal place representation caused by reduced magnesium block of NMDA receptors in the dentate gyrus

BACKGROUND: Voltage-dependent block of the NMDA receptor by Mg(2+) is thought to be central to the unique involvement of this receptor in higher brain functions. However, the in vivo role of the Mg(2+) block in the mammalian brain has not yet been investigated, because brain-wide loss of the Mg(2+) block causes perinatal lethality. In this study, we used a brain-region specific knock-in mouse expressing an NMDA receptor that is defective for the Mg(2+) block in order to test its role in neural information processing. RESULTS: We devised a method to induce a single amino acid substitution (N595Q) in the GluN2A subunit of the NMDA receptor, specifically in the hippocampal dentate gyrus in mice. This mutation reduced the Mg(2+) block at the medial perforant path–granule cell synapse and facilitated synaptic potentiation induced by high-frequency stimulation. The mutants had more stable hippocampal place fields in the CA1 than the controls did, and place representation showed lower sensitivity to visual differences. In addition, behavioral tests revealed that the mutants had a spatial working memory deficit. CONCLUSIONS: These results suggest that the Mg(2+) block in the dentate gyrus regulates hippocampal spatial information processing by attenuating activity-dependent synaptic potentiation in the dentate gyrus