134 research outputs found
Articulated Multi-Instrument 2D Pose Estimation Using Fully Convolutional Networks
Instrument detection, pose estimation and tracking in surgical videos is an important vision component for computer assisted interventions. While significant advances have been made in recent years, articulation detection is still a major challenge. In this paper, we propose a deep neural network for articulated multi-instrument 2D pose estimation, which is trained on a detailed annotations of endoscopic and microscopic datasets. Our model is formed by a fully convolutional detection-regression network. Joints and associations between joint pairs in our instrument model are located by the detection subnetwork and are subsequently refined through a regression subnetwork. Based on the output from the model, the poses of the instruments are inferred using maximum bipartite graph matching. Our estimation framework is powered by deep learning techniques without any direct kinematic information from a robot. Our framework is tested on single-instrument RMIT data, and also on multi-instrument EndoVis and in vivo data with promising results. In addition, the dataset annotations are publicly released along with our code and model
Gap generation in the XXZ model in a transverse magnetic field
The ground state phase diagram of the 1D XXZ model in transverse magnetic
field is obtained. It consists of the gapped phases with different types of
long range order (LRO) and critical lines at which the gap and the LRO vanish.
Using scaling estimations and a mean-field approach as well as numerical
results we found critical indices of the gap and the LRO in the vicinity of all
critical lines.Comment: 4 pages, 1 figure, Late
Synthetic and Real Inputs for Tool Segmentation in Robotic Surgery
Semantic tool segmentation in surgical videos is important for surgical scene
understanding and computer-assisted interventions as well as for the
development of robotic automation. The problem is challenging because different
illumination conditions, bleeding, smoke and occlusions can reduce algorithm
robustness. At present labelled data for training deep learning models is still
lacking for semantic surgical instrument segmentation and in this paper we show
that it may be possible to use robot kinematic data coupled with laparoscopic
images to alleviate the labelling problem. We propose a new deep learning based
model for parallel processing of both laparoscopic and simulation images for
robust segmentation of surgical tools. Due to the lack of laparoscopic frames
annotated with both segmentation ground truth and kinematic information a new
custom dataset was generated using the da Vinci Research Kit (dVRK) and is made
available
Dynamical Properties of Quantum Spin Systems in Magnetically Ordered Product Ground States
The one‐dimensional spin‐s XYZmodel in a magnetic field of particular strength has a ferro‐ or antiferromagnetically ordered product ground state. The recursion method is employed to determine T=0 dynamic structure factors for systems with s=1/2, 1, 3/2. The line shapes and peak positions differ significantly from the corresponding spin‐wave results, but their development for increasing values of s suggests a smooth extrapolation to the spin‐wave picture
Quantum Discord and entropic measures of quantum correlations: Optimization and behavior in finite spin chains
We discuss a generalization of the conditional entropy and one-way
information deficit in quantum systems, based on general entropic forms. The
formalism allows to consider simple entropic forms for which a closed
evaluation of the associated optimization problem in qudit-qubit systems is
shown to become feasible, allowing to approximate that of the quantum discord.
As application, we examine quantum correlations of spin pairs in the exact
ground state of finite spin chains in a magnetic field through the quantum
discord and information deficit. While these quantities show a similar
behavior, their optimizing measurements exhibit significant differences, which
can be understood and predicted through the previous approximations. The
remarkable behavior of these quantities in the vicinity of transverse and
non-transverse factorizing fields is also discussed.Comment: 10 pages, 3 figure
Dynamical structure factor of the anisotropic Heisenberg chain in a transverse field
We consider the anisotropic Heisenberg spin-1/2 chain in a transverse
magnetic field at zero temperature. We first determine all components of the
dynamical structure factor by combining exact results with a mean-field
approximation recently proposed by Dmitriev {\it et al}., JETP 95, 538 (2002).
We then turn to the small anisotropy limit, in which we use field theory
methods to obtain exact results. We discuss the relevance of our results to
Neutron scattering experiments on the 1D Heisenberg chain compound .Comment: 13 pages, 14 figure
A new family of matrix product states with Dzyaloshinski-Moriya interactions
We define a new family of matrix product states which are exact ground states
of spin 1/2 Hamiltonians on one dimensional lattices. This class of
Hamiltonians contain both Heisenberg and Dzyaloshinskii-Moriya interactions but
at specified and not arbitrary couplings. We also compute in closed forms the
one and two-point functions and the explicit form of the ground state. The
degeneracy structure of the ground state is also discussed.Comment: 15 pages, 1 figur
Carotid plaque surface echogenicity predicts cerebrovascular events: An Echographic Multicentric Swiss Study.
BACKGROUND AND PURPOSE
To determine the prognostic value for ischemic stroke or transitory ischemic attack (TIA) of plaque surface echogenicity alone or combined to degree of stenosis in a Swiss multicenter cohort METHODS: Patients with ≥60% asymptomatic or ≥50% symptomatic carotid stenosis were included. Grey-scale based colour mapping was obtained of the whole plaque and of its surface defined as the regions between the lumen and respectively 0-0.5, 0-1, 0-1.5, and 0-2 mm of the outer border of the plaque. Red, yellow and green colour represented low, intermediate or high echogenicity. Proportion of red color on surface (PRCS) reflecting low echogenictiy was considered alone or combined to degree of stenosis (Risk index, RI).
RESULTS
We included 205 asymptomatic and 54 symptomatic patients. During follow-up (median/mean 24/27.7 months) 27 patients experienced stroke or TIA. In the asymptomatic group, RI ≥0.25 and PRCS ≥79% predicted stroke or TIA with a hazard ratio (HR) of respectively 8.7 p = 0.0001 and 10.2 p < 0.0001. In the symptomatic group RI ≥0.25 and PRCS ≥81% predicted stroke or TIA occurrence with a HR of respectively 6.1 p = 0.006 and 8.9 p = 0.001. The best surface parameter was located at 0-0.5mm. Among variables including age, sex, degree of stenosis, stenosis progression, RI, PRCS, grey median scale values and clinical baseline status, only PRCS independently prognosticated stroke (p = 0.005).
CONCLUSION
In this pilot study including patients with at least moderate degree of carotid stenosis, PRCS (0-0.5mm) alone or combined to degree of stenosis strongly predicted occurrence of subsequent cerebrovascular events
Dynamical properties of quantum spin systems in magnetically ordered product ground states
Investigating the effect of intra-operative infiltration with local anaesthesia on the development of chronic postoperative pain after inguinal hernia repair. A randomized placebo controlled triple blinded and group sequential study design [NCT00484731]
<p>Abstract</p> <p>Background</p> <p>Inguinal hernia repair is one of the most frequently performed procedures in Switzerland (15'000/year). The most common complication postoperatively is development of chronic pain in up to 30% of all patients irrespective of the operative technique.</p> <p>Methods/Design</p> <p>264 patients scheduled for an inguinal hernia repair using one of three procedures (Lichtenstein, Barwell and TEP = total extraperitoneal hernioplasty) are being randomly allocated intra-operatively into two groups. Group I patients receive a local injection of 20 ml Carbostesin<sup>® </sup>0.25% at the end of the operation according to a standardised procedure. Group II patients get a 20 ml placebo (0.9% Saline) injection. We use pre-filled identically looking syringes for blinded injection, i.e. the patient, the surgeon and the examinator who performs the postoperative clinical follow-ups remain unaware of group allocation. The primary outcome of the study is the occurrence of developing chronic pain (defined as persistent pain at 3 months FU) measured by VAS and Pain Matcher<sup>® </sup>device (Cefar Medical AB, Lund, Sweden).</p> <p>The study started on July 2006. In addition to a sample size re-evaluation three interim analyses are planned after 120, 180 and 240 patients had finished their 3-months follow-up to allow for early study termination.</p> <p>Discussion</p> <p>Using a group sequential study design the minimum number of patients are enrolled to reach a valid conclusion before the end of the study.</p> <p>To limit subjectivity, both a VAS and the Pain Matcher<sup>® </sup>device are used for the evaluation of pain. This allows us also to compare these two methods and further assess the use of Pain Matcher<sup>® </sup>in clinical routine.</p> <p>The occurrence of chronic pain after inguinal hernia repair has been in focus of several clinical studies but the reduction of it has been rarely investigated. We hope to significantly reduce the occurrence of this complication with our investigated intervention.</p> <p>Trial Registration</p> <p>Our trial has been registered at ClinicalTrials.gov. The trial registration number is: [NCT00484731].</p
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