CaDIS: Cataract dataset for surgical RGB-image segmentation

Video feedback provides a wealth of information about surgical procedures and is the main sensory cue for surgeons. Scene understanding is crucial to computer assisted interventions (CAI) and to post-operative analysis of the surgical procedure. A fundamental building block of such capabilities is the identification and localization of surgical instruments and anatomical structures through semantic segmentation. Deep learning has advanced semantic segmentation techniques in the recent years but is inherently reliant on the availability of labelled datasets for model training. This paper introduces a dataset for semantic segmentation of cataract surgery videos complementing the publicly available CATARACTS challenge dataset. In addition, we benchmark the performance of several state-of-the-art deep learning models for semantic segmentation on the presented dataset. The dataset is publicly available at https://cataracts-semantic-segmentation2020.grand-challenge.org/

Comparison of spinal cord stimulation profiles from intra- and extradural electrode arrangements by finite element modelling

Spinal cord stimulation currently relies on extradural electrode arrays that are separated from the spinal cord surface by a highly conducting layer of cerebrospinal fluid. It has recently been suggested that intradural placement of the electrodes in direct contact with the pial surface could greatly enhance the specificity and efficiency of stimulation. The present computational study aims at quantifying and comparing the electrical current distributions as well as the spatial recruitment profiles resulting from extra- and intra-dural electrode arrangements. The electrical potential distribution is calculated using a 3D finite element model of the human thoracic spinal canal. The likely recruitment areas are then obtained using the potential as input to an equivalent circuit model of the pre-threshold axonal response. The results show that the current threshold to recruitment of axons in the dorsal column is more than an order of magnitude smaller for intradural than extradural stimulation. Intradural placement of the electrodes also leads to much higher contrast between the stimulation thresholds for the dorsal root entry zone and the dorsal column, allowing better focusing of the stimulus

2018 Robotic Scene Segmentation Challenge

In 2015 we began a sub-challenge at the EndoVis workshop at MICCAI in Munich using endoscope images of ex-vivo tissue with automatically generated annotations from robot forward kinematics and instrument CAD models. However, the limited background variation and simple motion rendered the dataset uninformative in learning about which techniques would be suitable for segmentation in real surgery. In 2017, at the same workshop in Quebec we introduced the robotic instrument segmentation dataset with 10 teams participating in the challenge to perform binary, articulating parts and type segmentation of da Vinci instruments. This challenge included realistic instrument motion and more complex porcine tissue as background and was widely addressed with modifications on U-Nets and other popular CNN architectures. In 2018 we added to the complexity by introducing a set of anatomical objects and medical devices to the segmented classes. To avoid over-complicating the challenge, we continued with porcine data which is dramatically simpler than human tissue due to the lack of fatty tissue occluding many organs

A Unique Case of Primary Ewing’s Sarcoma of the Cervical Spine in a 53-Year-Old Male: A Case Report and Review of the Literature

Extraskeletal Ewing’s sarcoma (EES) is a rare presentation, representing only 15% of all primary Ewing’s sarcoma cases. Even more uncommon is EES presenting as a primary focus in the spinal canal. These rapidly growing tumors often present with focal neurological symptoms of myelopathy or radiculopathy. There are no classic characteristic imaging findings and thus the physician must keep a high index of clinical suspicion. Diagnosis can only be definitively made by histopathological studies. In this report, we discuss a primary cervical spine EES in a 53-year-old man who presented with a two-month history of left upper extremity pain and acute onset of weakness. Imaging revealed a cervical spinal canal mass. After undergoing cervical decompression, histopathological examination confirmed a diagnosis of Ewing’s sarcoma. A literature search revealed fewer than 25 reported cases of primary cervical spine EES published in the past 15 years and only one report demonstrating this pathology in a patient older than 30 years of age age=38. Given the low incidence of this pathology presenting in this age group and the lack of treatment guidelines, each patient’s plan should be considered on a case-by-case basis until further studies are performed to determine optimal evidence based treatment

A new device concept for directly modulating spinal cord pathways: initialin vivoexperimental results

We describe a novel spinal cord (SC) stimulator that is designed to overcome a major shortcoming of existing stimulator devices: their restricted capacity to selectively activate targeted axons within the dorsal columns. This device overcomes that limitation by delivering electrical stimuli directly to the pial surface of the SC. Our goal in testing this device was to measure its ability to physiologically activate the SC and examine its capacity to modulate somatosensory evoked potentials (SSEPs) triggered by peripheral stimulation. In this acute study on adult sheep (n = 7), local field potentials were recorded from a grid placed in the subdural space of the right hemisphere during electrical stimulation of the left tibial nerve and the spinal cord. Large amplitude SSEPs (>200 µV) in response to SC stimulation were consistently obtained at stimulation strengths well below the thresholds inducing neural injury. Moreover, stimulation of the dorsal columns with signals employed routinely by devices in standard clinical use, e.g., 50 Hz, 0.2 ms pulse width, produced long-lasting changes (>4.5 h) in the SSEP patterns produced by subsequent tibial nerve stimulation. The results of these acute experiments demonstrate that this device can be safely secured to the SC surface and effectively activate somatosensory pathways

Sheep 1: Event related cortical oscillations.

<p>A) Average evoked potential distribution for epidural (blue) and intradural (red) spinal cord stimulation at 0 mm with 5 volts. Major cortical sulci are denoted by dotted lines. B) Time-varying high-gamma band (75–150 Hz) envelope for epidural (blue) and intradural (red) spinal cord stimulation in selected channels. C) Time-Frequency analysis of two representative channels during epidural stimulation. The y-axis denotes frequency in hertz and the x axis denotes time in seconds centered at stimulus onset. The color scale represents relative power change with respect to pre-stimulus values in decibels (dB).</p

Ipsilateral Versus contralateral spinal cord stimulation.

<p>High gamma response recorded from a subdural grid placed on the right cerebral hemisphere plotted as a function of spinal cord stimulation voltage (scale is log10 separated). The red trace denotes ipsilateral SCS (right-sided stimulation) and the blue trace denotes contralateral SCS (left-sided stimulation) in Sheep 1 intradural series (A), Sheep 4 intradural series (B), and Sheep 4 epidural series (C). The numbers above the dotted line in C denote the distance in millimeters of the neurostimulating probe from the dorsal aspect of the spinal dura mater.</p

Summary of voltage thresholds needed to evoke high gamma band response (VT).

<p>(A) comparison between midline epidural stimulation and intradural stimulation. Y-axis represents VT. X-axis denotes the distance of the neurostimulator from the dorsal surface of the spinal cord. (B) Comparison between Contralateral and ipsilateral spinal cord stimulation for intra- and epidural stimulation. (C) summary of VT (y-axis) using spinal electrical stimulation of the midline in three sheep. X-axis represents the distance of the neurstimulator from the midline. (D) Comparing VT between ipsilateral and contralateral dorsal column electrical stimulation at multiple distances (X-axis).</p

Experimental arrangement.

<p>A) Axial view of the spinal cord illustrating the different stimulator positions (intradural, epidural, midline, and lateral). B) Schematic depiction of the orientation of the bipolar stimulating electrode contacts relative to the spinal cord. The contacts were oriented in parallel with the long axis of the spinal cord, with the cathode contact being rostral to the anode contact. C and D) Photographs of the sheep’s brain before and after removal of the 96 contact subdural grid (Sheep 3). E) Photograph of the spinal cord surgical field. A mounting arm (1) is attached to the spinous process and connected to the micromanipulator (3) that is adjusted via the control (2). With this device the location of the neurostimulator (4) can be varied as needed over the mid-line of the exposed dorsal spinal cord (5) and maintained in a stable position. F) A close-up view of the neurostimulator placed in contact with the pial surface at the spinal cord midline (the dura is incised and sutured open). The field is flooded with 0.9% normal saline (NSS). In this experiment, a four contact subdural strip was also carefully inserted rostrally within the subdural space to record spinal cord potentials. The leads for the subdural strip are housed inside the white cable seen running through the lower center of the photo.</p