A biologically inspired spiking model of visual processing for image feature detection

To enable fast reliable feature matching or tracking in scenes, features need to be discrete and meaningful, and hence edge or corner features, commonly called interest points are often used for this purpose. Experimental research has illustrated that biological vision systems use neuronal circuits to extract particular features such as edges or corners from visual scenes. Inspired by this biological behaviour, this paper proposes a biologically inspired spiking neural network for the purpose of image feature extraction. Standard digital images are processed and converted to spikes in a manner similar to the processing that transforms light into spikes in the retina. Using a hierarchical spiking network, various types of biologically inspired receptive fields are used to extract progressively complex image features. The performance of the network is assessed by examining the repeatability of extracted features with visual results presented using both synthetic and real images

A novel approach to robot vision using a hexagonal grid and spiking neural networks

Many robots use range data to obtain an almost 3-dimensional description of their environment. Feature driven segmentation of range images has been primarily used for 3D object recognition, and hence the accuracy of the detected features is a prominent issue. Inspired by the structure and behaviour of the human visual system, we present an approach to feature extraction in range data using spiking neural networks and a biologically plausible hexagonal pixel arrangement. Standard digital images are converted into a hexagonal pixel representation and then processed using a spiking neural network with hexagonal shaped receptive fields; this approach is a step towards developing a robotic eye that closely mimics the human eye. The performance is compared with receptive fields implemented on standard rectangular images. Results illustrate that, using hexagonally shaped receptive fields, performance is improved over standard rectangular shaped receptive fields

The value of Statistical Shape Models to Spine Surgery

The increased use of 3D models of organs or bones by the surgeon has lead to rapid development of new methods to automaKze model generaKon

Time-Action Analysis of Catheter Manipulation During Navigation Tasks in Bifurcations

Endovascular intervention is a form of minimally invasive intervention that allows catheters to be placed in practically any location of the vascular tree. However, to provide access to all these remote locations, an extensive array of catheters is needed. A specific catheter is choose based on experience, without any objective indication of its suitability during the actual procedure (Bakker, N. H., Tanase, D., Reekers, J. A., and Grimbergen, C. A., 2002, "Evaluation of Vascular and Interventional Procedures with Time-Action Analysis: A Pilot Study," J. Vasc. Intervent. Radiol., 13(5), pp. 483-488). The aim of this study is to evaluate several catheters using time-action analysis during a navigation task in bifurcations of various geometries. The relation between the geometry of bifurcations, the catheters, and the time taken to perform specific actions is investigated. Nine novices manipulated five widely used selective catheters with a 0.035" guidewire in a model. In the model, four bifurcations of various diameters and angles were selected. Each bifurcation was cannulated six times with two different yet suitable catheters. The participants had no direct vision of the model but navigated the instruments using the images that were captured by a camera and displayed on a screen. All images presented to the participant were recorded and used for detailed time-action analysis of the various actions to cannulate a branch (e.g., catheter or guidewire retracted, rotated, and advanced). On average, the participants needed 28.3 s to cannulate a branch. When the ratio between the diameter of the main and side branch was high, the average time per task increased significantly, as did the number of attempts to navigate into a branch. However, neither the choice between the two suitable catheters for each bifurcation, nor the angles of the bifurcation made a significant difference in navigation time. Time-action analysis enabled objective measurement of the time spent on various actions to cannulate a branch. The results revealed that most time was spent on retracting and rotating the catheter. This was comparable for all catheters and branches, showing that all the instruments were manipulated in a similar way and presented the same difficulties

A statistical shape model of the human second cervical vertebra

Purpose: Statistical shape and appearance models play an important role in reducing the segmentation processing timeof a vertebra and in improving results for 3D model development. Here, we describe the different steps in generating astatistical shape model (SSM) of the second cervical vertebra (C2) and provide the shape model for general use by the scientific community. The main difficulties in its construction are the morphological complexity of the C2 and its variability in the population. Methods: The input dataset is composed of manually segmented anonymized patient computerized tomography (CT)scans. The alignment of the different datasets is done with the procrustes alignment on surface models, and then, the registration is cast as a model-fitting problem using a Gaussian process. A principal component analysis (PCA)-based modelis generated which includes the variability of the C2. Results: The SSM was generated using 92 CT scans. The resulting SSM was evaluated for specificity, compactness andgeneralization ability. The SSM of the C2 is freely available to the scientific community in Slicer (an open source soft-ware for image analysis and scientific visualization) with a module created to visualize the SSM using Statismo, a framework for statistical shape modeling. Conclusion: The SSM of the vertebra allows the shape variability of the C2 to be represented. Moreover, the SSM willenable semi-automatic segmentation and 3D model generation of the vertebra, which would greatly benefit surgery planning

A statistical shape model of the human second cervical vertebra.

PURPOSE: Statistical shape and appearance models play an important role in reducing the segmentation processing time of a vertebra and in improving results for 3D model development. Here, we describe the different steps in generating a statistical shape model (SSM) of the second cervical vertebra (C2) and provide the shape model for general use by the scientific community. The main difficulties in its construction are the morphological complexity of the C2 and its variability in the population. METHODS: The input dataset is composed of manually segmented anonymized patient computerized tomography (CT) scans. The alignment of the different datasets is done with the procrustes alignment on surface models, and then, the registration is cast as a model-fitting problem using a Gaussian process. A principal component analysis (PCA)-based model is generated which includes the variability of the C2. RESULTS: The SSM was generated using 92 CT scans. The resulting SSM was evaluated for specificity, compactness and generalization ability. The SSM of the C2 is freely available to the scientific community in Slicer (an open source software for image analysis and scientific visualization) with a module created to visualize the SSM using Statismo, a framework for statistical shape modeling. CONCLUSION: The SSM of the vertebra allows the shape variability of the C2 to be represented. Moreover, the SSM will enable semi-automatic segmentation and 3D model generation of the vertebra, which would greatly benefit surgery planning

Steerable Guidewire for Magnetic Resonance Guided Endovascular Interventions

In endovascular interventions, thin, flexible instruments are inserted through the skin into the blood vessels to diagnose and treat various diseases of the vascular system. One drawback is that the instruments are difficult to maneuver in the desired direction due to limitations in shape and flexibility. Another disadvantage is that the interventions are performed under intermittent fluoroscopy/angiography imaging. Magnetic resonance imaging (MRI) may offer advantages over X-ray guidance. It presents a good soft tissue contrast without the use of nephrotoxic media or ionizing radiation. The aim of this study is to develop a guidewire that is compatible with MRI and includes a steerable segment at the tip. This added degree-of-freedom may improve the maneuverability of the devices thereby the efficiently and safety of the navigation. A 1.6 m (5 ft, 3 in.) long and 0.035 in. diameter guidewire that consists of MR compatible materials and has a flexible tip was designed. The only metallic part was a nitinol rod that was implemented at the distal flexible tip. To limit the risk of heating in the MRI, this rod was kept shorter than 30 mm. The tip could be deflected in one direction by pulling on a Dyneema wire that was placed in the lumen of the shaft of the guidewire. To drive the steerable tip, a handle that could be easily attached/detached from the instrument was designed and implemented. Using the handle, the tip of the 1.60 m long guidewire prototype could be actuated to reach angles from 30 deg to 250 deg. The handle could easily be placed on and removed from the guidewire, so conventional 0.035 in.-compatible catheters could slide over from the proximal end. However, in order to make the guidewire more efficient to enter a bifurcation, the stiffness of the tip should progressively increase from its proximal to its distal end. The guidewire was imaged in a 1.5T MRI using real-time imaging without producing artifacts that would have shaded the anatomy. It was possible to assemble a guidewire with a steerable segment in the required size, using MR compatible materials. Therefore, the current design is a promising proof of concept and allowed us to clearly identify the features that need to be improved in order to come to a clinically applicable instrument