Kamyar Abhari

A region-based P300 speller for brain-computer interface

A brain-computer interface (BCI) is a system that conveys messages and commands directly from the human brain to a computer. The BCI system described in this work is based on the P300 wave. The P300 is a positive peak of an event-related potential (ERP) that occurs 300 ms after a stimulus. One of the best-known and most widely used P300 applications is the P300 speller designed by Farwell-Donchin in 1988. The Farwell-Donchin paradigm has been a benchmark for P300 BCIs. In this paradigm, a 6 X 6 matrix of letters and numbers is displayed, and the subject focuses on a target character while rows and columns of characters flash. Through detection of P300 for one row and one column, the target character can be identified. In this paper, it is shown that there is a human perceptual error in the Farwell-Donchin paradigm. To eliminate this error, a new region-based paradigm is presented. Using experimental results, it is shown that the new paradigm has several advantages over the Farwell-Donchin paradigm and achieves better accuracy.

The Role of Augmented Reality in Training the Planning of Brain Tumor Resection

The environment in which a surgeons is trained profoundly effects their preferred method for visualizing patient images. While classical 2D viewing might be preferred by some older experts, the new generation of residents and novices has been raised navigating in 3D through video games, and are accustomed to seeing 3D reconstructions of the human anatomy. In this study, we evaluate the performance of different groups of users in 4 different visualization modalities (2D planes, orthogonal planes, 3D reconstruction and augmented reality). We hypothesize that this system will facilitate the spatio-visual abilities of individuals in terms of assessing patient-specific data, an essential requirement of many neurosurgical applications such as tumour resection. We also hypothesize that the difference between AR and the other modalities will be greater in the novice group. Our preliminary results indicate that AR is better or as good as other modalities in terms of performance.

Visual Enhancement of MR Angiography Images to Facilitate Planning of Arteriovenous Malformation Interventions

The primary purpose of medical image visualization is to improve patient outcomes by facilitating the inspection, analysis, and interpretation of patient data. This is only possible if the users’ perceptual and cognitive limitations are taken into account during every step of design, implementation, and evaluation of interactive displays. Visualization of medical images, if executed effectively and efficiently, can empower physicians to explore patient data rapidly and accurately with minimal cognitive effort. This article describes a specific case study in biomedical visualization system design and evaluation, which is the visualization of MR angiography images for planning arteriovenous malformation (AVM) interventions. The success of an AVM intervention greatly depends on the surgeon gaining a full understanding of the anatomy of the malformation and its surrounding structures. Accordingly, the purpose of this study was to investigate the usability of visualization modalities involving contour enhancement and stereopsis in the identification and localization of vascular structures using objective user studies. Our preliminary results indicate that contour enhancement, particularly when combined with stereopsis, results in improved performance enhancement of the perception of connectivity and relative depth between different structures.

Use of a Mixed-Reality System to Improve the Planning of Brain Tumour Resections: Preliminary Results

The lack of intuitive visualization techniques for neurosurgical planning is a challenging hurdle faced by neurosurgeons and neurosurgery residents. Within this context, this paper describes the development and evaluation of an Augmented Reality (AR) system geared towards planning brain tumour resection interventions. Successful resection of a tumour or hematoma requires careful pre-operative planning to avoid damaging the brain. We hypothesize that our proposed AR system facilitates the planning of tumour resection operations by making more effective use of the visuospatial abilities of individuals to assess patient-specific data. To test our hypothesis, a number of experiments were conducted where subjects were asked to perform relevant spatial judgment tasks using three different conventional visualization approaches as well as the proposed AR system. Our preliminary results indicate that, compared to traditional methods, the proposed AR system a) greatly improves the user performance in tasks involving 3D spatial reasoning about the tumour relative to the anatomical context, b) reduces error associated with mental transformation, and c) supports generic spatial reasoning skills, independent of the sensory-motor tasks performed.

A novel integrative method for analyzing eye and hand behaviour during reaching and grasping in an MRI environment

The development of noninvasive neuroimaging techniques, such as fMRI, has rapidly advanced our understanding of the neural systems underlying the integration of visual and motor information. However, the fMRI experimental design is restricted by several environmental elements, such as the presence of the magnetic field and the restricted view of the participant, making it difficult to monitor and measure behaviour. The present article describes a novel, specialized software package developed in our laboratory called Biometric Integration Recording and Analysis (BIRA). BIRA integrates video with kinematic data derived from the hand and eye, acquired using MRI-compatible equipment. The present article demonstrates the acquisition and analysis of eye and hand data using BIRA in a mock (0 Tesla) scanner. A method for collecting and integrating gaze and kinematic data in fMRI studies on visuomotor behaviour has several advantages: Specifically, it will allow for more sophisticated, behaviourally driven analyses and eliminate potential confounds of gaze or kinematic data.

Perceptual enhancement of arteriovenous malformation in MRI angiography displays

The importance of presenting medical images in an intuitive and usable manner during a procedure is essential. However, most medical visualization interfaces, particularly those designed for minimally-invasive surgery, suffer from a number of issues as a consequence of disregarding the human perceptual, cognitive, and motor systems limitations. This matter is even more prominent when human visual system is overlooked during the design cycle. One example is the visualization of the neuro-vascular structures in MR angiography (MRA) images. This study investigates perceptual performance in the usability of a display to visualize blood vessels in MRA volumes using a contour enhancement technique. Our results show that when contours are enhanced, our participants, in general, can perform faster with higher level of accuracy when judging the connectivity of different vessels. One clinical outcome of such perceptual enhancement is improvement of spatial reasoning needed for planning complex neuro-vascular operations such as treating Arteriovenous Malformations (AVMs). The success of an AVM intervention greatly depends on fully understanding the anatomy of vascular structures. However, poor visualization of pre-operative MRA images makes the planning of such a treatment quite challenging.

Does stereo-endoscopy improve neurosurgical targeting in 3rd ventriculostomy?

Endoscopic third ventriculostomy is a minimally invasive surgical technique to treat hydrocephalus; a condition where patients suffer from excessive amounts of cerebrospinal fluid (CSF) in the ventricular system of their brain. This technique involves using a monocular endoscope to locate the third ventricle, where a hole can be made to drain excessive fluid. Since a monocular endoscope provides only a 2D view, it is difficult to make this perforation due to the lack of monocular cues and depth perception. In a previous study, we had investigated the use of a stereo-endoscope to allow neurosurgeons to locate and avoid hazardous areas on the surface of the third ventricle. In this paper, we extend our previous study by developing a new methodology to evaluate the targeting performance in piercing the hole in the membrane. We consider the accuracy of this surgical task and derive an index of performance for a task which does not have a well-defined position or width of target. Our performance metric is sensitive and can distinguish between experts and novices. We make use of this metric to demonstrate an objective learning curve on this task for each subject.

Distribution of guidance models for cardiac resynchronization therapy in the setting of multi-center clinical trials

Multi-center trials provide the unique ability to investigate novel techniques across a range of geographical sites with sufficient statistical power, the inclusion of multiple operators determining feasibility under a wider array of clinical environments and work-flows. For this purpose, we introduce a new means of distributing pre-procedural cardiac models for image-guided interventions across a large scale multi-center trial. In this method, a single core facility is responsible for image processing, employing a novel web-based interface for model visualization and distribution. The requirements for such an interface, being WebGL-based, are minimal and well within the realms of accessibility for participating centers. We then demonstrate the accuracy of our approach using a single-center pacemaker lead implantation trial with generic planning models.