| 1. |
- Eklund, Anders, et al.
(författare)
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A Brain Computer Interface for Communication Using Real-Time fMRI
- 2010
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Ingår i: Proceedings of the 20th International Conference on Pattern Recognition. - Los Alamitos, CA, USA : IEEE Computer Society. - 9781424475421 ; , s. 3665-3669
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Konferensbidrag (refereegranskat)abstract
- We present the first step towards a brain computer interface (BCI) for communication using real-time functional magnetic resonance imaging (fMRI). The subject in the MR scanner sees a virtual keyboard and steers a cursor to select different letters that can be combined to create words. The cursor is moved to the left by activating the left hand, to the right by activating the right hand, down by activating the left toes and up by activating the right toes. To select a letter, the subject simply rests for a number of seconds. We can thus communicate with the subject in the scanner by for example showing questions that the subject can answer. Similar BCI for communication have been made with electroencephalography (EEG). The subject then focuses on a letter while different rows and columns of the virtual keyboard are flashing and the system tries to detect if the correct letter is flashing or not. In our setup we instead classify the brain activity. Our system is neither limited to a communication interface, but can be used for any interface where five degrees of freedom is necessary.
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| 2. |
- Eklund, Anders, et al.
(författare)
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Balancing an Inverted Pendulum by Thinking A Real-Time fMRI Approach
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present a method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverse pendulum by activating the left or right hand or resting. The brain activity is classified each second by a neural network and the classification is sent to a pendulum simulator to change the force applied to the pendulum. The state of the inverse pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverse pendulum both with real activity and imagined activity. The developments here have a potential to aid people with communication disabilities e.g., locked in people. It might also be a tool for stroke patients to be ableto train the damaged brain area and get real-time feedback of when they do it right.
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| 3. |
- Eklund, Anders, et al.
(författare)
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Using Real-Time fMRI to Control a Dynamical System
- 2009
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Ingår i: ISMRM 17th Scientific Meeting & Exhibition. - Linköping : Linköping University Electronic Press.
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Konferensbidrag (refereegranskat)abstract
- We present e method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverse pendulum by activating the left or right hand or resting. The brain activity is clasified each second by a neural network and the classification is sent to a pendulum simulator to change the state of the pendulum. The state of the inverse pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverse pendulum during a 7 minute test run.
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| 4. |
- Eklund, Anders, et al.
(författare)
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Using Real-Time fMRI to Control a Dynamical System by Brain Activity Classification
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present a method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverted pendulum by activating the left or right hand or resting. The brain activity is classified each second by a neural network and the classification is sent to a pendulum simulator to change the force applied to the pendulum. The state of the inverted pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverted pendulum during several minutes, both with real activity and imagined activity. In each classification 9000 brain voxels were used and the response time for the system to detect a change of activity was on average 2-4 seconds. The developments here have a potential to aid people with communication disabilities, such as locked in people. Another future potential application can be to serve as a tool for stroke and Parkinson patients to be able to train the damaged brain area and get real-time feedback for more efficient training.
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| 5. |
- Eklund, Anders, 1981-, et al.
(författare)
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Using Real-Time fMRI to Control a Dynamical System by Brain Activity Classification
- 2009. - 1
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Ingår i: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2009. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642042676 - 9783642042683 ; , s. 1000-1008
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Konferensbidrag (refereegranskat)abstract
- We present a method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverted pendulum by activating the left or right hand or resting. The brain activity is classified each second by a neural network and the classification is sent to a pendulum simulator to change the force applied to the pendulum. The state of the inverted pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverted pendulum during several minutes, both with real activity and imagined activity. In each classification 9000 brain voxels were used and the response time for the system to detect a change of activity was on average 2-4 seconds. The developments here have a potential to aid people with communication disabilities, such as locked in people. Another future potential application can be to serve as a tool for stroke and Parkinson patients to be able to train the damaged brain area and get real-time feedback for more efficient training.
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| 6. |
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| 7. |
- Gyllensvärd, Frida, 1980-
(författare)
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Efficient Methods for Volumetric Illumination
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern imaging modalities can generate three-dimensional datasets with a very high detail level. To transfer all the information to the user in an efficient way there is a need for three-dimensional visualization. In order to enhance the diagnostic capabilities the utilized methods must supply the user with fast renderings that are easy to interpret correctly.It can thus be a challenge to visualize a three-dimensional dataset in a way that allows the user to perceive depth and shapes. A number of stereoscopic solutions are available on the market but it is in many situations more practical and less expensive to use ordinary two-dimensional displays. Incorporation of advanced illumination can, however, improve the perception of depth in a rendering of a volume. Cast shadows provide the user with clues of distances and object hierarchy. Simulating realistic light conditions is, however, complex and it can be difficult to reach interactive frame rates. Approximations and clever implementations are consequently required.This thesis presents efficient methods for calculation of illumination with the objective of providing the user with high spatial and shape perception. Two main types of light conditions, a single point light source and omni-directional illumination, are considered. Global transport of light is efficiently estimated using local piecewise integration which allows a graceful speed up compared to brute force techniques. Ambient light conditions are calculated by integrating the incident light along rays within a local neighborhood around each point in the volume.Furthermore, an approach that allows the user to highlight different tissues, using luminous materials, is also available in this thesis. A multiresolution data structure is employed in all the presented methods in order to support evaluation of illumination for large scale data at interactive frame rates.
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| 8. |
- Henrysson, Anders, 1976-
(författare)
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Bringing Augmented Reality to Mobile Phones
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With its mixing of real and virtual, Augmented Reality (AR) is a technology that has attracted lots of attention from the science community and is seen as a perfect way to visualize context-related information. Computer generated graphics is presented to the user overlaid and registered with the real world and hence augmenting it. Promising intelligence amplification and higher productivity, AR has been intensively researched over several decades but has yet to reach a broad audience.This thesis presents efforts in bringing Augmented Reality to mobile phones and thus to the general public. Implementing technologies on limited devices, such as mobile phones, poses a number of challenges that differ from traditional research directions. These include: limited computational resources with little or no possibility to upgrade or add hardware, limited input and output capabilities for interactive 3D graphics. The research presented in this thesis addresses these challenges and makes contributions in the following areas:Mobile Phone Computer Vision-Based TrackingThe first contribution of thesis has been to migrate computer vision algorithms for tracking the mobile phone camera in a real world reference frame - a key enabling technology for AR. To tackle performance issues, low-level optimized code, using fixed-point algorithms, has been developed.Mobile Phone 3D Interaction TechniquesAnother contribution of this thesis has been to research interaction techniques for manipulating virtual content. This is in part realized by exploiting camera tracking for position-controlled interaction where motion of the device is used as input. Gesture input, made possible by a separate front camera, is another approach that is investigated. The obtained results are not unique to AR and could also be applicable to general mobile 3D graphics.Novel Single User AR ApplicationsWith short range communication technologies, mobile phones can exchange data not only with other phones but also with an intelligent environment. Data can be obtained for tracking or visualization; displays can be used to render graphics with the tracked mobile phone acting as an interaction device. Work is presented where a mobile phone harvests a sensor-network to use AR to visualize live data in context.Novel Collaboration AR ApplicationsOne of the most promising areas for mobile phone based AR is enhancing face-to-face computer supported cooperative work. This is because the AR display permits non-verbal cues to be used to a larger extent. In this thesis, face-to-face collaboration has been researched to examine whether AR increases awareness of collaboration partners even on small devices such as mobile phones. User feedback indicates that this is the case, confirming the hypothesis that mobile phones are increasingly able to deliver an AR experience to a large audience.
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| 9. |
- Lindholm, Stefan, et al.
(författare)
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Spatial Conditioning of Transfer Functions Using Local Material Distributions
- 2010
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Ingår i: IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS. - : IEEE. - 1077-2626. ; 16:6, s. 1301-1310
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Tidskriftsartikel (refereegranskat)abstract
- In many applications of Direct Volume Rendering (DVR) the importance of a certain material or feature is highly dependent on its relative spatial location. For instance, in the medical diagnostic procedure, the patients symptoms often lead to specification of features, tissues and organs of particular interest. One such example is pockets of gas which, if found inside the body at abnormal locations, are a crucial part of a diagnostic visualization. This paper presents an approach that enhances DVR transfer function design with spatial localization based on user specified material dependencies. Semantic expressions are used to define conditions based on relations between different materials, such as only render iodine uptake when close to liver. The underlying methods rely on estimations of material distributions which are acquired by weighing local neighborhoods of the data against approximations of material likelihood functions. This information is encoded and used to influence rendering according to the users specifications. The result is improved focus on important features by allowing the user to suppress spatially less-important data. In line with requirements from actual clinical DVR practice, the methods do not require explicit material segmentation that would be impossible or prohibitively time-consuming to achieve in most real cases. The scheme scales well to higher dimensions which accounts for multi-dimensional transfer functions and multivariate data. Dual-Energy Computed Tomography, an important new modality in radiology, is used to demonstrate this scalability. In several examples we show significantly improved focus on clinically important aspects in the rendered images.
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| 10. |
- Ljung, Patric, 1968-, et al.
(författare)
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Forensic Virtual Autopsies by Direct Volume Rendering
- 2007
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Ingår i: IEEE signal processing magazine (Print). - Piscataway, NJ, USA : IEEE. - 1053-5888 .- 1558-0792. ; 24:6, s. 112-116
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents state-of-the-art methods, which address the technical challenges in visualizing large three-dimensional (3D) data and enable rendering at interactive frame rates.
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