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ABSTRACT: In our research, people use actions to expose hidden targets as planar images displayed either in situ or ex situ (displaced remotely). We show that because ex situ viewing impedes relating actions to their perceptual consequences, it impairs localizing targets, including compensating for surface deformation, and directing movement toward them. Using a 3D analogue of anorthoscopic perception, we demonstrate that spatio-temporal integration of contiguous planar slices is possible when action and perception are co-located, but not when they are separated. Ex situ viewing precludes the formation of a spatial frame of reference that supports complex visualization from action.
Vision research 12/2010; 50(24):2618-26. · 2.29 Impact Factor
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ABSTRACT: The present research investigates how mental visualization of a 3D object from 2D cross sectional images is influenced by displacing the images from the source object, as is customary in medical imaging. Three experiments were conducted to assess people's ability to integrate spatial information over a series of cross sectional images in order to visualize an object posed in 3D space. Participants used a hand-held tool to reveal a virtual rod as a sequence of cross-sectional images, which were displayed either directly in the space of exploration (in-situ) or displaced to a remote screen (ex-situ). They manipulated a response stylus to match the virtual rod's pitch (vertical slant), yaw (horizontal slant), or both. Consistent with the hypothesis that spatial colocation of image and source object facilitates mental visualization, we found that although single dimensions of slant were judged accurately with both displays, judging pitch and yaw simultaneously produced differences in systematic error between in-situ and ex-situ displays. Ex-situ imaging also exhibited errors such that the magnitude of the response was approximately correct but the direction was reversed. Regression analysis indicated that the in-situ judgments were primarily based on spatiotemporal visualization, while the ex-situ judgments relied on an ad hoc, screen-based heuristic. These findings suggest that in-situ displays may be useful in clinical practice by reducing error and facilitating the ability of radiologists to visualize 3D anatomy from cross sectional images.
Journal of Experimental Psychology Applied 03/2010; 16(1):45-59. · 1.75 Impact Factor
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ABSTRACT: We have developed a method for extracting anatomical shape models from n-dimensional images using an image analysis framework we call Shells and Spheres. This framework utilizes a set of spherical operators centered at each image pixel, grown to reach, but not cross, the nearest object boundary by incorporating "shells" of pixel intensity values while analyzing intensity mean, variance, and first-order moment. Pairs of spheres on opposite sides of putative boundaries are then analyzed to determine boundary reflectance which is used to further constrain sphere size, establishing a consensus as to boundary location. The centers of a subset of spheres identified as medial (touching at least two boundaries) are connected to identify the interior of a particular anatomical structure. For the automated 3D algorithm, the only manual interaction consists of tracing a single contour on a 2D slice to optimize parameters, and identifying an initial point within the target structure.
International Journal of Biomedical Imaging 01/2010; 2010:980872.
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David Wang,
Nikhil Amesur,
Gaurav Shukla,
Angela Bayless,
David Weiser,
Adam Scharl,
Derek Mockel,
Christopher Banks,
Bernadette Mandella,
Roberta Klatzky, George Stetten
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ABSTRACT: We describe a case series constituting the first clinical trial by intravenous (IV) team nurses using the sonic flashlight (SF) for ultrasound guidance of peripherally inserted central catheter (PICC) placement.
Two IV team nurses with more than 10 years of experience with placing PICCs and 3 to 6 years of experience with ultrasound attempted to place PICCs under ultrasound guidance in patients requiring long-term IV access. One of two methods of ultrasound guidance was used: conventional ultrasound (CUS; 60 patients) or a new device called the SF (44 patients). The number of needle punctures required to gain IV access was recorded for each patient.
In both methods, 87% of the cases resulted in successful venous access on the first attempt. The average number of needle sticks per patient was 1.18 for SF-guided procedures compared with 1.20 for CUS-guided procedures. No significant difference was found in the distribution of the number of attempts between the two methods. Anecdotal comments by the nurses indicated the comparative ease of use of the SF display, although the relatively small scale of the SF image compared with the CUS image was also noted.
We have shown that the SF is a safe and effective device for guidance of PICC placement in the hands of experienced IV team nurses. The advantage of placing the ultrasound image at its actual location must be balanced against the relatively small scale of the SF image.
Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 06/2009; 28(5):651-6. · 1.25 Impact Factor
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ABSTRACT: Spatial representations can be derived not only by direct perception, but also through cognitive mediation. Conventional or ex-situ ultrasound displays, which displace imaged data to a remote screen, require both types of process. To determine the depth of a target hidden beneath a surface, ultrasound users must both perceive how deeply the ultrasound transducer indents the surface and interpret the on-screen image to visualize how deeply the target lies below the transducer. Combining these perceptual and cognitive depth components requires a spatial representation that has been called amodal. We report experiments measuring errors in perceptual and cognitively mediated depth estimates and show that these estimates can be concatenated (linked) without further error, providing evidence for an amodal representation. We further contrast conventional ultrasound with an in-situ display whereby an ultrasound image appears to float at the precise location being imaged, enabling the depth of a target to be directly perceived. The research has the potential to enhance ultrasound-guided surgical intervention.
Current Directions in Psychological Science 12/2008; 17(6):359-364. · 3.93 Impact Factor
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ABSTRACT: The present study investigated how people learn to correct errors in actions directed toward cognitively encoded spatial locations. Subjects inserted a stylus to reach a hidden target localized by means of ultrasound imaging and portrayed with a scaled graph. As was found previously (Wu et al., 2005), subjects initially underestimated the target location but corrected their responses when given training with feedback. Three experiments were conducted to examine whether the error correction occurred at (1) the mapping from the input to a mental representation of target location; (2) the mapping from the representation of target location to the intended insertion response, or (3) the mapping from intended response to action. Experiment 1 and Experiment 3 disconfirmed Mappings 1 and 3, respectively, by showing that training did not alter independent measures of target localization or the action of aiming. Experiment 2 showed that the output of Mapping 2, the planned response -- measured as the initial insertion angle -was corrected over trials, and the correction magnitude predicted the response to a transfer stimulus with a new represented location.
Spatial Cognition and Computation 11/2008; 8(4):333-356. · 1.22 Impact Factor
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ABSTRACT: The purpose of this study was to examine how discrete segments of contiguous space arising from perceptual or cognitive channels are mentally concatenated. We induced and measured errors in each channel separately, then summed the psychophysical functions to accurately predict pointing to a depth specified by both together. In Experiment 1, subjects drew a line to match the visible indentation of a probe into a compressible surface. Systematic perceptual errors were induced by manipulating surface stiffness. Subjects in Experiment 2 placed the probe against a rigid surface and viewed the depth of a hidden target below it from a remote image with a metric scale. This cognitively mediated depth judgment produces systematic under-estimation (Wu et al. in IEEE Trans Vis Comput Grap 11(6):684-693, 2005; confirmed here). In Experiment 3, subjects pointed to a target location detected by the indented probe and displayed remotely, requiring mental concatenation of the depth components. The model derived from the data indicated the errors in the components were passed through the integration process without additional systematic error. Experiment 4 further demonstrated that this error-free concatenation was intrinsically spatial, rather than numerical.
Experimental Brain Research 02/2008; 184(3):295-305. · 2.39 Impact Factor
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ABSTRACT: We have derived and evaluated parameters from ultrasound images of the neck to permit a computer to automatically characterize and differentiate between the carotid artery and jugular vein at image acquisition time during vascular interventions, given manually placed seed points. Our goal is to prevent inadvertent damage to the carotid artery when targeting the jugular vein for catheterization. We used a portable 10 MHz ultrasound system to acquire cross sectional B-mode ultrasound images of these great vessels at 10 fps. An expert user identified the vessels in the first frame by touching the vessels on the screen with his fingertip, and the computer automatically tracked the vessels and calculated a best-fit ellipse for each vessel in each subsequent frame. Vessel location and radii were further analyzed to produce parameters that proved useful for differentiating between the carotid artery and jugular vein. These parameters include relative location of the vessels, distension of the vessel walls, and consistent phase difference between the arterial and venous pulsations as determined by temporal Fourier analysis.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention. 02/2006; 9(Pt 1):654-61.
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ABSTRACT: We present several case studies which examine the role that the Insight Toolkit (ITK) played in three medical image analysis courses and several conference tutorials. These courses represent the first use of ITK in a teaching environment, and we believe that a discussion of the teaching approach in each case and the benefits and challenges of ITK will be useful to future medical image analysis course development. ITK was found to provide significant value in a classroom setting since it provides both working "canned" algorithms, including some recently developed methods that are unavailable elsewhere, as well as a framework for developing new techniques and applications. Several areas of difficulty, particularly in regards to code complexity and advanced object-oriented design techniques, have been identified which may make the learning curve of ITK somewhat more complex than a language such as Matlab.
Medical Image Analysis 01/2006; 9(6):605-11. · 4.42 Impact Factor
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ABSTRACT: Real-time tomographic reflection (RTTR) permits in situ visualization of tomographic images so that natural hand-eye coordination can be used directly during invasive procedures. The method uses a half-silvered mirror to merge the visual outer surface of the patient with a simultaneous scan of the patient's interior without requiring a head-mounted display or tracking. A viewpoint-independent virtual image is reflected precisely into its actual location. When applied to ultrasound, we call the resulting RTTR device the sonic flashlight. We previously implemented the sonic flashlight using conventional two-dimensional ultrasound scanners that produce B-mode slices. Real-time three-dimensional (RT3D) ultrasound scanners recently have been developed that permit RTTR to be applied to slices with other orientations, including C-mode (parallel to the face of the transducer). Such slice orientation may offer advantages for image-guided intervention.
Using a prototype scanner developed at Duke University (Durham, NC) with a matrix array that electronically steers an ultrasound beam at high speed in 3D, we implemented a sonic flashlight capable of displaying C-mode images in situ in real time.
We present the first images from the C-mode sonic flashlight, showing bones in the hand and the cardiac ventricles.
The extension of RTTR to matrix array RT3D ultrasound offers the ability to visualize in situ slices other than the conventional B-mode slice, including C-mode slices parallel to the face of the transducer. This orientation may provide a broader target, facilitating certain interventional procedures. Future work is discussed, including display of slices with arbitrary orientation and use of a holographic optical element instead of a mirror.
Academic Radiology 06/2005; 12(5):535-43. · 1.69 Impact Factor
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ABSTRACT: We have extended the real-time tomographic reflection display of the Sonic Flashlight to a laser guidance system that aims to improve safety and accuracy of needle insertion, especially for deep procedures. This guidance system is fundamentally different from others currently available. Two low-intensity lasers are mounted on opposite sides of a needle aimed parallel to the needle. The needle is placed against a notch in the Sonic Flashlight mirror such that the laser beams reflect off the mirror to create bright red spots on the flat panel display. Due to diffuse reflection from these spots, the virtual image created by the flat panel display contains the spots, identifying the projected destination of the needle at its actual location in the tissue. We have implemented our design and validated its performance, identifying several areas for potential improvement.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention. 02/2005; 8(Pt 1):647-53.
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ABSTRACT: We have developed a system architecture that will allow a surgeon to employ direct hand-eye coordination to conduct medical procedures in a remote microscopic environment. In this system, a scaled real-time video image of the workspace of a small robotic arm, taken from a surgical microscope camera, is visually superimposed on the natural workspace of a surgeon via a half-silvered mirror. The robot arm holds a small tool, such as a microsurgical needle holder or microsurgical forceps, and the surgeon grasps a second tool connected to a position encoder, in this case, a second robot arm. The views of the local and remote environments are superimposed such that the tools in the local and remote environments are visually merged. The position encoder and small robot arm are linked such that movement of the tool by the operator produces scaled-down movement by the small robot tool. To the surgeon, it seems that his hands and the tool he or she is holding are moving and interacting with the remote environment, which is really microscopic and at a distance. Our current work focuses on using a position-controlled master-slave robot linkage with two 3 degree of freedom haptic devices, and we are pursuing the use of a 6-to-7 degree of freedom master-slave linkage to produce more realistic interaction.
Imaging. 03/2004; 5367:697-704.
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ABSTRACT: From the discovery of X-rays over a century ago, clinicians have been presented with a wide assortment of imaging modalities yielding maps of localized structure and function within the patient. Some imaging modalities are tomographic, meaning that the data are localized into voxels, rather than projected along lines of sight as with conventional X-ray images. Tomographic modalities include magnetic resonance (MR), computerized tomography (CT), ultrasound, and others. Tomographic images, with their spatially distinct voxels, are essential to our present work.
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ABSTRACT: We have successfully created a software environment in which ultrasound data can be manipulated by, ITK (the Insight Tool-Kit), in real-time. We were able to access each frame generated within the resident computer of a TerasonTM Ultrasound Machine, convert it into the ITK image format, and demonstrate the concurrent operation of ITK on the same computer by writing the images to an external hard drive. At a rate of 10 frames per second, 512 by 512 pixel grayscale frames were written by ITK methods to the external hard drive through USB 2.0 while the ultrasound scan was occurring without thrashing or delay in system performance. This simple exercise demonstrates the potential of ITK in processing ultrasound images in real-time in addition to the more traditional off-line processing. University of Biomedical Engineering, Carnegie Mellon University, Pittsburgh PA 15213, USA University of Pittsburgh Medical Center, Pittsburgh PA 15261, USA Department of Biomedical Engineering, University of Pittsburgh, Pittsburgh PA 15261, USA
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ABSTRACT: We have previously developed an algorithm for locating boundaries in an image with sub-pixel resolution, as well as estimating boundary width and image intensity within the adjoining objects. The algorithm operates by finding the parameters of a cumulative Gaussian curve that best approximates an intensity profile taken across a boundary. If intensity is sampled along the image gradient across a boundary, it is reasonable to assume the profile approximates a finite portion of a cumulative Gaussian. Given that assumption, the first derivative of the profile should be the corresponding portion of a Gaussian, completely described by its mean, standard deviation, and amplitude. We present here a simple and rapid method to find those parameters, given that we only have a potentially skewed sample of the Gaussian. The parameters are approximated first for the finite sample, and then both ends of the Gaussian are extrapolated using the resulting parameters. New parameters are then calculated and the procedure is repeated. The optimization rapidly converges, yielding boundary location (mean) with sub-pixel accuracy as well boundary width (standard deviation). Integration then reproduces the cumulative Gaussian, and a least-squares fit is applied to estimate the constant of integration, from which intensity of the adjoining regions can be estimated. University of Biomedical Engineering, Carnegie Mellon University, Pittsburgh PA 15213, USA University of Pittsburgh Medical Center, Pittsburgh PA 15261, USA Department of Biomedical Engineering, University of Pittsburgh, Pittsburgh PA 15261, USA
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ABSTRACT: A hierarchy of path data types and basic path filters were added to ITK, providing a general framework for curves that map a scalar value to a point in n-dimensional space. The framework supports curves that are either continuous (parametric curves) or discrete (chain-codes). Example usage of the entire framework is demonstrated using a previously published 2D active contour algorithm that was converted to ITK. NLM NSF
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ABSTRACT: Using the path framework we previously added to ITK, we implemented a novel algorithm for n-dimensional path optimization, which we call the ND Swath (NDS). NDS uses dynamic programming to globally optimize the placement of a path within an image, subject to several constraints and a user-supplied merit function. The NDS algorithm is presented in this paper along with a description of how it was implemented using ITK. NLM NSF
