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At least 865 records · Page 48Linked to original sources
PubMed2006

Multilayer image grid reconstruction technology: four-dimensional interactive image reconstruction of microsurgical neuroanatomic dissections.

OBJECTIVE: Cadaveric dissection is the gold standard for training physicians in various surgical specialties. However, limitations in acquiring and storing sufficient cadaveric material, recent pressures in training opportunities, and progress in digital image technology have led to advances in virtual or artificial visual means to augment surgical training. For training neurosurgeons, the appearance of reality is still crucial for learning anatomic structures and procedures. We developed a four-dimensional (including time) multilayer digital image reconstruction technology (MIGRT) that allows users to manipulate a "volumetric" set of photographic image data from exquisite cadaveric intracranial dissections and to navigate through stages of neurosurgical procedures as the dissection progresses. METHODS: A robotic microscope with two digital cameras was used to capture dissection images, usually in stereoscopic mode. A grid space was created to define positions at which images are captured. Images were acquired from identical angles at the same grid coordinates but at different stages of various dissections. RESULTS: Image data are reconstructed according to the sequence of acquisition into a multilayer image grid system by the MIGRT software. The single interactive, four-dimensional montage is viewable a on common computer platform. CONCLUSION: MIGRT uniquely focuses on capturing anatomic content that preserves natural appearances, including procedure, texture, and color, which is far superior and preferable to images and a reconstructed image environment based on artificial or animated concepts. MIGRT shows time-dependent changes in procedures, provides depth perception by stereoscopy or unique sequential motion, and allows simultaneous interactivity at each step of the procedure.

Brain↗
PubMed1999

Active electrolocation of objects in weakly electric fish

Weakly electric fish produce electric signals (electric organ discharges, EODs) with a specialised electric organ creating an electric field around their body. Objects within this field alter the EOD-induced current at epidermal electroreceptor organs, which are distributed over almost the entire body surface. The detection, localisation and analysis of objects performed by monitoring self-produced electric signals is called active electrolocation. Electric fish employ active electrolocation to detect objects that are less than 12 cm away and have electric properties that are different from those of the surrounding water. Within this range, the mormyrid Gnathonemus petersii can also perceive the distance of objects. Depth perception is independent of object parameters such as size, shape and material. The mechanism for distance determination through electrolocation involves calculating the ratio between two parameters of the electric image that the object projects onto the fish's skin. Electric fish can not only locate objects but can also analyse their electrical properties. Fish are informed about object impedance by measuring local amplitude changes at their receptor organs evoked by an object. In addition, all electric fish studied so far can independently determine the capacitative and resistive components of objects that possess complex impedances. This ability allows the fish to discriminate between living and non-living matter, because capacitance is a property of living organisms. African mormyrids and South American gymnotiforms use different mechanisms for capacitance detection. Mormyrids detect capacitance-evoked EOD waveform distortions, whereas gymnotiforms perform time measurements. Gymnotiforms measure the temporal phase shift of their EODs induced at body parts close to the object relative to unaffected body parts further away.

Journal Article↗
PubMed2000

Robotic-assisted internal fixation of hip fractures: a fluoroscopy-based intraoperative registration technique.

The internal fixation of proximal femoral (hip) fractures is the most frequently performed orthopaedic surgery procedure. When using a sliding compression hip screw, a commonly used fixation device, accurate positioning of the device within the femoral neck-head is achieved by initially drilling a pilot hole. A cannulated component of the hip screw is then inserted over the guide wire (surgical drill bit), which is used to drill the pilot hole. However, in practice, this fluoroscopically controlled drilling process is severely complicated by a depth perception problem and, as such, a surgeon can require several attempts to achieve a satisfactory guide wire placement. A prototype robotic-assisted orthopaedic surgery system has therefore been developed, with a view to achieving accurate right-first-time guide wire insertions. This paper describes the non-invasive digital X-ray photogrammetry-based registration technique which supports the proposed robotic-assisted drilling scenario. Results from preliminary laboratory (in vitro) trials employing this registration technique indicate that the cumulative error associated with the entire X-ray guided robotic system is within acceptable limits for the guide wire insertion process.

Fluoroscopy↗
PubMed1980

Sensory development of Felis catus.

The sensory development of 22 kittens was observed for 12 weeks. Vision-related responses began as a palpebral reflex at 1.8 days and continued as a light blink response at 5.7 days (mean values). The eyes unsealed between days 6 and 17 and the pupillary reflex was well developed within a few days. Depth perception began at 13.2 days mean. Auditory development progressed rapidly after the opening of the external canals between days 7 and 14. Pain and rooting reflexes were present at birth, while auriculonasocephalic and Galant's reflexes were highly variable.

Aging↗
PubMed1997

A protocol for telemedical consultation.

We have developed a protocol for telemedical consultations. This has been used by emergency nurse practitioners to consult doctors in a main hospital accident and emergency department, using videoconferencing at 384 kbit/s. A telemedical consultation should simulate a face-to-face one. The protocol starts with an explanation for the patient of what will happen, followed by the necessary introductions. After relaying the history, the generalist should show the abnormal part to the specialist. Attention should be paid to colour. Depth perception is often enhanced by rotating the camera through 180 degrees. The diagnosis and management, together with their implications, should be discussed with the patient by the specialist. Referral and follow-up should also be discussed. Proper clinical record-keeping is essential. In the first 15 months of using the protocol, we completed more than 300 teleconsultations. An analysis of the first 50 teleconsultations showed that about half were for discussing a radiograph and about half were for examining a patient.

Clinical Protocols↗
PubMed2001

Ideal cue combination for localizing texture-defined edges.

Many visual tasks can be carried out by using several sources of information. The most accurate estimates of scene properties require the observer to utilize all available information and to combine the information sources in an optimal manner. Two experiments are described that required the observers to judge the relative locations of two texture-defined edges (a vernier task). The edges were signaled by a change across the edge of two texture properties [either frequency and orientation (Experiment 1) or contrast and orientation (Experiment 2)]. The reliability of each cue was controlled by varying the distance over which the change (in frequency, orientation, or contrast) occurred-a kind of "texture blur." In some conditions, the position of the edge signaled by one cue was shifted relative to the other ("perturbation analysis"). An ideal-observer model, previously used in studies of depth perception and color constancy, was fitted to the data. Although the fit can be rejected relative to some more elaborate models, especially given the large quantity of data, this model does account for most trends in the data. A second, suboptimal model that switches between the available cues from trial to trial does a poor job of accounting for the data.

Contrast Sensitivity↗
PubMed2006

Toward the improvement of image-guided interventions for minimally invasive surgery: three factors that affect performance.

OBJECTIVES: The objectives were to measure the impact of specific features of imaging devices on tasks relevant to minimally invasive surgery (MIS) and to investigate cognitive and perceptual factors in such tasks. BACKGROUND: Although image-guided interventions used in MIS provide benefits for patients, they pose drawbacks for surgeons, including degraded depth perception and reduced field of view (FOV). It is important to identify design factors that affect performance. METHOD: In two navigation experiments, observers fed a borescope through an object until it reached a target. Task completion time and object shape judgments were measured. In a motion perception experiment, observers reported the direction of a line that moved behind an aperture. A motion illusion associated with reduced FOV was measured. RESULTS: Navigation through an object was faster when a preview of the object's exterior was provided. Judgments about the object's shape were more accurate with a preview (compared with none) and with active viewing (compared with passive viewing). The motion illusion decreased with a rectangular or rotating octagonal viewing aperture (compared with circular). CONCLUSIONS: Navigation performance may be enhanced when surgeons develop a mental model of the surgical environment, when surgeons (rather than assistants) control the camera, and when the shape of the image is designed to reduce visual illusions. APPLICATION: Unintentional contact between surgical tools and healthy tissues may be reduced during MIS when (a) visual aids permit surgeons to maintain a mental model of the surgical environment, (b) images are bound by noncircular apertures, and (c) surgeons manually control the camera.

Humans↗
PubMed1975

A note on illusions.

The crucial factor in illusion is not in perception but rather in the assumption that all two-dimensional drawings represent two-dimensional reality. This leads in some cases to making unwarranted comparisons between parts of the figures.

Color Perception↗
PubMed1984

Evidence for color-contingent organizational aftereffects.

An effort was made to produce negative organizational aftereffects in response to a perceptually ambiguous stimulus that can be seen as a cube in either of two orientations. 6 subjects were adapted to alternative disambiguated versions of the ambiguous cube, shown either in green or magenta light. When tested with the ambiguous figure shown in either green or magenta light, 5 subjects showed negative aftereffects while one subject showed a positive aftereffect. The aftereffects showed an average change in preferred organization of 25%. The results are interpreted in terms of both cognitive and hard-wired processes.

Adult↗
PubMed1991

A freehand method for drawing stereoscopic pictures.

A method for the freehand drawing of anaglyphs is described. Usually textbooks cover the topic of stereopsis in an abstract way, making it difficult for students to grasp. The present method enables students to draw anaglyphs by hand and should make the concept of binocular disparity more easily learned.

Attention↗
PubMed1993

Colour and spatial performance.

An experiment was conducted to examine the influence of colour on spatial performance as measured with traditional tests for 29 adults. Spatial performance was significantly higher when testing material with highly saturated colours was used in comparison to colours of low saturation and achromatic shades.

Adult↗
PubMed1995

A size illusion from simultaneous changes in length and direction of a line pattern.

A circle was attached to one of three lines which were changing in length and direction simultaneously. This configuration of moving lines had been found previously to induce the perception of depth. Of 26 observers 20 reported that the moving circle appeared smaller in size than a physically equal stationary circle which was located outside the changing, depth-inducing configuration.

Depth Perception↗
PubMed2003

Role of perceptual and motor abilities in instep-kicking performance of young soccer players.

The present study made a dynamic analysis of the ground reaction forces developed on the supporting foot during instep kicking to investigate the relation between specific perceptual and motor abilities and the performance of this skill. 45 young soccer players (11-13 years of age) participated in a series of laboratory tests assessing simple, choice, and discrimination reaction time, sustained attention, depth perception, and sense of kinesthesis. Kicking performance measured by the amount of impulse (calculated as the integral of force) developed on the supporting foot during kicking. There was a significant correlation of the kicking impulse with choice reaction time (r = -.54) and attention reaction time (r = -.41). Stepwise regression analysis indicated that choice reaction time accounted for 29% of the variation in the anterior/posterior kicking impulse and 16.4% of the variation in the medio/lateral kicking impulse. The significant relation between kicking impulse and measures concerning speed of information processing suggests that processes associated with fast response selection may play an important role in instep-kicking performance. These findings can provide useful information for designing of training schemes and testing protocols.

Adolescent↗
PubMedDate not supplied

Modelling and simulation in medicine and life sciences.

Modelling and Simulation in Medicine and Life Sciences' was the topic of a workshop held in Copenhagen at MIE'96 and of a session in Zakopane in 1997. A survey of some of the papers presented at these meetings and selected for this issue is made. The selection was made according to the topics, referring to modelling and simulation of fundamental biological processes: dynamic behaviour of the human respiratory system, wave propagation in normal and infarcted myocardium, electrical field generated by the heart, human chest conductivity, and depth perception in binocular vision.

Computer Simulation↗