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At least 235 records · Page 13Linked to original sources
PubMed1999

Weakening the robustness of perspective: evidence for a modified theory of compensation in picture perception.

Viewed from the center of projection, a perspective picture presents the pictorial depth information of a scene. Knowing the center of projection, one can reconstruct the depicted scene. Assuming another viewpoint is the center of projection will cause one to reconstruct a transformed scene. Despite these transformations, we appreciate pictures from other viewpoints. The compensation hypothesis states that the visible picture surface allows observers to compensate for transformations by locating the center of projection and experiencing pictorial space from there. We show that observers neither completely compensate for nor experience transformations of space as geometry would predict. We propose a modified compensation hypothesis according to which different degrees of visibility of the picture surface invoke different degrees of compensation.

Female↗
PubMed1989

[Neocortical dysplasias].

Neocortical dysplasia is the morphological expression of neocortical malformation. Its expression prevails in the areas surrounding the Sylvian fossa (opercula). Delayed opercularization, abnormal inclination angle of the Sylvian fissure and abnormal gyral patterns surrounding the fossa are the main abnormalities, made visible by MRI-sections, especially the lateral projections. The present study, which is part of a broader study on neocortical maldevelopment, involves the search for correlations between macroscopic and microscopic neocortical dysplasia, with the object of improving MRI diagnosis of neocortical dysplasia.

Cerebral Cortex↗
PubMedDate not supplied

Human cochlear aqueduct and its accessory canals.

The anatomy of the adult human cochlear aqueduct and its surrounding structures, and their normal variations at tomography, microdissection and plastic molding are described. The mean length of the aqueduct is 12.9 mm and the mean width of its funnel-shaped external aperture 4.2 mm. The mean width of the narrowest portion is 0.14 mm. No difference in aqueductal width was found between the youngest and oldest age groups. Complete bony obstruction was revealed at microdissection in 3 out of 82 specimens. In the remaining 79 the entire aqueduct was patent. The aqueduct usually runs parallel to the internal auditory canal when seen from above, and the AP projection is therefore most suitable for tomography. At tomography the entire aqueduct was visualized in 60% of the specimens. The isthmic portion was not visible in 40%. Major reasons for nonvisualization of the entire aqueduct are: 1) a luminal width less than 0.1 mm, 2) a high jugular fossa, 3) a posteriorly directed aqueductal convexity (10%), and 4) bony obliteration (4)%). Accessory canals close to and often wider than the aqueduct may complicate tomographic evaluation of the aqueductal patency. Nonvisualization of the aqueduct at tomography does not necessarily indicate nonpatency.

Adult↗
PubMed1995

A virtual reality environment for enhanced oral implantology.

The quality of clinical decision making is limited by the performance of human cognitive processing of complex visual information. In the field of oral implantology, treatment planning is still based on the holistic interpretation and mental reconstruction of cross sectional 2d-image data. This surpasses widely human cognitive competence and hampers treatment planning in three dimensions that are essential in implantology. To overcome these problems, a virtual reality environment for enhanced treatment planning in oral implantology is presented, which provides a fully three-dimensional perception of an individual clinical situation. It enables the clinician to perceive and handle the objects of her work in a virtual world as needed for the task of diagnosis and treatment. Human visual decoding effort is thus reduced, and estimating the real position and orientation of implants during planning is enabled in any direction. Immersive three-dimensional perception is achieved by hybrid stereoscopic rendering techniques combined with large screen projections. The virtual world in which treatment planning takes place allows the clinician to move and interact with the individual anatomy simultaneously with three degrees of freedom. A set of virtual tools enables the clinician to perform a virtual treatment "in advance." The design and placement of implants, as it is interactively controlled by the clinician, is simulated in real-time. Thus the results of actions become immediately visible and provide visible feedback for interactive adjustment. In addition, the presented virtual reality environment for oral implant treatment planning includes algorithms for detection of inappropriate treatment in the concerned bone regions, according to the current design of the implant. These algorithms take both the individual properties of a patient's bone and the type of implants used into account.

Computer Simulation↗
PubMed1992

Stability of capillary gels for automated sequencing of DNA.

Recent interest in capillary gel electrophoresis has been fueled by the Human Genome Project and other large-scale sequencing projects. Advances in gel polymerization techniques and detector design have enabled sequencing of DNA directly in capillaries. Efforts to exploit this technology have been hampered by problems with the reproducibility and stability of gels. Gel instability manifests itself during electrophoresis as a decrease in the current passing through the capillary under a constant voltage. Upon subsequent microscopic examination, bubbles are often visible at or near the injection (cathodic) end of the capillary gel. Gels have been prepared with the polyacrylamide matrix covalently attached to the silica walls of the capillary. These gels, although more stable, still suffer from problems with bubbles. The use of actual DNA sequencing samples also adversely affects gel stability. We examined the mechanisms underlying these disruptive processes by employing polyacrylamide gel-filled capillaries in which the gel was not attached to the capillary wall. Three sources of gel instability were identified. Bubbles occurring in the absence of sample introduction were attributed to electroosmotic force; replacing the denaturant urea with formamide was shown to reduce the frequency of these bubbles. The slow, steady decline in current through capillary sequencing gels interferes with the ability to detect other gel problems. This phenomenon was shown to be a result of ionic depletion at the gel-liquid interface. The decline was ameliorated by adding denaturant and acrylamide monomers to the buffer reservoirs. Sample-induced problems were shown to be due to the presence of template DNA; elimination of the template allowed sample loading to occur without complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoanalysis↗
PubMed2001

Cerebellopontine angle meningioma with a high jugular bulb.

A cerebellopontine angle meningioma originating from the skull base over a high jugular bulb is quite rare. We report a case of a 68-year-old woman who had a right cerebellopontine angle meningioma with a prominent high jugular bulb. CT and MRI revealed a round tumour which attached to a bony prominence over the high jugular bulb. The apex of the jugular bulb was 3 mm higher than the floor of the internal auditory canal. The tumour was removed via a suboccipital retrosigmoid approach. The bony projection was drilled off carefully using a diamond drill; the jugular bulb became visible through the thinned bone. When a meningioma of this type is removed including bony changes, special attention is needed to avoid injury to the jugular bulb.

Aged↗
PubMed1993

Collaborating with nonphysician professionals in practice-based research. Dizziness Research Group.

Although much has been written about the importance of collaboration among physicians in practice-based research, the relationship between the clinical investigator and nonphysician professionals in this setting has received less attention. Nurses, physician assistants, and other office support staff can provide valuable insights pertinent to research design and project implementation. Because nonphysician professionals frequently play a large part in implementing a research project, how well the investigator collaborates with them often determines the success or failure of the project. We suggest the following guidelines: 1. Consider the research interests of the nonphysician collaborators. 2. Adapt the project to office routine. 3. Limit the demands on staff. 4. Use detailed protocols. 5. Orient all collaborators. 6. Be available and visible. 7. Provide feedback and reward to all collaborators.

Allied Health Personnel↗
PubMed1999

Staging of prostate cancer using 3-dimensional transrectal ultrasound images: a pilot study.

PURPOSE: We used conventional transrectal ultrasound images for 3-dimensional (D) reconstruction of the prostate, and determined its value in staging clinically localized prostate cancer. MATERIALS AND METHODS: A total of 36 patients with newly diagnosed clinically localized prostate cancer were studied. All patients underwent conventional transrectal ultrasonography with 3-D reconstruction. Images were examined and analyzed blindly, and findings were compared to histopathological staging following radical prostatectomy. RESULTS: Pathological staging of specimens revealed 15 sites of extracapsular extension in 10 patients, of whom 8 had positive margins and 2 had seminal vesicle invasion. The 3-D imaging identified 12 sites of extracapsular extension in 9 patients with 80% sensitivity, 96% specificity and 90% positive predictive value. Of the 2 patients with seminal vesicle invasion 1 was identified correctly on 3-D images. Overall staging accuracy of 3-D imaging was 94%. CONCLUSIONS: The 3-D reconstruction of conventional transrectal ultrasonography imaging is superior to 2-D imaging for staging localized prostate cancer. However, this advantage relies entirely on the visibility of prostate cancer lesions on conventional ultrasonography. Further studies are warranted to evaluate this technology for the management of prostate cancer.

Aged↗
PubMed2000

A council of elders: creating a multi-voiced dialogue in a community of care.

In an era of 'medical care delivery systems', there is an increasing need for the patient's voice to be heard, for it to be invited, listened to, and taken seriously. This challenge is particularly evident in geriatrics education, a domain of clinical training in which educators and clinicians alike must struggle to overcome adverse attitudes towards the elderly ('ageism'). In this paper we introduce a 'Council of Elders' as an educational innovation in which we invited community elders to function as our 'Senior Faculty', to whom medical residents present their challenging and heartfelt dilemmas in caring for elder patients. In the conversations that ensue, the elders come to function not simply as teachers, but collaborators in a process in which doctors, researchers, and elders together create a community of resources, capable of identifying novel ways to overcome health-related difficulties which might not have been apparent to either group separately. Using the first meeting of the Council as an exemplar, we describe and discuss the special nature of such meetings and also the special preparations required to build a dialogic relationship between participants from very different worlds--different generations, different cultures (including the professional culture and the world of lived experience). Meetings with the council have become a required part of the primary care residency program--a very different kind of 'challenging case conference' in which moral dilemmas can be presented, discussed and reflected upon. It is not so much that elders give good advice in their responses--although they often do--as that they provide life world and value orientation as young residents gain a better sense of the elder's experience and what matters most to them. This project has been particularly worthwhile in addressing the problem of ageism--a way to render visible stereotypes and adverse physician values, with implications for decision-making with the patient, not for the patient.

Aged↗
PubMed2005

Cardio navigation: planning, simulation, and augmented reality in robotic assisted endoscopic bypass grafting.

BACKGROUND: The aim of this study is to optimize the set-up and port placement in robotic surgery and enhance intraoperative orientation by video overlay of the angiographic coronary tree. METHODS: In three mongrel dogs and two sheep an electrocardiogram-triggered computed tomographic scan and coronary angiography were performed after placing cutaneous fiducials. The regions of interest (ie, heart, ribs, coronaries, internal thoracic artery) were segmented semiautomatically to create a virtual model of the animal. In this model the target regions of the total endoscopic bypass procedure along the internal thoracic artery and anastomotic area were defined. Algorithms for weighing visibility, dexterity, and collision avoidance were calculated after defining nonadmissible areas using a virtual model of the manipulator. Intraoperatively, registration of the animal and the telemanipulator was performed using encoder data of the telemanipulator by pointing to the fiducials. After pericardiotomy, the reconstructed coronary tree was projected into the videoscopic image using a semiautomatic alignment procedure. In dogs, the total endoscopic bypass procedure was completed on the beating heart. The first human case applying preoperative planning, intraoperative registration, and augmented reality was subsequently performed. RESULTS: The rigid transformation linked the patient's preoperative frame and the robot coordinate frame with a root mean square error of 9 to 15 mm. The predicted port placement derived from the model initially varied from the one chosen due to an incomplete formulation of the weighing procedure. After only a few iterations, the algorithm became robust and predicted a collision free triangle. Video overlay of the angiographic coronary tree into the videoscopic image was feasible. CONCLUSIONS: Surgical planning and augmented reality are likely to enhance robotic surgery in the future. A more complete understanding of the surgical decision process is required to better formalize the planning algorithms.

Algorithms↗
PubMed2002

The contribution of trabecular bone to the visibility of the lamina dura: an in vitro radiographic study.

OBJECTIVE: The objective of this study was to determine the degree to which trabecular bone contributes to the radiographic visibility of lamina dura. STUDY DESIGN: Segments of human cadaver mandible were obtained and split longitudinally. Two identical radiographs were made of each segment (1) before the removal of any additional bone and after (2) the removal of a small amount of the lamina dura at the apex of a tooth, (3) block removal of trabecular bone, and (4) smoothing of the endosteal surface of the external cortex. The radiographs were projected in random pairs for each sample. Six dentists judged whether a difference in the amount of lamina dura could be detected between 2 sets of radiographs. RESULTS: Chi-square analysis revealed a significant radiographic difference between radiographs made initially and after removal of the lamina dura and trabecular bone. CONCLUSIONS: Fewer than half of the changes of lamina dura loss alone could be detected radiographically by the observing dentists, whereas nearly all cases of the loss of periapical lamina dura in conjunction with loss of trabecular bone could be detected.

Aged↗
PubMed1981

Radiographic screening for breast carcinoma. III. Appearance of carcinoma and number of projections to be used at screening.

The films of 117 patients with mammary carcinoma detected at population screening were reviewed. Sixteen per cent (19) of the women proved to have non-invasive and 43 per cent (50) small invasive carcinomas (diameter less than or equal to 10 mm). Calcifications were the dominating abnormality in 95 per cent of the non-invasive carcinomas, while a tumour mass was the most frequent abnormality in small invasive carcinomas. It was found that the appearance of small tumours may vary considerably from one projection to another and also on films in one and the same projection. Thus, approximately 20 per cent of small invasive carcinomas were either not visible or equivocal in one of the two projections used at screening. The corresponding figure for larger invasive carcinomas (diameter greater than 10 mm) was approximately 7 per cent. It is concluded that films in two projections, preferably the craniocaudal and oblique, should be obtained at screening.

Aged↗
PubMedDate not supplied

Increasing the length of the middle crura for better tip projection in primary rhinoplasty.

Cartilage grafts have been a very popular method for achieving tip projection in difficult noses. Sometimes asymmetries and graft visibility are undesirable complications. Remodeling the alar cartilages, using a cartilage flap from the lateral crura, rotated over the original domes, is another alternative for achieving tip refinement and projection. The surgical technique is described and clinical results are presented.

Adolescent↗
PubMed1991

Cerebral MR angiography with multiple overlapping thin slab acquisition. Part I. Quantitative analysis of vessel visibility.

Multiple overlapping thin slab acquisition (MOTSA) is a novel time-of-flight magnetic resonance (MR) angiography technique that combines many of the advantages of multiple-section two-dimensional and direct three-dimensional volume methods. To rigorously evaluate the vascular detail that can be obtained with MOTSA MR angiography, the authors have quantified the frequency of visibility of intracranial arterial segments and have correlated their visibility with vessel size as measured at cut-film angiography and with the position and orientation of the arterial segment. Intracranial arterial segments at least 0.9 mm in diameter (the voxel dimension used in the current application) are consistently visualized with the MOTSA technique. The fraction of small vessels visualized is improved when voxel dimensions are reduced. Visibility is noticeably better in the primary images compared with the maximum-intensity-projection (MIP) images. Top-of-slab saturation and resulting decreased vessel intensity occurred infrequently and did not result in marked image degradation in the axial images.

Adult↗
PubMedDate not supplied

Presentation skills for the reluctant speaker.

Presentation skills are vital to clinical systems managers. This article covers four steps to successful presentations: 1) tailoring for an audience, 2) organizing a presentation, 3) mastering presentation techniques, and 4) creating effective visual aids. Tailoring for the audience entails learning about the audience and matching the presentation to their knowledge, educational level, and interests. Techniques to curry favor with an audience include: establishing common ground, relating through universal experiences, and pushing "hot buttons." Tasks involved in organizing the presentation for maximum audience interest begin with arranging the key points in a transparent organizational scheme. Audience attention is sustained using "hooks," such as graphics, anecdotes, humor, and quotations. Basic presentation techniques include appropriate rehearsal, effective eye contact with an audience, and anxiety-reducing strategies. Visual aids include flip charts, slides, transparencies, and computer presentations. Criteria for selecting the type of visual aids are delineated based on audience size and type of presentation, along with respective advantages and disadvantages. The golden rule for presentations is "Never show a slide for which you have to apologize." Rules to maximize visibility and effectiveness, including use of standard templates, sans serif fonts, dark backgrounds with light letters, mixed cases, and effective graphics, ensure that slides or projected computer images are clear and professional. Taken together, these strategies will enhance the delivery of the presentation and decrease the speaker's anxiety.

Clinical Competence↗
PubMed1978

The determination of anatomical cross-sections using a radiotherapy simulator.

A system for obtaining anatomical cross-sections for treatment planning using a radiotherapy simulator is described. A fluorescent screen is viewed by a low light level Isocon television camera and the video signal is digitized and stored. Many projections of the phantom are obtained by rotating the simulator gantry. A convolution algorithm has been used to reconstruct chest sections in which skin and lung outlines are visible. The technique could also be used to make corrections to radiotherapy dose distributions where irradiation of lung tissue is involved.

Humans↗
PubMed2003

Transurethral ureterorenolithotripsy using new automated irrigation/suction system controlling pressure and flow compared with standard irrigation: a randomized pilot study.

PURPOSE: To compare in a random fashion an automated irrigation/suction pump system with the standard pressurized technique during transurethral ureterorenolithotripsy. PATIENTS AND METHODS: Between July 2001 and December 2001, 47 patients were prospectively included. Prior to randomization, rigid instruments were allocated to 25 patients (group R) and flexible instruments to 22 patients (group F) according to stone location. The groups R and F were then randomized separately, and the pressurized technique was employed in groups R1 and F1, while the automated system was employed in groups R2 and F2. Operative time, amount of liquid consumed, and stone-free rate at the end of the procedure were analyzed. RESULTS: For the entire series, ureteroscopy time using the automated system (mean 42 +/- 17[SD] minutes; range 15-90 minutes) was 35% less than with the pressurized technique (mean 65 +/- 25 minutes; range 20-135 minutes) (P = 0.04 Wilcoxon score). The stone-free rate was significantly higher in groups R2 + F2 (92%) than in groups R1 + F1 (69%) (P = 0.048). CONCLUSION: With the ENDO FMS UROLOGY system, there was a significant reduction in the mean ureteroscopy time: 32% less with the rigid instrument and 53% less with the flexible instrument. This seems to be attributable to a wider working space and highly improved visibility. The integrated suction at constant flow allows efficient evacuation of stone fragments while limiting cavity pressure. These results, obtained on 47 patients, should be confirmed by larger randomized studies.

Humans↗
PubMed2005

[What drugs users say and do not say, using experiences and the projective technique].

This study aimed to get to know some visible and hidden meanings in drugs users' experience. The interviews were associated with the Projective Technique (free and thematic drawing), based on which we analyzed the subjective content and what was expressed by the users. The results demonstrated the existence of family deterioration, stigma and prejudice.

Adult↗