Interpretation of three-dimensional structure from two-dimensional endovascular images: implications for educators in vascular surgery

AbstractPurposeEndovascular therapy has had a major effect on vascular surgery; surgeons perform tasks in three dimensions (3D) while viewing two-dimensional (2D) displays. This fundamental change in how surgeons perform operations has educational implications related to learning curves and patient safety. We studied the effects of experience, training, and visual-spatial ability on 3D perception of 2D angiographic images of abdominal aortic aneurysms (AAA).MethodsA novel computer-based method was developed to produce 3D depth maps based on subjects' interpretations of 2D images. Seven experts (certified vascular surgeons) and 20 novices (medical or surgical trainees) were presented with a 2D AAA angiographic image. With software specifically designed for this study, a depth map representing each subject's 3D interpretation of the 2D angiogram was produced. The novices were then randomized into a control group and a treatment group, who received a 5-minute AAA anatomy educational session. All subjects repeated the exercise on a second AAA image. Finally, all novices were given tests of visual-spatial ability, including the Surface Development Test and the Mental Rotations Test. Comparisons between experts and novices were made with depth map comparison, a subject's perception of overall object contour.ResultsThe depth maps were significantly different (depth map comparison, P < .001) between the expert and both novice groups for the first image. After the educational intervention, the control group and the treatment group exhibited significantly different depth maps (depth map comparison, P < .001), with treatment group depth maps more similar to those of the expert group. There were no significant correlations between the visual-spatial tests and the novice depth map comparison with the expert group.ConclusionsThis is the first study to examine perception of endovascular images in an educational context. Perception of overall surface contour of 3D structures from 2D angiographic images is affected by experience and training. With application of methods of vision science to an important problem in surgery, this research represents a first step in understanding the nature of visual perceptual processes involved in execution of an increasingly common clinical task. These results have implications for understanding and studying the endovascular learning curve.Clinical relevanceThis research represents a unique collaboration in an effort to understand and solve one of the greatest problems facing surgical educators and surgeons. This research uses applied tools in vision science to understand the perceptual constraints involved in minimally invasive surgery. Specifically, we examined the mental three-dimensional maps experts use when viewing two-dimensional displays. Furthermore, we compared experts with novices in an effort to assist surgical trainees

Independent effects of familiarity and mating preferences for ornamental traits on mating decisions in guppies

The avoidance of familiar individuals as mates can act to maximize the benefits of polyandry or might help to minimize inbreeding in small or highly philopatric populations. As previous mates are also familiar, the effects of familiarity and mating history can often be confounded. Here, we disentangle these effects on mating decisions in the guppy, Poecilia reticulata, and examine their influence on sexual selection. In 3 experiments, males and females were 1) able to mate, 2) had visual and olfactory contact, or 3) had visual contact only. Familiarity was successfully acquired via visual cues, and females were in all cases more likely to mate with unfamiliar than with familiar males, indicating that familiarity is a more important determinant of mating outcome than mating history. Males did not court unfamiliar females any more than familiar females and did not differentially allocate sperm. Familiarity did not alter the strength of sexual selection on male coloration: we found overall positive selection for bright, large males. Female preferences for unfamiliar males and ornamental traits may therefore be largely independent. Copyright 2006.mate choice; mating history; polymorphism; polyandry; sexual selection; sperm competition

Experimental analysis of some factors affecting parental expenditure and investment in Gasterosteus aculeatus (Gasterosteidae)

Parental investment is the cost of providing parental care. Parental investment was measured in the paternal stickleback, Gasterosteus aculeatus, by comparing future survival (measured indirectly as energy content of the body) and growth of parental and non-parental males. The time taken by parental males to renest was also measured. Male energy content was unaffected after a single parental cycle and no difference in growth rate was detected. Re-nesting was delayed. The effect of stressing parental males by exposing them to potential predators of their offspring and reducing their ration level, was also investigated. Stressed males had reduced energy contents in comparison with unstressed parental males. The time taken by stressed males to re-nest was unaffected. Males on low rations did not fan significantly less than well-fed males. Males exposed to brood predators did fan significantly less than parental males not exposed to brood predators, but the former did spend nearly 60% of their time attacking the predators when present.</p