Outline Shape Research Articles

A simulation of the effects of set-up error and changes in breastvolume on conventional and intensity-modulated treatments in breastradiotherapy

The effect of interfractional patient movement on dosimetry has beeninvestigated for breast radiotherapy. Errors in patient set-up and changes inbreast volume were simulated individually to determine how each contributes tothe total dosimetric error. Two treatment techniques were investigated: aconventional treatment and an intensity-modulated treatment delivered usingcompensators. Six patients were investigated and anterior-posterior (AP) andsuperior-inferior (SI) displacements were simulated by displacing theisocentre in both directions by 2, 5 and 10 mm. A model of the breast wasdeveloped from the six patients to simulate changes in breast volume. In thismodel, the breast was described as a set of semi-ellipses. The volume of thebreast was changed by varying the magnitude of the semi-major and semi-minoraxes. Anisotropic changes in breast volume were also investigated. Thedosimetric error was evaluated for each dose plan by calculating the volumeoutside the 95-105% dose range resulting from the simulations. A number ofparameters describing the size and shape of the breast were also investigatedto determine whether a susceptibility of outline sets to interfractionalpatient movement could be predicted. A parameter describing the increase inthe breast volume outside the 95-105% dose range was calculated for AP andSI set-up errors of ±3 mm and changes in breast volume of 5%.Results revealed that set-up errors were likely to cause larger increases inthe volume outside the 95-105% dose range than changes in breast volume fortypical set-up errors and changes in breast volume that occur duringtreatment. The magnitude of the set-up errors and changes in breast volumewere observed to be dependent on the shape outline set. Statisticallysignificant linear correlation was observed between the increase in the volumeoutside the 95-105% dose range and several of the evaluation parameters.

The statistical analysis of plant part appearance — a review

Visual appearance is widely used in assessing the variety or cultivar of crop samples, and in biological taxonomy in general. With computer storage capabilities becoming more easily accessible, image databases of plant specimens can be readily constructed. To make full use of this powerful facility, an important task is to compare different images, or to summarise them. This review addresses the question of how this may be done, given that images are stored as typically 10 5–10 7 highly structured measurements. Image analysis is a wide subject area, and this review covers those parts of it which are relevant to this task. The task is subdivided into four (2×2) categories according to whether we are interested in outline shape only or in colour details, and whether the global position of object details is important, or only their local distribution. We refer to these approaches as local shape, global shape, colour distribution and colour detail (eigenimage analysis). As far as possible, we avoid a priori ideas regarding what features of objects are important, and seek methods which capture the full variability of their appearance. The techniques are illustrated by reference to work on carrots.

Generalized figure-control algorithm for large segmented telescope mirrors

A fundamental discovery in segmented-mirror active optics is described: symmetrizing the geometry of the sensor–actuator array provides a computationally effective symmetrization of the mathematical description for the figure control of a Keck-type telescope mirror. The author establishes a universal mathematical control model and provides an efficient algorithm to solve this model equation set. This model can be applied to multifarious Keck-type mirror configurations with a similar sensor–actuator geometry design, no matter what kind of outline shapes and how many segments they have. With the underlying symmetry, a further extension of this algorithm is possible without increasing the number of parameters to be estimated for the recently proposed extremely large telescopes, such as the 30-m California Extremely Large Telescope (CELT) and the 100-m OverWhelmingly Large (OWL) telescope. Moreover, careful choice of boundary conditions in conjunction with the proper choice of minimization algorithm yields results that exceed the performance of the current existing techniques given by Nelson and Mast [Appl. Opt.21, 2631 (1982)]. This method allows noise performance analysis. Several computer simulation models for application of this algorithm are given for the Keck 10-m Telescope and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope’s (LAMOST’s) MA (Reflecting Schmidt plate) and MB (spherical primary mirror).

In vitro efficacy of nikkomycin Z against the human isolate of the microsporidian species Encephalitozoon hellem.

Since 1985 microsporidia have been recognized as a cause of emerging infections in humans, mainly in immunocompromised human immunodeficiency virus-positive subjects. As chitin is a basic component of the microsporidian infective stage, the spore, we evaluated in vitro the susceptibility of a human-derived strain of Encephalitozoon hellem to nikkomycin Z, a peptide-nucleoside antibiotic known as a competitive inhibitor of chitin synthase enzymes. Transmission electron microscopy showed that this drug, at 25 microgram/ml, reduced the number of parasitic foci by about 35% +/- standard deviation after 7 days of culture (P < 0.0001) and induced cell damage of both mature and immature spores and also other sporogonic and merogonic stages. In particular, an irregular outline of the cell shape and an abnormally condensed cytoplasm in meronts and sporonts were documented. Also, the polar tubule and the polaroplast membranes appeared disarrayed in the sporoblast stage. The spore wall showed an enlarged endospore and delaminated exospore. Mature spores had a complete cytoplasmic disorganization and a swollen and delaminated cell wall. No ultrastructural cell damage was observed in uninfected control cultures treated with the drug.

Improvements To The Method Of Fourier Shape Analysis As Applied In Morphometric Studies

Fourier outline shape analysis is a powerful tool for the morphometric study of two‐dimensional form in organisms lacking many biologically homologous landmarks. Several improvements to the method are described herein; these modifications are incorporated into the new computer programs Hangle, Hmatch and Hcurve. First, automated tracing of outlines using image capture software, although desirable, results in high frequency pixel ‘noise’ that can corrupt the Fourier analysis. Program Hangle eliminates this noise using optional and variable levels of outline smoothing. Secondly, a widely used Fourier technique, elliptic Fourier analysis (EFA, Kuhl and Giardina 1982), yields coefficients that are not computationally independent of each other, a condition that hampers and compromises statistical analysis. In addition, EFA increasingly downweights successively more detailed features of the outline. Program Hangle solves both of these problems. Lastly, Fourier methods in general are sensitive to the placement of the starting position of the digitized trace. This problem is acute when the organisms under study have no unambiguously defined, homologous point on the outline from which to start the trace. Program Hangle allows the user to normalize for starting position using various properties of individual outlines. Alternatively, Hmatch takes a new approach and can be used to normalize using properties of the entire population under study.key words: Fourier shape analysis, morphometric studies, new computer programs, foraminiferal outlines.

Sentence and Word Outline Shape as Co-primes for Target Words Presented to the Two Visual Hemifields

A lexical decision experiment tested visual field stimulation of word targets after priming the central visual field by the target word outline shape and/or an incomplete sentence. In general, RT was shorter and accuracy better for target words presented to the RVF. Responses were quicker and more accurate to target words presented to either visual hemifield after priming by either a congruent incomplete sentence or a congruent word outline shape (WOS). However, the joint effect of WOS and an incomplete sentence as co-primes was different when the succeeding word target appeared in the RVF than when it appeared in the LVF. While a congruent WOS and incomplete sentence acting as co-primes reduced RT to LVF targets orthogonally, the two variables operated interactively as co-primes on target words presented to the RVF.

Sex Differences in Proximal Humeral Outline Shape: Elliptical Fourier Functions

A method is presented for the numerical analysis of sex differences in size and shape of the proximal humeral outlines using elliptical Fourier functions (EFFs). A skeletal sample consisting of right and left humeri pairs of 69 individuals, 36 males and 33 females, was used. The proximal superior view in the plane of the proximo-distal axis of each humerus was photographed and then 54 boundary points were located on the two-dimensional outline tracings. These points were digitized and used to compute EFFs with 27 harmonics. From the EFFs, a set of expected points on the proximal humeral outline was generated using the centroid as an origin. Superimposition of the male and female outlines on this centroid provided a detailed picture of the relative sex differences in size and shape with respect to that center. The bounded area of the proximal humeral outline showed statistically significant sex differences. Additionally, statistical results of the amplitudes derived from the "area-standardized" EFFs and visual assessments of the mean outline plots indicated significant sex differences in shape of the proximal humeral outlines. Focusing on localized regional differences, the greater tubercle was located more postero-medially and the lesser tubercle was located more anteriorly in the males compared to the females. Sex determinations from the proximal humeri were also examined with discriminant functions based on the amplitudes, which represent shape characteristics of the outline, and the hounded area. Using a cross-validation method, predictions of the percentages of cases correctly classified with the discriminant functions were ranged from 92.8% to 95.7% for the right and left humeral data. These results suggest that differences in size and shape of the proximal humeral outlines may be better predictors of sex when compared with conventional measurements of the humerus.

Heritability, phenotypic and genetic correlations of size and shape of Drosophila mediopunctata wings.

We have studied the morphology of wings of Drosophila mediopunctata employing the ellipse method, a procedure that allows precise descriptions of wing size (SI), wing shape outline (SH), and placement of longitudinal wing veins. We have found that the SH and the points which determine the position of the apices of the third, fourth and fifth longitudinal wing veins show high heritability in nature (the lower bound for the natural heritability is above 0.25). The values found are similar to those obtained for the broad-sense heritabilities (H2) in the laboratory. However, SI and the point which determines the apex of the second longitudinal wing vein showed small lower bounds for heritability in nature, 0.05 and 0.07, respectively, in spite of the high estimates of H2 in the laboratory. These results suggest that size and shape have different genetic properties. We observed a high positive phenotypic correlation between the SH, the fourth and the fifth longitudinal wing veins, which contrasts with a negative correlation between these traits and the second longitudinal vein. That is, as the SH gets longer, the apices of the second and fifth veins become closer to each other. Positive genetic correlations in the field were detected between SH, the fourth and the fifth longitudinal veins and also between the third and the fourth veins.

The Financing of Hydropower, Irrigation and Water Supply Infrastructure in Developing Countries

A companion paper in the previous issue of this journal (Briscoe, 1999) describes the changing face of infrastructure financing in developing countries. This paper deals with the financing of major infrastructure in the water-related sectors-hydropower, water supply and sanitation, irrigation, and overall water resources management (including the environment). The overall level of investment in water-related infrastructure in developing countries is estimated to be of the order of $65 billion annually, with the respective shares about $15 billion for hydro, $25 billion for water and sanitation and $25 billion for irrigation and drainage. About 90% of this investment comes from domestic sources, primarily from the public sector. Water-related infrastructure accounts for a large chunk-about 15%-of all government spending. This heavy dependence on the public sector means that the global 'winds of change' in the respective roles of government and the private sector have major implications for the financing and structure of the water economy. The paper describes how each of the 'sub-sectors' is adapting to these winds of change. First, in recent years competition and private sector provision have emerged as the characteristicsof the new electricity industry. This change poses a fundamental challenge to hydro which, to a much greater degree than thermal, has risks (hydrological, geological, social and environmental) which are better assumed by the public than the private sector. The future of private hydro, and thus of hydro itself, depends heavily on the ability of the public sector to both share risks with the private sector, and to provide predictable social and environmental rules of the game. Second, the urban water supply sector is in the early stages of equally profound change. In recent years there has been a dramatic shift towards the private sector, in developed and developing countries alike. An outline of the future shape of a competitive urban water sector is emerging: it is one in which a growing number of private companies will compete with revitalized (and often corporatized) public utilities. Capital will, increasingly, come from the private capital markets, with the critical government role being that of light, transparent benchmarking and regulation. Third, the adaptation to the winds of change is least advanced in the public irrigation sector, which has long been characterized by public financing and 'rent seeking' by bureaucracies, politicians and private beneficiaries. It is only in recent years, and only in a few countries, that the irrigation sector has modernized. In these cases irrigation has become like any other utility, in which accountable, autonomous agencies provide users with the services the users want. In many instances, farmers have become responsible for the costs of operating and maintaining their systems; in some instances they are responsible for meeting the full costs of replacement, rehabilitation and new investments. Where these changes have taken place, there have not only been sharp swings in the relative proportion of private and public spending, but there have been dramatic improvements in the efficiency of investment and operation and, in most cases, major positive environmental impacts.

Heritability, phenotypic and genetic correlations of size and shape of Drosophila mediopunctata wings

We have studied the morphology of wings of Drosophila mediopunctata employing the ellipse method, a procedure that allows precise descriptions of wing size (SI), wing shape outline (SH), and placement of longitudinal wing veins. We have found that the SH and the points which determine the position of the apices of the third, fourth and fifth longitudinal wing veins show high heritability in nature (the lower bound for the natural heritability is above 0.25). The values found are similar to those obtained for the broad-sense heritabilities (H2) in the laboratory. However, SI and the point which determines the apex of the second longitudinal wing vein showed small lower bounds for heritability in nature, 0.05 and 0.07, respectively, in spite of the high estimates of H2 in the laboratory. These results suggest that size and shape have different genetic properties. We observed a high positive phenotypic correlation between the SH, the fourth and the fifth longitudinal wing veins, which contrasts with a negative correlation between these traits and the second longitudinal vein. That is, as the SH gets longer, the apices of the second and fifth veins become closer to each other. Positive genetic correlations in the field were detected between SH, the fourth and the fifth longitudinal veins and also between the third and the fourth veins.

Recurrent V1-V2 interaction in early visual boundary processing.

A majority of cortical areas are connected via feedforward and feedback fiber projections. In feedforward pathways we mainly observe stages of feature detection and integration. The computational role of the descending pathways at different stages of processing remains mainly unknown. Based on empirical findings we suggest that the top-down feedback pathways subserve a context-dependent gain control mechanism. We propose a new computational model for recurrent contour processing in which normalized activities of orientation selective contrast cells are fed forward to the next processing stage. There, the arrangement of input activation is matched against local patterns of contour shape. The resulting activities are subsequently fed back to the previous stage to locally enhance those initial measurements that are consistent with the top-down generated responses. In all, we suggest a computational theory for recurrent processing in the visual cortex in which the significance of local measurements is evaluated on the basis of a broader visual context that is represented in terms of contour code patterns. The model serves as a framework to link physiological with perceptual data gathered in psychophysical experiments. It handles a variety of perceptual phenomena, such as the local grouping of fragmented shape outline, texture surround and density effects, and the interpolation of illusory contours.

Recognizing silhouettes and shaded images across depth rotation.

Outline-shape information may be particularly important in the recognition of depth-rotated objects because it provides a coarse shape description which gives first-pass information about the structure of an object. In four experiments, we compared recognition of silhouettes (showing only outline shape) with recognition of fully shaded images of objects, by means of a sequential-matching task. In experiments 1 and 2, the first stimulus was always a shaded image, and the second stimulus was either a shaded image or a silhouette. Recognition costs associated with a change in viewpoint were no greater for silhouettes than they were for shaded images. Experiments 3 and 4 replicated the design of the earlier experiments, but showed a silhouette as the initial stimulus, rather than a shaded image. In these cases, recognition costs associated with a change in viewpoint were greater for silhouettes than for shaded images. Combined, these results indicate that, while visual representations clearly include additional information, outline shape plays an important role in object recognition across depth rotation.

Geographic Variation in Fluted Projectile Points: A Hemispheric Perspective

This paper examines geographic variation in fluted point morphology across North and South America. Metric data on 449 North American points, 31 Central American points, and 61 South American points were entered into a database. Ratios calculated from these metric attributes are used to quantify aspects of point shape across the two continents. The results of this analysis indicate gradual, progressive changes in fluted point outline shape from the Great Plains of western North America into adjacent parts of North America as well as into Central and South America. The South American “Fishtail” form of fluted point is seen as the culmination of incremental changes in point shape that began well into North America. A geographically gradual decline in fluting frequency also is consistent with the stylistic evolution of the stemmed “Fishtail” points. Although few in number, the available radiocarbon dates do suggest that “Fishtail” fluted points in southern South America are younger than the earliest dates associated with Clovis points in western North America. All of these data converge on the conclusion that South American “Fishtail” points evolved from North American fluted points.

Effects of outline shape in object recognition.

Effects of outline shape in object recognition.

Effects of outline shape in object recognition.

Effects of outline shape in object recognition.

Perception of Slope in Photographs

Perceptions of characteristics of space such as slope, distance, and depth are frequently inaccurate, both in the real world and in pictures. We carried out experiments to study factors that influence the accuracy of perceived slope in photographs. Slopes varied in angle from 5° to 45° inclinations against the horizontal, and in the information available to the observer (outline shape and texture characteristics). We found that perceived slope is correlated with real slope ( r=0.99), but that observers consistently overestimate slope. The latter depends not only on the available information, but also on the focal length of the lens with which slopes were photographed. Overestimation is less pronounced for the wide-angle lens compared to the standard lens. A comparison of free viewing and viewing from the correct station-point showed that the latter leads to less overestimation of slope. Since the viewing distance was too far under free viewing, the results are compatible with geometrical optics. In a further experiment the effects of magnification and minification were studied by deliberately viewing the photographs from fixed points closer or further away than the station-point; this led to an increase and decrease in overestimation, respectively. Finally, results are frequently dependent on task characteristics: magnitude judgements of photographs without an anchoring point can only be accurate to a level of scale. Thus using an action-based matching task may lead to more accurate slope perception. We therefore carried out a comparison experiment using a matching task to check for the generality and action-dependence of our results. Practical implications for the use of photographs as surrogates for natural viewing are discussed.

Why Do Some People Take a Long Time to See Complex Random-Dot Stereograms?

Some observers take a long time to see the appropriate surface shapes depicted in complex random-dot stereograms (RDSs) whereas others report seeing them quickly. We have hypothesised that this may be due in part to some observers being more affected than others by the cue conflicts that are typically present in RDSs, for which disparity is often at odds with accommodation, texture, and outline shape cues. We report two experiments in which we investigated whether a measure of dominance of texture/outline cues over disparity cues in stereograms of ridges could predict latencies to see RDSs of ‘wedding cakes’ viewed from above. Latencies were measured for correctly reporting the number of layers in the wedding cakes. The ridge cue dominance index was obtained by using amplitude judgements of convex parabolic vertical and horizontal ridge stereograms embodying texture/outline vs disparity cue conflicts (Buckley and Frisby, 1993 Vision Research33 919 – 934). In the first experiment ( N=38) disparity cues in the wedding cakes were depicted with inconsistent dot texture elements, ie the dots signalled flatness as there were no density differences between the cake layers. Observers giving greater weight to texture/outline in the vertical-ridge amplitude task showed significantly longer latencies to the wedding cakes. In a second experiment with different observers ( N=35), 18 were shown wedding cakes with textures consistent with disparity (diamonds drawn with correct perspective and density) and 17 saw the same disparity cues carried by inconsistent textures (diamonds signalling flatness). Large and significant correlations were found between the cue dominance index from vertical ridges and the latencies to wedding cakes depicted with inconsistent textures: observers with higher texture/outline cue dominance showed longer latencies. This result was remarkable given the lack of any readily apparent differences between the consistent and inconsistent textures in the wedding-cake stimuli. Equivalent correlations for wedding cakes depicted with consistent textures were small and nonsignificant. We conclude that individual differences in latencies to complex RDSs can be partly explained by differences in observers' susceptibility to texture/disparity cue conflicts embodied in those RDSs.

FLOWER SIZE AND SHAPE: IMPLICATIONS IN POLLINATION

In 42 plant species, the flowers' en face planar projected areas, contour lengths, and the ratios between them (= contour densities) were measured in relation to their pollinators, type of reward, and flower shape. A significant correlation exists between the planar projected area and contour density, which indicates that small flowers have broken outlines. Beetles were found to be associated more with large, rounded (bowl-shaped) flowers. Small bees, in contrast to medium and large bees, were associated significantly more with small flowers having broken outlines (i.e., high contour densities). Each factor examined (pollinator, flower shape, and reward) and each possible interaction among them, is significantly related to the values of each morphological variable. This implies that each category of pollinator (beetles, small, and medium-large bees) is associated with a syndrome of dependent floral characteristics (size, shape, and reward). We propose that the greater contour density of smaller flowers compensates for their smaller size by increasing visibility and the broken outline shapes act as “form guides” in the orientation, landing, and foraging by pollinators of flowers.

Extraction of Shape Skeletons from Grayscale Images

Shape skeletons have been used in computer vision to represent shapes and discover their salient features. Earlier attempts were based on morphological approach in which a shape is eroded successively and uniformly until it is reduced to its skeleton. The main difficulty with this approach is its sensitivity to noise and several approaches have been proposed for dealing with this problem. In this paper, we propose a new method based on diffusion to smooth out the noise and extract shape skeletons in a robust way. In the process, we also obtain segmentation of the shape into parts. The main tool for shape analysis is a function called the “edge-strength” function. Its level curves are smoothed analogs of the successive shape outlines obtained during the morphological erosion. The new method is closely related to the popular method of curve evolution, but has several advantages over it. Since the governing equation is linear, the implementation is simpler and faster. The same equation applies to problems in higher dimension. Unlike most other methods, the new method is applicable to shapes which may have junctions such as triple points. Another advantage is that the method is robust with respect to gaps in the shape outline. Since it is seldom possible to extract complete shape outlines from a noisy grayscale image, this is obviously a very important feature. The key point is that the edge strength may be calculated from grayscale images without first extracting the shape outline. Thus the method can be directly applied to grayscale images.

Landmark methods for forms without landmarks: morphometrics of group differences in outline shape

Morphometrics, a new branch of statistics, combines tools from geometry, computer graphics and biometrics in techniques for the multivariate analysis of biological shape variation. Although medical image analysts typically prefer to represent scenes by way of curving outlines or surfaces, the most recent developments in this associated statistical methodology have emphasized the domain of landmark data: size and shape of configurations of discrete, named points in two or three dimensions. This paper introduces a combination of Procrustes analysis and thin-plate splines, the two most powerful tools of landmark-based morphometrics, for multivariate analysis of curving outlines in samples of biomedical images. The thin-plate spline is used to assign point-to-point correspondences, called semi-landmarks, between curves of similar but variable shape, while the standard algorithm for Procrustes shape averages and shape coordinates is altered to accord with the ways in which semi-landmarks formally differ from more traditional landmark loci. Subsequent multivariate statistics and visualization proceed mainly as in the landmark-based methods. The combination provides a range of complementary filters, from high pass to low pass, for effects on outline shape in grouped studies. The low-pass version is based on the spectrum of the spline, the high pass, on a familiar special case of Procrustes analysis. This hybrid method is demonstrated in a comparison of the shape of the corpus callosum from mid-sagittal sections of MRI of 25 human brains, 12 normal and 13 with schizophrenia.