Magnification Differences Research Articles

Age estimation of adults from dental radiographs

Previous studies have shown that with advancing age the size of the dental pulp cavity is reduced as a result of secondary dentine deposit, so that measurements of this reduction can be used as an indicator of age. The aim of the present study was to find a method which could be used to estimate the chronological age of an adult from measurements of the size of the pulp on full mouth dental radiographs. The material consisted of periapical radiographs from 100 dental patients who had attended the clinics of the Dental Faculty in Oslo. The radiographs of six types of teeth from each jaw were measured: maxillary central and lateral incisors and second premolars, and mandibular lateral incisors, canines and first premolars. To compensate for differences in magnification and angulation on the radiographs, the following ratios were calculated: pulp/root length, pulp/tooth length, tooth/root length and pulp/root width at three different levels. Statistical analyses showed that Pearson's correlation coefficient between age and the different ratios for each type of tooth was significant, except for the ratio between tooth and root length, which was, therefore, excluded from further analysis. Principal component analyses were performed on all ratios, followed by regression analyses with age as dependent variable and the principal components as independent variables. The principal component analyses showed that only the two first of them had significant influence on age, and a good and easily calculated approximation to the first component was found to be the mean of all the ratios. A good approximation to the second principal component was found to be the difference between the mean of two width ratios and the mean of two length ratios, and these approximations of the first and second principal components were chosen as predictors in regression analyses with age as the dependent variable. The coefficient of determination ( r 2) for the estimation was strongest when the ratios of the six teeth were included ( r 2 = 0.76) and weakest when measurements from the mandibular canines alone were included ( r 2 = 0.56). Measurement on dental radiographs may be a non-invasive technique for estimating the age of adults, both living and dead, in forensic work and in archaeological studies, but the method ought to be tested on an independent sample.

Natural history of minute sessile colonic adenomas based on radiographic findings

With the development of colonoscopy and double-contrast barium enema, detection of minute sessile colonic adenomas has increased. We evaluated progression of these lesions radiologically and attempted to clarify the natural history. A total of 125 minute sessile adenomas (< or = 5 mm in size) with histologic confirmation were examined by double-contrast barium enema at an interval of more than one year. The average follow-up period was 24 (range, 12-36; standard deviation, 9.4) months. To allow for differences in magnification, adenomas increasing in size by 2 mm or more were defined as growing, and the other lesions were defined as unchanged. Eighty-six adenomas showed no interval change in size. Four adenomas decreased 1 mm in size, and 27 adenomas increased 1 mm in size. The remaining eight adenomas (6 percent) increased by 2 or 3 mm in size. None of the adenomas showed any morphologic changes. There was also no difference in degree of histologic atypia between growing and unchanged adenomas. None of the adenomas developed into carcinomas during the follow-up period. These data show that most minute sessile adenomas remain unchanged in size and morphology over the long term. Accordingly, these adenomas probably should be followed up radiologically or endoscopically to avoid excessive polypectomy.

Broadband alignment scheme for a stepper system using combinations of diffractive and refractive lenses

By using broadband illumination, a stepper alignment system is less sensitive to asymmetric coverage of photoresist around alignment targets and realizes high accuracy. However, a projection lens causes chromatic aberrations at the wavelengths in the broadband light. To correct the chromatic aberrations, we employed a Schupmann system composed of a projection lens, an achromat lens, and a refractive-diffractive hybrid lens. With the proposed system the spread of image planes and the magnification difference in the spectral range from 550 to 650 nm can be reduced to 50 µm and 0.05%, whereas without the correction system these values are 11.28 mm and 1.18%, respectively.

SECOND ORDER UV CONTAMINATION IN ASTRONOMICAL SPECTRA

ABSTRACT Observations of the planetary nebula Me 2-1 are used to discuss some effects of contamination produced by the second order ultraviolet spectrum in the first order red, longer than approximately 6200 A. It is found that this contamination is present with some instrument set-ups, and that the contaminating lines are displaced in wavelength with respect to the predictions from diffraction theory by an amount which varies slightly for different set-ups. From the theoretical and empirical analysis of these displacements, it is concluded that the shift in wavelength is due to the presence of chromatic difference in magnification in spectrograph cameras including any transmission element, as is the case in teh semi-solid Schmidt-Cassegrain cameras used in our observations.

Experimental determination of the chromatic difference of magnification of the human eye and the location of the anterior nodal point.

Theory predicts that retinal image size will vary with wavelength. However, this chromatic difference of magnification (CDM) is likely to be very small (< 1% between 400 and 700 nm) under natural viewing conditions. There has been only one attempt to measure CDM experimentally, and the results were inconsistent with optical theory. Using a technique described by Ogle [Research in Binocular Vision, Hafner, New York (1964)], which is sensitive to even small interocular differences in retinal image size, we measured the apparent tilts in the frontoparallel plane induced by interocular differences in wavelength. We obtained the ocular CDM by determining the afocal lens magnification necessary to cancel the apparent frontoparallel plane tilt caused by interocular differences in wavelength. We show that (1) the ocular CDM can be considerably less than theoretical model predictions, (2) the relationship among delta Rx (wavelength-dependent refractive error), CDM, and pupil position is consistent with our theoretical model, (3) CDM increases considerably when an artificial pupil in front of the eye is used, (4) the location of the anterior nodal point of the eye may be inferred from the data, and (5) unlike in the case for delta Rx, large intersubjective differences may exist for CDM. The results suggest caution in the use of artificial pupils experimentally with polychromatic stimuli because of amplification of CDM and concomitant losses of image contrast.

Multimeridional apparent frontoparallel plane: relation between stimulus orientation angle and compensating tilt angle.

The classical apparent frontoparallel plane (AFPP) setting is typically obtained by having the subject move a series of parallel rods farther or closer until they line up in a plane perceived to be parallel to the face plane. If there is a size difference between the two ocular images, the AFPP setting defined by the rods will exhibit a tilt from the objective frontoparallel plane, about an axis parallel to the rods. The multimeridional apparent frontoparallel plane (MAFPP) is an extension of this procedure to rod orientations other than the vertical meridian. In previous studies, it was found that oblique tilt angle settings corresponding to rod orientations of 45 degrees and 135 degrees are equal to square root 2 times the tilt angle for the vertical rod orientation for the same interocular magnification difference along the meridian perpendicular to the rods. In this study, we measured the tilt angles produced by a series of oblique rod orientations between 15 degrees and 165 degrees, inclusive. Throughout the 150 degrees range tested, the tilt angles were found to be consistently proportional to the cosecant of the rod orientation angle, the factor square root 2 previously used being a specific example of this relation. Within this range, neither empirical cues nor the induced effect cause the cosecant relation to break down. It is suggested that the MAFPP procedure can be applied more extensively than previously anticipated.

Effect of Ocular Chromatic Aberration on Monocular Visual Performance

This brief review outlines the theory of ocular chromatic aberration and describes the three primary forms in which the aberration appears: chromatic difference of focus, chromatic difference of magnification, and chromatic difference of position. Our central theme is that all three aspects of chromatic aberration have as their common basis the chromatic dispersion of light. The magnitude of each form of the aberration is related to the others by simple linear formulas in which a key parameter is the location of the pupil relative to the nodal point of the eye. The way in which retinal image quality is affected by chromatic aberration is described and we assess the impact of the aberration on visual performance.

Relation between the Chromatic Difference of Refraction and the Chromatic Difference of Magnification for the Reduced Eye

We provide a simple model for calculating the chromatic difference of magnification for the human eye. Spectral differences in image size are proportional to the eye's longitudinal chromatic aberration and the axial distance between the entrance pupil and nodal point. We verify that the model provides magnification estimates equal to previously published predictions, and we show the significant increase in this aberration produced by experimental use of artificial pupils.

Local magnification effects in the atom probe

Differences in the local magnification and curvature of phases in field evaporated field ion specimens have been shown to be an important consideration in atom probe analysis. A series of experiments has been performed on a high purity iron-45% chromium alloy that has been aged within a low temperature miscibility gap to produce a chromium-enriched α' phase and an iron-rich α phase. The effects of local magnification on field ion and field evaporation microscopy, and on three-dimensional and probe aperture atom probe analyses are discussed. It has been shown that the average composition of an atom probe experiment should be calculated from the number of atoms of each element divided by the total number of atoms but that the distance scale should be determined from distance-monitored type experiments. The reason for this is that the greater number of atoms per unit area in a darkly imaging region exactly compensates for the reduced probability of being sampled by the probe aperture.

Local magnification effects in the atom probe

Abstract Differences in the local magnification and curvature of phases in field evaporated field ion specimens have been shown to be an important consideration in atom probe analysis. A series of experiments has been performed on a high purity iron-45% chromium alloy that has been aged within a low temperature miscibility gap to produce a chromium-enriched α' phase and an iron-rich α phase. The effects of local magnification on field ion and field evaporation microscopy, and on three-dimensional and probe aperture atom probe analyses are discussed. It has been shown that the average composition of an atom probe experiment should be calculated from the number of atoms of each element divided by the total number of atoms but that the distance scale should be determined from distance-monitored type experiments. The reason for this is that the greater number of atoms per unit area in a darkly imaging region exactly compensates for the reduced probability of being sampled by the probe aperture.

Postfusional latency in stereoscopic slant perception and the primitives of stereopsis.

Random dot stereograms of slanted surfaces were constructed, each representing one or two slanted surfaces in different relative arrangements and with different axes. Latency to fusion and from fusion to stereoscopic resolution was measured for each stimulus. It was found that latency to fusion was always very brief but that latency to stereoscopic resolution varied markedly, depending upon the orientation and arrangement of the stereoscopic surfaces. A gradient of discontinuities at a surface boundary produced an instant slant response for that surface, whereas a gradient of absolute disparities across the surface did not, except under conditions where vertical declination (a form of orientation disparity) was present. We conclude that stereopsis is not based on the primitives used in matching the images for fusion and that it is, at least initially, a response to disparity discontinuities which play no role in the fusion process. We also conclude that vertical declination is responded to globally as a slant around a horizontal axis but that other forms of orientation disparity are ineffective. The evidence from our experiments does not support the existence of a stereoscopic ability to respond globally to differences in magnification (or spatial frequency). It is suggested that stereoscopic perception of slant around a vertical axis is slow because it results from the integration of local processes.

Depth Distortion During Slit-lamp Biomicroscopy of the Fundus

The apparent depth of an optic nerve cup or apparent height of a fundus lesion changes with the optics used by an examiner. With slit-lamp biomicroscopy of the fundus, both the auxiliary fundus lens and the biomicroscope contribute to differences in magnification that produces distortion of the object. It is important to understand these differences so that inaccurate conclusions are not drawn and inappropriate therapy will not be instituted when the examiner uses different instruments for making serial observations or uses an unfamiliar instrument.

Monocular aniseikonia: a motion parallax analogue of the disparity-induced effect.

Mayhew and Longuet-Higgins have recently outlined a computational model of binocular depth perception in which the small vertical disparities between the two eyes' views of a three-dimensional scene are used to determine the 'viewing parameters' of fixation distance (d) and the angle of asymmetric convergence of the eyes (g). The d/g hypothesis, as it has been called, correctly predicts that a fronto-parallel surface, viewed with a vertically magnifying lens over one eye, should appear to be rotated in depth about a vertical axis. We report here a comparable illusion for surfaces specified by monocular motion parallax information, which can be explained more simply by considering the differential invariants of the optic flow field. In addition, our observations suggest that the disparity-induced effect is not a 'whole field' phenomenon nor one limited to small magnification differences between the eyes.

Nonreversible Mirrors Equivalent To Saddle Mirrors

A saddle mirror is a toroidal mirror with the principal curvatures of opposite sign. The mirror can form images of objects without reversing them. This means that a right-handed object can be imaged into a right-handed image that is erect. However, the saddle mirror is not easy to construct accurately. It is possible to devise some equivalent mirrors that have either cylindrical or plane surfaces for the special situation when one is interested in an image that is also free from anamorphic magnification difference. A few such optical devices are presented in this paper.

The mapping of visual space onto foveal striate cortex in the macaque monkey

Visuotopic maps of foveal striate cortex have been obtained by means of single cell recordings from four hemispheres in two awake, behaving macaque monkeys. The numbers of successful separate striate penetration sites in the four hemispheres were 42, 58, 81, and 61, for a total of 242. The resolution of the maps is 10 min of visual angle, nearly an order of magnitude finer than previous maps. No striate receptive field center was found more than 5 min into the ipsilateral visual field. The four maps were sufficiently compatible with one another that they could be combined into one. There are only minor magnification differences between the right and left hemispheres and between the upper and lower quadrants. There is a vertical/horizontal magnification anisotropy of about 1.5:1 in central foveal cortex (0 to 20 min). The composite map can be approximated by the complex logarithmic equation, w = 7.7 * ln (x + iy + 0.33), where w is expressed in millimeters and x and y are expressed in degrees.

Sensitivity for vertical retinal image differences.

The detection of horizontal disparities between the right and left retinal images is accepted as an important component in the visual perception of depth. It has occasionally been pointed out that a disparity will also occur in the vertical when a target is nearer to one eye than the other and could be used as a second component. Here it is shown that while it is possible to detect size differences between the retinal images in the vertical direction, the sensitivity is at least one order of magnitude less than the horizontal differences. It had been generally accepted that vertical disparities cannot be detected (literature summarized by Tschermak), but there are clear reports of the ability of subjects to respond to relative differences in the vertical magnification of the images of the two eyes, the so-called induced size effect. It manifests itself in the appearance of a visual scene as if there had been an opposite horizontal magnification and is, therefore, in the correct direction if it is to be utilized in asymmetrical convergence.

Image Reversal in Microscopy

Image Reversal in Microscopy

Quantified analysis of a carotid angiogram.

To compensate for differences in anatomy and magnification, a hand-held programmable calculator remodels the profile of the lateral view of a skull to fit the outline of a reference skull. The statistical analysis of 85 normalized carotid angiograms yeilds a numbered map of supratentorial structures. It is then possible to obtain, within 20 min and without sophisticated equipment, an objective analysis of any new angiogram.

The Big Rib Sign: Localization of Basal Pulmonary Pathology in Lateral Projection Utilizing Differential Magnification of the Two Hemithoraces

Basal pulmonary pathology which silhouettes the hemidiaphragm in lateral view may not be detectable in routine postero-anterior projection. In such cases, correct lateralization of pathology to the left or right hemithorax depends on accurate identification of the silhouetted left and right hemidiaphragm in lateral view. A prospective analysis of the sensitivity and accuracy of five techniques for identifying the left and right hemidiaphragms in more than 100 patients revealed that the most accurate method for lateralizing juxtadiaphragmatic pathology was the "big rib" sign, a technique based upon the relative difference in magnification between the left and right ribs. Techniques based upon the visceral gas bubble or upon obscuration of the anterior portion of the left hemidiaphragm by the heart proved less useful. Techniques based upon the position and configuration of the major fissures or upon higher and lower position of the two hemidiaphragms were ineffective.

Cellular density of normal corneal endothelium.

With the aid of the specular microscope photographs were made of the endothelium of 72 subjects, 41 men and 31 women, aged from 24 to 86 years. The number of endothelial cells was counted by projecting the photographs and counting the cells in a given area. The average variation per eye was 4.9% with a standard deviation of 3.7. A difference in magnification associated with differences in the thickness of the cornea was not found. There was a significant negative correlation (Pearson) between age and cell density: correlation coefficient 0.395, significance P = 0.001. Regression analysis of this correlation gave the following equation: CL = 3081 - 8.8 L, where CL = cell density at age L. The error is 97 cells more or less than this figure.