Chart Images Research Articles

Development of a quantitative analysis method for measuring the change in vascular structure of malignant tumors in small experimental animals

The aim of this study was to develop a detailed and quantitative X-ray imaging evaluation method for analyzing the vascular structure of malignant tumors in small experimental animals. A microfocus tube X-ray imaging system and a computed radiography system were used to capture images directly at 7× magnification. Various parameters of the vascular structures in the digital images were quantitatively analyzed with image analysis software after the vascular structure patterns were extracted by a mathematical morphology filter. The evaluation included the following three stages: assessment of the digital images drawn with graphics software, evaluation of digital X-ray images of vascular structure model phantoms made from copper wire, and assessment of the angiography of the mouse tumor model. In the quantitative analysis of the digital images, each vascular structure parameter increased as the thickness, length, and area of the test chart increased. In contrast, nonvascular structure parameters decreased with increases in the thickness, length, and area of the test chart. The results of the analysis of the digital X-ray images of model phantoms were similar to those of the digital test chart image. Vascular structure parameter values were higher in the tumor model mouse than in the control mouse. In contrast, values of parameters that measured the nonblood vessel parameters were lower in the tumor model mouse than in the control mouse. The results of our preliminary investigation suggest that our quantitative X-ray imaging evaluation method may be useful for analyzing the vascular structure of tumors in small experimental animals.

An automatic system for rainfall signal recognition from tipping bucket gage strip charts

A system aimed at recognizing automatically the rainfall signal recorded by tipping bucket gages in paper strip charts is presented. The system consists of three modules. The first two modules automatically extract the rainfall signal from the digitized strip chart image: they are based not only on image analysis techniques, but also on the mechanical features of the recording instrument and on considerations arising from the examination of the strip charts. Thus the proposed system results much more robust and efficient than general purpose software designed for image vectorialization. The third module is a graphical user interface that permits verification of the results furnished by the previous modules and to interactively change those parts requiring correction, if any. The system, successfully tested on a large set of strip charts, represents a very powerful tool for automatic recovering of ancient rainfall data. Thus it can be employed to extract long series of high resolution rainfall signals from which several hydrological threads would certainly benefit.

Optomechanical eye model with imaging capabilities for objective evaluation of intraocular lenses

To develop an in vitro procedure providing data on the visual performance obtainable with intraocular lenses (IOLs), for objective comparison between IOL models and direct correlation with the relative visual performance attainable in vivo. University Hospital San Raffaele, Milan, Italy. An optomechanical eye model was developed to allow simulated in vivo testing of IOLs. The experimental eye mimics the optics and geometry of the Gullstrand's eye model, with an aspheric poly(methyl methacrylate) cornea, variable pupil, and IOL holder. Its detection system is designed to reproduce the mean resolution of the human fovea. The imaging capabilities of the model eye were measured using monofocal IOLs. The tests included qualitative information, such as appearance of optotype chart images, and quantitative information, such as simulated visual acuity tests for far and near distance at variable contrasts. Objective numerical IOL evaluation was made possible on the basis of the visual acuity recorded with the eye model. The maximum recorded far acuity for the monofocal IOLs was about 20/14 at full contrast, progressively decreasing for reduced contrast. Best corrected near acuity ranged between 20/14.7 and 20/15.4. The optomechanical eye model provided objective grading of IOLs through the evaluation of simulated visual acuity, which can be scaled usefully to human vision. The eye model also allowed the qualitative visualization of IOL imaging properties, making it potentially useful in characterizing and distinguishing different IOL types.

Sea‐ice draft from submarine‐based sonar: Establishing a consistent record from analog and digitally recorded data

Measurements of arctic sea‐ice draft have been taken by Navy submarines for nearly five decades. The data are in two inherently different forms, analog paper charts and digitally recorded data. “Raw” analog drafts digitized from paper charts are biased toward thicker ice by over 30 cm compared with the digital drafts. This is due to the coarser temporal resolution of the paper charts compared the digital data. We examine coincident analog and digital data to determine how they can be made equivalent in mean draft and draft distribution (the histogram of draft vs. fractional frequency of observation). Image processing techniques are used to thin vertical features in the scanned chart images; this produces a “final” analog mean draft that is essentially unbiased (2 ± 6 cm) relative to the digital mean and final draft distributions that are in good agreement.

A single marine overlay display is more efficient than separate chart and radar displays

Performance with marine chart and radar images displayed on adjacent screens was compared to performance with chart and radar images overlaid on a single screen. Eighteen college students and nine mariners read statements about the radar image, the chart image, or both images and answered ‘True’ or ‘False’ to each statement after viewing the displays. Accuracy was equal for separate and overlay displays, but viewing time was shorter and efficiency (accuracy/viewing time) was higher for overlay displays. Observers then re-aligned radar displays that had been translated and rotated out of alignment with the charts. They took longer but were more accurate on the overlays. Students and mariners performed similarly on both tasks.

Optical and Near‐Infrared Photometry of Distant Galaxy Clusters

We present optical and near-infrared photometry of 45 clusters of galaxies at 0.1 < z < 1.3. Galaxy catalogs in each cluster were defined at the longest wavelenth available, generally the K-band, down to approximately two magnitudes below M*. We include finding chart images of the band used for catalog definition. The photometry has been used in previously published papers to examine the origin and evolution of galaxies in distant clusters.

Influence of Non-Linear Image Processing on Spatial Frequency Response of Digital Still Cameras

The spatial frequency response (SFR) for a digital still camera is affected by non-linear image processing. We analyze the influence of image enhancement processing and gamma correction on SFR characteristics by varying the edge chart contrast. SFR expressions depending on the chart image contrast are proposed, as is a measurement method of resolving power based on the slanted edge.

Morphological analysis and recognition of scanned raster nautical chart

In current practice in the development of hydrographic information systems, the automatic acquisition of spatial data has been considered to be very difficult. One of the key problems is recognition and correct separation of a feature from a complex graphic background. For these problems, this article presents a new concept of graph subsets to describe graph structures and composition rules of symbols in nautical charts. Based on this concept, morphological methods and operations in graph theory are unified into a coherent mathematical framework specially designed for analysis and recognition of binary chart images. In particular, an experimental system composed of feature extraction, symbol recognition, geometric reasoning, and intelligent control is developed for automatic digitization of nautical charts.

An experiment in computational measurement of chart image density

An experiment in computational measurement of chart image density

Effects of Scattered X-Rays upon Radiographic Contrast and Patient Dose

AbstractScattered X-rays are produced when diagnostic X-ray images of patients are taken. It is generally believed that scattered X-rays should be eliminated as much as possible because they degrade the image quality, namely the sharpness and the radiographic contrast. However, excessive elimination of the scattered X-rays decreases photographic density. This results in a greater patient dose to achieve proper density. It is therefore desirable to determine the ideal content of scattered X-rays, object by object, balancing the tivo objectives of high image quality and low patient dose.In this study, the effects of the scattered X-rays upon the image quality were investigated by measuring the radiographic contrast of aluminium square-wave chart images, with various scatter fractions. Relative patient doses were determined using mAs values. As a result, a contrast-dose diagram is proposed. This diagram is very useful to determine exposure conditions, balancing high image quality and low patient dose in clin...

Compression of digitized map images

An efficient way to store and retrieve digitized chart images using a lossy vector quantization (VQ) compression technique is presented. A VQ codebook is located using the fast pairwise nearest neighbor (PNN) clustering algorithm. A k-d tree data structure is used for efficient image compression. Some unique features of this approach are that compressed files use a predictable amount of storage, and can be decompressed quickly for display on equipment ranging from portable personal computers to advanced graphics workstations. The method also applies to panchromatic and multispectral satellite imagery. In this application, digitized chart images with compression ratios of 24:1 exhibited good quality. In certain applications, even higher compression ratios are feasible.

矩形波チャートを用いた MTF 測定用器具

The Fourier transformation of line spread function obtained from slit image is generally used for modulatry transfer function (MTF) measurements. However, the square wave chart method (contrast method) is better than the slit method for ordinary clinical applications. A new device for measuring MTF was thus developed, in which square wave chart image and Aluminium block images for obtaining characteristic curves are simultaneously exposed on the same film. MTF by the contrast method was found equivalent to that by the slit method. Differences between three phase and inverterunits at a tube voltage of 60kV aren't recognized.

Pebble Morphology of an Ancient Conglomerate: The Middelvlei Gold Placer, Witwatersrand, South Africa

ABSTRACT A highly weathered outcrop afforded an opportunity to obtain pebbles for a morphometric clast study of a normally well indurated Early Proterozoic conglomerate, the Middelvlei gold placer. This quartz-pebble conglomerate occurs towards the base of the Central Rand Group of the Witwatersrand Supergroup, South Africa, and is a principal gold orebody mined in a goldfield known as the West Wits Line. The placer has been regarded as fluvial mainly because of a unimodal paleocurrent distribution, repeated fining-upward conglomerate-sandstone sequences, and the lenticular nature of its beds. More than 1,000 quartz pebbles from five separate conglomerate beds were measured. Pebble form was defined by maximum projection sphericity, coefficient of flatness and oblate-prolate index, all calculated from long, intermediate, and short pebble axes. A normal distribution was obtained for the first two form indices. For all five conglomerate beds, the means of all three indices are significantly greater than empirical lower limits determined by previous workers to distinguish fluvial from beach pebbles in modern gravels, confirming the fluvial origin of the beds. Although the range of pebble sizes in this study is relatively small, a significant decrease in sphericity with increasing size was found. Pebble roundness was determined for 444 undamaged pebbles by visual comparison with chart images of Krumbein (1941). Comparison of the overall mean of 0.59 with figures obtained in studies of modern rivers suggests relatively long transport distances, of the order of 160 km, for the placer.