Colour representation of biomedical data

Recent developments in digital display technology have opened a wide range of possibilities for biomedical imaging. The opportunity to use colour is an important feature of video-display systems in clinical practice. Colour coding of biomedical data is a complex matter, which, however, may lead in many cases to an enhanced diagnostic interpretation of the images displayed. In the paper procedures for colour mapping are described and illustrated by three practical examples in the fields of scintigraphy, electrocardiography and neurophysiology. The results show an extensive applicability for colour representation of biomedical data, provided the mapping procedures are carefully selected.     

Microprocessor-based image processing system for dynamic foot pressure studies

A microprocessor-based system is described for data capture and analysis of dynamic foot pressure images. A run-length encoding video digitiser captures up to 32 frames at a rate of 25 per second and stores the data in memory. These data are displayed on a colour monitor and can be analysed to produce pressure against time curves or printed or plotted as isopressure contour plots.     

Effectiveness of colour in displaying radionuclide images

The use of digital technology in medical imaging gives the potential for improving the way in which images are displayed. One possibility is to represent intensity information by false colours rather than the conventional grey shades. Although this has several potential advantages, it has not been widely accepted. The aim of this study was to compare the performance of grey scale coding with three colour scales: the hot-body scale, a blue-green-red scale derived from the Uniform Chromaticity Scale, and a contrasting-colour scale. Two perceptual tasks were studied using computer-simulated images of the type produced in nuclear medicine. The first was to test the ability to perceive changes in image sharpness. The grey scale, hot-body scale and blue-green-red scale performed equally well but the contrasting-colour scale was significantly worse than others. The second pattern measured the ability to detect small changes in image intensity. The contrasting colour scale was best for this task and the grey scale worst. While the best colour scale depends on the information which is to be extracted from the image, both the hot-body scale and the blue-green-red scale appeared to offer a satisfactory compromise.     

Cephalometry with a video display computer

A new technique to develop cephalometric analyses for orthodontic problems is illustrated. A digital analyzer of images is employed in our laboratory, and this allows us to get the X-ray picture digitized and displayed on both a black and white and a colour TV screen. All the cephalometric points are selected by an operator who watches a coloured cross which can be moved on the colour TV screen by means of a keyboard. A suitable software was developed to calculate linear and angular measurements. The cephalometric coloured lines appear at the top of the X-ray image and the data are displayed on a monitor, from which a print-out is obtained. Such a technique has some advantages: the X-ray image can be processed before the cephalometric analysis to enhance details, thus making the analysis more accurate; the cephalometric lines can be seen on the X-ray image displayed on the colour TV screen and can be photographed or stored on floppy or rigid disc.     

Plastic embedding procedure for 15 microns sections of large undecalcified tissue blocks.

A method is described that produces sections (15 microns) of large specimens (with dimensions up to 140 x 100 x 200 mm). They are suitable for comparison to CT images of that specimen and can be used as a basis for three-dimensional reconstructions. Frozen unfixed parts of the human body are embedded in polyurethane and scanned with CT. Undecalcified slices, 6 mm thick, of these specimens are cut with a bandsaw. These slices are successfully embedded in polyester resin by means of fixation, dehydration, and subsequent impregnation with this resin. Sections of 15 microns are obtained by cutting the trimmed and sandpapered polyester blocks with an LKB multirange microtome. They are collected on adhesive tape and stained according to Weigert-Azan, sealed between adhesive acetate sheets and photographed on colour slide film. As an example photographs of sections of the human elbow and lumbar spine region are presented.     

Colour agnosia impairs the recognition of natural but not of non-natural scenes

Scene recognition can be enhanced by appropriate colour information, yet the level of visual processing at which colour exerts its effects is still unclear. It has been suggested that colour supports low-level sensory processing, while others have claimed that colour information aids semantic categorization and recognition of objects and scenes. We investigated the effect of colour on scene recognition in a case of colour agnosia, M.A.H. In a scene identification task, participants had to name images of natural or non-natural scenes in six different formats. Irrespective of scene format, M.A.H. was much slower on the natural than on the non-natural scenes. As expected, neither M.A.H. nor control participants showed any difference in performance for the non-natural scenes. However, for the natural scenes, appropriate colour facilitated scene recognition in control participants (i.e., shorter reaction times), whereas M.A.H.'s performance did not differ across formats. Our data thus support the hypothesis that the effect of colour occurs at the level of learned associations.     

Colour agnosia impairs the recognition of natural but not of non-natural scenes

Scene recognition can be enhanced by appropriate colour information, yet the level of visual processing at which colour exerts its effects is still unclear. It has been suggested that colour supports low-level sensory processing, while others have claimed that colour information aids semantic categorization and recognition of objects and scenes. We investigated the effect of colour on scene recognition in a case of colour agnosia, M.A.H. In a scene identification task, participants had to name images of natural or non-natural scenes in six different formats. Irrespective of scene format, M.A.H. was much slower on the natural than on the non-natural scenes. As expected, neither M.A.H. nor control participants showed any difference in performance for the non-natural scenes. However, for the natural scenes, appropriate colour facilitated scene recognition in control participants (i.e., shorter reaction times), whereas M.A.H.'s performance did not differ across formats. Our data thus support the hypothesis that the effect of colour occurs at the level of learned associations.     

Detection of Hard Exudates in Colour Fundus Images Using Fuzzy Support Vector Machine-Based Expert System

Diabetic retinopathy is a major cause of vision loss in diabetic patients. Currently, there is a need for making decisions using intelligent computer algorithms when screening a large volume of data. This paper presents an expert decision-making system designed using a fuzzy support vector machine (FSVM) classifier to detect hard exudates in fundus images. The optic discs in the colour fundus images are segmented to avoid false alarms using morphological operations and based on circular Hough transform. To discriminate between the exudates and the non-exudates pixels, colour and texture features are extracted from the images. These features are given as input to the FSVM classifier. The classifier analysed 200 retinal images collected from diabetic retinopathy screening programmes. The tests made on the retinal images show that the proposed detection system has better discriminating power than the conventional support vector machine. With the best combination of FSVM and features sets, the area under the receiver operating characteristic curve reached 0.9606, which corresponds to a sensitivity of 94.1 % with a specificity of 90.0 %. The results suggest that detecting hard exudates using FSVM contribute to computer-assisted detection of diabetic retinopathy and as a decision support system for ophthalmologists.     

Laser reflectance imaging of human organs and comparison with perfusion images

Based on the principle of backscattering of laser radiation from tissues, a non-invasive PC-AT based reflectance imaging technique is developed. The laser beam from a semiconductor laser operating at 670 nm is guided to the tissue site by an optical fibre. The backscattered radiation is collected by another fibre placed in the same probe, and is detected by a photodiode-amplifier assembly. This probe is moved manually over the organs under observation, and the data after the ADC, interpolation and median filtering are displayed in the form of reflectance image of the organ along with grey scale. By this technique images of the human hands and forearms are obtained, which depend on the variations in their colour, composition and blood flow. A comparison is made with perfusion images, obtained by a Periflux laser Doppler flowmeter. These show that the reflectance images provide greater details of the tissue structure than the perfusion images.     

Plastic embedding procedure for 15 μm sections of large undecalcified tissue blocks

A method is described that produces sections (15 μm) of large specimens (with dimensions up to 140 × 100 × 200 mm). They are suitable for comparison to CT images of that specimen and can be used as a basis for three dimensional reconstructions. Frozen unfixed parts of the human body are embedded in polyurethane and scanned with CT. Undecalcified slices, 6 mm thick, of these specimens are cut with a bandsaw. These slices are successfully embedded in polyester resin by means of fixation, dehydration, and subsequent impregnation with this resin. Sections of 15 μm are obtained by cutting the trimmed and sandpapered polyester blocks with an LKB multirange microtome. They are collected on adhesive tape and stained according to Weigert-Azan, sealed between adhesive acetate sheets and photographed on colour slide film. As an example photographs of sections of the human elbow and lumbar spine region are presented. © 1992 Wiley-Liss, Inc.     

The determination of cholesterol in serum by persulphuric acid oxidation

A method for the determination of total cholesterol in serum is described. Optimum conditions are found for the isolation of the steroid free from extraneous chromogens, and a new sensitive colour reagent is introduced. The procedure is convenient for routine application, the final colour being light-stable and reasonably time-stable at room temperature. Comparisons are made with one other method and with another colour reagent. It is concluded that, for accurate results, treatment of the serum with alcoholic alkali followed by extraction with a hydrophobic solvent is essential. The choice of the colour-developing reagent is then no longer dependent on specificity for cholesterol, but becomes inter alia a matter of ease of operation, and of sensitivity, stability, and reproducibility of the final colour. These points are discussed in relation to other methods.     

Colour helps to solve the binocular matching problem

The spatial differences between the two retinal images, called binocular disparities, can be used to recover the three-dimensional (3D) aspects of a scene. The computation of disparity depends upon the correct identification of corresponding features in the two images. Understanding what image features are used by the brain to solve this binocular matching problem is an important issue in research on stereoscopic vision. The role of colour in binocular vision is controversial and it has been argued that colour is ineffective in achieving binocular vision. In the current experiment subjects were required to indicate the amount of perceived depth. The stimulus consisted of an array of fronto-parallel bars uniformly distributed in a constant sized volume. We studied the perceived depth in those 3D stimuli by manipulating both colour (monochrome, trichrome) and luminance (congruent, incongruent). Our results demonstrate that the amount of perceived depth was influenced by colour, indicating that the visual system uses colour to achieve binocular matching. Physiological data have revealed cortical cells in macaque V2 that are tuned both to binocular disparity and to colour. We suggest that one of the functional roles of these cells may be to help solve the binocular matching problem.     

Colour-spatial vision

A critical survey is made of neurophysiological and psychophysiological investigations of colour vision. A neuronal model of colour-spatial vision is suggested. The model allows a unified explanation of the whole range of psychophysiological phenomena: the mixing of colours of high-frequency image components, the McCollough type colour after-effects, the simultaneous and successive colour contrast, the hue constancy perception, the appearance of non-spectral colours by mixing of monochromatic lights. A suggestion is made as to the existence of two main mechanisms of colour vision. The first of these, by means of Fourier transforms, gives a set of coefficients which describes the spatial distribution of light (quantity of energy) and hue (quality of energy) in the visual field. The second mechanism establishes colour names in each chromatically homogenous area of the field described by the first mechanism. Both mechanisms cooperate on the basis of their common spatial organization.     

A rapid colorimetric method for the estimation of urinary chlorides

A rapid and reproducible method for chloride estimation in urine is described. The colour produced is stable and obeys Beer's law over a wide range of concentrations using a simple colorimeter and filter. The method gives good agreement with both the potentiometric titration method of Sanderson (1952) and the mercurimetric titration method of Schales and Schales (1941). The precision of the colorimetric method, though inferior to that of the potentiometric method, is similar to that of the mercurimetric method.     

Enzyme-linked immunosorbent microassay for quantification of specific antibodies to collagen type I, II, III.

An enzyme-liked immunosorbent assay (ELISA) is described for determination of antibodies to collagen type I, II, III in serum or other body fluids. Polystyrene microplates are coated with either collagen I, II or III, and samples of body fluids being tested are incubated in the plates. Antibodies which attach specifically to the collagen are detected with anti-IgG antibody conjugated with peroxidase. Bound peroxidase is quantitatively estimated by the colour reaction produced with the substrate 5-aminosalicylic acid.     

A novel coloured latex test for the detection and identification of more than one antigen

A novel latex agglutination test employing coloured latex particles is described. The latex reagent contains two or more differently coloured latex suspensions, each colour having been coated before mixing with at least one specific antibody, so that two or more antigens can be detected and identified with a single reagent. The antigen is identified by observing the colour of the agglutinated particles against a contrasting change in the colour of the background.     

Towards a computer-aided diagnosis system for vocal cord diseases

OBJECTIVE: The objective of this work is to investigate a possibility of creating a computer-aided decision support system for an automated analysis of vocal cord images aiming to categorize diseases of vocal cords. METHODOLOGY: The problem is treated as a pattern recognition task. To obtain a concise and informative representation of a vocal cord image, colour, texture, and geometrical features are used. The representation is further analyzed by a pattern classifier categorizing the image into healthy, diffuse, and nodular classes. RESULTS: The approach developed was tested on 785 vocal cord images collected at the Department of Otolaryngology, Kaunas University of Medicine, Lithuania. A correct classification rate of over 87% was obtained when categorizing a set of unseen images into the aforementioned three classes. CONCLUSION: Bearing in mind the high similarity of the decision classes, the results obtained are rather encouraging and the developed tools could be very helpful for assuring objective analysis of the images of laryngeal diseases.     

Rapid wax plate modeling

An accelerated method for the production of wax plate models from serial sections is described. Serial sections are projected on the back of 1 mm wax plates and the sharp image produced on the front of the plate is cut out directly with a knife. The construction of a simple projection apparatus which permits back-lighted projection is described and illustrated. The apparatus is built of common-size lumber and a small sheet of Plexiglas. It consists of a screen for the image and a wooden track on which a light source and microscope can be moved back and forth for different magnifications. Commercially available wax plates can be used. A method and the equipment needed to produce larger plates are described. The cut-out images when piled up to form the model are welded together and strengthened by inserting heated straight pins. The exterior of the model is smoothed with an electrically heated glass instrument which provides constant heat of desired temperatures. The construction of the glass instrument is illustrated.     

Percussion circuits and brain function – A hypothesis

It is proposed that percussion reactions take place in cells of the sensory organs and the brain. The percussion pulses produced by such reactions are the basis of the recording of information and images generated by the five sensory organs. Also proposed and described are the mechanisms by which this information and these images can be recalled for use in the present time.     

A sensitive method for the colorimetric determination of urea

A method is described for the direct colorimetric determination of urea in biological fluids. The method depends on the reaction (first described by Wheatley, 1948) between urea, diacetylmonoxime, and phenylanthranilic acid in the presence of controlled amounts of oxidant; chloride ions are included to sensitize the reaction; manganous ions stabilize the resultant colour; and phosphate enables reasonable reproducibility to be achieved.