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PubMed2003

Difference in polymerization color changes of dental resin composites by the measuring aperture size.

The objective of this study was to evaluate the influence of the illuminating/viewing aperture diameter of 11 mm/8 mm and 3 mm/3 mm and measuring geometry on the color and polymerization color changes of dental resin composites. Color of resin composites of 12 mm in diameter was measured on a reflection spectrophotometer with SCE and SCI geometry under D65 illumination. Before polymerization, difference in the three-color coordinates by the material was prominent in spite of the fact that the shade designation of all materials was the same. After polymerization, L* value decreased in hybrid composites but not in packable composites, and changes in a* value were small. When the same aperture size was used, polymerization color change with the SCE was generally higher than those with the SCI. Measured color was different by the aperture size, and the color difference was 16.82-27.05 before polymerization and 20.09-28.51 after polymerization. General trends of polymerization color change were similar in both aperture sizes. Polymerization color changes with 3-mm aperture size were higher than those with 8-mm aperture size in hybrid resin composites in both geometries (p < 0.05); however, the color change was material dependent in the case of packable resin composites.

Color↗

PubMed2001

Correlation of color Doppler sonographic findings with pH measurements in gastroesophageal reflux in children.

PURPOSE: We conducted a prospective study of color Doppler sonography in children with suspected gastroesophageal reflux (GER). The purpose of this study was to compare the accuracy of color Doppler sonography with that of continuous 24-hour pH monitoring of the esophagus in diagnosing GER and to determine how to interpret the reflux episodes detected on color Doppler sonography in children at high risk for reflux. METHODS: Color Doppler sonography and 24-hour esophageal pH monitoring were performed in 54 children ranging in age from 2 months to 10 years (mean, 3 years). The stomach of each patient was filled for adequate gastric distention just before the color Doppler sonographic examination. We counted the number of reflux episodes over a period of 15 minutes. One day after the sonographic examination, the reflux was evaluated with esophageal pH monitoring, and the resultant reflux index (ReI) was obtained. The ReI was considered to be pathologic when it was equal to or greater than 11.99%. The number of refluxes on color Doppler sonography and the ReI were correlated for each patient. RESULTS: The 2 tests showed an 81.5% agreement in the detection of GER. When pH monitoring was taken as the reference test, color Doppler sonography had a high sensitivity (95.5%) for diagnosing GER but a very low specificity (11.0%), with a positive predictive value of 84.3% and a negative predictive value of 33.3%. There was no statistically significant correlation between the frequencies of GER detected on color Doppler sonography and the ReIs on pH monitoring (p = 0.1103). There was no correlation between the reflux grades on sonography and the ReI grades on pH monitoring (p = 0.422). CONCLUSIONS: Color Doppler sonography is highly sensitive and easier to use than pH monitoring. Although there are no definite criteria for evaluating the severity of GER on color Doppler imaging, this modality may be useful in screening children for GER.

Child↗

PubMed1995

Color Doppler sonography: anatomic and physiologic assessment of the thyroid.

The purpose of this study was to assess the potential application of color Doppler sonography in thyroid imaging. Thyroid nodules and other thyroid pathology detected by color Doppler ultrasound and nuclear scintigraphy were compared in 115 patients. The majority of "cold" nodules demonstrated a peripheral rim of color flow and no internal color flow with color Doppler sonography. A large number of "hot" nodules demonstrated internal color flow. Color Doppler sonography was helpful in delineating nodules in otherwise inhomogeneous glands. We determined that color Doppler cannot reliably distinguish benign from malignant thyroid nodules; fine-needle aspiration biopsy remains the most accurate method in differentiating benign and malignant lesions. We suggest that color Doppler sonography plays only a limited role in the evaluation of nodular thyroid disease at this time. The color Doppler appearance of other thyroid disorders (including toxic multinodular goiter, Graves' disease, and thyroiditis) is discussed.

Adolescent↗

PubMed1994

Acquisition of color opponent representation by a three-layered neural network model.

This paper discusses color representation in the visual system by analysis of a three-layered neural network model. The model incorporates physiological knowledge of color representation at the sensor level (broad-band trichromatic representation by cones) and the higher level (narrow-band color representation by color-coded cells in V4). We trained the model to perform a mapping between these color representations by the back propagation algorithm and analyzed the acquired characteristics of the hidden units. It turned out that the hidden units learned characteristics similar to those of the color opponent cells found in the visual system. It was concluded that the R-G and Y-B color opponent representations reflect the efficiency of the color representation in the visual system from investigations on the efficiency of color representation in the hidden layer and on the capability of the color recognition task of the model.

Color Perception↗

PubMed1989

Directionally selective response of cells in the middle temporal area (MT) of the macaque monkey to the movement of equiluminous opponent color stimuli.

Based on the fact that a great majority of cells in the middle temporal (MT) area of the macaque respond to movement of luminance contours with directional selectivity, this area has been thought to be concerned with the analysis of visual motion. However, objects can be discriminated from the background not only by differences in luminance but also by differences in color. It is possible that color signals are also used for motion analysis in MT. In the present study, we examined whether MT cells respond to movement of a pattern composed of pure color-contours. Using a color TV system, a moving color bar was displayed on a uniform background whose color was opponent with that of the bar. The main bar/background color combination we examined was magenta/cyan. Yellow/blue and cyan/magenta combinations were also examined for some cells. The response of MT cells to movements of opponent-color stimuli was recorded while the bar/background luminance ratio was changed from 1/10 to 10/1. In half of 89 cells tested in 3 monkeys, the response decreased considerably (disappeared completely in some cells) at a luminance ratio close to the human equiluminous condition. In the other half, a directional response persisted at any bar/background luminance ratio, though the response decreased to a varied extent (30-90% of the maximum response) near the ratio 1 (human equiluminous condition). The average magnitude of the equiluminous response to the magenta/cyan stimulus for the overall population was about 35% of the maximal response when the length of the bar (0.5 degrees in width) and the movement amplitude were set to be optimal for individual cells, i.e. smaller than 15 degrees and 10 degrees of visual angle, respectively. This fall to 23% when the bar length and movement amplitude were limited to 2 degrees. The same cell responded to pure color-contours of yellow/blue as well as of cyan/magenta combinations. Thus, MT can detect the direction of movement of pure color-contours, although the sensitivity is less than for luminance contours.

Animals↗

PubMed1991

Three monochrome displays from a single, true color video display controller.

Some nuclear medicine computer displays, as well as many image processing workstations are "true color" machines characterized by independent memory and grey scale mapping for each of the red, green and blue color channels. Other color image display systems produce a color image from a single grey scale map composed of red, green, and blue intensity values ("pseudo color"). In the true color system the final image is obtained by overlays of three independent color images. In an effort to present complete nuclear medicine studies for diagnosis from cathode-ray tubes (CRTs) we have employed a true color display to present three times as much spatial information as the system was designed for by directing each color output from the display controller to a different monochrome black and white (b/w) monitor. Therefore our system displays a 512 x 512 x 24-bit true-color image, or three 512 x 512 x 8-bit monochrome images, or any combination of smaller size matrices. Monitor requirements, cabling, and general software considerations are detailed here. The ability to display complete nuclear medicine studies on CRTs (as currently presented on film) has been provided by adding monitors and software revisions to a commercially available nuclear medicine computer system.

Color↗

PubMed2005

Replicated linkage for eye color on 15q using comparative ratings of sibling pairs.

: The aim of the study was to perform a genetic linkage analysis for eye color, for comparative data. Similarity in eye color of mono- and dizygotic twins was rated by the twins' mother, their father and/or the twins themselves. For 4,748 twin pairs the similarity in eye color was available on a three point scale ("not at all alike"-"somewhat alike"-"completely alike"), absolute eye color on individuals was not assessed. The probability that twins were alike for eye color was calculated as a weighted average of the different responses of all respondents on several different time points. The mean probability of being alike for eye color was 0.98 for MZ twins (2,167 pairs), whereas the mean probability for DZ twins was 0.46 (2,537 pairs), suggesting very high heritability for eye color. For 294 DZ twin pairs genome-wide marker data were available. The probability of being alike for eye color was regressed on the average amount of IBD sharing. We found a peak LOD-score of 2.9 at chromosome 15q, overlapping with the region recently implicated for absolute ratings of eye color in Australian twins [Zhu, G., Evans, D. M., Duffy, D. L., Montgomery, G. W., Medland, S. E., Gillespie, N. A., Ewen, K. R., Jewell, M., Liew, Y. W., Hayward, N. K., Sturm, R. A., Trent, J. M., and Martin, N. G. (2004). Twin Res. 7:197-210] and containing the OCA2 gene, which is the major candidate gene for eye color [Sturm, R. A. Teasdale, R. D, and Box, N. F. (2001). Gene 277:49-62]. Our results demonstrate that comparative measures on relatives can be used in genetic linkage analysis.

Adolescent↗

PubMed1993

Visual mechanisms that signal the direction of color changes.

Evidence is presented for a visual capacity specialized to sense the chromatic direction of change in colors over time. Discrimination thresholds were measured between pairs of suprathreshold color changes presented in consecutive intervals. In one interval, the color of a spatially uniform disk was changed at a constant speed along the circumference of a circle in an equiluminant color plane. In the other, an instantaneous change, which can be described as a vector in the equiluminant plane, was added to the circular color modulation. Averaging across conditions showed that the threshold for discriminating between a pair of purely temporal color changes was approximately proportional to the cosine of the color angle between them. The model that is presented to account for these results is based on parallel directional-color mechanisms that are tuned to different directions in color-space and are responsive to change in one color direction but not its opposite.

Color Perception↗

PubMedDate not supplied

Electrophysiological studies of color processing in human visual cortex.

Electrophysiological recordings from human visual cortex were carried out with electrodes chronically implanted in 13 patients for localization of an epileptogenic focus. Visual evoked potentials (VEPs) elicited by red or blue checkerboard stimuli were recorded using an adaptation stimulus-test stimulus design in which color was the most salient feature. A "significant color effect," defined as a statistically significant effect of the adaptation stimulus on test stimulus VEPs evoked by the same or a different color, was determined for various cortical regions: medial lingual gyrus, 20%; lateral lingual gyrus, 38%; posterior fusiform gyrus, 50%; anterior fusiform gyrus, 0%; inferior temporal gyrus, 5%; occipital pole, 30%; lateral surface of non-visual cortex, 6%; inferior parietal and temporal cortex, 5%. The time course of the significant color effects suggests that wave length-selective neuronal activity occurs initially at the first stage of cortical processing in the medial lingual gyrus, followed by progressively later activation of the lateral lingual gyrus, the posterior fusiform gyrus, and the inferior temporal gyrus. In two patients, stimulation of the lateral lingual and fusiform gyri elicited color sensations in the contralateral half-field, whereas stimulation of the medial lingual and cuneate gyri evoked retinotopically appropriate quadrantic "shimmering" devoid of color. These results suggest that a region of inferior occipital cortex, primarily the posterior portion of the fusiform gyrus, is involved in color perception and may be homologous with area V4 in monkeys. There is also a region of dorsolateral surface cortex which exhibits a fairly high percentage of significant color effects and when stimulated may evoke sensations of color. This region may be the same as the dorsolateral region thought to be involved in selective attention to color.

Adult↗

PubMed2005

Comparison of CIELAB DeltaE(*) and CIEDE2000 color-differences after polymerization and thermocycling of resin composites.

OBJECTIVES: Though instrumental technologies have been widely used for quantifying color of esthetic dental materials, the sizes for the perceptible or acceptable color-difference varied. Instead of the CIELAB DeltaE(*)(DeltaE(ab)(*)) formula, the CIEDE2000 (DeltaE(00)) formula that included weighting and parametric functions was introduced. The objective of this study was to determine the correlation between color-difference values of DeltaE(ab)(*) and DeltaE(00) after polymerization and thermocycling of dental resin composites. METHODS: Color-differences were calculated between unpolymerized and polymerized, and between polymerized and thermocycled resin composites. Color was measured relative to the standard illuminant D65 over a white background with SCE geometry. Regression analyses were performed between the color difference values of DeltaE(ab)(*) and DeltaE(00). RESULTS: There were significant correlations between DeltaE(ab)(*) values and DeltaE(00) values after polymerization and thermocycling (p<0.01), and the correlation coefficient was 0.99 and 0.98, respectively. SIGNIFICANCE: Within the limit of this study, the results suggest that two color-difference formulas can be used interchangeably for the evaluation of the color-difference of resin composites after polymerization and thermocycling. However, for the evaluation of changes in separate color parameters such as lightness, chroma and hue, the DeltaE(00) formula could be considered for the color evaluation of esthetic dental materials after confirming with human observer responses.

Algorithms↗

PubMed2006

Color changes of resin composites in the reflectance and transmittance modes.

OBJECTIVES: The objective of this study was to evaluate the changes in color and color coordinates after accelerated aging of resin composites depending on the measuring modes of reflectance and transmittance. METHODS: Color of seven resin composites (1-mm thick specimens) was measured in the reflectance mode and in the transmittance mode. After the baseline color measurement, the specimens were aged for total energy of 150 kJ/m2. Color change after aging was calculated in the reflectance mode and in the transmittance mode. Based on the data of A2 shade composites, the influence of measuring mode on the color change (DeltaEab*) and changes in three color coordinates (DeltaL*, Deltaa* and Deltab*) after aging was analyzed by ANOVA (p<0.01). RESULTS: Measuring mode influenced DeltaEab*, DeltaL* and Deltaa* values. There were significant correlations between the color changes measured in the reflectance mode and in the transmittance mode (r=0.91). SIGNIFICANCE: The color changes in the transmittance mode can roughly be estimated based on the reflected color changes.

Analysis of Variance↗

PubMed2005

When visual perception causes feeling: enhanced cross-modal processing in grapheme-color synesthesia.

In synesthesia, stimulation of one sensory modality (e.g., hearing) triggers a percept in another, non-stimulated sensory modality (e.g., vision). Likewise, perception of a form (e.g., a letter) may induce a color percept (i.e., grapheme-color synesthesia). To date, the neural mechanisms underlying synesthesia remain to be elucidated. We disclosed by fMRI, while controlling for surface color processing, enhanced activity in the left intraparietal cortex during the experience of grapheme-color synesthesia (n = 9). In contrast, the perception of surface color per se activated the color centers in the fusiform gyrus bilaterally. The data support theoretical accounts that grapheme-color synesthesia may originate from enhanced cross-modal binding of form and color. A mismatch of surface color and grapheme induced synesthetically felt color additionally activated the left dorsolateral prefrontal cortex (DLPFC). This suggests that cognitive control processes become active to resolve the perceptual conflict resulting from synesthesia.

Acoustic Stimulation↗

PubMed2005

Color stability of provisional crown and fixed partial denture resins.

STATEMENT OF PROBLEM: Provisional resins are used extensively during fixed prosthodontic treatment and exhibit varying degrees of color change/discoloration over time. Data are needed to help predict color stability of provisional resins. PURPOSE: The purpose of this in vitro study was to measure the color change of 12 provisional prosthodontic materials after immersion in artificial saliva and artificial saliva-coffee solutions for 1, 2, and 4 weeks. MATERIAL AND METHODS: Twelve provisional materials were studied. Methacrylates consisted of Alike, Jet, Temporary Bridge Resin, Unifast, and Zeta CC. Bis-acryl resins included Instatemp, Integrity, Luxatemp, Protemp Garant, Provipont, Provitec, and Temphase. Ten specimens (25.4 mm x 25.4 mm x 2.4 mm) of each material were fabricated. Five specimens were stored at 37 degrees C in artificial saliva and 5 were stored in a solution of artificial saliva (400 cc) and coffee (800 cc). Baseline color was measured using a colorimeter. Further color measurements were made after 1, 2, and 4 weeks of immersion. CIE L *a *b * values were recorded and color differences (DeltaE) between baseline and each storage interval were calculated using a 2-way ANOVA with Bonferroni adjustment for multiple comparisons in conjunction with an overall alpha=.05. RESULTS: Results indicated the presence of strong interaction between material and storage solution regardless of the aspect of color considered (P<.0001 for DeltaE, DeltaL *, Deltaa *, and Deltab *). Coffee solution relative to saliva solution had the most significant impact on color change for Luxatemp, Protemp, and Temphase materials at 4 weeks, but the greatest overall color change for both coffee and saliva solutions was found for Provipont (DeltaE=9.40 coffee; 8.51 saliva) and the least overall color change for both solutions was found for Zeta CC (DeltaE=0.31 coffee; 0.23 saliva). CONCLUSIONS: Under the conditions of this study, 12 provisional crown and fixed partial denture resins demonstrated varying tendency to discolor over a range of time periods when immersed in artificial saliva and artificial saliva-coffee solutions.

Acrylic Resins↗

PubMed2003

The effect of current bleaching agents on the color of light-polymerized composites in vitro.

STATEMENT OF PROBLEM: Bleaching agents may affect the color of existing composite restorations. PURPOSE: The purpose of this study was to compare the effect of 10% carbamide peroxide and 10% hydrogen peroxide on the color of light-polymerized hybrid, macrofilled, and polyacid-modified composites. MATERIAL AND METHODS: Two light-polymerized hybrid composites (3M Valux and Spectrum TPH), 1 macrofilled condensable composite (Solitaire), and 2 polyacid-modified composites (Dyract AP and Compoglass) were used. The hybrid composites served as controls. The color of 8 specimens of each material was analyzed by use of a spectrophotometer before bleaching. The specimens were then divided randomly into 2 subgroups (n=4). One group was immersed in 10% carbamide peroxide solution and the other in 10% hydrogen peroxide, for 8 hours each for 14 consecutive days. After bleaching, color changes (Delta E) were determined for each material and compared by use of the Kruskal-Wallis test, followed by the Mann-Whitney U test (P<.05). RESULTS: After bleaching with carbamide peroxide, the color changes (Delta E) for Dyract AP (2.18; SD = 1.41), Compoglass (1.14; SD = 0.26) and Solitaire (1.56; SD = 0.89) were higher than the color changes recorded for 3M Valux (0.63; SD = 3.60), and Spectrum TPH (0.66; SD = 1.24). The differences between materials bleached with carbamide peroxide were not statistically significant. After bleaching with hydrogen peroxide, the color changes for Dyract AP (9.39; SD = 0.53) and Compoglass (5.15; SD = 0.52) were higher than the changes recorded for Spectrum TPH (4.53; SD = 1.53) and 3M Valux (3.41; SD = 4.40), whereas the color change of Solitaire (3.69; SD = 0.57) was significantly higher than that of 3M Valux (P=.01). The color changes for all restorative materials tested were clinically detectable after the application of 10% hydrogen peroxide. However, clinically noticeable discoloration was observed only for Dyract AP treated with 10% carbamide peroxide. CONCLUSION: In comparison to 10% carbamide peroxide, 10% hydrogen peroxide caused more color changes in the composites tested.

Carbamide Peroxide↗

PubMed2000

Time course of chromatic adaptation for color appearance and discrimination.

Adaptation to a steady background has a profound effect on both color appearance and discrimination. We determined the temporal characteristics of chromatic adaptation for appearance and discrimination along different color directions. Subjects were adapted to a large uniform background made up of a CRT screen and a 45x64 degrees wall, illuminated by computer controlled lamps. After an instant change in background color along a red-green or blue-yellow color axis, we measured thresholds for the detection of increments along the same axes at fixed times between 25 ms and 121 s. Analogously, color appearance was determined using achromatic matching. Three components of adaptation could be identified by their temporal characteristics. A slow exponential time course of adaptation with a half-life of about 20 s was common to appearance and discrimination. A faster component with a half-life of 40-70 ms--probably due to photoreceptor adaptation--was also common to both. Exclusive for color appearance, there was a third, extremely rapid mechanism with a half-life faster than 10 ms. This instantaneous process explained more than 50% of total adaptation for color appearance and could be shown to act in a multiplicative manner. We conclude that this instantaneous adaptation mechanism for color appearance is situated at a later processing stage, after mechanisms common to appearance and discrimination, and is based on multiplicative spatial interactions rather than on local, temporal adaptational processes. Color appearance, and thus color constancy, seems to be determined in large part by cortical computations.

Adaptation, Physiological↗

PubMed2001

Nonlocal interactions in color perception: nonlinear processing of chromatic signals from remote inducers.

The perceived color of an object depends on the chromaticity of its immediate background. But color appearance is also influenced by remote chromaticities. To quantify these influences, the effects of remote color fields on the appearance of a fixated 2 degrees test field were measured using a forced-choice method. Changes in the appearance of the test field were induced by chromaticity changes of the background and of 2 degrees color fields not adjacent to the test field. The appearance changes induced by the color of the background corresponded to a fraction of between 0.5 and 0.95 of the cone contrast of the background change, depending on the observer. The magnitude of induction by the background color was modulated on average by 7.6% by chromaticity changes in the remote color fields. Chromaticity changes in the remote fields had virtually no inducing effect when they occurred without a change in background color. The spatial range of these chromatic interactions extended over at least 10 degrees from the fovea. They were established within the first few hundred milliseconds after the change of background color and depended only weakly on the number of inducing fields. These results may be interpreted as reflecting rapid chromatic interactions that support robustness of color vision under changing viewing conditions.

Color Perception↗

PubMed2001

Sensitivity to modulation of color distribution in multicolored textures.

We evaluated the discriminability of color distributions in square-element textures. Each texture contained 225 colors, represented by a distribution of color vectors in color space defined by the L-M and S-(L+M) axes. Each color distribution was systematically manipulated by modulating the distribution of the vector lengths sinusoidally as a function of the direction in the color space. The results showed that it is difficult to resolve a color distribution modulated in more than three cycles per 360 degrees in the chromatic direction. The difference in components along the cardinal axes is not a critical factor in the discrimination of the color distribution. An analysis using a line-element model suggested that the discrimination of the color distribution is mediated by multiple chromatic channels that are tuned to a variety of directions in the color space with a half-height-half-bandwidth of about 40 degrees in the chromatic direction.

Color Perception↗

PubMed2000

Prenatal diagnosis of placenta previa accreta by transabdominal color Doppler ultrasound.

OBJECTIVE: The aim of this study was to evaluate the efficacy of transabdominal color Doppler ultrasound in diagnosing placenta previa accreta. DESIGN: Eighty patients with persistent placenta previa underwent transabdominal B-mode and color Doppler ultrasound evaluation in the second and third trimesters because they had a high risk of placenta accreta. Color Doppler imaging criteria used included diffuse intraparenchymal placental lacunar flow; focal intraparenchymal placental lacunar flow; bladder-uterine serosa interphase hypervascularity; prominent subplacental venous complex; and loss of subplacental Doppler vascular signals. The color Doppler images were interpreted prospectively for signs of placenta previa accreta according to the exhibited color Doppler sonographic features. RESULTS: Sixteen of the 80 patients exhibited characteristic color Doppler imaging patterns highly specific for placenta accreta according to the preceding criteria, and 14 of these had histopathological proof of placenta accreta. Two patients had false-positive color Doppler imaging evidence mistaken for interphase hypervascularity caused by bladder varices. Thirteen patients underwent hysterectomy in the group suspicious for accreta. Of the 64 patients with negative color Doppler imaging results, three had placenta accreta, while two required cesarean hysterectomy; the remaining patient underwent uterine artery ligation for bleeding from the lower uterine segment. The sensitivity of color Doppler imaging in the diagnosis of placenta previa accreta was 82.4% (14/17) and the specificity was 96.8% (61/63). The positive and negative predictive values were 87.5% (14/16) and 95.3% (61/64), respectively. CONCLUSIONS: Variable vascular morphological patterns of placenta previa accreta were exhibited and categorized by transabdominal color Doppler sonography in the antenatal period. The identification of these specific vascular patterns had a positive impact on the peripartum clinical management of the affected patients.

Abdomen↗