High-fidelity single-photon full-color imaging via frequency-spectrum cross-channel correlation

Color formulation in maxillofacial elastomer by genetic algorithm

Complex environments with random disturbances could induce dynamic scaling factors during single-pixel measurements, affecting reconstruction quality and color accuracy. In this Letter, we report high-fidelity full-color correspondence imaging (CI) in complex environments with random disturbances. A series of mixed illumination patterns, i.e., sinusoidal and random patterns, are designed and alternately projected onto an unknown target scene. At the receiving end, a trichroic prism is employed to guide optical waves into red, green, and blue channels, which are individually detected using a single-pixel detector. A series of dynamic scaling factors are estimated using the single-pixel light intensities collected when random patterns are used, which are further applied to correct the single-pixel light intensities collected when sinusoidal patterns are used. Then, a physics-enhanced neural network (PENet) without any training data is designed to perform the reconstruction. Finally, a color target scene can be retrieved by combining the reconstructions at three channels. A series of experiments are conducted to illustrate that the proposed method can achieve high-fidelity reconstruction with high accuracy of colors in complex scattering media with random disturbances. This study provides a promising solution for high-fidelity full-color imaging in complex environments with random disturbances.

BackgroundThe aim of this study was to evaluate the 50%:50% perceptibility thresholds (PT) and acceptability thresholds (AT) for color differences in ceramic shade tabs observed by dentists and patients using CIEDE2000 color difference formula. Material and MethodsTwenty-two combinations of ceramic shade tabs from the VITA 3D Master shade guide were assembled to be used for the visual comparison analyses. The color difference between each shade tab pair was numerically determined by spectrophotometry using the VITA EasyShade V, and calculated using the CIEDE2000 formula (ΔE00). Twenty dentists and twenty patients were recruited for this study. All participants performed the visual assessment of the provided shade tab pairs under D65 illumination and a grey background, and requested to determine if they could perceive a color difference between them (PT) and whether they considered the combination clinically acceptable (AT). The correlation between numeric data of color difference between the shade tabs, and the perceptibility and acceptability thresholds given by the participants was analyzed by logistic regression (α=0.05; β=0.0085).ResultsThe PT for dentists was ΔE00= 2.29, and ΔE00= 2.27 for patients. The AT for dentists was ΔE00=2,41, and ΔE00=2,83 for patients. The results showed a statistically significant difference between PT and AT thresholds for both dentists and patients. However, there was no statistically significant differences in PT (p=0.39) or AT (p=0.54) between patients and dentists.ConclusionsWithin the limitations of this study, it was possible to conclude that while the PT and AT vary significantly within each group, they are statistically similar between dentists and patients when discriminating color differences in ceramic tabs. Key words:Color difference, esthetic, aesthetic, spectrophotometry, CIEDE2000.

The available image quality assessment (IQA) methods based on gradient calculation are mostly implemented without considering visual perception threshold (VPT) and color information. However, incorporating VPT with IQA model can reduce redundant information and human visual system (HVS) is extremely sensitive to color variation. An improved image quality assessment in gradient domain is proposed which utilizes minimum amount of gradient coefficients to capture the color and structure distortion of degraded image by applying a VPT to remove the unperceived gradient coefficients. The difference of perceived gradient coefficients between distorted and reference image is measured to acquire image quality score. Experimental results on two benchmarking databases (LIVEII and TID2008) indicate the rationality and validity of the proposed method.KeywordsImage quality assessmentHuman visual systemGradient calculationVisual perception threshold

The study of T2-weighted hyperintense lesions resulting from autoimmune inflammatory injury and associated volumes within the CNS remains fundamental to the diagnosis and disease surveillance of MS. We investigated the dynamic changes of individual T2-weighted hyperintense MS lesions on MRI and hypothesized that variations may be present below the threshold of visual perception when evaluating longitudinal data. A retrospective study was performed of people with MS, incorporating data from 3 consecutive MRI time points acquired within a single academic center. All included MRI studies lacked formal imaging interpretations of newly enlarging or contracting T2-weighted hyperintensities. Well-defined, noncoalescing, individual T2-weighted hyperintense lesions were targeted. A total of 8-12 lesions were randomly selected in a blinded fashion at MRI time point 1 and 3D lesion volumes were followed over MRI time points 2 and 3. The impact of treatment on lesion expansion and relationship to brain MRI advancement, patient-reported progression of disease, and physician-identified progression was also studied. The study cohort comprised 115 people (81 (70.4%) women; mean disease duration of 9.36 years [standard deviation: 7.72 years]) who were primarily White (79.1%). A total of 1426 focal T2-weighted hyperintense MS lesions were identified on MRI time point 1 and longitudinally followed over MRI time points 2 and 3. In the evaluation of raw changes in individual T2-weighted hyperintense lesion volumes from MRI time point 1 to MRI time point 2, a similar number of individuals were observed with predominantly expanding (49/115; 42.6%) or contracting (51/115; 44.3%) lesions. However, most lesions expanded in volume (48/115; 41.7%) versus those that contracted (45/115; 39.1%) when evaluating MRI time point 3 to time point 1. Those individuals not on active treatment had a 67.15% reduction in the odds of more individual lesions predominantly contracting in volume relative to those on low-efficacy disease modifying therapy treatment (95% CI = [-83.89% to -33.01%], P = .0008) and 74.02% reduction relative to high-efficacy treatment individuals (95% CI = [-87.37% to -46.56%], P < .0001). Dynamic changes in T2-weighted hyperintense lesions are abundant, occurring below the threshold of visual perception and are present more frequently in untreated individuals.

Color and translucency of zirconia infrastructures and porcelain-layered systems

Does background color influence visual thresholds?

The degree of polarization of rainbows of order k with k≥3 is bounded in the interval [75%, 78%], where 75% is the limit for k→∞. A polarization filter can improve the signal-to-background ratio of the third and fourth rainbows by a factor of 2, which may lift their visibilities in natural circumstances above the threshold of human visual perception. Under optimal circumstances, the latter may be true for the recently photographed green fingerprint of the fifth rainbow, even without the aid of a polarization filter. The prospects for observing the sixth rainbow are unclear. There exists a possibility that the signal of the natural seventh rainbow (appearing at 64° from the Sun) may be separated from its background if photographed under perfect conditions through a polarization filter.

This study evaluates anthropometric outcomes of a modified Onizuka technique for unilateral cleft lip (CL) repair using 3-dimensional (3D) photogrammetry, with emphasis on anatomic subunit reconstruction without preoperative numerical measurements. A prospective cohort study was conducted at a tertiary craniofacial center. Sixty-one patients with unilateral CL and/or palate who underwent CL repair using the modified Onizuka technique were enrolled. The technique relocates key landmarks to the footplate of the medial crus, preserves an 80° angular design at the peak of Cupid's bow, and uses a V-Y advancement flap for frenulum reconstruction. Concurrent primary rhinoplasty and gingivoplasty were performed. Anthropometric symmetry was assessed via 3D imaging at ≥1-year follow-up, including nostril width, columellar height, central and medial lip height, lateral lip height and length, and hemi-Cupid's bow width. The cohort comprised 60.7% males, with 70.5% having left-sided clefts and 67.2% having complete clefts. Median age at surgery was 5.0 months. All intraclass correlation coefficient values exceeded 0.75, indicating good to excellent reliability. No statistically significant differences were observed between cleft and noncleft sides (all P>0.05). Mean differences were <0.2mm, below the threshold of human visual perception. The modified Onizuka technique achieves symmetric outcomes in unilateral CL repair, validated by objective 3D metrics. Its emphasis on anatomic subunit reconstruction without preoperative numerical marking offers a versatile, reproducible approach for diverse cleft phenotypes.

The purpose of this study was to determine perceptibility and acceptability thresholds for color differences in light and dark skin-colored maxillofacial elastomers. A total of 15 pairs of light specimens (mimicking white, Asian, and Hispanic skin) and 15 pairs of dark specimens (mimicking African-American skin) were made using skin-colored maxillofacial silicone elastomers, combined with opacifiers and pigments. Color match/mismatch and acceptable/unacceptable mismatch of each pair of specimens were visually evaluated by 45 evaluators under controlled conditions of a viewing booth. Color differences were calculated using CIELAB and CIEDE2000 formulae. After calculating the model parameters, receiver operating characteristics (ROC) curves and area under the ROC curve (AUC) were analyzed. Repeated measures ANOVA and Tukey's HSD test were used in a statistical analysis (alpha= 0.05). CIELAB/CIEDE2000 perceptibility and acceptability thresholds for light specimens were 1.1/0.7 and 3.0/2.1, respectively. Corresponding values for dark specimens were 1.6/1.2 and 4.4/3.1, respectively. Differences in primary specimen color and type of threshold were found to be significant (p < 0.001). Only the primary specimen color effect was found to be significant in AUC comparisons. Within the limitations of this study, both main effects of threshold type (perceptibility and acceptability) and primary color (light and dark) on 50:50% color-difference thresholds of colored maxillofacial elastomers were found significant for both color-difference formulae used (CIELAB, CIEDE2000). In addition, significant interaction between the two main effects was found, indicating a stronger effect of skin type on acceptability than perceptibility thresholds. Primary specimen color (light vs. dark) was found to be the only significant main effect on the AUC of ROC curves constructed from logistic regression.

Perceptibility and acceptability thresholds for color differences of light and dark maxillofacial skin replications

PURPOSEThe aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns.MATERIALS AND METHODSA total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 µm, 80 µm, and 120 µm) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE00) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE00 data were analyzed by using two-way ANOVA before and after thermocycling (α = .05).RESULTSThere was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE00 was under the perceptibility threshold in the group of 40 µm cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE00 < 1.8) for all other groups. After thermocycling, the ΔE00 values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values.CONCLUSIONThe cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 µm cement thickness. All study groups revealed perceptible color change after thermocycling.

To determine 50:50% perceptibility threshold (PT) and 50:50% acceptability threshold (AT) for computer-simulated samples of human gingiva using CIEDE2000 and CIELAB color difference formulas. Each of the 60 pairs of simulated human gingiva was displayed on a calibrated monitor, together with three pairs of upper central incisors of different lightness. The color of gingiva left and right from the midline was compared. A total of 30 observers (15 dentists, 15 laypersons) participated in the study. CIEDE2000 and CIELAB formulas were used to calculate the thresholds and a Takagi-Sugeno-Kang Fuzzy Approximation model was used as fitting procedure. Paired t-test (α = 0.05) was used in evaluation of statistical significance of differences. The PT and AT for CIEDE2000 and 95% confidence intervals were 1.1 [0.4, 1.7] and 2.8 [1.8, 4.0], respectively. Corresponding CIELAB values were 1.7 [0.2, 2.6] and 3.7 [2.1, 5.7]. Significant differences (P < .01) were recorded between PT and AT, between the corresponding threshold values in CIEDE2000 and CIELAB formulas as well as between dentists and laypersons. The difference between the perceptibility and acceptability threshold for gingiva was statistically significant in both CIEDE2000 and CIELAB. The same was true for differences between the corresponding thresholds using two color difference formulas, and between dentists and laypersons. Visual thresholds of human gingiva were not dependent upon lightness of adjacent teeth. Overall, CIEDE2000 color difference formula provided better fit than CIELAB formula in the evaluation of color difference thresholds of human gingiva. The data on visual thresholds for healthy human gingiva can be used as quality control tool/guide for selection and evaluation of dental materials, interpretation of color-related findings in clinical dentistry and research, and for standardization in dentistry. It is of particular value that this study was designed based on in-vivo color evaluation of healthy keratinized gingiva of subjects of different ethnicities, age groups, and gender.

Perceptibility and acceptability thresholds for colour differences in dentistry

The aim of the present study was to assess the perceptibility and acceptability threshold values for color differentiation at the restoration and mucosa levels. One restored single-tooth implant and the contralateral reference tooth were spectrophotometrically assessed in 20 patients. Perceptibility and acceptability were evaluated by dentists, dental technicians, and laypeople. Dental technicians had the highest sensitivity in the perception of tooth color differences (ΔE = 2.7), followed by dentists (ΔE = 3.3) and laypeople (ΔE = 4.4). Acceptability threshold values were generally higher than perceptibility threshold in all groups. Dental technicians exhibited the highest sensitivity in the perception of mucosa color differences (50% perceptibility at ΔE = 2.65), followed by dentists (ΔE > 3.7) and laypeople (ΔE > 6). Color differences were tolerated with varying degrees among the three groups. Laypeople accepted higher color differences at the mucosa level.