High Contrast Background Research Articles

Fotogrametría SFM aplicada a la determinación taxonómica de restos arqueofaunísticos

<p>Photogrammetry has recently been incorporated into archaeological research, replacing much more expensive techniques while still generating high resolution results. This technique converts two dimensional (2D) images into three-dimensional (3D) models, allowing for the complex analysis of geometric and spatial information. It has become one of the most used methods for the 3D recording of cultural heritage objects. Among its possible archaeological uses are: digitally documenting an archaeological dig at low cost, aiding the decision-making process (Dellepiane et al., 2013); spatial surveying of archaeological sites; 3D model generation of archaeological objects and digitisation of archaeological collections (Adami et al., 2018; Aparicio Resco et al., 2014; Cots et al., 2018; Iturbe et al., 2018; Moyano, 2017).</p><p>The objective of this paper is to show the applicability of 3D models based on SfM (Structure from Motion) photogrammetry for archaeofauna analyses. We created 3D models of four camelid (Lama glama) bone elements (skull, radius-ulna, metatarsus and proximal phalange), aiming to demonstrate the advantages of 3D models over 2D osteological guides, which are usually used to perform anatomical and systematic determination of specimens.</p><p>Photographs were taken with a 16 Megapixel Nikon D5100 DSLR camera mounted on a tripod, with the distance to the object ranging between 1 and 3 m and using a 50mm fixed lens. Each bone element was placed on a 1 m tall stool, with a green, high contrast background. Photographs were shot at regular intervals of 10-15º, moving in a circle. Sets of around 30 pictures were taken from three circumferences at vertical angles of 0º, 45º and 60º. In addition, some detailed and overhead shots were taken from the dorsal and ventral sides of each bone element. Each set of dorsal and ventral photos was imported to Agisoft Photoscan Professional. A workflow (Fig. 4) of alignment, tie point matching, high resolution 3D dense point cloud construction, and creation of a triangular mesh covered with a photographic texture was performed. Finally the dorsal and ventral models were aligned and merged and the 3D model was accurately scaled. In order to determine accuracy of the models, linear measurements were performed and compared to a digital gauge measurement of the physical bones, obtaining a difference of less than 0.5 mm.</p><p>Furthermore, five archaeological specimens were selected to compare our 3D models with the most commonly used 2D camelid atlas (Pacheco Torres et al., 1986; Sierpe, 2015). In the particular case of archaeofaunal analyses, where anatomical and systematic determination of the specimens is the key, digital photogrammetry has proven to be more effective than traditional 2D documentation methods. This is due to the fact that 2D osteological guides based on drawings or pictures lack the necessary viewing angles to perform an adequate and complete diagnosis of the specimens. Using new technology can deliver better results, producing more comprehensive information of the bone element, with great detail and geometrical precision and not limited to pictures or drawings at particular angles. In this paper we can see how 3D modelling with SfM-MVS (Structure from Motion-Multi View Stereo) allows the observation of an element from multiple angles. The possibility of zooming and rotating the models (Figs. 6g, 6h, 7d, 8c) improves the determination of the archaeological specimens.</p><p>Information on how the 3D model was produced is essential. A metadata file must include data on each bone element (anatomical and taxonomic) plus information on photographic quantity and quality. This file must also contain the software used to produce the model and the parameters and resolution of each step of the workflow (number of 3D points, mesh vertices, texture resolution and quantification of the error of the model). In short, 3D models are excellent tools for osteological guides.</p>

Image saliency and co-saliency detection by low-rank multiscale fusion

Saliency and co-saliency detection aim to distinguish conspicuous foreground objects from single and multiple images, thus are essential in many multimedia and vision applications. To achieve balanced efficiency and accuracy, most recent successful saliency detectors are based on superpixels. However, saliency detection with single-scale superpixel segmentation may fail in capturing intrinsic salient objects of complex natural scenes with small-scale high-contrast backgrounds. To tackle this problem, we present a simple strategy using multiscale superpixels to jointly detect salient object via low-rank optimisation. Specifically, we first build a multiscale superpixel pyramid and derive the corresponding saliency map by multimodal saliency features and priors at each single scale. Then, we use joint low-rank analysis of multiscale saliency maps to obtain a more reliable and adaptively-fused saliency map, which properly takes all scales saliency into account. We further propose a GMM generative co-saliency prior to enable the above approach to detect co-salient objects from multiple images. Extensive experiments on benchmark datasets validate the effectiveness and superiority of the proposed saliency and co-saliency detector over state-of-the-arts.

Robust nanoscopy of a synaptic protein in living mice by organic-fluorophore labeling

Extending superresolution fluorescence microscopy to living animals has remained a challenging frontier ever since the first demonstration of STED (stimulated emission depletion) nanoscopy in the mouse visual cortex. The use of fluorescent proteins (FPs) in in vivo STED analyses has been limiting available fluorescence photon budgets and attainable image contrasts, in particular for far-red FPs. This has so far precluded the definition of subtle details in protein arrangements at sufficient signal-to-noise ratio. Furthermore, imaging with longer wavelengths holds promise for reducing photostress. Here, we demonstrate that a strategy based on enzymatic self-labeling of the HaloTag fusion protein by high-performance synthetic fluorophore labels provides a robust avenue to superior in vivo analysis with STED nanoscopy in the far-red spectral range. We illustrate our approach by mapping the nanoscale distributions of the abundant scaffolding protein PSD95 at the postsynaptic membrane of excitatory synapses in living mice. With silicon-rhodamine as the reporter fluorophore, we present imaging with high contrast and low background down to ∼70-nm lateral resolution in the visual cortex at ≤25-µm depth. This approach allowed us to identify and characterize the diversity of PSD95 scaffolds in vivo. Besides small round/ovoid shapes, a substantial fraction of scaffolds exhibited a much more complex spatial organization. This highly inhomogeneous, spatially extended PSD95 distribution within the disk-like postsynaptic density, featuring intricate perforations, has not been highlighted in cell- or tissue-culture experiments. Importantly, covisualization of the corresponding spine morphologies enabled us to contextualize the diverse PSD95 patterns within synapses of different orientations and sizes.

Robust Automated detection of Nanocarriers’ Toxicity using Microscopic Image Analysis

Nanocarriers’ usage turned out to be a revolutionizing factor in the field of medical diagnosis and therapies. One of these therapies includes drug delivery system, where the nanocarriers are utilized for targeted and controlled delivery of drug to the diseased sites. Toxicity is one of the crucial issues which can arise during this process and needs to be addressed seriously and as early as possible. This paper reports an automated system for the relatively new and undiscovered area, where cell detection and evaluation play a major role in toxicity prediction of nanocarriers during the drug delivery process. The toxicity level was decided on the basis of dead cells count present in the microscopic images. The algorithm takes a few seconds to run and the overall accuracy of the proposed algorithm was found to be approx. 97% and 83% for different sets of images. The various image peculiarities which led to error include high cells clustering, poor contrast, and noisy background

Large-scale controlled bio-inspired fabrication of 3D CeO2:Eu3+ hierarchical structures for evaluation of highly sensitive visualization of latent fingerprints

Abstract Novel CeO2:Eu3+ (1–9 mol%) nanophosphors (NPs) with flower-like hierarchical structures with controlled shape and size were effectively synthesized by hydrothermal method using Epigallocatechin gallate as a bio-surfactant. Optimized NPs were explored as an effective labeling agent for the visualization of latent fingerprints on different porous and non-porous surfaces. Visualized fingerprints revealed first, second and third-level ridge particulars with high contrast, high selectivity and low background interference. X-ray photoelectron spectral studies evident that the presence of oxygen vacancies were responsible for the surface modification of these superstructures. The induced oxygen vacancies were also strongly influenced the photoluminescenceproperties of the prepared samples. 3D flower-like hierarchical architectures were explored by tuning different experimental parameters. Growth mechanism of 3D architectures developed through two dimensional flakes involves nucleation, growth, Ostwald ripening and recrystallization. The photometric properties evident that the prepared samples exhibit intense red color with color purity ∼80%. Investigation on visible light photocatalytic degradation of methylene blue has been examined using these powders. Results discussed were noteworthy for exploring these phosphor materials in multi-functional applications such as optoelectronics, forensic and photocatalysis.

Effective visualization of latent fingerprints with red fluorescent La2(MoO4)3:Eu3+ microcrystals

Lanthanide phosphors have recently been proven as a novel type of fluorescent label that can be extensively used in analytical detection. La2(MoO4)3:Eu3+ phosphors with uniform twinned hemispheres morphology have been successfully synthesized via a sodium citrate mediated hydrothermal method. The crystal structure has been determined by X-ray powder diffraction (XRD) and the microstructures were characterized by scanning electron microscopy (SEM). The La2(MoO4)3:Eu3+ microcrystals emitted strong emission at 616 nm under the 269 nm excitation. The photoluminescence (PL) emission intensities were enhanced with the increment of Eu3+ ion concentration and the optimal doping concentration was 15 mol%. The as-prepared La2(MoO4)3:Eu3+ was further applied in developing latent fingerprint images, which exhibited clear and well-defined details with high contrast and low background interference under 254 nm excitation. This work shows that La2(MoO4)3:Eu3+ powder is a versatile fluorescent label for the detection of LFPs for individual identification in forensic science.

Dual Colorimetric and Fluorescent Imaging of Latent Fingerprints on Both Porous and Nonporous Surfaces with Near-Infrared Fluorescent Semiconducting Polymer Dots.

Semiconducting polymer dots (Pdots) have recently been proven as a novel type of ultrabright fluorescent probes that can be extensively used in analytical detection. Here, we developed a dual visual sensor based on Pdots for fingerprint imaging. We first designed and synthesized two types of near-infrared (NIR) fluorescent polymers and then embedded ninhydrin into the Pdot matrix. The resulting Pdot assays showed the colorimetric and fluorescent dual-readout abilities to detect latent fingerprints on both porous and nonporous surfaces. The developed fingerprints clearly revealed first-, second-, and third-level details with high contrast, high selectivity, and low background interference. We also grafted the chemical groups on the nanoparticle surface to investigate the mechanisms involved in the fingerprint development processes. We further utilized this assay in note paper and checks for latent fingerprint imaging. We believe that this dual-readout method based on Pdots will create a new avenue for research in fingerprint detection and anticounterfeiting technology.

Risky Courtship: Background Contrast, Ornamentation, and Display Behavior of Wolf Spiders Affect Visual Detection by Toad Predators

AbstractMales that search widely for females and perform conspicuous courtship displays run a high risk of being detected by their predators. Therefore, gains in reproductive success might be offset by increased mortality due to predation. Male brush‐legged wolf spiders (Schizocosa ocreata) with larger decorative traits (foreleg tufts) are preferred by females as mates, but are more readily detected by predators. However, predation risk may also be influenced by the interaction between components of signals and the environment in which signaling occurs. Courting male spiders were readily accepted as prey by a sympatric predator, the American toad (Anaxyrus americanus). We used video playback to tease apart the interactive effect between visual signals and the signaling environment on the ability of toads to detect courting spiders as a function of distance, background contrast, the presence or absence of male foreleg tufts, and behavioral activity. The response of toads to video sequences of male spiders was similar to their response to live male spiders. Toad response varied over distance toward spiders displayed against high contrast (sunny) vs. low contrast (shaded) backgrounds. Beyond 30 cm, more toads detected courting male spiders against light, ‘sunny’ backgrounds and detected them faster when compared to the same spider stimulus against darker, ‘shady’ backgrounds. In choice tests, toads oriented more often toward courting males with leg tufts than those without. Toad responses also varied with male spider behavior in that only videos of moving males were attacked. Latency to orient and detection by toads was significantly greater for walking males than courting males, and this effect was most evident at distances between 30 cm and 50 cm. Results supported that courting wolf spiders are at significant risk of predation by visually acute predators. Distance, background contrast, and the presence of foreleg decorations influence detection probability. Thus, the same complex visual signals that make males conspicuous and are preferred by females can make males more vulnerable as prey to toads.

A membrane-activatable near-infrared fluorescent probe with ultra-photostability for mitochondrial membrane potentials.

Mitochondrial membrane potential (MMP) is a frequently used indicator for mitochondrial function. Herein, we report a photostable near-infrared (NIR) fluorescent dye for monitoring MMP. This new probe, named NIMAP, is non-fluorescent in aqueous solution and can be activated by cell membranes, providing high fluorescence contrast and low background fluorescence. NIMAP has been validated for monitoring MMP in living mammalian cells and in mice. Due to the large fluorescence response, low fluorescence background, high photostability, and excellent tissue penetration resulting from red-shifted excitation and emission in the "optical window" above 600 nm, broad applications of this new probe are expected.

Rare Earth Fluorescent Nanomaterials for Enhanced Development of Latent Fingerprints.

The most commonly found fingerprints at crime scenes are latent and, thus, an efficient method for detecting latent fingerprints is very important. However, traditional developing techniques have drawbacks such as low developing sensitivity, high background interference, complicated operation, and high toxicity. To tackle this challenge, we have synthesized two kinds of rare earth fluorescent nanomaterials, including the fluoresce red-emitting YVO4:Eu nanocrystals and green-emitting LaPO4:Ce,Tb nanobelts, and then used them as fluorescent labels for the development of latent fingerprints with high sensitivity, high contrast, high selectivity, high efficiency, and low background interference, on various substrates including noninfiltrating materials, semi-infiltrating materials, and infiltrating materials.

18F-FP-PEG2-β-Glu-RGD2: A Symmetric Integrin αvβ3-Targeting Radiotracer for Tumor PET Imaging

Radiolabeled cyclic arginine-glycine-aspartic (RGD) peptides can be used for noninvasive determination of integrin αvβ3 expression in tumors. In this study, we performed radiosynthesis and biological evaluation of a new 18F-labeled RGD homodimeric peptide with one 8-amino-3,6-dioxaoctanoic acid (PEG2) linker on the glutamate β-amino group (18F-FP-PEG2-β-Glu-RGD2) as a symmetric PET tracer for tumor imaging. Biodistribution studies showed that radioactivity of 18F-FP-PEG2-β-Glu-RGD2 was rapidly cleared from blood by predominately renal excretion. MicroPET-CT imaging with 18F-FP-PEG2-β-Glu-RGD2 revealed high tumor contrast and low background in A549 human lung adenocarcinoma-bearing mouse models, PC-3 prostate cancer-bearing mouse models, and orthotopic transplanted C6 brain glioma models. 18F-FP-PEG2-β-Glu-RGD2 exhibited good stability in vitro and in vivo. The results suggest that this tracer is a potential PET tracer for tumor imaging.

Detection of admittivity anomaly on high-contrast heterogeneous backgrounds using frequency difference EIT

This paper describes a multiple background subtraction method in frequency difference electrical impedance tomography (fdEIT) to detect an admittivity anomaly from a high-contrast background conductivity distribution. The proposed method expands the use of the conventional weighted frequency difference EIT method, which has been used limitedly to detect admittivity anomalies in a roughly homogeneous background. The proposed method can be viewed as multiple weighted difference imaging in fdEIT. Although the spatial resolutions of the output images by fdEIT are very low due to the inherent ill-posedness, numerical simulations and phantom experiments of the proposed method demonstrate its feasibility to detect anomalies. It has potential application in stroke detection in a head model, which is highly heterogeneous due to the skull.

Trade-offs in female signal apparency to males offer alternative anti-harassment strategies for colour polymorphic females.

Colour polymorphisms are known to influence receiver behaviour, but how they affect a receiver's ability to detect and recognize individuals in nature is usually unknown. I hypothesized that polymorphic female damselflies represent an evolutionary stable strategy, maintained by trade-offs between the relative apparency of morphs to male receivers. Using field experiments on Enallagma hageni and focal studies of E.hageni and Enallagma boreale, I tested for the first time the predictions that (i) green heteromorphs and blue andromorphs gain differential protection from sexual harassment via background crypsis and sexual mimicry, respectively, and (ii) female morphs behaviourally optimize their signal apparency to mate-searching males. First, based on male reactions elicited by females, against a high-contrast background, the two morphs did not differ in being detected by males, and once detected, they did not differ in being recognized (eliciting sexual reactions). However, on green ferns, heteromorphs were less likely to be detected (elicited only fly-bys) than andromorphs, but once detected, the morphs did not differ in being recognized. In contrast, when perched on a dowel with two male signal distractors, andromorphs were detected less often, and once detected, they were recognized less often than heteromorphs. Second, in fields where females foraged, andromorphs perched higher on vegetation than heteromorphs and were more often in the vicinity of males. Neither harassment rates nor evasive behaviours differed between morphs. Males aggregated in high density near shore where solitary females were rare. Equilibrium frequencies of these and other colour morphs should reflect the relative ease with which receivers detect and recognize them in the context where they are encountered.

Polar Red‐Emitting Rhodamine Dyes with Reactive Groups: Synthesis, Photophysical Properties, and Two‐Color STED Nanoscopy Applications

The synthesis, reactivity, and photophysical properties of new rhodamines with intense red fluorescence, two polar residues (hydroxyls, primary phosphates, or sulfonic acid groups), and improved hydrolytic stability of the amino-reactive sites (NHS esters or mixed N-succinimidyl carbonates) are reported. All fluorophores contain an N-alkyl-1,2-dihydro-2,2,4-trimethylquinoline fragment, and most of them bear a fully substituted tetrafluoro phenyl ring with a secondary carboxamide group. The absorption and emission maxima in water are in the range of 635-639 and 655-659 nm, respectively. A vastly simplified approach to red-emitting rhodamines with two phosphate groups that are compatible with diverse functional linkers was developed. As an example, a phosphorylated dye with an azide residue was prepared and was used in a click reaction with a strained alkyne bearing an N-hydroxysuccinimid (NHS) ester group. This method bypasses the undesired activation of phosphate groups, and gives an amphiphilic amino-reactive dye, the solubility and distribution of which between aqueous and organic phases can be controlled by varying the pH. The presence of two hydroxyl groups and a phenyl ring with two carboxyl residues in the dyes with another substitution pattern is sufficient for providing the hydrophilic properties. Selective formation of a mono-N-hydroxysuccinimidyl ester from 5-carboxy isomer of this rhodamine is reported. The fluorescence quantum yields varied from 58 to 92% for free fluorophores, and amounted to 18-64% for antibody conjugates in aqueous buffers. The brightness and photostability of these fluorophores facilitated two-color stimulated emission depletion (STED) fluorescence nanoscopy of biological samples with high contrast and minimal background. Selecting a pair of fluorophores with absorption/emission bands at 579/609 and 635/655 nm enabled two-color channels with low cross-talk and negligible background at approximately 40 nm resolution.

Effects of early visual experience on the background preference in juvenile cuttlefish Sepia pharaonis

Although cuttlefish are capable of showing diverse camouflage body patterns against a variety of background substrates, whether they show background preference when given a choice of substrates is not well known. In this study, we characterized the background choice of post-embryonic cuttlefish (Sepia pharaonis) and examined the effects of rearing visual environments on their background preferences. Different rearing backgrounds (enriched, uniformly grey and checkerboard) were used to raise cuttlefish from eggs or hatchlings, and four sets of two-background-choice experiments (differences in contrast, shape, size and side) were conducted at day 1 and weeks 4, 8 and 12 post-hatch. Cuttlefish reared in the enriched environment preferred high-contrast backgrounds at all post-embryonic stages. In comparison, those reared in the impoverished environments (uniformly grey and checkerboard) had either reversed or delayed high-contrast background preference. In addition, cuttlefish raised on the uniformly grey background, exposed to a checkerboard briefly (0.5 or 3 h) at week 4 and tested at week 8 showed increased high-contrast background preference. Interestingly, cuttlefish in the enriched group preferred an object size similar to their body size at day 1 and week 4, but changed this preference to smaller objects at week 12. These results suggest that high-contrast backgrounds may be more adaptive for juvenile cuttlefish, and visually enriched environments are important for the development of these background preference behaviours.

Reducing the effects of metal artefact using high keV monoenergetic reconstruction of dual energy CT (DECT) in hip replacements

The aim of this study was to determine whether high keV monoenergetic reconstruction of dual energy computed tomography (DECT) could be used to overcome the effects of beam hardening artefact that arise from preferential deflection of low energy photons. Two phantoms were used: a Charnley total hip replacement set in gelatine and a Catphan 500. DECT datasets were acquired at 100, 200 and 400 mA (Siemens Definition Flash, 100 and 140 kVp) and reconstructed using a standard combined algorithm (1:1) and then as monoenergetic reconstructions at 10 keV intervals from 40 to 190 keV. Semi-automated segmentation with threshold inpainting was used to obtain the attenuation values and standard deviation (SD) of the streak artefact. High contrast line pair resolution and background noise were assessed using the Catphan 500. Streak artefact is progressively reduced with increasing keV monoenergetic reconstructions. Reconstruction of a 400 mA acquisition at 150 keV results in reduction in the volume of streak artefact from 65 cm(3) to 17 cm(3) (74 %). There was a decrease in the contrast to noise ratio (CNR) at higher tube voltages, with the peak CNR seen at 70-80 keV. High contrast spatial resolution was maintained at high keV values. Monoenergetic reconstruction of dual energy CT at increasing theoretical kilovoltages reduces the streak artefact produced by beam hardening from orthopaedic prostheses, accompanied by a modest increase in heterogeneity of background image attenuation, and decrease in contrast to noise ratio, but no deterioration in high contrast line pair resolution.

Increased Surround Modulation of Perceived Contrast in the Elderly

The appearance of a stimulus depends on its background, with high-contrast backgrounds resulting in lower perceived contrast. Increased perceptual surround suppression effects have been reported in the elderly. Our experiments tested whether enhanced surround suppression in the elderly arises because of age-dependent differences in brightness induction mechanisms that are sensitive to phase information at the border of the central stimulus. Fifteen younger (18 to 33 years) and 18 older (61 to 84 years) adults participated. Using a method of constant stimuli, perceived contrast was measured for a sine wave grating with and without an annular surround. Annuli were either in-phase with the central grating (suppresses the perceived central contrast) or out-of-phase (typically enhances perceived central contrast). The experiment was repeated using stimuli where the contrast was reduced for younger observers to approximately match the effective contrast available to older adults. With the surround present, the older group matched the contrast of the central target to an average lower contrast than younger adults [F(1,31) = 17.4, p < 0.001]. The magnitude of contrast suppression differences between older and younger observers was invariant of annulus grating phase [F(1,31) = 0.036, p = 0.85] and was of similar magnitude when the stimuli were approximately matched between groups for differences in contrast detection [F(1,31) = 0.06, p = 0.81]. Normal ageing increases perceived contrast surround suppression, irrespective of information at the stimulus border between center and surround. Conditions that result in perceived contrast enhancement on average in younger adults result in contrast suppression in the elderly. Our findings suggest that age-related differences are likely in the appearance of objects in natural environments where background contrast varies.

DNA methylation profiling in nanochannels.

We report the profiling of the 5-methyl cytosine distribution within single genomic-sized DNA molecules at a gene-relevant resolution. This method linearizes and stretches DNA molecules by confinement to channels with a dimension of about 250×200 nm(2). The methylation state is detected using fluorescently labeled methyl-CpG binding domain proteins (MBD), with high signal contrast and low background. DNA barcodes consisting of methylated and non-methylated segments are generated, with both short and long concatemers demonstrating spatially resolved MBD binding. The resolution of the technique is better than 10 kbp, and single-molecule read-lengths exceeding 140 kbp have been achieved.

Noninvasive imaging of tumor integrin expression using 18F-labeled RGD dimer peptide with PEG4 linkers

Various radiolabeled Arg-Gly-Asp (RGD) peptides have been previously investigated for tumor integrin alpha(v)beta(3) imaging. To further develop RGD radiotracers with enhanced tumor-targeting efficacy and improved in vivo pharmacokinetics, we designed a new RGD homodimeric peptide with two PEG(4) spacers (PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) between the two monomeric RGD motifs and one PEG(4) linker on the glutamate alpha-amino group ((18)F-labeled PEG(4)-E[PEG(4)-c(RGDfK)](2), P-PRGD2), as a promising agent for noninvasive imaging of integrin expression in mouse models. P-PRGD2 was labeled with (18)F via 4-nitrophenyl 2-(18)F-fluoropropionate ((18)F-FP) prosthetic group. In vitro and in vivo characteristics of the new dimeric RGD peptide tracer (18)F-FP-P-PRGD2 were investigated and compared with those of (18)F-FP-P-RGD2 ((18)F-labeled RGD dimer without two PEG(4) spacers between the two RGD motifs). The ability of (18)F-FP-P-PRGD2 to image tumor vascular integrin expression was evaluated in a 4T1 murine breast tumor model. With the insertion of two PEG(4) spacers between the two RGD motifs, (18)F-FP-P-PRGD2 showed enhanced integrin alpha(v)beta(3)-binding affinity, increased tumor uptake and tumor-to-nontumor background ratios compared with (18)F-FP-P-RGD2 in U87MG tumors. MicroPET imaging with (18)F-FP-P-PRGD2 revealed high tumor contrast and low background in tumor-bearing nude mice. Biodistribution studies confirmed the in vivo integrin alpha(v)beta(3)-binding specificity of (18)F-FP-P-RGD2. (18)F-FP-P-PRGD2 can specifically image integrin alpha(v)beta(3) on the activated endothelial cells of tumor neovasculature. (18)F-FP-P-PRGD2 can provide important information on integrin expression on the tumor vasculature. The high integrin binding affinity and specificity, excellent pharmacokinetic properties and metabolic stability make the new RGD dimeric tracer (18)F-FP-P-PRGD2 a promising agent for PET imaging of tumor angiogenesis and for monitoring the efficacy of antiangiogenic treatment.

Use of Visual Search in the Assessment of Pattern-Related Visual Stress (PRVS) and Its Alleviation by Colored Filters

Visual search measures have been used to evaluate the effects of pattern-related visual stress (PRVS), and its alleviation by colored filters, but tasks and results have varied between studies. Performance on a high-difficulty search task was measured in individuals having low- and high-PRVS susceptibility. Two PRVS groups (low and high) were formed on the basis of participants' responses to a visual symptoms questionnaire and perceptions of a high-contrast grating pattern. Each participant searched for multiple instances of a single-digit number (target) within an array of similar numbers (distractors). Performance was measured by response time and error count. A three-factor, mixed-factorial ANOVA design was used to investigate the effects of PRVS group, a high-contrast background PATTERN, an overlay of an individually-selected COLOR. Individuals classified with high visual stress were found to experience significantly greater improvement in reading performance (F((1,26)) = 24.579, P < 0.001) and reduction in the number of errors (F((1,26)) = 9.502, P = 0.005) when performing the Wilkins Rate of Reading Test with a colored overlay than those with low visual stress. Error count was significantly higher in the high-PRVS group, when subjects were performing a visual search task, in the absence of either PATTERN or COLOR, but response time was not significantly different. Neither response time nor error count was significantly affected by background PATTERN and/or colored overlay. Results of this and previous studies confirm that visual search measures may be helpful in the assessment of PRVS, but several important methodological issues may limit their application in this context.