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In contrast to the conventional view that analysts forecast optimistically, we provide evidence of the Negativity Bias. Analysts show negative forecast bias associated with their relative local inc...

In line with the theory of event coding, many studies on tool use show that perceived visual and haptic information interacts with action execution. In two experiments, we investigated the temporal persistence of after-effects within an event file, and after-effects in temporally overlapping event files with the n-1 replication task. Each trial consisted of two phases: In phase 1, participants moved a cursor with a pen on a covered tablet while a gain varied the relation between hand and cursor amplitude (Experiment 1). In phase 2, participants replicated the hand amplitude of phase 1 of the previous trial without visual feedback. Any systematic over- and undershoot would be indicative for after-effects. When the cursor amplitude varied and the hand amplitude remained constant, we did not find any after-effects but adjustment of the internal model. For varying hand amplitudes, after-effects appeared in terms of a contrast and assimilation effect between temporally overlapping event files and within an event file, respectively. In Experiment 2, we confirmed that the observed pattern of over- and undershoots fully reflect assimilation/contrast due to perception-action interaction. The findings extend the current view on the temporal stability of short-term binding in sensorimotor transformation tasks: In the n-1 replication task, after-effects appeared only in trials with varying hand amplitudes. We replicated the contrast effect and assimilation effect, and the assimilation effect persisted for up to approximately 20 s.

ObjectiveTo correlate peripheral enhancement on contrast-enhanced computed tomography (CE-CT) of post-chemotherapy colorectal liver metastases (CRLM) patients with the pathological findings.MethodsForty-four patients with CRLM who underwent hepatic resection after preoperative chemotherapy between 2008 and 2013 were included. Two radiologists blinded to the histopathology findings performed a consensus categorization of the marginal contrast effects of CRLM on CE-CT as follows: Group 1, smooth margin without enhancement; Group 2, smooth margin with an enhanced rim; and Group 3, fuzzy margin with/without an enhanced rim. The Kruskal-Wallis test was used to compare the imaging findings with the histological findings.ResultsThe percentage of infarct-like necrosis was significantly higher in CRLM with smooth margins than in those with fuzzy margins (pConclusionsOur findings suggest that the type of necrosis is related to the nature of the margins, and the presence of residual cells are related to peripheral enhancement.Advances in knowledgeIn CRLM, following chemotherapy, the presence of residual cells and dangerous haloes is related to the contrast effect of the tumor margins, suggesting that tumor angiogenesis affects the contrast effect.

Existing colour appearance models could barely predict simultaneous colour contrast effect and our previous studies were intended to focus on hue and lightness contrast. Thus, there is a lack of study on the chroma contrast effect. The overall goal is to develop a comprehensive colour contrast model to consider all the target/background colour combinations. In this study, a psychophysical experiment was carried out to investigate the simultaneous contrast effect on chroma using Albers’ pattern via colour matching method on a self-luminous display. Five coloured targets were studied. A total of 49 test/background combinations were presented, 1,078 matches were accumulated. The results clearly showed that the chroma of a target considered moved toward the opposite direction of the surrounding colours, which indicated the chroma contrast effect should be integrated into the colour appearance model. A chroma contrast function based on CAM16 colour appearance model was derived based on the data with high accuracy.

Although a wealth of studies have evidenced successive negative contrast effects in instrumental or operant procedures, relatively few studies have determined if and how a sudden downshift in reward quality alters foraging behaviour. In light of research by ecologists and psychologists in the area of risk-sensitive foraging, this area would serve as an adequate framework to examine the effects of a sudden downshift in reward quality on foraging behaviour. Therefore, the purpose of the current experiment was to explore if and how a sudden downshift in reward quality altered risk-sensitive foraging in rats. Subjects chose between a variable and fixed option that returned the same mean amount of sugar pellets, but one group of subjects (i.e., contrast group) were downshifted from 100% to 20% sugar pellets, whereas an unshifted control group received 20% sugar pellets throughout the study. Consistent with past risk-sensitive foraging research where reward quality was manipulated, subjects in the contrast group displayed significantly more risk-prone choices when reward quality was decreased from 100% to 20% sugar. However, the change in choice was inconsistent with contrast effects observed in prior contrast experiments. In addition to choice behaviour, other behavioural measures (e.g., rejected food, latency to choice) were significantly different between the unshifted control and contrast group and across conditions in the contrast group (e.g., latency to choice and rejected food significantly increased when reward quality changed from 100% to 20% sugar). These findings revealed a contrast effect and were similar to past contrast studies where reward quality was downshifted. Thus, when foragers experience a sudden downshift in reward quality, they may display significant behavioural changes and, in turn, display a bias for patches that yield a greater reward quality despite potentially lower payoffs. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

We report on the construction of a system for managing prior information and injection condition used for contrast enhance CT examination using radiology information system (RIS). Contrast dose administration system using the RIS was possible to retrospectively investigate optimal injection conditions from the database. As the prior information, we designed the patient's profile information of the hospital information system (HIS) to reflect the patient's height, weight, and kidney function (eGFR, Cre), which is necessary information for contrast enhance CT examination, in the RIS. By adding E-Box (DICOM Gateway) to the injector, it became possible to reflect the amount of contrast agent used in patients and injection conditions at contrast enhance CT examination. The contrast agent use information is transmitted to RIS by using modality performed procedure step (MPPS). Database of injection condition at contrast enhance CT examination using the RIS, to determine the optimal injection conditions retrospectively. By utilizing the massive amount of clinical information stored in the RIS, the amount of contrast agent and injection condition at contrast enhance CT examination could be optimized. Reproducibility of the contrast effect can be secured. In the CE, evidence system linked with RIS, when considering the reproducibility at follow-up observation and comparative diagnosis in clinical practice, the contrast effect could be made constant. Contrast dose administration system using the RIS was useful.

People demonstrate shallower delay discounting when they have recently made decisions about smaller amounts of money than when they have recently made decisions about larger amounts of money. That is, recent reward amounts produce a contrast effect on delay discounting. We tested whether a similar contrast effect occurs for delays. We recruited two groups of participants via Mechanical Turk. The shorter-delay group made choices about delays ranging from one day to one month, and the longer-delay group made choices about delays ranging from 14 months to 30 years. Both groups then made choices about the same, intermediate delays (one week to 21 months); the longer delay group showed significantly shallower delay discounting, indicating a contrast effect. This suggests that delay discounting is affected not just by absolute delay length, but by the relative delay length.

The basic principles and diagnostic methods of magnetic resonance imaging (MRI) for beginning surgeons are described in this review. MRI is an important technique that is essential for diagnoses in the maxillofacial area. It is a scanning method that obtains tomographic images of the human body using a magnetic field. In contrast to computed tomography, it does not utilize X-rays and, therefore, represents a noninvasive test that lacks radiation exposure. It is particularly effective for soft-tissue diagnoses. MRI involves imaging protons in vivo. Protons emit a signal when a radio frequency pulse is applied in a magnetic field; the MRI device then forms an image from these signals. The basic images produced are T1- and T2-weighted images; comparison of these images is the first step of MRI-based diagnosis. Short-T1 inversion recovery images, which eliminate the signal from fat, are also useful for diagnosis. Gadolinium is used as a contrast agent for MRI. Taking sequential images at fixed intervals while injecting the contrast agent and then graphing the contrast effect along the time axis produces a time–signal intensity curve, which is useful for identifying features such as malignant neoplasms based on the graph pattern.

BACKGROUND Test bolus tracking (TBT) method has been used in coronary CT examination, because it is possible to examine the optimum contrast timing. However, the scan timing highly depends on an operators' recognition of peak in test bolus, thus there is a possibility of variation in contrast effect. PURPOSE The aim of this study is to improve the variation of contrast effect among the operators. METHODS The training for the operators was conducted to acknowledge them the optimal trigger points. The mean CT value and standard deviation of the ascending aorta were calculated to compare before and after the training. RESULTS The mean CT value of the ascending aorta after the training was 485.02±73.06 HU, compared to 462.53±78.26 HU before the training. Standard deviation was significantly lower than before the training. CONCLUSION The variation of contrast effect between the operators has been reduced by the training, and reproducibility of the examination has been improved.

Incentive contrast effects include changes in behavioral responses after a reward upshift (positive contrast) or downshift (negative contrast). Proposed influences on these behavioral changes are emotional state reactions after experiencing or anticipating a change in reward outcome. Rat ultrasonic vocalizations have been shown to be indicators of emotional state during behavior and anticipatory periods. The objective of the present study was to monitor rodent ultrasounds during incentive contrast using a classical runway procedure called instrumental successive negative contrast. The procedure is one that has been used often to examine incentive relativity because of its reliability in measuring negative contrast effects. Rats were trained to run in the alleyway to receive a high (12 pellets) or low magnitude (1 pellet) outcome. The high magnitude was then shifted to the low and running speeds in the alleyway for the reward and USV emission were compared. Replicating previous work, a negative contrast effect was observed with postshift running speeds significantly slower in the shifted group compared to the unshifted group. USVs did not follow the same pattern with an apparent lack of significant differences between the groups following the reward downshift. We also tested another group of animals using a visual predictive cue in the same runway test. When visual cues predicted high or low magnitude outcome, no incentive contrast was found for the running speeds following an outcome downshift, but a weak contrast effect was observed for the USV emission. These results demonstrate a separation between USVs and behavioral indicators of incentive contrast suggesting that concomitant shifts in negative affect may not be necessary for anticipatory relative reward processes.

Microbubble-based contrast agents are commonly used in ultrasound imaging to help differentiate the blood pool from the endocardial wall. It is essential to use an agent which produces high image intensity relative to the surrounding tissue, commonly referred to contrast effect. When exposed to ultrasound waves, microbubbles produce an intense backscatter signal in addition to the contrast produced by the fluctuating size of the microbubbles. However, over time, the microbubble concentration depletes, leading to reduced visual enhancement. The retention time associated with contrast effect varies according to the frequency and power level of the ultrasound wave, as well as the contrast agent used. The primary objective of this study was to investigate and identify the most appropriate image acquisition parameters that render optimal contrast effect for two intravenous contrast agents, Optison™ and Definity™. Several controlled in vitro experiments were conducted using an experimental apparatus that featured a perfused tissue-emulating phantom. A continuous flow of contrast agent was imaged using ultrasound at different frequencies and power levels, while a pulse wave Doppler device was used to monitor the concentration of the contrast agent solution. The contrast effect was determined based on the image intensity inside the flow pipe mimicking the blood-pool relative to the intensity of the surrounding phantom material mimicking cardiac tissue. To identify the combination of parameters that yielded optimal visualization for each contrast agent tested, the contrast effect was assessed at different microbubble concentrations and different ultrasound imaging frequencies and transmission power levels.

Introduction: Contrast-enhanced ultrasound (CEUS) using new contrast agents which offer a stable contrast effect in vivo is a noninvasive modality to detect vulnerability of carotid plaque, ulceration and neovascularization. A recent study showed the superiority for the detection of small ulcers using CEUS to color-Doppler ultrasound (CDUS), which used computed tomographic angiography (CTA) as the reference technique. Hypothesis: We assumed CEUS enables us to detect disruption of carotid plaques that could not be detected by CDUS and CTA. We aimed to investigate the diagnostic accuracy for detecting the disruption of the carotid plaques comparing with histopathological findings. Methods: From July 2010 to July 2015, we enrolled 68 internal carotid stenosis (ICS) patients undergoing carotid endarterectomy (CEA) and preoperatively examined CEUS using Perflubutane (Sonazoid), CDUS and CTA. We compared the findings of the plaque disruptions detected by these three modalities with the histopathological findings of ulceration and present/recent plaque rupture. Results: Of 68 subjects (age 72±6.6years old, 66 men), 44 (64%) had symptomatic ICS. Pathologically, ulceration and present/recent plaque rupture were found in 58 cases (85.3%). The diagnostic accuracy for detecting the disruption of carotid plaque by CEUS was significantly superior to other modalities (Table 1). CEUS could find disrupted carotid plaque more accurately than CTA. Conclusions: The assessment of the disruption of the plaques using CEUS was well correlated with pathological findings of plaque rupture, which may help us to evaluate the plaque vulnerability in vivo real time.

We compared the contrast effect of high and medium iodine-concentration contrast materials for preoperative CT eva- luation of breast cancer patients. Female breast cancer patients who underwent enhanced CT of the chest and upper abdomen before surgery were analyzed retrospectively. High (370 mg I/mL, 100 mL) or medium (300 mg I/mL, 125 mL) concentrations of contrast material were injected for 60 sec, followed by saline flush, and postcontrast CT images were obtained 90 sec after contrast injection. CT values were assessed for the breast tumor, normal breast parenchyma, liver, aorta, and muscle. For the high and medium concentration agents, 45 and 49 patients were analyzed, respectively. No significant differences between the two contrast agents were found in terms of CT values of the breast tumor, normal breast parenchyma, liver, aorta, or muscle. The tumor-background differences in CT values did not differ significantly between the two agents. A comparable contrast effect was indicated in single-phase CT of breast cancer patients between high and medium iodine-concentration contrast material when the total iodine dose and injection duration were identical.

The goal of the current project was to further develop a measure of gain control--the Contrast-Contrast Effect (CCE)--for use in clinical studies of schizophrenia. The CCE is based on an illusion in which presenting a medium contrast patch surrounded by a high-contrast patch induces individuals to perceive that center patch as having lower contrast than when the patch is presented in isolation. Thus, in the CCE, impaired gain control should lead to more accurate perceptions of the center patch. We tested 132 individuals with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, schizophrenia or schizoaffective disorder and 130 demographically similar healthy controls. The results indicated that the CCE effect can be obtained with standard equipment, simplified scoring, and a short interstimulus interval (100 ms), revealing a robust suppression of perceived contrast of the center patch when surrounded by a high-contrast annulus. Furthermore, we found a significant reduction in the effect of the high-contrast surround among individuals with schizophrenia, though the effect size was smaller than original reported by Dakin. However, when we eliminated subjects who performed poorly on "catch" trials that controlled for off-task performance, the reduced surround effect among patients was no longer significant in the main analyses. Importantly, this suggests that at least part of the reduced surround effect (if not all) in schizophrenia could be attributable to impaired attentional mechanisms that contribute to off-task performance. Additional analyses suggested that the length of the task could be shortened without losing power to detect surround effects in healthy individuals.

Gadolinium is the central metal that is used as magnetic resonance imaging (MRI) contrast media. Because the metal has toxicity on its own, it causes fibrosis or sclerosis of skin or internal organs, which may lead to disability in joint movement, or even death in the worst case. In the current study, the T 1 contrast media, Dotarem, was diluted to various molarities to measure the signal intensity of T 1-weighted images as a function of the molarity. The molarity that showed the maximum measurement value of the signal intensity was examined to determine the proper amount of contrast media injected for the MRI scan. The change in the intensity of the signal from the tumor tissue was determined based on the passage of time after injection. The distribution of the maximum signal intensities depending on the time to repeat showed that the signal distribution had >95% of the maximum values when the dilution concentration was in the range of 0.00095–0.00135 mmol/ml. Thus, it is most desirable when 0.084 mmol/kg (patient weight) of contrast media is injected. In experiments involving tumors 0.084, 0.1, and 0.15 mmol/kg were injected to measure the average signal intensity for each molarity. Compared to the signal intensity at a molarity of 0.084 mmol/kg, the three patient’s signal intensities were measured to increase by 6.2, 7.6, and 5.7% at a molarity of 0.1 mmol/kg, and by 21.4, 18.8, and 17.7% at a molarity of 0.15 mmol/kg. However, according to the correlation between the contract media injection amount and the signal intensity increase, the contrast effect was not improved much despite the increase in the injection amount by 19.04 and 78.5%. This study revealed that the optimal level of contrast media of 0.084 mmol/kg body weight should be administered by considering the body weight of patients and the effects of media to reduce side effects of a high dose of contrast media and to prevent environmental pollution.

Negative anticipatory contrast (NAC) corresponds to the suppression in consumption of a first rewarding substance (e.g., saccharin 0.15%) when it is followed daily by a second preferred substance (e.g., sucrose 32%). The NAC has been interpreted as resulting from anticipation of the impending preferred reward and its comparison with the currently available first reward [Flaherty, C.F., Rowan, G.A., 1985. Anticipatory contrast: within-subjects analysis. Anim. Learn. Behav. 13, 2–5]. In this context, one should expect that devaluation of the preferred substance after the establishment of the NAC would either reduce or abolish the contrast effect. However, contrary to this prediction, the results of the present study show that the NAC is insensitive to devaluation of the second, preferred, substance. This allows one to question that interpretation. The results reported in this study support the view that the NAC effect is controlled by memory of the relative value of the first solution, which is updated daily by means of both a gustatory and/or post-ingestive comparison of the first and second solutions, and memory of past pairings.

It is known that our senses are influenced by contrast effects and aftereffects. For haptic perception, the curvature aftereffect has been studied in depth but little is known about curvature contrast. In this study we let observers explore two shapes simultaneously. The shape felt by the index finger could either be flat or convexly curved. The curvature at the thumb was varied to quantify the curvature of a subjectively flat shape. We found that when the index finger was presented with a convex shape, a flat shape at the thumb was also perceived to be convex. The effect is rather strong, on average 20% of the contrasting curvature. The contrast effect was present for both raised line stimuli and solid shapes. Movement measurements revealed that the curvature of the path taken by the metacarpus (part of the hand that connects the fingers) was approximately the average of the path curvatures taken by the thumb and index finger. A failure to correct for the movement of the hand could explain the contrast effect.

The purpose of this study is to test the performance of multispin nitroxyl contrast agents in improving the sensitivity of MR detection for nitroxyl contrast agents. The relation between T 1 relaxivity and the number of paramagnetic centers in a molecule was investigated. Compound 1 is a single molecule of methoxycarbonyl-PROXYL (MC-PROXYL). Two and three MC-PROXYL molecules were chemically coupled to obtain Compounds 2 and 3, which have two and three nitroxyl spins in the molecule, respectively. A good linear relation, the slope of which increased depending on the number of nitroxyl spins in the molecule, was obtained between T 1 -weighted (fast low-angle shot) MR image contrast enhancement at 7 T and the concentration of nitroxyl contrast agents. T 1 -weighted MR image contrast enhancement and T 1 relaxivity levels of nitroxyl contrast agents were increased depending on the number of nitroxyl spins in the molecule. Multicoupling nitroxyl molecules can enhance the T 1 -weighted contrast effect while maintaining the quantitative behavior of the molecule for up to three spins.

The contrast effects of three different contrast media preparations (iohexol 180 mgI/ml, iohexol 240 mgI/ml and iotrolan 240 mgI/ml) in conventional and CT myelography were compared. Three beagle dogs were used and the study employed a cross-over method (total of 9) for each contrast media. The result of CT myelography showed that the contrast effect of iohexol (180 mgI/ml), which had low viscosity, was highest in cranial sites, and the contrast effect of high-viscosity iotrolan (240 mgI/ml) was highest in caudal sites 5 min after injection of the contrast media preparations. This shows that the diffusion of contrast media preparations in the subarachnoid space is influenced by viscosity. The results of conventional myelography also showed that the diffusion of contrast media preparations is influenced by viscosity. Therefore, it is important to identify the location of spinal lesions in veterinary practice, and low viscosity contrast medium preparation with wide spread contrast effects is considered suitable for myelography.

The study of contrast investigates how rewards influence behaviour when animals are exposed to two or more levels of rewards compared to when they experience only a single level. The appearance of an exaggerated response to a shift in reward is referred to as a contrast effect and is an empirically well-established phenomenon. Although contrast effects could be important in foraging behaviour, no direct experimental tests of contrast effects in foraging by mammalian herbivores exist. During foraging, mammalian herbivores can encounter a range of plants that vary in the amount of nutrients and toxins. They may thus compare food items by taste, which in turn can give rise to contrast effects. In feeding experiments with fallow deer, Dama dama, we investigated the presence of simultaneous negative contrast. We found that the deer consumed less from a bowl of pellets containing 1% tannin when they shifted to it from a bowl with pellets containing only 0.25% tannin than when they shifted from another bowl with pellets containing 1% tannin. We estimated a fourfold difference between treatments in test food consumption at the highest levels of preloading, but none at the lowest levels. We found no support for successive negative contrast in experiments where the deer approached food in a runway, comparing a current reward with the memory of a previous reward. We suggest that simultaneous negative contrast can influence foraging decisions in mammalian herbivores.

When behavior suggests that the value of a reinforcer depends inversely on the value of the events that precede or follow it, the behavior has been described as a contrast effect. Three major forms of contrast have been studied: incentive contrast, in which a downward (or upward) shift in the magnitude of reinforcement produces a relatively stronger downward (or upward) shift in the vigor of a response; anticipatory contrast, in which a forthcoming improvement in reinforcement results in a relative reduction in consummatory response; and behavioral contrast, in which a decrease in the probability of reinforcement in one component of a multiple schedule results in an increase in responding in an unchanged component of the schedule. Here we discuss a possible fourth kind of contrast that we call within-trial contrast because within a discrete trial, the relative value of an event has an inverse effect on the relative value of the reinforcer that follows. We show that greater effort, longer delay to reinforcement, or the absence of food all result in an increase in the preference for positive discriminative stimuli that follow (relative to less effort, shorter delay, or the presence of food). We further distinguish this within-trial contrast effect from the effects of delay reduction. A general model of this form of contrast is proposed in which the value of a primary or conditioned reinforcer depends on the change in value from the value of the event that precedes it.

A modified CIECAM02 colour appearance model, named CIECAM02-m2, is proposed to enable CIECAM02 to predict the simultaneous contrast effect. The structure of the CIECAM02-m2 is a development from CIECAM02, and contains two different procedures for modifying the reference white; one is for lightness and the other is for hue. The model was tested using a data set accumulated in this study and the LUTCHI data. The CV values for three colour attributes between predictions and experimental data were used to evaluate the accuracy of the model. The low CV values obtained show the performance of the CIECAM02-m2 model to predict the simultaneous contrast effect satisfactorily. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 121 – 129, 2007

We investigated the characteristics and utility of gadobenate dimeglumine (Gd-BOPTA) for MRI of the mouse liver. Mice were imaged under isoflurane anesthesia using a T1-weighted, three-dimensional fast low-angle shot (3D FLASH) sequence before and after intravenous or subcutaneous injection of Gd-BOPTA, and the time course of the contrast effect was examined. The appropriate dose for subcutaneous injection was determined visually, and the inter- and intra-observer reproducibilities in liver volumetry were evaluated with and without contrast injection. When mice were imaged sequentially before and after Gd-BOPTA injection and isoflurane anesthesia was maintained throughout the experiment, a long-lasting contrast effect was noted in the liver. Subcutaneous injection caused delayed, but favorable, enhancement. Washout from the liver was definitely accelerated in conscious mice in comparison with anesthetized mice. Visual evaluation indicated that a dose of 0.1 mmol/kg was appropriate for clear delineation of the entire liver margin, and the application of Gd-BOPTA significantly improved the inter- and intra-observer reproducibilities of liver volumetry. In conclusion, the intravenous or subcutaneous injection of Gd-BOPTA has a favorable contrast effect for the mouse liver, resulting in clear visualization of the liver border and improved reproducibility of liver volumetry. The possible influence of anesthesia on the pharmacokinetics of a contrast agent should be considered in determining the optimal scan timing. Copyright © 2007 John Wiley & Sons, Ltd.

Targeted nanobubbles have been reported to improve the contrast effect of ultrasound imaging due to the enhanced permeation and retention effects at tumor vascular leaks. In this work, the contrast enhancement abilities and the tumor targeting potential of a self-made VEGFR2-targeted nanobubble ultrasound contrast agent was evaluated in - vitro and in-vivo . Size distribution and zeta potential were assessed. Then the contrast-enhanced ultrasound imaging of the VEGFR2 targeted nanobubbles were evaluated with a custom-made experimental apparatus and in normal Wistar rats. Finally, the in-vivo tumor-targeting ability was evaluated on nude mice with subcutaneous tumor. The results showed that the target nanobubbles had uniform distribution with the average diameter of 208.1 nm, polydispersity index (PDI) of 0.411, and zeta potential of -13.21 mV. Significant contrast enhancement was observed in both in-vitro and in-vivo ultrasound imaging, demonstrating that the self-made target nanobubbles can enhance the contrast effect of ultrasound imaging efficiently. Targeted tumor imaging showed less promising result, due to the fact that the targeted nanobubbles arriving and permeating through tumor vessels were not many enough to produce significant enhancement. Future work will focus on exploring new imaging algorithm which is sensitive to targeted nanobubbles, so as to correctly detect the contrast agent, particularly at a low bubble concentration.

In fluoroscopic contrast study for interventional procedure, liquid contrast agent may be diluted in body fluid, losing its contrast effect. We developed a novel contrast agent of “foam state” to maintain contrast effect for enough time and performed a comparative study of physical properties and its usefulness in experimental intervention in animal model. The mean size of microbubble of foam contrast was13.8±3.6 µm. The viscosity was201.0±0.624 cP (centipoise) and the specific gravity was 0.616. The foam decayed slowly and it had 97.5 minutes of half-life. In terms of the sustainability in a slow flow environment, foam contrast washed out much more slowly than a conventional contrast. In experimental colonic stent placement, foam contrast revealed significantly better results than conventional contrast in procedure time, total amount of contrast usage, and the number of injections (p<0.05). Our foam contrast has high viscosity and low specific gravity and maintains foam state for a sufficient time. Foam contrast with these properties was useful in experimental intervention in animal model. We anticipate that foam contrast may be applied to various kinds of interventional procedures.

The quality of magnetic resonance cholangiopancreatography (MRCP) images is frequently degraded by high signal from the gastrointestinal tract. The aim of this study is to evaluate pineapple juice (PJ) as an oral negative contrast agent in MRCP. Preliminary in vitro evaluation demonstrated that PJ shortened T(2) relaxation time and hence decreased T(2) signal intensity on a standard MRCP sequence to a similar degree to a commercially available negative contrast agent (ferumoxsil). Electrothermal atomic absorption spectrometry assay demonstrated a high manganese concentration in PJ of 2.76 mg dl(-1), which is likely to be responsible for its T(2) imaging properties. MRCP was subsequently performed in 10 healthy volunteers, before and at 15 min and 30 min following ingestion of 400 ml of PJ. Images were assessed blindly by two Consultant Radiologists using a standard grading technique based on contrast effect (degree of suppression of bowel signal), and image effect (diagnostic quality). There were statistically significant improvements in contrast and image effect between pre and post PJ images. There was particularly significant improvement in visualization of the pancreatic duct, but no significant difference between 15 min and 30 min post PJ images. Visualization of the ampulla, common bile duct, common hepatic and central intrahepatic ducts were also significantly improved at 15 min following PJ. Our results demonstrate that PJ, may be used as an alternative to commercially available negative oral contrast agent in MRCP.

The aim of this animal study was to evaluate the feasibility of contrast-enhanced magnetic resonance (MR) angiography with two hepatobiliary contrast agents, Gd-DTPA-DeA and Gd-EOB-DTPA. Coronal images of the rat abdomen were acquired using a three-dimensional spoiled gradient recalled sequence before and after the administration of Gd-DTPA-DeA, Gd-EOB-DTPA, or Gd-DTPA. Four sets of postcontrast images were collected every 90 s. Contrast ratios were calculated for the abdominal aorta on the source images, and the retention index was defined as the ratio of the contrast ratio on the last imaging to that on the first postcontrast imaging. Partial minimum intensity projection (MIP) images covering the abdominal aorta were generated from the first and second postcontrast imagings, and the image quality was visually evaluated. The contrast ratio on the first postcontrast imaging was the highest for Gd-DTPA-DeA, followed by Gd-EOB-DTPA and Gd-DTPA. Retention indices were higher with Gd-DTPA-DeA than with Gd-EOB-DTPA and Gd-DTPA, implying a prolonged contrast effect with Gd-DTPA-DeA. On the MIP image from the first postcontrast imaging, delineation of the abdominal aorta tended to be better with Gd-DTPA-DeA and Gd-EOB-DTPA than with Gd-DTPA, and the difference was evident at low injection doses. Image quality for the second postcontrast imaging was higher with Gd-DTPA-DeA than with the other two agents, suggesting a longer imaging window for Gd-DTPA-DeA. In conclusion, Gd-DTPA-DeA and Gd-EOB-DTPA showed stronger contrast enhancement for the rat abdominal aorta and provided MR angiograms of higher image quality when compared with Gd-DTPA at the same injection dose. These hepatobiliary agents may make it possible to perform contrast-enhanced MR angiography even at a low injection dose.

Phantom measurements and Monte Carlo calculations have been performed for the purpose of characterizing the dose perturbation caused by radiographic contrast inside the MammoSite breast brachytherapy applicator. Specifically, the dose perturbation is quantified as a heterogeneity correction factor (HCF) for various balloon radii and contrast concentration levels. The dose perturbation is larger for larger balloon radii and higher contrast concentrations. Based on a validated Monte Carlo simulation, the calculated HCF values are 0.99 for a 2 cm radius balloon and 0.98 for a 3 cm radius balloon at 6% contrast concentration levels, and 0.89 and 0.87 for 2 and 3 cm radius balloons, respectively, at 100% contrast concentrations. For a typical implanted balloon radius of 2.4 cm, the HCF values decrease from 0.99 at 6% contrast concentration to 0.90 at 100% contrast concentration. For balloons implanted in patients at our institution, the mean HCF is 0.99, corresponding to a dose reduction of approximately 1%. The contrast effect results in a systematic reduction in the delivered dose, therefore the minimal amount of radiographic contrast necessary should be used.

The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074

Observers had to find one of fifteen different meaningful white and coloured computer commands on a simulated multi-colour user interface. Average search time was recorded as a function of chromaticity, position, and length of the search commands. After eliminating the effects of display position and command length, the range of search time values was found to extend by a factor of 2 when the search objects became coloured by different types of chromaticity contrast. This implies that chromaticity contrast is an efficient tool to control the conspicuity of the display elements. It was suggested to put the coloured display items (symbols, characters, etc.) on several ‘conspicuity levels’ depending on the designer's intent of emphasis. A formula and guidelines for an algorithm have been suggested. The relationship between conspicuity and the concept of brightness was discussed.

RATIONALE AND OBJECTIVES. To evaluate the changes in the microbubble population of a currently available ultrasound contrast agent (USCA) through attenuation measurements to optimize its clinical use. MATERIALS AND METHODS. The microbubble population from a galactose-based USCA (Levovist, Schering AG, Germany) was characterized in vitro using attenuation measurements. The effect of dose (0.1, 0.5, and 1 mL), concentrations (200, 300, and 400 mg mL - 1 ) and time since reconstitution (2, 12, 22, and 32 minutes) was evaluated using two broadband pulses at different peak negative pressures (0.39 and 0.49 MPa) for a total of 72 injections. RESULTS. Two minutes after reconstitution, a linear relationship was found between attenuation measurements and the amount of USCA (slope 0.92 dB.mg.cm - 1 ml - 1 , R = 0.86). For a given dose and concentration, the microbubble stability was significantly reduced with the increase of the time since reconstitution, particularly for the lower concentrations. CONCLUSIONS. The persistence and contrast effect of Levovist can be improved by using recommended minimum time since reconstitution and maximum concentration.

Objectives. We sought to compare the visual image quality of film-based and digitized panoramic radiographs through use of a hole-containing test wedge. Study Design. An aluminum wedge containing 100 cells, of which 90 were given shallow holes, was exposed in the film-based Orthophos CD panoramic unit. Two radiographs subjectively exhibiting optimum contrast were selected. Films were digitized with a charge-coupled device flatbed scanner at 300 dpi. Films and digitized images were rated cellwise by 2 similar groups of 50 observers each with respect to spot perception. Results. The mean sensitivity was 0.26 ± 0.09 for film and 0.20 ± 0.07 for digitized images (P =.000), with a pronounced decline in the latter in regions of high background density. The average specificity was 0.93 ± 0.07 for film versus 0.92 ± 0.08 for digitized images (P = 0.213). Conclusion. Film yielded a significantly higher sensitivity, but this absolute difference was actually small compared with that of the digitized images. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:388-94)

Contrast agents based on gas-filled microspheres share the problem of time limited opacification due to low stability of microbubbles. The aim of this study was to test if gold-bound microtubules provide backscattering that allows microtubules to be potentially useful as an ultrasound (US) contrast agent. Gold colloids were immobilized on protein microtubule walls. Latex balloons were filled with gold-bound microtubules or conventional left heart contrast agent and were ultrasonographically imaged in fundamental and harmonic modes. Feasibility of anti-β-tubulin antibody conjugation to gold-bound microtubules was confirmed using immune fluorescence analysis. Gold particles were successfully bound to microtubules. Contrast intensities in latex balloons filled with gold-bound microtubules (141 ± 35) were comparable to those with Levovist™ (180 ± 35) and did not decrease significantly during continuous US imaging for 20 min (135 ± 34 vs. Levovist™ 5.0 ± 2.0). Anti-β-tubulin antibodies were successfully conjugated to gold-bound microtubules. Gold-bound microtubules provide a persistent contrast effect, suggesting their use as an ultrasonic contrast agent with the feasibility of antibody conjugation. (E-mail:helmut_kuecherer@med.uni-heidelberg.de)

We performed a prospective study to determine whether a limited biopsy approach with contrast enhanced color Doppler ultrasound targeted biopsy of the prostate would detect cancer as well as gray scale US guided systematic biopsy with a larger number of biopsy cores.We examined 230 male screening volunteers with a total prostate specific antigen of 1.25 ng./ml. or greater and free-to-total prostate specific antigen less than 18%. Two independent examiners evaluated each subject and a single investigator performed 5 or fewer contrast enhanced targeted biopsies into hypervascular regions in the peripheral zone during intravenous infusion of the US contrast agent Levovist (Schering, Berlin, Germany). Subsequently another examiner performed 10 systematic prostate biopsies. The cancer detection rates of the 2 techniques were compared.Cancer was detected in 69 of the 230 patients (30%), including 56 (24.4%) by contrast enhanced targeted biopsy and in 52 (22.6%) by systematic biopsy. Cancer was detected by targeted biopsy alone in 17 patients (7.4%) and by systematic biopsy alone in 13 (5.6%). The overall cancer detection rate by patient was not significantly different for targeted and systematic biopsy (p = 0.58). The detection rate for targeted biopsy cores (10.4% or 118 of 1,139 cores) was significantly better than for systematic biopsy cores (5.3% or 123 of 2,300 cores, p0.001). Contrast enhanced targeted biopsy in a patient with cancer was 2.6-fold more likely to detect prostate cancer than systematic US guided biopsy.Contrast enhanced color Doppler targeted biopsy detected as many cancers as systematic biopsy with fewer than half the number of biopsy cores. Although an increase in cancer detection was achieved by combining targeted and systematic techniques in this screening population, contrast enhanced targeted biopsy alone is a reasonable approach for decreasing the number of biopsy cores.

In the 50 years from 1967 (the year that, as a student, I met Edwin Carstensen) to 2017, diagnostic ultrasound has progressed from A mode to M mode to B&W static 2D to gray-scale static 2D to real-time 2D to static 3D to real-time 3D (“4D”). Along the way, other modes and features appeared including analog-to-digital, color-, power- and spectral-Doppler, coded excitation, harmonic imaging, panoramic imaging, spatial compounding, contrast agents, elastography and virtual beam forming. Contrast agents have been in wide use globally for years, although limited in the U.S. by the FDA to cardiac application until recently. Contrast agents operate on the ability of gas bubbles to strongly reflect ultrasound. In a 1968 study conducted by Professors Carstensen and Gramiak and me, it was shown that the contrast effect was due to bubbles in the radiologic contrast agent. As an electrical engineering graduate student at the time, I could not know that this was the launching of a 50-year medical academic career in so...

Magnetic resonance imaging (MRI) enables the evaluation of organ structure and function. Oxygen-enhanced MRI (O2-enhanced MRI) is a method for evaluating the pulmonary ventilation function using oxygen as a contrast agent. We created the Cine View of Relative Enhancement Ratio Map (Cine RER map) in O2-enhanced MRI to easily observe the contrast effect for clinical use. Relative enhancement ratio (RER) was determined as the pixel values of the Cine RER map. Moreover, six healthy volunteers underwent O2-enhanced MRI to determine the appropriate scale width of the Cine RER map. We calculated each RER and set 0 to 1.27 as the scale width of the Cine RER map based on the results. The Cine RER map made it possible to observe the contrast effect over time and thus is a convenient tool for evaluating the pulmonary ventilation function in O2-enhanced MRI.

To compare the contrast agent effect of a full dose and half the dose of gadobenate dimeglumine in brain tumours at 7 Tesla (7 T) MR versus 3 Tesla (3T).Ten patients with primary brain tumours or metastases were examined. Signal intensities were assessed in the lesion and normal brain. Tumour-to-brain contrast and lesion enhancement were calculated. Additionally, two independent readers subjectively graded the image quality and artefacts.The enhanced mean tumour-to-brain contrast and lesion enhancement were significantly higher at 7 T than at 3T for both half the dose (91.8 ± 45.8 vs. 43.9 ± 25.3 [p = 0.010], 128.1 ± 53.7 vs. 75.5 ± 32.4 [p = 0.004]) and the full dose (129.2 ± 50.9 vs. 66.6 ± 33.1 [p = 0.002], 165.4 ± 54.2 vs. 102.6 ± 45.4 [p = 0.004]). Differences between dosages at each field strength were also significant. Lesion enhancement was higher with half the dose at 7 T than with the full dose at 3T (p = .037), while the tumour-to-brain contrast was not significantly different. Subjectively, contrast enhancement, visibility, and lesion delineation were better at 7 T and with the full dose. All parameters were rated as good, at the least.Half the routine contrast agent dose at 7 T provided higher lesion enhancement than the full dose at 3T which indicates the possibility of dose reduction at 7 T.• The contrast effect of gadobenate dimeglumine was assessed at 7 T and 3T. • In brain tumours, contrast effect was higher at 7 T than at 3T. • Tumour-to-brain contrast at 7 T half dose and 3T full dose were comparable. • 7 T half dose lesion enhancement was higher than 3T full dose enhancement. • Our results indicate the possibility of contrast agent dose reduction at 7 T.

Nanoscale bubbles (nanobubbles) have been reported to improve contrast in tumor-targeted ultrasound imaging due to the enhanced permeation and retention effects at tumor vascular leaks. In this work, a self-made nanobubble ultrasound contrast agent was preliminarily characterized and evaluated in-vitro and in-vivo. Fundamental properties such as morphology appearance, size distribution, zeta potential, bubble concentration (bubble numbers per milliliter contrast agent suspension) and the stability of nanobubbles were assessed by light microscope and particle sizing analysis. Then the concentration intensity curve and time intensity curves (TICs) were acquired by ultrasound imaging experiment in-vitro. Finally, the contrast-enhanced ultrasonography was performed on rat to investigate the procedure of liver perfusion. The results showed that the nanobubbles had good shape and uniform distribution with the average diameter of 507.9 nm, polydispersity index (PDI) of 0.527, and zeta potential of -19.17 mV. Significant contrast enhancement was observed in in-vitro ultrasound imaging, demonstrating that the self-made nanobubbles can enhance the contrast effect of ultrasound imaging efficiently in-vitro. Slightly contrast enhancement was observed in in-vivo ultrasound imaging, indicating that the nanobubbles are not stable enough in-vivo. Future work will be focused on improving the ultrasonic imaging performance, stability, and antibody binding of the nanoscale ultrasound contrast agent.

We evaluated the detection of early venous filling of gliomas by 2D time resolved dynamic contrast enhanced MR digital subtraction angiography (MR-DSA) with echo-sharing technique and compared the results with those of conventional contrast digital subtraction angiography (C-DSA). C-DSA and MR-DSA examinations were performed in eight patients with malignant gliomas and compared with regard to the visualization of early filling veins; time intensity curves of arteries, early filling veins and normal veins were made, and rise time and time to peak were evaluated. MR-DSA visualized 12 out of 17 early filling veins depicted on C-DSA. The failure of five veins to be depicted may be due to the overlapping of other structures, such as other vessels and tumor stain. On time intensity curves, the mean difference in rise time was 0.9 sec between the artery and early filling vein, and the mean difference of time to peak was 1.6 sec. C-DSA has been the modality of choice in demonstrating early venous filling, a useful finding in the differential diagnosis of gliomas. However the high temporal resolution of MR-DSA with echo-sharing technique provides sufficient visualization of early venous filling of gliomas. Additional information for precise differential diagnosis may be obtained by adding MR-DSA to the imaging protocol for gliomas.

A heuristic algorithm for enhancement of fluoroscopic images of varying contrast is proposed. The new technique aims at identifying a suitable type of enhancement for different locations in an image. The estimation relies on simple preliminary classification of image parts into one of the following types: uniform, sharp (with sufficient contrast), detail-containing (structure present) and unknown (for the cases where it is difficult to make a decision). Different smoothing techniques are applied locally in the different types of image parts. For those parts that are classified as detail-containing, probable object boundaries are identified and local sharpening is carried out to increase the contrast at these places. The adopted approach attempts to improve the quality of an image by reducing available noise and simultaneously increasing the contrast at probable object boundaries without increasing the overall dynamic range. In addition, it allows noise to be cleaned, that at some locations is stronger than the fine structure at other locations, whilst preserving the details.

Echocardiographic quantification of myocardial perfusion after IV contrast is possible, based on the intensity of the received intermittent second harmonic signal. To investigate the influence of respiration on the intensity of myocardial signals, we examined nine patients with normal coronary angiograms. At baseline, end-expiratory and end-inspiratory images were obtained in broadband radiofrequency (RF) and intermittent second harmonic modes, the latter repeated during IV contrast at rest and at peak stress. In mid-septum at baseline, end-inspiratory integrated backscatter intensity was 4 dB higher (p < 0.05, both in second harmonic and fundamental domains) than end-expiratory intensity. In second harmonic imaging, contrast increased signal intensity by 4 dB (p < 0.05) in six examined segments, but the increase in the midseptal region (2 dB) was not significant. Contrast-enhanced intensity at end-inspiration was higher (3 dB, p < 0.01) than baseline intensity at end-expiration. We conclude that the increase in myocardial signal intensity during inspiration may resemble the contrast effect in intermittent second harmonic mode. The respiratory variation persists after contrast and may mask or exaggerate the effect of myocardial contrast.

A method of identifying the dose per image when quantum mottle no longer dominates the image statistics is presented as a first step towards quantitative optimization in native and subtracted digital fluorography. The method is based on measurements of threshold contrast over a range of receptor doses and the application of a simple model of the threshold contrast detection task to estimate the magnitude of system noise sources. The point at which system and quantum noise sources are equal in magnitude is proposed as the practical upper limit for dose per image. The method is applied to a typical digital fluorography system and the results are placed into the context of the range of dose per image values found from a regional survey of digital fluorography units. While there is broad agreement between the dose per image values in the survey with values predicted from the experimental method, the considerable spread in survey doses suggests there are instances where the use of a high dose per image is unjustified.

A contrast detail analysis was performed to compare perception of low-contrast details on X-ray images derived from digital storage phosphor radiography and from a flat panel detector system based on a cesium iodide/amorphous silicon matrix. The CDRAD 2.0 phantom was used to perform a comparative contrast detail analysis of a clinical storage phosphor radiography system and an indirect type digital flat panel detector unit. Images were acquired at exposure levels comparable to film speeds of 50/100/200/400 and 800. Four observers evaluated a total of 50 films with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. The overall results show that low-contrast detail perception with digital flat panel detector images is better than with state of the art storage phosphor screens. This is especially true for the low-exposure setting, where a nearly 10% higher correct observation ratio is reached. Given its high detective quantum efficiency the digital flat panel technology based on the cesium iodide scintillator/amorphous silicon matrix is best suited for detection of low-contrast detail structures, which shows its high potential for clinical imaging.

Contextual shifts were observed for sweetness of a fruit beverage and for estimated tactile roughness of sandpapers. Midrange stimuli were judged to be less intense in the context of stronger items and more intense in the context of weaker items, a contrast effect. The use of a reference standard decreased the size of the contrast shift for the labeled magnitude scale but not for magnitude estimation.

Aim: To compare technical parameters and clinically relevant aspects of on- and off-resonance MTC sequences in mid- and high-field MR systems. Material and Methods: Both on- and off-resonance techniques were combined with an FFE sequence using 0.5 and 1.5 Tesla superconducting systems. Parameters were systematically measured by scanning a cadaveric knee joint. Signal-to-noise ratios and MT ratios for fat, cartilage and reference solution (copper sulphate) were determined. Minimal TR and the energy absorption rate were also compared. Results: The MT effect at 1.5 T was more pronounced. However, using optimized parameters, clinically adequate MT contrast was achieved with both techniques and both MT units. The most important parameters for the off-resonance method are pulse angle and off-centre frequency; for the on-resonance method, pulse angle and number of composite pulse elements. Energy absorption was below 2 W/kg. Minimal TR was prolonged by up to 400 %. Conclusion: In order to produce MTC images, optimized parameters should be applied. Using optimized pulse parameters, adequate MTC imaging is achievable with mid- and high-field systems using on- and off-resonance techniques. To ensure comparability of MTC studies, the pulse parameters need to be given, and, ideally, standardized.

We aimed to evaluate whether the histopathologic variability of fibroadenomas accounts for their varied appearance in contrast enhanced power Doppler (PD). Forty patients with fibroadenomas (aged 19 to 61 years) underwent power Doppler ultrasound (US) prior to and following IV bolus injection of a microbubble contrast agent. A 3-min computer-assisted assessment of the color pixel density (CPD) was used for objective evaluation of the increase in color Doppler signals. Enhancement characteristics were correlated to histopathologic features of microvessel density and epithelial hyperplasia, patient's age, tumor size, use of exogenous hormones and menopausal status. Epithelial hyperplasia was diagnosed in 19 patients. Compared to baseline values, patients with epithelial hyperplasia showed a significant increase in mean CPD following contrast media administration (p < 0.01). There was a significant correlation to patient's age (p < 0.0001) and tumor size (p < 0.0001), but not to the use of exogenous hormones and menopausal status. Microvessel counts did not show a significant correlation to CPD at baseline (p = 0.07) or with CPD on contrast enhanced PD (p = 0.13), or with patient age (p = 0.43) or tumor size (p = 0.34). Intratumoral epithelial hyperplasia, primarily occurring in young patients, may contribute to the differential diagnostic overlap in some fibroadenomas and thus limit the ability of PD to distinguish between benign and malignant masses on the basis of enhancement characteristics.

The Object of this investigation was Image Detector Systems. The Object of this investigation was to compare different intraoral, analog and digital X-ray image detector systems with respect to the diagnostic performance and to the relation of dose and image quality. Methods: Three different intraoral film types and one digital system were compared. The same basic image quality-related technical parameters were measured, Contrast detail diagrams and images of pig teeths were captured and evaluated by visual inspection. Results: The digital system has a speed that is at twice as high as least of the most sensitive analog system. Compared to the analog system, the digital system visualizes better low contrast structures such as carious defects, but shows problems in visualisation of high dynamic ranges such as crown margins or fillings: insufficient suitable dynamic range. Larger objects such as incisors could not be imaged in one exposure due to the small area of the digital detector (24.3 × 18.2 mm). Retakes may be required due to the small dynamic range and detector area. Conclusions: The complete imaging of a tooth with crown and apical region, as required in the radiological guidlines is in doubt with digital systems having small active areas. The image quality of digital systems differs significantly from that of analog systems, nevertheless, the achievable image quality fulfills the requirements of intraoral dental radiology.

The article presents a discussion of the basic signal behavior of contrast-modified RARE(TSE,FSE…)-sequences which have been modified such that the echo train used for image encoding is preceded by a long echo interval in order to introduce the T2-contrast of conventional spin-echo sequences while maintaining the high imaging speed of TSE. Sequences aimed at breathhold abdominal imaging as well as for the detection of hemorrhages in the CNS have been implemented and optimized. The significant difference in image contrast at identical echo times compared to unmodified TSE is demonstrated for different tissues. Magn Reson Med 43:577–582, 2000. © 2000 Wiley-Liss, Inc.

It is known that light-box luminance is an important factor in the detection of objects on radiographs. Existing methods for image contrast enhancement do not consider the luminance effect so that the enhancement may be inappropriate for the processed image displayed on a video monitor. Based on the properties of human visual system (HVS), an adaptive local contrast enhancement (ALCE) method was developed to enhance the medical image displayed on the video monitor by investigating the influence on human eyes of display luminance difference between a conventional light-box and a video monitor. The HVS model indicated parts of a radiograph unclear to human eyes at a given display luminance. By calculating the contrast of the image pixel by pixel, we found the parts of an image that are needed to be amplified at low display luminance and provided these parts with adequate enhancement. The processed image displayed on a video monitor was visually equivalent to the raw radiograph displayed on a light-box. A quantitative evaluation method of image quality assessment was used to compare the ALCE-processed image with others.

Purpose: The aim of this study was to assess whether lesion heterogeneity through pixel-by-pixel analysis of contrast- enhanced MR parameter maps would improve breast lesion differentiation. Method: Forty-nine female patients with primary tumors of the breast were imaged using contrast- enhanced MRI. The rate of transfer of contrast medium between the lesion and plasma was calculated via compartmental modeling over semiautomatically delineated regions of interest. The distributions of transfer rate values were subdivided into 10 segments for each lesion. The rate of change of the statistical moments of the transfer rate measured over the 10 segments allowed a quantitative measure of heterogeneity. Results: In this patient group of 25 malignant and 25 benign lesions, improved differentiation was achieved by using a measure of lesion heterogeneity. The sensitivity and specificity obtained were 88 and 88%. respectively, compared with 84 and 76% when using the mean value of the transfer rate coefficient. Conclusion: Pixel-by-pixel analysis of contrast medium transfer rate maps allows the examination of lesion heterogeneity and offers improved lesion differentiation. The new method used to quantify lesion heterogeneity relies on the manner in which the exchange rate parameter varies when calculated over different segments of the distribution