Good Contrast Effect Research Articles

Diagnostic Value of Contrast-Enhanced Dual-Energy Computed Tomography in the Pancreatic Parenchymal and Delayed Phases for Pancreatic Cancer.

Background/Objectives: The usefulness of dual-energy computed tomography (DECT) for low absorption in the parenchymal phase and contrast effects in the delayed phase for pancreatic cancer is not clear. Therefore, the diagnostic capability of low-KeV images obtained using DECT for pancreatic cancer in the pancreatic parenchymal and delayed phases was evaluated quantitatively and qualitatively. Methods: Twenty-five patients with pancreatic cancer who underwent contrast-enhanced DECT were included. A total of 50 and 70 KeV CT images, classified as low-keV and conventional CT-equivalent images, were produced, respectively. The tumor-to-pancreas contrast (Hounsfield units [HU]) in the pancreatic parenchymal and delayed phases was calculated by subtracting the CT value of the pancreatic tumor from that of normal parenchyma. Results: The median tumor-to-pancreas contrast on 50 KeV CT in the pancreatic parenchymal phase (133 HU) was higher than that on conventional CT (68 HU) (p < 0.001). The median tumor-to-pancreas contrast in the delayed phase was -28 HU for 50 KeV CT and -9 HU for conventional CT (p = 0.545). For tumors < 20 mm, the tumor-to-pancreas contrast of 50 KeV CT (-39 HU) had a significantly clearer contrast effect than that of conventional CT (-16.5 HU), even in the delayed phase (p = 0.034). Conclusions: These 50 KeV CT images may clarify the low-absorption areas of pancreatic cancer in the pancreatic parenchymal phase. A good contrast effect was observed in small pancreatic cancers on 50 KeV delayed-phase images, suggesting that DECT is useful for the visualization of early pancreatic cancer with a small tumor diameter.

Study on anode single-phase flow pressure drop law of proton exchange membrane fuel cell

This article briefly describes the research status of water flooding and pressure drop (PD) of the fuel cell. Then, a mathematical model of the single-phase flow PD of the fuel cell anode is established using hydrodynamics theory and referring to existing research. Then, the three-dimensional fuel cell model is established with Gambit software, and the grid is divided. Then, the numerical simulation of the single-phase flow of the fuel cell is carried out with Fluent software. Through the analysis of the simulation data, the relationship between the fuel cell anode pressure drops and some main influencing factors under steady-state conditions is explored, and the fuel cell anode’s single-phase flow pressure drop model is preliminarily verified. Anodes are highly sensitive to water flooding. The study of the single-phase flow PD law has a good contrast effect on the abnormal pressure drop during water flooding of fuel cells, which can be used to diagnose water flooding.

Analysis of the Relationship Between Periampullary Diverticulum and Recurrent Bile Duct Stones After Endoscopy on Magnetic Resonance Imaging of Magnetic Nanoparticles

The objective of this work was to investigate the effect of magnetic resonance cholangiopancreatography (MRCP) based on super-paramagnetic iron oxide nanoparticles (SPIONs) on the recurrence diagnosis of periampullary diverticulum (PAD) and bile duct stone (BDS), so as to provide a scientific research basis for the recidivation factors of bile duct stones in clinic. Patients with PAD diagnosed in hospital from July 2019 to March 2021 (who had undergone endoscopic gallstone surgery) were selected for study in this work. They were rolled into two groups, the parapapillary group (123 cases) and the cholangiopancreatic duct directly opening in the diverticulum group (97 cases), according to the clinical classification. Then, 100 patients without PAD who had undergone bile duct node therapy were selected as the control group. The recidivation of BDS, serological index, and biliary pressure index before and after treatment were compared. The relationship between PAD and recidivation of bile duct stones was analyzed. The results showed that the average particle size, hydration kinetic particle size, effective time, and duration of polyethylene glycol (PEG)/polyethyleneimine (PEI)/poly aspartic acid-super-paramagnetic iron oxide nanoparticles(PASP-SPIONs) were better than PEG/PEI-SPIONs and SPIONs. The recidivation rate of BDS in Groups R and X was remarkably higher than the rate in control group (P < 0.05). Before treatment, common bile duct pressure in the control group was lower obviously than that in Groups R and X (P < 0.05). After treatment, the indexes including total bilirubin, direct bilirubin, and alkaline phosphatase in control group were lower than those in Groups R and X (P < 0.05). The incidence of complications in Groups R and X was much higher than in contrast to the control group (P < 0.05). Therefore, PEG/PEI/PASP-SPIONs had good contrast effect and could be used as magnetic resonance imaging contrast agent. Complications such as common bile duct pressure and infection were increased by PAD, which may be the main factor for the recidivation of BDS.

Nontoxic Gd3+ and Tb3+ co-induced polyelectrolyte nano-aggregates (GTIPAs) for luminescence/magnetic resonance dual-modality imaging

Multimodal nanoprobes are of great significance in clinical diagnosis, because they integrate the advantages of multiple imaging methods. The combination of multiple imaging modes provides more comprehensive and complex information than single-mode imaging, which can greatly improve clinical diagnoses. In this paper, Gd3+ and Tb3+ co-induced polyelectrolyte nanoaggregates (GTIPAs) are introduced as a novel dual-mode imaging probe. Containing gadolinium and terbium, GTIPAs are regular spherical nanoparticles, whose diameters are about 150 nm. As a fluorescent nanomaterial, GTIPAs have strong and stable luminescence intensity. At the same time, as an MRI contrast agent, GTIPAs exhibit a good contrast effect and a high longitudinal relaxation rate. In addition, the polyelectrolytes reduce the cytotoxicity of the complexes, confering excellent biocompatibility and water solubility. Therefore, GTIPAs are non-toxic luminescence/magnetic resonance dual-mode imaging probes.

One-pot synthesis of water-soluble superparamagnetic iron oxide nanoparticles and their MRI contrast effects in the mouse brains.

Water-soluble superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by the thermal decomposition of iron (III) acetylacetonate (Fe(acac)3) in the mixture of poly(ethylene glycol) (PEG) and poly(ethylene imine) (PEI). The average sizes of the SPIONs are in the range of 6-12nm, which could be tuned by adjusting the synthesis temperature and molecular weight of PEI. Benefiting from the coating of hydrophilic PEG and PEI, the resulted SPIONs showed excellent colloidal stability in deionized water and other physiological buffers. The XRD patterns indicate that the obtained SPIONs are magnetite. The PEG/PEI-SPIONs exhibited high r2/r1 ratio. In vivo magnetic resonance imaging (MRI) of the mouse brains after intravenous injection of the SPIONs showed their good contrast effect. Considering the facile fabrication process and excellent imaging performance of the water soluble PEG-SPIONs and PEG/PEI-SPIONs, it is believed that the SPIONs will find great potential in advanced MRI.

Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrastT1- andT2-weighted magnetic resonance imaging

The development of new types of high-performance nanoparticulate MR contrast agents with eitherpositive (T1) or dual-contrast (both positive and negative,T1 + T2) ability is of great importance. Here we report a facile synthesisof ultrasmall PEGylated iron oxide nanoparticles for dual-contrastT1- andT2-weighted MRI. The produced superparamagnetic iron oxide nanoparticles(SPIONs) are of high crystallinity and size uniformity with an average diameter of5.4 nm, and can be individually dispersed in the physiological buffer with highstability. The SPIONs reveal an impressive saturation magnetization of 94 emu g − 1 Fe3O4, the highestr1 of 19.7 mM − 1 s − 1 and thelowest r2/r1 ratio of 2.0 at 1.5 T reported so far for PEGylated iron oxide nanoparticles.T1- andT2-weightedMR images showed that the SPIONs could not only improve surrounding water proton signals in theT1-weighted image, but induce significant signal reduction in theT2-weighted image. The good contrast effect of the SPIONs asT1 + T2 dual-contrast agents might be due to its high magnetization, optimal nanoparticle size forT1 + T2 dual-contrast agents, high size monodispersity and excellent colloidal stability. In vitro cellexperiments showed that the SPIONs have little effect on HeLa cell viability.

An experimental intraoperative quantitative echocardiographic study of myocardial perfusion in dogs

Myocardial contrast echocardiography is a valuable technique for demonstration and delineation of regions of myocardial underperfusion secondary to coronary occlusion and/or significant coronary stenosis. Various contrast materials have been used. The aim of this study was to determine whether myocardial contrast echocardiography by the original contrast agent AQ-DDT (albumin based), produced in the Institute for Cardiovascular Diseases, Clinical Center of Serbia in Belgrade can be used in the detection and quantification of regions of myocardial perfusion defects. In 14 adult open chest dogs the perfusion defect was produced by selective coronary ligations (30 seconds) and was observed with epicardial contrast two-dimensional echocardiography. For administration of contrast a modified pigtail catheter was positioned in the aorta just above the aortic valves. In this way the perfusion regions of the left main and right coronary artery were included. The left anterior descending and left circumflex artery could not be selectively injected with contrast agent and their individual perfusion areas were not clearly demonstrated. In all cases contrast echocardiography images of the left ventricle were obtained in a short-axis cross-sectional view at the mid-papillary muscle level. Forty-two injections of AQ-DDT for perfusion analysis were done, and were recorded on a VHS recorder. Quantification of the quality in demonstrating myocardial perfusion was scored as good, poor or without visual echocardiographic effect, by an investigator experienced in echocardiography, immediately and one month later. There was 100% agreement in the scoring. Our results indicated that agent AQ-DDT produces a good contrast effect (echocardiography visualization) in dogs and has the potential to demonstrate regional perfusion defects of the myocardium. Its potential role in human medicine, for diagnosis and evaluation of the results of interventional therapy, especially during aortocoronary bypass graft surgery, should be evaluated.

Study on Contrast Effect of Microbubbles as Ultrasound Contrast Agents

In this study, the contrast effect from different sized microbubbles is investigated both theoretically and experimentally. Theoretically, the reference backscattered power is defined to evaluate the contrast effect of different sized microbubbles dispersed in the heart. In this study, the calculation results of two kinds of microbubbles of sizes 35 µm and 2.2 µm are discussed. From the calculation results obtained, it is found that the contrast effect from microbubbles of size 35 µm is better than that from microbubbles of size 2.2 µm. The reason being that as the size of microbubbles decreases, a large portion of ultrasonic energy is lost due to absorption. Based on the same reason, microbubbles less than 10 µm will cause an acoustic shadowing effect at a higher concentration of microbubbles, according to the calculation results. Experimentally, microbubbles of an average size of 35 µm are produced, and by filtration, microbubbles of an average size of 2.1 µm are collected. Then, the contrast effect produced from microbubbles before and after filtration are compared. It is observed that for both kinds of microbubbles, a good contrast effect is observed at a relatively low concentration of microbubble dispersion. However, distortion of images occurs at high concentrations. The acoustic shadowing effect is observed for microbubbles of an average size of 2.1 µm which can also be expected from the calculation results. On the other hand, the multiple-scattering effect which results in blurred images, occurs for microbubbles of an average size of 35 µm.

Oral Magnetic Particles

Oral magnetic particles (OMP) have been evaluated in a clinical phase II trial program comprising 216 patients in 7 European centers. Adult patients referred for MR imaging for various abdominal pathologies were examined. The patients received OMP at a concentration of 0.1 g/l (ultralow field) or 0.5 g/l (mid/high field) and OMP was diluted in water or in a more viscous liquid formulation. Depending on the area of interest, OMP was ingested in a volume of 300 to 800 ml. OMP was well tolerated with no serious adverse events and the patient acceptability was good. OMP had a good contrast effect on all applied pulse sequences. The viscous formulation of OMP was homogeneously distributed through the entire gastrointestinal tract without inducing disturbing susceptibility artifacts. The postcontrast diagnostic information was improved in 70% of the cases. Based on the encouraging results in phase II, OMP has been advanced to phase III clinical trials.

Oral Magnetic Particles

Oral magnetic particles (OMP) have been evaluated in a clinical phase II trial program comprising 216 patients in 7 European centers. Adult patients referred for MR imaging for various abdominal pathologies were examined. the patients received OMP at a concentration of 0.1 g/l (ultralow field) or 0.5 g/l (mid/high field) and OMP was diluted in water or in a more viscous liquid formulation. Depending on the area of interest, OMP was ingested in a volume of 300 to 800 ml. OMP was well tolerated with no serious adverse events and the patient acceptability was good. OMP had a good contrast effect on all applied pulse sequences. the viscous formulation of OMP was homogeneously distributed through the entire gastrointestinal tract without inducing disturbing susceptibility artifacts. the postcontrast diagnostic information was improved in 70% of the cases. Based on the encouraging results in phase II, OMP has been advanced to phase III clinical trials.

Superparamagnetic Particles as Oral Contrast Medium in MR Imaging of Malignant Lymphoma

Non-biodegradable superparamagnetic particles, in plain and viscous aqueous suspensions, were used as an oral contrast medium in 34 patients with known or suspected malignant lymphoma. The contrast effect, the occurrence of artifacts, and the distribution were evaluated in the plain and the viscous aqueous suspensions, and the diagnostic information received from abdominal MR examinations performed without bowel contrast medium was compared with that of post-contrast examinations. Magnetic particles in the concentration of 0.5 g/l displayed a good contrast effect at 0.5 T, and helped in differentiating the intestine from adjacent tissues, resulting in increased diagnostic information in abdominal MR imaging. In the patients given the viscous aqueous suspension the occurrence of artifacts caused by the magnetic particles decreased considerably, and the distribution was homogeneous and improved compared with that in patients given the plain aqueous suspension.

Effect of Superparamagnetic Particles as Oral Contrast Medium at Magnetic Resonance Imaging

Non-biodegradable superparamagnetic particles were used as an oral contrast medium in different concentrations, and evaluated in 25 human volunteers. The aim of the study was to determine the most appropriate concentration of the contrast medium, and to evaluate the effect, distribution, safety and tolerance. With the concentration of 1.0 g/l a substantial reduction of the signal intensity in the bowel was achieved in both T1 and T2 weighted images. The intraabdominal structures were well differentiated from the bowels containing contrast medium. 'Metal' artifacts and blurring of adjacent structures, probably due to an increased local concentration, were observed at higher dosages. The distribution of the preparation in the gastrointestinal tract varied between individuals. As a rule a good contrast effect was achieved in the small bowel with the exception of the duodenum. The contrast medium was well accepted and did not cause any side effects of clinical importance. The results suggest that the preparation is well tolerated by humans and may be a useful contrast medium for abdominal MR imaging.

Intracoronary echo-contrast agents: abnormalities in myocardial function in a normal and reduced coronary perfusion model in dogs.

Two-dimensional echocardiography using echo-contrast enhancing agents is a promising technique for evaluating myocardial perfusion. However, the potential deleterious effects of injection of echo-enhancing agents into the coronary circulation have not been well evaluated. We utilized two experimental canine models in which the left anterior descending coronary artery was cannulated and perfused continuously by the left common carotid at normal and reduced coronary flows. Analysis of myocardial function included regional left ventricular systolic function by ultrasonic crystals, subendocardial ST segment shifts, left ventricular dP/dr analysis and measurements of coronary blood flow. One ml of each echo-contrast agent was injected into the left anterior descending coronary artery during normal coronary flow. Echo-enhancing agents included: sonicated 70% sorbitol, 50% dextrose, and 6% dextran, hand-agitated Renografin-saline, and unagitated 0.15% hydrogen peroxide, 20% fat emulsion and oxygenated Oxypherol, a perfluorocarbon compound. Two-dimensional echocardiography determined that all echo-enhancing agents except for 20% fat emulsion and Oxypherol produced good myocardial enhancement. All echo-enhancing agents which produced a good contrast effect did so at the expense of significant reversible contractile abnormalities. Each produced more than a 50% reduction in percent segment shortening. Sorbitol and hydrogen peroxide produced the most severe contractile disturbances. In the normal flow model, sorbitol produced systolic bulging and hydrogen peroxide an 83% reduction in percent segment shortening. Hydrogen peroxide induced systolic bulging in the reduced coronary flow model. Other abnormalities induced by echo-enhancing agents included ST segment shifts and malignant ventricular arrhythmias. Six percent dextran produced a good contrast effect with the least harmful myocardial consequences.

Analytical applications of arsenazo III—II: Determination of thorium, uranium, protactinium, neptunium, hafnium and scandium

The particular analytical utility of arsenazo III is its capacity for forming especially stable complexes with certain elements. This permits determinations to be carried out in strongly acid media (for quinquevalent and quadrivalent elements—Pa, Np IV Th, Zr, Hf, U IV—up to 10 M HCl or H 2SO 4), which ensures good reproducibility, ease of working, and little interference by anions. The high sensitivity (0.1–0.01 μg ml , molar absorption coefficient 50–150 × 10 3) is a result of the good contrast effect of the reaction (pink → emerald-green, displacement of the absorption maximum 125 mμ), the nature of the spectrum, and the possibility of reaching extreme dilutions without dissociation of the complex.