Different Types Of Contrast Agents Research Articles

Iopromide safety assessment in a radiology department: A seven-year retrospective characterization of adverse events.

Since the mid-20th century, contrast agents have been widely used in radiology due to their ability to provide high-definition radiographic images and greater precision in diagnostic exams. Different types of contrast agents are used in image diagnosis, namely radiological media. Despite being considered safe, there are still uncertainties about their safety profile, interactions, and incidence of adverse drug reactions in real-world settings. To characterise the pattern of adverse events, during 7 years, in a radiology unit. We performed a retrospective observational and descriptive study at an Image Center in Portugal between August 2012 and October 2019. A total of 77,449 computed tomography (CT) were registered, and from those 15,640 cases of iopromide were used as a contrast agent. The authors have accessed, under the authorization, the data of adverse events and procedures after the event. Most of the hypersensitivity events were immediate or with a short time of onset, with the majority of cases developing events with skin involvement and mild degree, where the most common events were papules (n =60), pruritus (n =42), erythema (n =27) and urticaria (n =14). Severe events, including hypersensitivity, were mainly represented by vomiting (n =11), stridor (n =8), breathing difficulties (n =7) and syncope (n =3). Abdominal-pelvic CT exam presented a higher frequency of adverse events. Despite all the current information about iopromide usage, the utilization of this agent is not abstent of risks and its safety profile not fully established. Most frequent symptoms were local, as skin adverse events, including papules, pruritus and erythema. Common medications used to treat or control adverse events were frequently hydrocortisone, clemastine and methylprednisolone.

Magnetic Resonance Imaging and Iron-oxide Nanoparticles in the era of Personalized Medicine.

Medical imaging is an important factor for diagnosis. It can be used to diagnose patients, differentiate disease stages, and monitor treatment regimens. Although different imaging technologies are available, MRI is sensitive over other imaging modalities as it is capable of deep tissue penetration allowing to image the anatomical, structural, and molecular level of diseased organs. Thus, it can be used as screening tool for disease staging. One of the important components of imaging is contrast agents which are used to increase the sensitivity of MRI technology. While different types of contrast agents are available, iron-oxide based nanoparticles (IONPS) are widely used as these are easy to formulate, functionalize, biocompatible and cost effective. In addition to its use as contrast agents, these have been used as drug carriers for the treatment of different types of diseases ranging from cancer, cardiovascular diseases, neurological disorders, autoimmune diseases, and infectious diseases. For the last two decades, there has been advancement in nanotheranostics, where IONPs are formulated to carry drug and be used as contrast agents in one system so that these can be used for image-guided therapy and monitor real-life treatment response in diseased tissue. This technology can be used to stratify patients into responders and non-responders and reduce adverse drug toxicity and lead to a tailored treatment. However, success of nanotheranostics depends on several factor, including identification of disease associated biomarkers that can be targeted on IONPs during formulation. While many challenges exist for the clinical translation of nanotheranostics, it still has the potential to be implemented in personalized treatment strategy. In this review article, we discussed the use of MRI technology and IONPs in relation to their application in disease diagnosis and nanotheranostics application in personalized medicine.

Exogenous Contrast Agents in Photoacoustic Imaging: An In Vivo Review for Tumor Imaging.

The field of cancer theranostics has grown rapidly in the past decade and innovative ‘biosmart’ theranostic materials are being synthesized and studied to combat the fast growth of cancer metastases. While current state-of-the-art oncology imaging techniques have decreased mortality rates, patients still face a diminished quality of life due to treatment. Therefore, improved diagnostics are needed to define in vivo tumor growths on a molecular level to achieve image-guided therapies and tailored dosage needs. This review summarizes in vivo studies that utilize contrast agents within the field of photoacoustic imaging—a relatively new imaging modality—for tumor detection, with a special focus on imaging and transducer parameters. This paper also details the different types of contrast agents used in this novel diagnostic field, i.e., organic-based, metal/inorganic-based, and dye-based contrast agents. We conclude this review by discussing the challenges and future direction of photoacoustic imaging.

Adverse Effects of Gadolinium-Based Contrast Agents: Changes in Practice Patterns.

Gadolinium-based contrast agents have been used for magnetic resonance imaging (MRI) examinations since the late 1980s with an excellent overall cumulative safety record. Initially favored for use in patients with renal impairment because of lack of significant nephrotoxic effect at clinical doses, in 2006, multiple reports convincingly linked the rare but serious disease nephrogenic systemic fibrosis to the administration of gadolinium-based contrast agents in patients with severe renal failure. This in turn led to new policies on administration of these agents, resulting in changes in practice patterns that have virtually resulted in the elimination of the disease after the year 2009. The purpose of this review is to summarize the factors that led to the emergence of nephrogenic systemic fibrosis, including the risk associated with different types of contrast agents based on their stability, and the changes in practice patterns and usage of gadolinium-based contrast agents in recent years that have been mainly driven by the discovery and association with nephrogenic systemic fibrosis. The article will conclude with a brief overview of new emerging safety concerns that could further impact the use of this class of contrast agents and impact practice patterns in the future.

Natural oral contrast agents for gastrointestinal magnetic resonance imaging

Magnetic resonance imaging is an exclusive imaging method which can distinguish injured tissues from the healthy tissues or organs without using ionizing radiation. Magnetic resonance imaging is able to provide quantitative data regarding the anatomical and physiological features of each specific organ. Magnetic resonance imaging is a non-invasive method, but contrast agents are necessary to enhance the visualization of inaccessible organs in some organs such as gastrointestinal (GI) imaging. Various types of contrast agents have been used in studies including intravascular administration and oral materials. Oral contrast agents can be the artificial materials or natural factors. Natural contrast agents consist of fruit juice or pulps. Some advantages have been reported regarding the natural types of contrast agents over the artificial agents including better taste and tolerability. We briefly reviewed the different types of contrast agents and focused on the studies in which natural oral contrast agents used to investigate their efficacy in increasing the gastrointestinal magnetic resonance imaging clarity.

Novel Integration of an Ultrasound Probe and a Rotational-Scanning SQUID Biosusceptometer for Diagnosing Liver Tumors

Ultrasound imaging, also called ultrasonography (US), is a popular medical imaging technique for diagnosing liver tumors. However, the specificity of US in discriminating liver tumors from other liver lesions is limited. Although microbubble contrast agents (CAs) can improve the specificity, using them yields inadequate sensitivity and spatial resolution. To locate liver tumors accurately, patients are subsequently imaged using magnetic resonance imaging (MRI) and superparamagnetic CAs, including iron-oxide magnetic nanoparticles (MNPs). The diagnosis is better for patients by the instrument integrating US and magnetic technologies, rather than by administering different types of CAs with the healthy and cost loading. Hence, on the basis of the utility of MNP CAs in MRI, a US system and a magnetic type of the rotational-scanning superconducting-quantum-interference-device biosusceptometry were integrated in this study. In a phantom test, a magnetic image of the MNP distribution showed good agreement with an optical photo. In an animal test, the tumor location was confirmed with the same results of magnetic and US images. Test results regarding the proposed platform indicated that US probes are compatible with magnetic methodologies and, thus, can be used to enhance the performance of tumor diagnosis and reduce the cost and healthy loading of patients.

Contrast-enhanced voiding urosonography phantom study: intravenous iodinated and gadolinium-based contrast agents may cause false-negative results in assessment of vesicoureteral reflux in children.

Contrast-enhanced voiding urosonography (ce-VUS) is commonly requested simultaneously to other diagnostic imaging necessitating intravenous contrast agents. To date there is limited knowldedge about intravesical interactions between different types of contrast agents. To assess the effect of excreted intravenous iodinated and gadolinium-based contrast agents on the intravesical distribution of ultrasound contrast within contrast-enhanced voiding urosonography. Iodinated (iomeprol, iopamidol) and gadolinium-based (gadoterate meglumine) contrast agents were diluted to bladder concentration and injected into balloons filled with saline solution. CT scans were performed to assess the contrast distribution in these phantoms. Regions of interest were placed at the top and bottom side of each balloon and Hounsfield units (HU) were measured. Three other balloons were filled with saline solution and contrast media likewise. The ultrasound contrast agent sulphur hexafluoride was added and its distribution was assessed using sonography. MDCT scans showed a separation of two liquid layers in all bladder phantoms with the contrast layers located at the bottom and the saline solution at the top. Significant differences of the HU measurements at the top and bottom side were observed (P < 0.001-0.007). Following injection of ultrasound contrast agent, US showed its distribution exclusively among the saline solution. False-negative results of contrast-enhanced voiding urosonography may occur if it is performed shortly after imaging procedures requiring intravenous contrast.

A new ex vivo method to evaluate the performance of candidate MRI contrast agents: a proof-of-concept study.

BackgroundMagnetic resonance imaging (MRI) plays an important role in tumor detection/diagnosis. The use of exogenous contrast agents (CAs) helps to improve the discrimination between lesion and neighbouring tissue, but most of the currently available CAs are non-specific. Assessing the performance of new, selective CAs requires exhaustive assays and large amounts of material. Accordingly, in a preliminary screening of new CAs, it is important to choose candidate compounds with good potential for in vivo efficiency. This screening method should reproduce as close as possible the in vivo environment. In this sense, a fast and reliable method to select the best candidate CAs for in vivo studies would minimize time and investment cost, and would benefit the development of better CAs.ResultsThe post-mortem ex vivo relative contrast enhancement (RCE) was evaluated as a method to screen different types of CAs, including paramagnetic and superparamagnetic agents. In detail, sugar/gadolinium-loaded gold nanoparticles (Gd-GNPs) and iron nanoparticles (SPIONs) were tested. Our results indicate that the post-mortem ex vivo RCE of evaluated CAs, did not correlate well with their respective in vitro relaxivities. The results obtained with different Gd-GNPs suggest that the linker length of the sugar conjugate could modulate the interactions with cellular receptors and therefore the relaxivity value. A paramagnetic CA (GNP (E_2)), which performed best among a series of Gd-GNPs, was evaluated both ex vivo and in vivo. The ex vivo RCE was slightly worst than gadoterate meglumine (201.9 ± 9.3% versus 237 ± 14%, respectively), while the in vivo RCE, measured at the time-to-maximum enhancement for both compounds, pointed to GNP E_2 being a better CA in vivo than gadoterate meglumine. This is suggested to be related to the nanoparticule characteristics of the evaluated GNP.ConclusionWe have developed a simple, cost-effective relatively high-throughput method for selecting CAs for in vivo experiments. This method requires approximately 800 times less quantity of material than the amount used for in vivo administrations.

Advanced Characterization of Contrast Agents with Ultrasound

Contrast agents are characterized with ultrasound. Flowing or unbound contrast agents are distinguished automatically from bound or relatively stationary contrast agents. The bound or relatively stationary contrast agents are highlighted on a display. A processor distinguishes different types of contrast agents or contrast agents in different binding states with relative signal strength or velocity. Attached contrast agents are differentiated from phagocytosed contrast agents. Monitoring absolute signal strength as a function of time may indicate binding. Any one or more of these features may be used.

Experimental nerve imaging at 1.5-T

Experimental lesions of the peripheral nerve system can be visualized in vivo by magnetic resonance imaging (MRI). Many studies of the rat peripheral nervous systems were performed on dedicated animal MR scanners with a high magnetic field strength for good spatial resolution. Here, we present an MR protocol to study experimental lesions of the rat nervous system with clinical 1.5-T MR scanners and commercially available coils. Using a three-sequence approach (T1-weighted imaging, fat-saturated T2-weighted imaging and fat-saturated T1-weighted imaging with Gd-DTPA in the same plane), the relevant signal changes of the lesioned nerve can be visualized and separated from other structures, e.g., blood vessels. Furthermore, we give an overview on different types of contrast agents used for peripheral nerve MR imaging and MR findings in selected experimental models of rat peripheral nerve injury.

Contrast Agents and Applications to Assess Tumor Angiogenesis In Vivo by Magnetic Resonance Imaging

Angiogenesis plays a key role in the development of cancer and is precondition for tumor growth, invasion and spread. Therefore, numerous angiogenesis inhibitors have been developed, of which some show potential to defeat cancer in preclinical and clinical trials. However, response to antiangiogenic treatments is often delayed and marked by high interindividual variability making a closely mashed and efficient observation of the patient necessary. Therefore, surrogate markers which specifically catch early response to tumor therapy are highly desirable. Functional parameters like relative blood volume, perfusion and vessel permeability can be assessed using T(1) and T(2)*-weighted dynamic contrast-enhanced (DCE) MRI. Various reports are available on this topic but results are controversial. During antiangiogenic therapies some authors describe pronounced changes in blood volume: others find effects only on vessel permeability or perfusion. These conflictive observations can be attributed to the different tumor models, therapies, measurement techniques and contrast agents (CA). Particularly the choice of the optimal CA is considered to be essential for a successful characterization of tumor angiogenesis. Often therapy effects on vessel permeability only become apparent, when blood pool CA are used. This article reviews the current state of DCE and molecular MRI of angiogenesis. Besides a general introduction of the different measurement and postprocessing methods and its previous applications, design, structure and use of different types of CA are the main focus of this article.

Use of contrast agents for liver MRI

Contrast-enhanced MRI is recognised as one of the most accurate imaging methods for investigating diseases of the liver. Uniquely several different types of contrast agents are available for liver MRI. They can be divided into non-specific extracellular fluid space (ECF), hepatocyte specific and reticulo-endothelial system (RES) specific agents. They are used to improve the detection of focal liver lesions by increasing normal-abnormal tissue contrast and to assist in lesion characterisation by demonstrating tissue perfusion and cellular function. ECF-gadolinium (Gd) chelates have been widely used in abdominal MRI for many years. They provide valuable information regarding the vascularisation and perfusion characteristics of lesions and assist in lesion detection, particularly of hypervascular lesions. The hepatocyte and RES-specific agents further improve lesion detection, provide important functional information and allow the distinction between hepatocellular and non-hepatocellular tumours. This article describes the different MR contrast agents and discusses their current status for diagnosing focal liver lesions. The importance of optimised technique and appropriate selection of contrast agent is emphasised.

A new ultrasound contrast imaging approach based on the combination of multiple imaging pulses and a separate release burst.

A new ultrasound contrast imaging technique is described that optimally employs the rupture of the contrast agent. It is based on a combination of multiple high frequency, broadband, imaging pulses and a separate release burst. The imaging pulses are used to survey the target before and after the rupture and release of free gas bubbles. In this way, both processes (imaging and release) can be optimized separately. The presence of the contrast agent is simply detected by correlating or subtracting the signal responses of the imaging pulses. Because the time delay between the imaging pulses can be very short, the subtraction is less affected by tissue motion and can be done in real time. In vitro measurements showed that by using a release burst, the detection sensitivity increased 12 to 43 dB for different types of contrast agents. In the presence of a moving phantom, the increase in sensitivity was 22 dB. This new method is very sensitive for contrast agent detection in fundamental imaging mode and, therefore, non-linear propagation effects do not limit the maximum obtainable agent-to-tissue ratio. However, because of the inherent destruction of the contrast agent, it has to operate in an intermittent way. Through experiments, we have demonstrated the potential of the method to achieve simultaneous high sensitivity for contrast detection, i.e., high agent-to-tissue ratio, and high spatial resolution performance for different types of contrast agents.