Blood pool agents (BPAs) are a class of magnetic resonance angiography contrast agents. [1] [2] Blood pool agents (also known as intravascular contrast agents) are differentiated from other contrast agents due to their high molecular weight and higher relaxivities. [3] Their large size prevents diffusion through the vascular epithelium and leakage into the interstitial space, and because of this they stay in the vascular system for a longer time period. Most contrast agents, leave the vascular system within a few minutes, however blood pool agents remain in the circulation for up to an hour, extending the window available for imaging. Longer image acquisition times allow better signal-to-noise ratio and improved image resolution.
Due to their extended time in the circulatory system, blood pool agents can be used for delayed steady-state imaging, and additionally these results can be combined with first pass arterial imaging. [2] [3] Their extended circulation time means that they are able to be used for both arterial and venous mapping. Additional uses include: detection of gastrointestinal bleeding; visualization of the vasculature associated with certain tumors; measuring tissue blood volume and perfusion; and detection of endovascular leaks (such as following stent-graft repair of an aortic aneurysm).[ citation needed ]
This class of BPAs is based on the noncovalent binding of low molecular weight Gd3+-based complexes to human serum albumin. The first commercial agent to be approved in this class is gadofosveset trisodium [4] (also known as Vasovist [5] or Ablavar, [6] and previously known as MS-325 [7] ). Many clinical and case studies documenting the use of this BPA have been published, [8] [9] [10] [11] [12] [13] [14] and its efficacy in enhancing blood vessels visibility has been demonstrated. [15] The manufacturer (Lantheus Medical) discontinued production in 2017 though, due to poor sales. [16]
Gadocoletic acid [17] (Bracco SpA), also known as B-22956 and B22956/1, is a Gd-DTPA derivative that is currently in development, but has not yet been approved for clinical use.
Gadobenic acid (MultiHance [18] ) is sometimes categorized as a BPA; however, as it only binds weakly to albumin and because hepatobiliary uptake of this compound occurs, this contrast agent should not be classified as a BPA.
Polymeric Gd3+ chelates are large in size, which prevents leakage into the interstitial space, and provides long imaging windows. Several polymeric gadolinium-based BPAs are currently in development but have not yet been approved for clinical use: Gadomelitol [19] (Guerbet, France), also known as Vistarem and P792 Gadomer-17 [20] (Schering AG, Berlin, Germany) also known as Gd-DTPA-17, SH L 643 A.
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy.
Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is performed by injecting a radio-opaque contrast agent into the blood vessel and imaging using X-ray based techniques such as fluoroscopy.
A coronary catheterization is a minimally invasive procedure to access the coronary circulation and blood filled chambers of the heart using a catheter. It is performed for both diagnostic and interventional (treatment) purposes.
Cerebral angiography is a form of angiography which provides images of blood vessels in and around the brain, thereby allowing detection of abnormalities such as arteriovenous malformations and aneurysms. It was pioneered in 1927 by the Portuguese neurologist Egas Moniz at the University of Lisbon, who also helped develop thorotrast for use in the procedure.
Magnetic resonance angiography (MRA) is a group of techniques based on magnetic resonance imaging (MRI) to image blood vessels. Magnetic resonance angiography is used to generate images of arteries in order to evaluate them for stenosis, occlusions, aneurysms or other abnormalities. MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs.
Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image" or mask from subsequent images, once the contrast medium has been introduced into a structure. Hence the term "digital subtraction angiography. Subtraction angiography was first described in 1935 and in English sources in 1962 as a manual technique. Digital technology made DSA practical starting in the 1970s.
Gadopentetic acid, sold under the brand name Magnevist, is a gadolinium-based MRI contrast agent.
Computed tomography angiography is a computed tomography technique used for angiography—the visualization of arteries and veins—throughout the human body. Using contrast injected into the blood vessels, images are created to look for blockages, aneurysms, dissections, and stenosis. CTA can be used to visualize the vessels of the heart, the aorta and other large blood vessels, the lungs, the kidneys, the head and neck, and the arms and legs. CTA can also be used to localise arterial or venous bleed of the gastrointestinal system.
MRI contrast agents are contrast agents used to improve the visibility of internal body structures in magnetic resonance imaging (MRI). The most commonly used compounds for contrast enhancement are gadolinium-based contrast agents (GBCAs). Such MRI contrast agents shorten the relaxation times of nuclei within body tissues following oral or intravenous administration.
Gadobutrol (INN) (Gd-DO3A-butrol) is a gadolinium-based MRI contrast agent (GBCA).
Susceptibility weighted imaging (SWI), originally called BOLD venographic imaging, is an MRI sequence that is exquisitely sensitive to venous blood, hemorrhage and iron storage. SWI uses a fully flow compensated, long echo, gradient recalled echo (GRE) pulse sequence to acquire images. This method exploits the susceptibility differences between tissues and uses the phase image to detect these differences. The magnitude and phase data are combined to produce an enhanced contrast magnitude image. The imaging of venous blood with SWI is a blood-oxygen-level dependent (BOLD) technique which is why it was referred to as BOLD venography. Due to its sensitivity to venous blood SWI is commonly used in traumatic brain injuries (TBI) and for high resolution brain venographies but has many other clinical applications. SWI is offered as a clinical package by Philips and Siemens but can be run on any manufacturer’s machine at field strengths of 1.0 T, 1.5 T, 3.0 T and higher.
Gadoteric acid, sold under the brand name Dotarem among others, is a macrocycle-structured gadolinium-based MRI contrast agent (GBCA). It consists of the organic acid DOTA as a chelating agent, and gadolinium (Gd3+), and is used in form of the meglumine salt (gadoterate meglumine). The paramagnetic property of gadoteric acid reduces the T1 relaxation time (and to some extent the T2 and T2* relaxation times) in MRI, which is the source of its clinical utility. Because it has magnetic properties, gadoteric acid develops a magnetic moment when put under a magnetic field, which increases the signal intensity (brightness) of tissues during MRI imaging.
The physics of magnetic resonance imaging (MRI) concerns fundamental physical considerations of MRI techniques and technological aspects of MRI devices. MRI is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels among others. Contrast agents may be injected intravenously or into a joint to enhance the image and facilitate diagnosis. Unlike CT and X-ray, MRI uses no ionizing radiation and is, therefore, a safe procedure suitable for diagnosis in children and repeated runs. Patients with specific non-ferromagnetic metal implants, cochlear implants, and cardiac pacemakers nowadays may also have an MRI in spite of effects of the strong magnetic fields. This does not apply on older devices, and details for medical professionals are provided by the device's manufacturer.
Cardiac magnetic resonance imaging perfusion, also known as stress CMR perfusion, is a clinical magnetic resonance imaging test performed on patients with known or suspected coronary artery disease to determine if there are perfusion defects in the myocardium of the left ventricle that are caused by narrowing of one or more of the coronary arteries.
Contrast CT, or contrast enhanced computed tomography (CECT), is X-ray computed tomography (CT) using radiocontrast. Radiocontrasts for X-ray CT are generally iodine-based types. This is useful to highlight structures such as blood vessels that otherwise would be difficult to delineate from their surroundings. Using contrast material can also help to obtain functional information about tissues. Often, images are taken both with and without radiocontrast. CT images are called precontrast or native-phase images before any radiocontrast has been administrated, and postcontrast after radiocontrast administration.
Gadofosveset is a gadolinium-based MRI contrast agent. It was used as the trisodium salt monohydrate form. It acts as a blood pool agent by binding to human serum albumin. The manufacturer discontinued production in 2017 due to poor sales.
Val Murray Runge is an American and Swiss professor of radiology and the editor-in-chief of Investigative Radiology. Runge was one of the early researchers to investigate the use of gadolinium-based contrast agents for magnetic resonance imaging (MRI), giving the first presentation in this field, followed two years later by the first presentation of efficacy. His research also pioneered many early innovations in MRI, including the use of tilted planes and respiratory gating. His publication on multiple sclerosis in 1984 represented the third and largest clinical series investigating the role of MRI in this disease, and the first to show characteristic abnormalities on MRI in patients whose CT was negative.
Perfusion MRI or perfusion-weighted imaging (PWI) is perfusion scanning by the use of a particular MRI sequence. The acquired data are then post-processed to obtain perfusion maps with different parameters, such as BV, BF, MTT and TTP.
An MRI sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular image appearance.
A specific branch of contrast-enhanced ultrasound, acoustic angiography is a minimally invasive and non-ionizing medical imaging technique used to visualize vasculature. Acoustic angiography was first developed by the Dayton Laboratory at North Carolina State University and provides a safe, portable, and inexpensive alternative to the most common methods of angiography such as Magnetic Resonance Angiography and Computed Tomography Angiography. Although ultrasound does not traditionally exhibit the high resolution of MRI or CT, high-frequency ultrasound (HFU) achieves relatively high resolution by sacrificing some penetration depth. HFU typically uses waves between 20 and 100 MHz and achieves resolution of 16-80μm at depths of 3-12mm. Although HFU has exhibited adequate resolution to monitor things like tumor growth in the skin layers, on its own it lacks the depth and contrast necessary for imaging blood vessels. Acoustic angiography overcomes the weaknesses of HFU by combining contrast-enhanced ultrasound with the use of a dual-element ultrasound transducer to achieve high resolution visualization of blood vessels at relatively deep penetration levels.