(MAA) Macroaggregated albumin is used in pulmonary perfusion scintigraphy to record the pulmonary circulation. Macroaggregated albumin is usually prepared by heating human serum albumin. The produced particle sizes range from 10 to 100 µm in diameter. The albumin may be labeled with 131I, 99mTc, or 113mI.

(CA) Contrast agents are used to change the imaging characteristics, resulting in additional information about anatomy, morphology or physiology of the human body. Radiocontrast agents (also called photon-based imaging agents) are used to improve the visibility of internal body structures in x-ray and CT procedures. Contrast agents are also used to increase the contrast between different tissues in MRI (magnetic resonance imaging) and ultrasound imaging. The ideal imaging agent provides enhanced contrast with little biological interaction.
First investigations with radiopaque materials are done shortly after the discovery of x-rays. These positive contrast agents attenuate x-rays more than body soft tissues due to their high atomic weight. Iodine and barium have been identified as suitable materials with high radiodensity and are used until today in x-ray and CT contrast agents. Iodine-based contrast agents are water-soluble and the solutions are used nearly anywhere in the body. Iodinated contrast materials are most administered intravenous, but can also be introduced intraarterial, intrathecal, oral, rectal, intravesical, or installed in body cavities. Barium sulfate is only used for opacification of the gastrointestinal tract. Negative contrast agents attenuate x-rays less than body soft tissues, for example gas.

Iodinated contrast media are differentiated in;

Intravascular iodinated contrast agents are required for a large number of x-ray and CT studies to enhance vessels and organs dependent on the blood supply. Injectable contrast agents are diluted in the bloodstream and rapidly distributed throughout the extracellular fluid. The main route of excretion is through the kidneys, related to the poor binding of the agent to serum albumin. The liver (gall bladder) and small intestine provide alternate routes of elimination particularly in patients with severe renal impairment. The use of special biliary contrast agents is suitable for gallbladder CT and cholecystograms because they are concentrated by the liver to be detectable in the hepatic bile.
The introduction of fast multi-detector row CT technology, has led to the development of optimized contrast injection techniques. The amount of contrast enhancement depends on the contrast agent characteristics, such as iodine concentration, osmolality, viscosity, and the injection protocol, such as iodine flux and iodine dose. Adverse reactions are rare and have decreased with the introduction of nonionic contrast agents.
See also Contrast Enhanced Computed Tomography, Abdomen CT, Contrast Media Injector, Single-Head CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector, CT Power Injector.

(GBPS) The gated blood pool scintigraphy is an examination to evaluate the ventricular performance. This scintigraphic blood pool imaging uses an electrocardiographic synchronizer or gating device to acquire data during repeated heart cycles at specific times in the heart cycle. Radionuclides, for example 99mTc-humanserumalbumin (HSA), are used as intravascular tracers.
GBPS allows to determinate the left ventricular function with heart minute volume, ejection fraction (EF) at rest and under exercise. Single photon emission computed tomography (SPECT) versus planar scintigraphic imaging improves cardiac evaluation due to the three dimensional nature. The GBPS method is not suitable to analyze the right ventricular function; that is best evaluated by first-pass ventriculography.
Echocardiography vs. GBPS has important disadvantages due to problems in quantitative evaluation, in patients with anatomic variations and dyskinetic left ventricles.

See also Myocardial Perfusion Imaging.