Contrast media

This article reviews the most recent papers on contrast media reported from October 1989 to September 1990. Areas of focus include water-soluble contrast agents and barium agents.     

Contrast media safety-an update

The value of contrast agents has for long been documented by their common daily use in imaging departments worldwide. In principle, they should be injected and leave the body immediately after use in the same condition or undergo natural metabolism without making any harm to the patient. However, this is not the case. It is of utmost importance to reduce the prevalence to as close as possible to zero. This can be done by identifying the patients at risk before administration of contrast agents. For acute non-renal adverse reactions, it is also important to be prepared for treating them instantly. The current review is a short state of the art regarding adverse reactions to contrast agents.     

Contrast media: future aspects

In spite of the dramatic development in CT, there was no major breakthrough in the iodinated contrast media development. New agents based on hybrid between MRI and CT compounds may be a new innovative alternative. This new approach may also open new indications such as radiotherapy.     

Contrast media in echography]

In medical US, the use of specific contrast media to increase the echogenicity of structures and organs changes their absorption of the US beam, and modifies the through-transmission velocity. This can be of great diagnostic value. Contrast media can help depict vessels and cavities, increase the sensitivity of Doppler examination, and make the differentiation of normal and pathologic tissues easier. The products which are currently available do not completely fulfill the needs of clinical researchers. The first papers reporting on some clinical applications of these contrast media in humans are now appearing in literature. Contrast media for diagnostic US can be classified in five groups: 1) free gas bubbles; 2) stabilized gas bubbles; 3) colloidal suspensions; 4) emulsions; 5) aqueous solutions. These agents are quite different, as to both chemical and physical features and distribution within living tissues. Different clinical applications are thus possible for each of them; a unique contrast medium which will meet all the needs of the various clinical situations seems inconceivable at present. Most probably, a variety of products will develop, each with its own application field; in clinical practice, it seems likely that different products will be used, according to the specific clinical needs.     

Contrast media: future aspects

In spite of the dramatic development in CT, there was no major breakthrough in the iodinated contrast media development. New agents based on hybrid between MRI and CT compounds may be a new innovative alternative. This new approach may also open new indications such as radiotherapy.     

Contrast media in hepatic MRI]

This article is a review of the current commercial MR contrast media (gadolinium chelates) and of the products that are not yet on the market and are under trial in man (super-magnetic iron oxides, manganese compounds) or only in animals (ferric chelate, liposomes containing gadolinium compounds, gadolinium chelate/human serum albumin compounds, hepatic asialoglycoprotein receptors).     

Contrast media as markers of GFR

Determination of the glomerular filtration rate (GFR) is generally considered as the most important parameter of quantifying renal function. The GFR is determined as renal or plasma clearance of an ideal filtration marker which is freely filtered by the kidney, does not undergo metabolism, tubular secretion or absorption. Markers that fulfil these demands are inulin, 51Cr-EDTA, 99mTc-DTPA, labelled or unlabelled contrast media. The renal clearance of inulin is the classic reference method for estimation of the GFR. This method is however not practical for routine clinical purposes. Radionucleids have therefore been used as alternative filtration markers since the 60s. Drawbacks related to radiation exposure especially in children and pregnant women and the safety in handling radiolabelled markers have led to an increasing interest in using non-radioactive markers. The development of simple and reliable methods to determine the concentration of contrast media in plasma and urine, such as high-performance liquid chromatography (HPLC) and X-ray fluorescence analysis have made this possible. The non-ionic low osmolar contrast medium iohexol has become the most commonly used contrast medium for GFR measurements in Europe. However, other contrast media with similar pharmacokinetics may be equally suitable as GFR markers.