Introduction to supplement: "Update to contrast media use and good practice"

Advances in medical technology have radically transformed the way we diagnose and treat diseases. Radiology has become one of the essential tools of modern medicine, making it possible to visualise the interior of the human body without the need for invasive procedures. Within this field, the use of contrast media has played a fundamental role in improving the quality and precision of radiological examinations.

The development of contrast media is closely linked to the progress of radiological techniques. Wilhelm Conrad Röntgen discovered X-rays in 1895, signalling the beginning of radiology. Just a year later, contrast media began to be used to improve the visibility of internal structures in radiological images. In 1896, Dr. Walter Cannon used barium sulfate to visualise the gastrointestinal tract in X-ray studies, laying the groundwork for the use of barium contrast media. In that same year, Eduard Haschek and Otto Lindenthal performed the first arteriogram on an amputated hand by injecting a cinnabar mixture; it was not until 1927 that Egas Moniz and his collaborator Almeida Lima performed the first in vivo cerebral arteriogram.¹

From the 1950s onwards, the use of ionic contrast agents became widespread, but the numerous adverse reactions they caused led to the search for new agents. It was the Swedish radiologist Torsten Almén who was the first to suggest that the intense pain caused by their administration could be related to the hyperosmolarity of these compounds. Consequently, to mitigate these effects, non-ionic contrasts were developed in the 1980s, which are much better tolerated than the previous ones,² and which we continue to use today.

The history of contrast in magnetic resonance imaging (MRI) dates back to the late 1980s, when it was discovered that gadolinium chelates could significantly improve image quality. Despite research into other agents, none have proven to be a viable alternative. In 1988, the first gadolinium-based contrast agent, gadopentetate dimeglumine, was approved for clinical use. Since then, eight additional gadolinium chelates have been developed and approved and have, to date, been the mainstay of intravenous contrast-enhanced MRI. Their use has exceeded expectations, with more than 30 million procedures currently being performed annually. New techniques are opening up interesting possibilities, not only in diagnosis, but also in the monitoring of increasingly specific therapies. This is one of the areas of greatest development, along with research into new contrast agents for MRI.³

In recent decades, research has advanced towards the development of contrast agents based on nanoparticles and microbubbles, especially for ultrasound. These new agents offer significant improvements in image resolution and allow for more specific applications, both for intravenous and endocavitary use.⁴

Research and development in the field of contrast media continues to advance, with the search for new agents that offer greater safety and efficacy, not only for diagnostic imaging, but also with therapeutic potential, especially in the field of oncology.

Emerging areas, such as nanomedicine and artificial intelligence, have the potential to revolutionise the field, improving both diagnostic accuracy and patient safety.⁵

The use of contrast media in radiological examinations is an indispensable tool which has revolutionised the diagnostic and therapeutic capacity of modern medicine. However, its application requires proper management by healthcare professionals, careful selection of subjects and the establishment of protocols that minimise unnecessary exposure.

This monograph, which originated in the online course on contrast media updates organised by our scientific society, the Sociedad Española de Radiología Médica (SERAM) [Spanish Society of Medical Radiology], has been a considerable challenge. Its purpose is to update and provide a comprehensive review of the different contrast media used in current radiological practice. We hope that it will become a useful reference tool for all members of radiology departments. We have selected the topics that generate the most controversy and those presenting the greatest difficulties in day-to-day management.

The series of articles begins with an introduction to iodinated contrasts, explaining their types, physical/chemical properties and their role in image enhancement. Appropriate dosing, timing and enhancement optimisation in visceral and vascular studies, including the use of injection pumps, are discussed below. The use of iodinated contrast in multi-energy equipment is also examined.

The fundamentals of contrast-enhanced ultrasound are explored, addressing the pharmacodynamics and pharmacokinetics, and its clinical utility. Gadolinium-based contrast agents and their extracellular distribution are discussed in detail, covering physical/chemical characteristics, modes of administration and new trends in their qualitative and quantitative analysis. Intestinal contrast techniques in MRI are also analysed. In addition, we also address adverse reactions to contrasts and their management, the safety of contrast media from the perspective of nursing staff, nephroprotection in the use of iodinated contrasts and, lastly, the responsibility of the radiologist in the management of contrasts, including informed consent and other issues.

Funding

This study received no specific grants from public agencies, the commercial sector or non-profit organisations.

Conflicts of interest

The authors declare that they have no conflicts of interest.