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Contrast Agent Protocol


Joseph Cavallo, MD, MBA, and Dushyant Sahani, MD, provide an overview of the different imaging technique protocols needed for contrast agents.

Joseph Cavallo, MD, MBA: You mentioned some organ-specific imaging that is very reliant on contrast in the emergency department [ED]. Specifically, there are multiple exams that would not be possible without contrast. Namely, evaluation for pulmonary embolism and a lot of our stroke-centered, arterial cerebral imaging, just to name 2 quick examples. Going further into the contrast agents, have you noticed variations between the different agents, whether it’s different formulations of iodine-containing computed tomography [CT] contrast or gadolinium-containing MRI [magnetic resonance imaging] contrast?

Dushyant Sahani, MD: That’s a great question. I would say there are differences in the formulation of contrast media and those differences come down to the pharmacokinetic, the distribution of the contrast media, their excretion pattern, and their intended target organs and safety profile. In general, I think there are differences even in CT contrast media where iodine is the main molecule, and it has been the main molecule for CT contrast media. We have seen different formulations and I feel, overall, when it comes to diagnostic performance—when you compare apples to apples in terms of the concentration of the contrast media, the iodine dose, and how you deliver the contrast media in terms of the protocol—they are pretty comparable. There might be differences in the safety profile of those contrast media, but in general, if you take all FDA-approved contrast media, they have a pretty robust safety profile. There might be differences between the different formulations of contrast media, and [the safety profile] might be exacerbated a little in patients who have inherent risk or fragile organs, [such as] liver injury, kidney disease, or [any] additional risk factors. They might have more differences [in] safety events in those patients. In summary, I would say there are a lot of similarities in terms of performance and safety profile, but there are also differences.

Joseph Cavallo, MD, MBA: In my experience, it’s not so much the agent that I’ve seen produce variation between imaging but more the physiology of the patient, or the specific delivery protocol, as you were talking about. Patients with heart failure or pregnant patients, for example, will often have some altered hemodynamics that can change the quality of the contrast enhancement. Those are usually more patient-inherent factors than something to do with the specific contrast formulation, as you mentioned.

Dushyant Sahani, MD: That’s a really accurate statement, If you look at outpatient imaging where the differences are not as much between patient types, the risk profile or the safety profile of contrast media is overall pretty comparable. Fortunately, [it is] rare to encounter any major serious adverse events with contrast media. I think we need to compliment the scientists who have discovered these agents and worked a lot to ensure they test the safety profile of the contrast media and the companies who have done a lot of trials to ensure [that] by the time the contrast agent is available and approved, it has met those safety and regulatory standards.

I think we are beneficiary of those benefits of the safe and effective contrast media, and I think we [can] extend all those benefits to our providers and patients and feel gratified that we are making a difference to care delivery. Radiologists all over the world are quite busy these days with the volumes, and it speaks a lot about the trust our referring physicians have in our imaging techniques, that…they have tremendous reliance on these imaging techniques for them to make those important decisions. It’s a mixed blessing at times when we are so busy, but we also see that volumes continue to rise. This is the trust of our referring physicians and safety profile of the contrast media. Because if you look at CT and MRI, I would say majority—when I say majority of exams for cardiovascular imaging, ED oncology imaging are done with using contrast media and [positron emission tomography] CT. Of course, it makes total sense. If the tracer is applied without that, you cannot do it. I would say 70% to 80% of exam would be not as effective if we did not use these good contrast media that we have available in the arsenal.

Joseph Cavallo, MD, MBA: Some of that safety comes from continued drug development and better formulations that have been introduced over the years. For example, with iodinated contrast, the early agents were very high in osmolality, and now we’re predominantly using low-osmolality agents that are only 2 to 3 times the osmolality of blood. We even have isotonic agents at this point.

Transcript is AI-generated and edited for clarity and readability.

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