Contrast agent

Before addressing the title question regarding safety, it’s important to understand what a contrast agent does during MRI prostate imaging. Multiparametric MRI (mpMRI) of the prostate relies on two or more imaging sequences, or parameters, each of which depicts certain tissue characteristics that the others do not. When the results are synchronized, we arrive at an integrated 3-dimensional portrait of a man’s prostate gland that reveals differences between normal and abnormal structures. Thus, we can identify prostate cancer (PCa), benign prostatic hyperplasia (BPH), and inflammation or infection.

One of the MRI sequences is Dynamic Contrast Enhancement (DCE) that requires a contrast agent. This is a specially formulated substance that is intravenously (IV) injected so it travels through the bloodstream. This reveals blood flow in clusters of small blood vessels, in contrast to surrounding areas. This is important, because PCa tumors develop their own blood supply to feed oxygen and nourishment to the self-reproducing cancer cells. The larger and more aggressive the tumor, the more visible its blood supply due to the contrast agent.

What DCE does, therefore, is provide key supplemental information that helps define tumor aggression.

How safe is the contrast agent?

The standard contrast agent used for spotlighting blood flow in areas like the brain, heart or prostate uses an element called gadolinium. Because of its magnetic properties, “Most MRI contrast agents are chelates of the rare-earth element gadolinium and produce an increased signal (‘positive contrast’) on T1-weighted images…”^[i] This increased signal intensity is what highlights blood flow.

Chelates (pronounced key-lates) are gadolinium atoms bonded to molecules that keep gadolinium from toxic interaction with other molecules in the body, and make it water-soluble so the body can flush it out. Chelation thus makes it safe to use gadolinium. There are two kinds of gadolinium chelation: linear and macrocyclic. See my earlier blog for a more detailed explanation.

We have known for some time that macrocyclic chelation is the safest type. However, when a 2013 published study reported trace deposits of gadolinium in the body, particularly in the brain, fear of long-term harm called gadolinium safety into question. It turned out that linear chelation was the primary source of such deposits, and subsequent studies have supported the use of macrocyclic chelation.

New report dispels fear

At the May, 2021 virtual meeting of the International Society for Magnetic Resonance in Medicine (ISMRM) and Society for MR Radiographers & Technologists (SMRT), Dr. Alexander Radbruch of Bonn University (Germany) presented findings from numerous human and animal studies showing that macrocyclic-based gadolinium agents do not build up in the brain.^[ii] He stated that research consistently pointed the finger at linear chelations as the source of trace accumulations in the brain. These build-ups appear to flush out over time, but the clinical implications of their presence are not yet known.

Not only is there no hard evidence that macrocyclic chelation is to blame for deposits in the brain, Dr. Radbruch took his safety conclusions one step further. His own research studies involve the use of macrocyclic gadolinium in a “new kind of imaging that looks at vessels carrying waste out of the brain.”^[iii]

At the Sperling Prostate Center, we have long known about the difference between the two chelations of gadolinium, and we exclusively use only the safest agents, those that are macrocyclic-based. A final note: gadolinium contrast is not indicated for patients with impaired kidney function, since the kidneys are the chief organs for flushing foreign substances from the body. However, when indicated, our use of imaging parameters that do not involve contrast is a standard of care. Thanks to our pioneering knowledge and experienced team, we are among top U.S. authorities in detecting and diagnosing PCa without DCE, when necessary. Patient safety is always a first and foremost principle in our professional ethics.

For more information on gadolinium-based contrast for prostate mpMRI, or for any questions about mpMRI for the prostate, contact our Center.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

References

[i] Ibrahim MA, Hazhirkarzar B, Dublin A. Gadolinium magnetic resonance imaging. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan. 2020 Jul 10.
[ii] Allegretto, Amerigo. “Macrocyclic gadolinium contrast not to blame for brain deposits.” AuntMinnie.com, May 18, 2021. https://www.auntminnie.com/index.aspx?sec=ser&sub=def&pag=dis&ItemID=132424
[iii] Ibid.