Nuclear localization of
gadolinium deposits

Gadolinium retention may be more widespread than previously thought

June 28, 2017
by Lauren Dubinsky, Senior Reporter
A new study published in Radiology revealed that gadolinium retention might be more widespread than previously thought.

Gadolinium contrast agents are used in 40 to 50 percent of MR scans performed today, according to Dr. Robert J. McDonald of the Mayo Clinic. Approximately 400 million doses of gadolinium have been administered since it was introduced in 1988.

In late 2014, evidence emerged that gadolinium was depositing within brain tissues. But many of those patients had underlying medical conditions like brain tumors or infections that can compromise the blood brain barrier.

McDonald and his team questioned whether the gadolinium deposition was related to the integrity of the blood-brain barrier, so they studied patients with normal brain pathology.

The team evaluated postmortem neuronal tissue samples from five patients who underwent four or more gadolinium-enhanced MR exams between 2005 and 2015, and 10 patients who underwent MR exams without the contrast agent.

The median age at the time of death was 68 years in the gadolinium-exposed group and 79 years in the control group. At the time of autopsy, all study patients had normal brain pathology.

The tissue samples were studied with transmission electron microscopy, mass spectroscopy and X-ray spectroscopy. They found dose-dependent gadolinium deposits in four neuroanatomical regions of the brain, in patients who underwent control-enhanced MR exams.

“Our results suggest current thinking with regard to the permeability of the blood-brain barrier is greatly oversimplified, as gadolinium appears to accumulate even among patients with normal brain tissue and no history of intracranial pathology.” McDonald said in a statement.

The regions of the brain that retained more gadolinium were the globus pallidus and dentate nucleus. Those regions are prone to mineralization and hemorrhage, which means the blood brain barrier may be less robust in those areas.

Free gadolinium is also similar in size and charge to calcium, which is often taken up in areas of the brain during the aging process. The body may be mistaking the contrast agent for calcium.

But McDonald notes that more research is needed to understand exactly how and why this deposition is occurring.

The good news is that the researchers didn't detect any histologic changes that suggest toxicity in patients who were exposed to gadolinium.

To support that, the FDA announced, in July 2015, that it has found no convincing evidence to date that gadolinium deposition is harmful. But the agency will continue to further investigate this matter.