Gadolinium-based contrast agents (GBCAs) have shown up as bright signals, or “hyperintensities,” in T1-weighted MR brain images of patients with no such contrast administered at present but 35 or more linear GBCA doses in the past.
Reporting the finding online Aug. 11 in Radiology, corresponding study author Martin Prince, MD, PhD, and colleagues at Weil Cornell describe their observations of the effect turning up in numerous brain structures upon review of PACS data on 13 brain-tumor patients at two tertiary referral hospitals.
The team reports that patients with a history of 39 to 59 linear GBCA-enhanced MR scans showed signal intensity increases on unenhanced T1-weighted images in the posterior thalamus (pulvinar), substantia nigra, red nucleus, cerebellar peduncle, colliculi, dentate nucleus and globus pallidus.
The dentate nucleus had the greatest signal intensity increase, 0.53 percent per injection—close to twice as much as the other structures.
“This shows that the constellation of brain signal intensity increases on unenhanced T1-weighted images can be more extensive than previously reported,” the authors write in their discussion.
They note that prior studies looking at gadolinium-related signal intensity increases on unenhanced T1-weighted images did not find intensities in the substantia nigra, red nucleus, posterior thalamus, cerebellar peduncle or colliculi.
“This likely reflects the smaller mean number of GBCA administrations in those studies, approximately 15 or fewer, compared with the number of GBCA administrations in our cohort,” they write.
The detection of gadolinium in so many locations “challenges our understanding of GBCA biodistribution since the blood-brain barrier has been thought to prevent the GBCA from entering the brain parenchyma,” write Prince and colleagues.
They point out that, in their cohort, all patients had brain tumors.
“This was a confounding variable, but there was no significant difference between signal intensity changes ipsilateral to the tumors versus those contralateral to the tumors,” they write. “This suggests that the blood-brain barrier breakdown associated with brain tumors does not confer any greater GBCA accumulation in nearby tissues.”
Along with the small sample size, the authors acknowledge as a study limitation the lack of data available for quantitative analysis in two of the 13 patients.
“As in the dentate nucleus and globus pallidus, when increased signal intensity is observed in the posterior thalamus, substantia nigra, red nucleus, cerebellar peduncles, or colliculi on unenhanced T1-weighted images,” they conclude, “one should consider the possibility that this is related to multiple prior administrations of a linear GBCA.”
Last month the American College of Radiology updated its guidelines on the use of contrast media, underscoring ongoing concerns over gadolinium.