Diffusion Tensor Imaging of the Dentate Nucleus After Repeated Administration of Gadobutrol in Children

This study aimed to investigate possible signal changes in the dentate nucleus (DN) on diffusion tensor imaging (DTI) after administration of gadobutrol in a pediatric cohort. Total of 50 pediatric patients (mean age: 6.2 ± 4.3 years) with normal renal function exposed exclusively to the macrocyclic GBCA (mcGBCA) gadobutrol and 50 age- and sex-matched control patients with nonpathological neuroimaging findings (and no GBCA administration). Mean diffusivity (MD) and fractional anisotropy (FA) values were determined in the DN. A paired t test was performed to compare FA, MD values, and DN-to-middle cerebral peduncle (MCP) T1WI SI ratios between children exposed to gadobutrol and controls. Pearson correlation analysis was conducted to determine any correlation between FA and MD values as well as T1WI SI ratios and confounding parameters. The mean FA values of DN was significantly lower in children with mcGBCA than in the control group (p < 0.001; non-GBCA group, 0.299 ± 0.03; mcGBCA group, 0.254 ± 0.05), but no significant difference of the T1WI SI ratio was noted between the mcGBCA group (0.946 ± 0.06) and the control group (0.963 ± 0.05; p = 0.336). There was also a significant MD value difference between mcGBCA group and control group (p < 0.001; non-GBCA group, 0.152 ± 0.02 × 10^-3 mm²/s; mcGBCA group, 0.173 ± 0.03 × 10^-3 mm²/s). A significant correlation was identified between FA/MD values and the number of mcGBCA administration (FA; correlation coefficient =  - 0.355, p = 0.011 and MD; correlation coefficient = 0.334, p = 0.018). The administration of the gadobutrol was associated with higher MD and lower FA values in DN suggesting a difference in cerebellar tissue integrity between children exposed to mcGBCAs and control group.

The Macrocyclic Gadolinium-Based Contrast Agents Gadobutrol and Gadoteridol Show Similar Elimination Kinetics From the Brain After Repeated Intravenous Injections in Rabbits

MATERIALS AND METHODS

Male white New Zealand rabbits (2.4-3.1 kg) in 2 study groups (n = 21 each) received 3 injections of either gadobutrol or gadoteridol at 0.9 mmol Gd/kg within 5 days (total dose, 2.7 mmol Gd/kg). Animals in one control group (n = 9) received 3 injections of saline (1.8 mL/kg). After 2, 6, and 12 weeks, 7 animals from each study group and 3 from the control group were killed and the Gd concentrations in the cerebellum, cerebrum, in blood and in urine were determined by inductively coupled plasma mass spectrometry. The chemical species of excreted Gd in urine were determined by high pressure liquid chromatography.

RESULTS

No significant (P > 0.05) differences in the Gd concentrations in the brain of rabbits were observed between the 2 macrocyclic GBCAs gadoteridol and gadobutrol at all time points. In the gadobutrol group, the mean Gd concentrations in the cerebellum and cerebrum decreased from 0.26 and 0.21 nmol Gd/g after 2 weeks, to 0.040 and 0.027 nmol Gd/g after 12 weeks, respectively, and in the gadoteridol group, from 0.25 and 0.21, to 0.037 and 0.023 nmol Gd/g, respectively. The plasma levels decreased from 0.11 and 0.13 nmol Gd/mL at 2 weeks for gadobutrol and gadoteridol to below the limit of quantification (<0.005 nmol Gd/mL) at 12 weeks. The urine concentration dropped in a biphasic course from 2 to 6 and from 6 to 12 weeks for both agents. The Gd excreted after 12 weeks was still present in the urine in the chemical form of the intact Gd complex for both agents.

CONCLUSIONS

Contrary to what had been reported in rats, no significant differences in the elimination kinetics from brain tissue in rabbits were observed after intravenous injection of multiple doses of the macrocyclic GBCAs gadobutrol and gadoteridol.

Effect of at Least 10 Serial Gadobutrol Administrations on Brain Signal Intensity Ratios on T1-Weighted MRI in Children: A Matched Case-Control Study

BACKGROUND. An association is recognized between linear gadolinium-based contrast agents (GBCAs) and intracranial gadolinium retention in children. The relation between macrocyclic GBCAs and gadolinium retention remains incompletely understood. OBJECTIVE. The purpose of this study was to assess whether 10 or more administrations of the macrocyclic GBCA gadobutrol are associated with increased signal intensity (SI) in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted MRI of children and to explore clinical variables potentially associated with T1 hyperintensity. METHODS. The case group consisted of 25 children (13 boys, 12 girls; mean age, 7 ± 4 years; range, 2-18 years) who underwent at least 10 (mean, 15 ± 6; range, 10-34) contrast-enhanced MRI examinations exclusively with gadobutrol. The control group consisted of 25 age- and sex-matched patients undergoing MRI who had never been exposed to gadolinium. Two observers in consensus using a 3-point scale assessed visual T1 hyperintensity in the DN and GP. One observer placed ROIs on T1-weighted images to mark the DN, GP, middle cerebellar peduncle (MCP), and pulvinar of the thalamus bilaterally to compute mean DN-to-MCP and GP-to-thalamus SI ratios. SI ratios were compared between the macrocyclic GBCA and control groups. In the macrocyclic GBCA group, Pearson correlation analysis was conducted between SI ratios and clinical variables. ROI measurements were repeated by the original reader and an independent reader, and interobserver and intraobserver agreement were computed by means of Lin concordance correlation coefficient (ρ_c). RESULTS. No patient had visual T1 hyperintensity in the DN or GP. No significant difference between the macrocyclic GBCA and control groups was observed for DN-to-MCP SI ratio (0.95 ± 0.05 vs 0.95 ± 0.03; p = .67) or GP-to-thalamus SI ratio (1.05 ± 0.06 vs 1.04 ± 0.06; p = .65). In the macrocyclic GBCA group, no significant correlation was observed between DN-to-MCP SI ratio or GP-to-thalamus SI ratio and age (r = 0.355, p = .08; r = 0.167, p = .42), number of contrast-enhanced MRI examinations (r = 0.247, p = .23; r = 0.203, p = .33), mean time between examinations (r = 0.193, p = .36; r = 0.047, p = .82), or cumulative macrocyclic GBCA dose (r = 0.434, p = .07; r = 0.270, p = .19). Interobserver and intraobserver agreement was substantial for DN-to-MCP SI and GP-to-TH SI ratios (ρ_c = 0.931-0.974). CONCLUSION. Ten or more serial gadobutrol administrations were not associated with T1 hyperintensity in the DN or GP of children. CLINICAL IMPACT. Selection of gadobutrol as an MRI contrast agent may reduce risk of gadolinium retention in children. The findings may help guide practices for GBCA administration to children.

[Increased signal intensities and gadolinium levels in the brain after administration of gadolinium-based MR contrast agents : Clinical observations and results from preclinical research]

BACKGROUND

Numerous clinical MRI studies have been published that describe an association between the repeated administration of (linear) gadolinium-based contrast agents and increased signal intensity in certain brain areas. In November 2017, the European Commission suspended the use of some of these contrast agents.

OBJECTIVES

The background for this decision, both regulatory and scientific, are presented and discussed.

MATERIALS AND METHODS

The regulatory decisions are evaluated and the clinical and preclinical literature is discussed.

RESULTS

Differences in the structure and stability of gadolinium-based contrast agent molecules explain the observed increased signal intensities in individual brain regions (e. g. dentate nucleus) after administration of multiple doses of linear contrast agents. This phenomenon was not observed after administration of multiple doses of macrocyclic contrast agents. Preclinical studies have confirmed these results.

CONCLUSION

To date, no clinical symptoms have been confirmed to be associated with the increased signal intensity or gadolinium presence in the brain.