Repeat and single dose administration of gadodiamide to rats to investigate concentration and location of gadolinium and the cell ultrastructure

Gadolinium based contrast agents (GBCA) are used to image patients using magnetic resonance (MR) imaging. In recent years, there has been controversy around gadolinium retention after GBCA administration. We sought to evaluate the potential toxicity of gadolinium in the rat brain up to 1-year after repeated gadodiamide dosing and tissue retention kinetics after a single administration. Histopathological and ultrastructural transmission electron microscopy (TEM) analysis revealed no findings in rats administered a cumulative dose of 12 mmol/kg. TEM-energy dispersive X-ray spectroscopy (TEM-EDS) localization of gadolinium in the deep cerebellar nuclei showed ~ 100 nm electron-dense foci in the basal lamina of the vasculature. Laser ablation-ICP-MS (LA-ICP-MS) showed diffuse gadolinium throughout the brain but concentrated in perivascular foci of the DCN and globus pallidus with no observable tissue injury or ultrastructural changes. A single dose of gadodiamide (0.6 mmol/kg) resulted in rapid cerebrospinal fluid (CSF) and blood clearance. Twenty-weeks post administration gadolinium concentrations in brain regions was reduced by 16-72-fold and in the kidney (210-fold), testes (194-fold) skin (44-fold), liver (42-fold), femur (6-fold) and lung (64-fold). Our findings suggest that gadolinium does not lead to histopathological or ultrastructural changes in the brain and demonstrate in detail the kinetics of a human equivalent dose over time in a pre-clinical model.

Extensive cerebrospinal fluid enhancement following gadolinium chelate administration: possible pathogenesis

Diffuse cerebrospinal fluid (CSF) enhancement following gadolinium administration is a rarely recognized phenomenon, and its mechanism is not fully understood. We report two cases of diffuse CSF enhancement following gadolinium administration and review the literature. We conclude that the contributing factors of this phenomenon include blood-CSF barrier disruption, increased dosage, impair renal clearance, delayed imaging after contrast administration, and use of different pulse sequences.

In vivo observation of dynamic perilymph formation using 4.7 T MRI with gadolinium as a tracer

OBJECTIVE

To investigate the pharmacokinetics of gadolinium in the perilymphatic fluid spaces of the cochlea in vivo using high-resolution MRI to obtain information concerning perilymph formation.

MATERIAL AND METHODS

A Bruker Biospec Avance 47/40 experimental MRI system with a magnetic field strength of 4.7 T was used. Anesthetized pigmented guinea pigs were injected with the contrast agent Gd-diethylenetriaminepentaacetic acid-bismethylamide and placed in the magnet. The signal intensity of Gd in the tissues was used as a biomarker for dynamic changes in the perilymphatic fluid.

RESULTS

The most rapid uptake of Gd in the perilymphatic fluid spaces occurred in the lower part of the modiolus, followed by the second turn of the scala tympani. Within the scala tympani, the distribution of Gd in the basal turn was significantly lower than that in the other turns. Destruction of the cochlear aqueduct was followed by an increase in Gd uptake in the perilymph instead of a reduction.

CONCLUSIONS

These findings offer further evidence that the pervasive perilymphatic fluid derives from the cochlear blood supply via the cochlear glomeruli, which are in close proximity to the scala tympani within the modiolus, and the capillary in the spiral ligament. Cerebrospinal fluid communicates with perilymph via the cochlear aqueduct but is not the main source of perilymph. These findings are of relevance to the treatment of inner ear diseases, as well as to our understanding of the flow and source of perilymphatic fluid.