Signal intensity of lanthanum carbonate on magnetic resonance images: phantom study

Lanthanum carbonate (LC) is used to treat hyperphosphatemia. The purpose of this study was to investigate the signal intensity (SI) of LC on magnetic resonance imaging (MRI) scans of phantoms.

LC tablets were thoroughly ground and mixed with distilled water or edible agar (0.05, 0.25, 0.5, and 2.5 mg/ml) in plastic bottles. Four intact tablets were placed in plastic bottles that did or did not contain distilled water or agar. Two radiologists consensually evaluated T1- and T2-weighted images (WIs) obtained with 1.5- and 3.0-T MRI systems for the SI of unground and ground tablets.

On T1- and T2WI, the SIs of the LC suspensions and the solvents alone were similar; the SIs of unground tablets alone and of the air were also similar. Unground tablets in phantoms filled with solvent exhibited lower SI than the solvent. Ground tablets in suspension were not visualized on MRI or computed tomography. These results remained unchanged regardless of differences in magnetic field strength or the solvent used.

Ground LC had no contrast enhancement effect on T1WI; on T2WI it did not affect the SI of the solvent. Unground LC tablets may be visualized as a "filling defect" on MRI.