Magnetic resonance imaging of an experimental model of intracranial metastatic disease. A study of lesion detectability

Abstract

Rationale and objectives: The detectability of brain metastases was evaluated in a rabbit model, with attention to magnetic resonance contrast dose and timing of image acquisition after injection of contrast medium.

Methods: Five New Zealand white rabbits were studied at 1.5 T 6 to 7 days and 11 to 12 days after surgical implantation of an adenocarcinoma tumor nidus. T1- and T2-weighted spin-echo images (0.9 x 0.9 x 2 mm3 voxel size) were obtained before administration of contrast medium. T1-weighted images were repeated 5, 15, and 30 minutes after intravenous injection of 0.1 mmol/kg gadoteridol. At 40 minutes, a supplemental dose of 0.2 mmol/kg (0.3 mmol/kg cumulative dose) was administered, with T1-weighted images repeated at 5, 15, and 30 minutes after the second injection.

Results: Six to 7 days after tumor implantation, lesion enhancement (percent change, with normalization to baseline and equilibrium values) was 42 +/- 9% at 5 minutes, 48 +/- 9% at 15 minutes, and 42 +/- 10% at 30 minutes after administration of 0.1 mmol/kg gadoteridol. After administration of 0.3 mmol/kg gadoteridol, lesion enhancement was 111 +/- 13% at 5 minutes, 116 +/- 8% at 15 minutes, and 100% at 30 minutes. On film review, 2 of 5 lesions were not detectable at 6 to 7 days after tumor implantation with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol provided for lesion identification in each instance. Eleven to 12 days after tumor implantation, one lesion was not detectable with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol again provided for lesion identification in all cases. Mean lesion enhancement increased from 39 +/- 15% to 104 +/- 10%.

Conclusions: The administration of 0.3 mmol/kg gadoteridol (high dose) compared with 0.1 mmol/kg gadoteridol (conventional dose) improves metastatic lesion detectability in the brain. The lesions identified only at high dose were confirmed by histopathology. Smaller lesions were not detected at a dose of 0.1 mmol/kg.