Evaluation of a Gadolinium-Based Nanoparticle (AGuIX) for Contrast-Enhanced MRI of the Liver in a Rat Model of Hepatic Colorectal Cancer Metastases at 9.4 Tesla

Purpose: The aim of this study was to compare a Gd-based nanoparticle (AGuIX) with a standard extracellular Gd-based contrast agent (Gd-DOTA) for MRI at 9.4 T in rats with hepatic colorectal cancer metastases. Materials and Methods: 12 rats with hepatic metastases were subjected to MRI using a 9.4 T animal scanner. T1w self-gated FLASH sequences (TR/TE = 45/2.5ms, alpha = 45 degrees, TA = 1:23 min, FOV = 5.12 x 5.12 cm(2), matrix = 256 x 256) were acquired before and at 10 time points after contrast injection. Each animal received 0.1 mmol/kg BW Gd-DOTA i.v. 2 days later AGuIX was applied at 0.01 mmol/kg BW(representing equal Gd doses). The SNR of normal liver (SNRliver), hyper- and hypoenhancing parts of tumors (SNRtumor, hyperenh/SNRtumor, hypoenhanc), erector spinae muscle (SNRmuscle), CNR and lesion enhancement (LE) were calculated based on ROI measurements. Results: Mean SNRliver (Gd-DOTA: 14.6+/-0.7; AGuIX: 28.2+/-2.6, p < 0.001), SNRtumor, hyperenhanc (Gd-DOTA: 18.6+/-1.2; AGuIX: 29.6+/-2.8, p < 0.001), SNRtumor, hypoenhanc (GdDOTA: 12.0+/-0.7; AGuIX: 15.4+/-0.7, p < 0.001), SNRmuscle (Gd-DOTA: 12.3+/-0.3; AGuIX: 14.0+/-0.7, p < 0.001), mean CNR (Gd-DOTA: -2.5+/-0.2; AGuIX: -7.5+/-1.0, p < 0.001) and LE (GdDOTA: 3.8+/-0.7; AGuIX: 14.9+/-2.8, p = 0.001) were significantly higher using AGuIX. Regardless of the larger molecular size, AGuIX demonstrates an early peak enhancement followed by a continuous washout. Conclusion: AGuIX provides better enhancement at 9.4 T compared to Gd-DOTA for equal doses of applied Gd. This is based on the molecule structure and the subsequent increased interaction with protons leading to a higher relaxivity. AGuIX potentially ameliorates the conspicuity of focal liver lesions and may improve the sensitivity in diagnostic imaging of malignant hepatic tumors.