MRI of liver: a comparison of CNR enhancement using high dose and low dose ferumoxide infusion in patients with colorectal liver metastases.

The purpose of this study was to compare the effects of high dose (HD) and low dose (LD) ferumoxides infusions on lesion-to-liver contrast-to-noise ratio (CNR) using four different T(2)-weighted MR sequences. Seventy-three patients with known colorectal liver metastases underwent T(2)-weighted fast spin echo (FSE) imaging before and after ferumoxides. After ferumoxides, T(2)-weighted dual echo (DE) and T(2)-weighted GRE FLASH images were also obtained. To evaluate the relationship between TE length and lesion-to-liver CNR, the same FLASH sequence was repeated in 18 LD patients after lengthening the TE. Ferumoxides was administered at a dose of 15 micromol/kg (HD) and 7.5 micromol/kg (LD) in 45 and 28 patients, respectively. The effects of HD and LD ferumoxides infusions were measured as the percentage signal intensity change (PSIC) in the liver and lesions, lesion-to-liver CNR and the change in lesion-to-liver CNR (DeltaCNR). In both LD and HD groups, all CNR values obtained after SPIO were significantly greater than those observed with unenhanced FSE (p < 0.01). There was no significant difference between the mean CNR values obtained with either dose for any sequence. With the FLASH sequence, CNR increased progressively with longer TE. At the longest TE of 26 ms, mean CNR was higher than that recorded with any of the other sequences. Although mean liver PSIC was significantly greater in the HD group than in the LD group (p < 0.01) because the mean lesion PSIC was also greater in the HD group, the mean DeltaCNR after ferumoxides was not significantly different in the two groups. LD SPIO enhanced MR significantly increases lesion-to-liver CNR compared with unenhanced images. At 1. 0 T, HD and LD ferumoxides infusions produce comparable lesion-to-liver CNR. Our results suggest that at 1.0 T ferumoxides may be administered at a dose of 7.5 micromol/kg without loss of image quality.