Lipid-rich atherosclerotic plaques detected by gadofluorine-enhanced in vivo magnetic resonance imaging

BACKGROUND

MRI of specific components in atherosclerotic plaque may provide information on plaque stability and its potential to rupture. We evaluated gadofluorine in atherosclerotic rabbits using a new MR sequence that allows plaque detection within 1 hour after injection and assessed enhancement in lipid-rich and non-lipid-rich plaques.

METHODS AND RESULTS

Twelve rabbits with aortic plaque and 6 controls underwent MRI before and up to 24 hours after gadofluorine injection (50 micromol/kg). Two T1-weighted, segmented gradient-echo sequences (TFL) were compared to enhance vessel wall delineation after injection: (1) an inversion-recovery prepulse (IR-TFL) or (2) a combination of inversion-recovery and diffusion-based flow suppression prepulses (IR-DIFF-TFL). With the use of IR-TFL at 1 hour after injection, the vessel wall was not delineated because of poor flow suppression; at 24 hours after injection, the enhancement was 37% (P<0.01). IR-DIFF-TFL showed significant enhancement after versus before contrast (1 hour: 164% [P<0.005]; 24 hours: 207% [P<0.001]). At 1 hour and 24 hours after injection, the contrast-to-noise ratio was higher with the use of IR-DIFF-TFL than with IR-TFL (1 hour: 13.0+/-7.7 versus -19.8+/-10.3 [P<0.001]; 24 hours: 15.2+/-5.9 versus 11.4+/-8.9, respectively [P=0.052]). There was no enhancement in the vessel wall after gadofluorine injection in the control group. A strong correlation was found (r2=0.87; P<0.001) between the lipid-rich areas in histological sections and signal intensity in corresponding MR images. This suggests a high affinity of gadofluorine for lipid-rich plaques.

CONCLUSIONS

Gadofluorine-enhanced MRI improves atherosclerotic plaque detection. The IR-DIFF-TFL method allows early detection of atherosclerotic plaque within 1 hour after gadofluorine injection.