In vivo carotid plaque MRI using quantitative T2* measurements with ultrasmall superparamagnetic XXXX particles: a dose-response study to statin therapy.

@entity1 @entity2993 @entity1933
This study investigates T(2)* quantification in carotid plaques before and after the administration of ultrasmall superparamagnetic @entity1933 particles (USPIOs) in a cohort of @entity1 receiving statin therapy. Phantom studies were performed using gels with varying concentrations of USPIOs. In the phantom study, 12 gels were prepared with a range of freely distributed concentrations of USPIO nanoparticles (0-0.05   mg/mL). Relative signal intensity measurements were obtained from a T(2)*-weighted sequence as well as quantitative T(2)* (qT(2)*) measurements. In the @entity1 study, 40 @entity1 with >40% carotid stenosis were randomised to low- and high-dose statin therapy (10 and 80   mg of @entity2993 ). Pre- and post- (36   h) USPIO-enhanced MRI were performed at baseline, and at 6 and 12 weeks. A linear mixed-effects model was applied to account for the inherent correlation of multiple-plaque measurements from the same @entity1 and to assess dose-response differences to statin therapy. In the phantom study, the T(2)*-weighted sequence demonstrated an initial increase (T(1) effect), followed by a decrease (T(2)* effect), in relative signal intensity with increasing concentrations of USPIO. The qT(2)* values decreased exponentially with increasing concentrations of USPIO. In the @entity1 study, there was a highly significant difference in post-USPIO T(2)* measurements in plaques between the low- and high-dose statin groups. This was observed for both the difference in qT(2)* measurements (post-USPIO minus pre-USPIO) (p   <   0.001) and for qT(2)* post-USPIO only (p   <   0.001). The post-USPIO qT(2)* values were as follows: baseline: low dose, 13.6        5.5   ms; high dose, 12.9        6.2   ms; 6 weeks: low dose, 13.3        6.7   ms; high dose, 14.3        7.7   ms; 12 weeks: low dose, 14.0        7.6   ms; high dose, 18.3        11.2   ms. It can be concluded that qT(2)* measurements provide an alternative method of quantifying USPIO uptake. These results also demonstrate that changes in USPIO uptake can be measured using post-USPIO imaging only.
