We used SPSS for Windows software (SPSS Japan, Tokyo, Japan) for statistical analysis. Differences in the uptake of D-and DM-USPIO in the arterial wall, in the uptake of iron by cultured macrophages, and in the SNR values from MRA scans obtained in vivo and in vitro were determined using the one-tailed Student's t-test. A P-value of P , 0.05 was considered statistically significant.