[Comparison of contrast resolution between dynamic MRI and dynamic CT in liver scanning]

Dynamic studies employing contrast agents have been used in the detection of hepatocellular carcinoma (HCC). Some studies have indicated that the detectability of small nodules in liver is significantly better with MRI dynamic study than with CT dynamic study. However, the reasons for this are unclear. In an attempt to clarify this difference, we compared contrast resolution using two contrast phantoms made for MRI and CT. Both phantoms were constructed using the same ratios of dilution of the contrast materials Gd-DTPA and iodine. The signal intensity of different dilution ratios of contrast medium were measured in order to compare the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and contrast. The results showed that the contrast of phantoms in MRI and CT dynamic studies was almost the same except for certain MRI scan techniques. In terms of SNR and CNR, MRI dynamic study was superior to CT dynamic study. In addition, T(1) relaxation of the contrast agent should be considered for suitable scanning, because the contrast of MRI was affected by scan parameters.