ABSTRACT. This study compared the efficacy of gadoxetic acid-enhanced MRI and gadopentetate dimeglumine-enhanced MRI in the detection of small hepatocellular carcinoma (HCC). Both MRI techniques were performed on 43 patients with a total of 59 HCCs (size range, 0.5-2.0 cm), with a mean interval between the two MRI studies of 3 days (range, 2-7 days). Two observers reviewed both data sets in consensus. Diagnostic accuracy and sensitivity were evaluated using the alternative-free response receiver operator characteristic (ROC) method. The gadoxetic acid set showed a trend toward increased area under the ROC curve (Az value50.958) compared with the gadopentetate dimeglumine set (Az value50.927), but the difference was not significant (p50.362). The sensitivity of the gadoxetic acid set (n551, 86.4%) was significantly higher than that of the gadopentetate dimeglumine set (n538, 64.4%) (p50.0001). Gadoxetic acid-enhanced MRI is a more sensitive diagnostic tool for detection of HCC than gadopentetate dimeglumine-enhanced MRI. Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (gadoxetic acid disodium or Gd-EOB-DTPA) is a recently introduced liver-specific MR contrast agent that has the combined properties of an extracellular space contrast (ECS) agent and a liver-specific agent [1][2][3][4][5][6][7][8]. This combination of gadolinium chelates and superparamagnetic iron oxide particles is considered the most reliable, non-invasive diagnostic MR tool for evaluating hepatocellular carcinoma (HCC), so the dual properties of gadoxetic acid make it a good candidate for the early detection and accurate characterisation of HCC [9][10][11][12]. Gadoxetic acid-enhanced MRI has demonstrated satisfactory results in both the characterisation of lesions during early dynamic phases and the detection of malignancies during the hepatobiliary phase when compared with conventional gadolinium chelate or CT [3][4][5][6]. Although gadoxetic acid MRI has a promisingly high sensitivity for detecting small malignant liver tumours by hepatocyte-phase imaging, it has a theoretical shortcoming in delineating hypervascular HCC during the early vascular phase of arterial perfusion. The dosage of commercially available gadoxetic acid is, at present, one-fourth that of conventional gadolinium chelates (0.025 mmol kg 21 vs 0.1 mmol kg
21). Thus, even though the T 1 relaxivity of gadoxetic acid measured in human blood is, at 1.5 T, double that of conventional gadolinium chelates [13], the degree of enhancement of hypervascular lesions and vessels in the vascular phases of gadoxetic acid-enhanced MRI is expected to be about half that provided by conventional gadolinium chelates.To the best our knowledge, no study has compared MRI using gadoxetic acid with MRI using conventional gadolinium chelates for diagnostic accuracy and sensitivity in detecting small HCC (#2.0 cm). Non-specific extracellular gadolinium chelates are still the most widely used MR contrast agents for HCC work-up, and hence the relative detecting capabilities of gadoxetic acid...