Background: As diffusion-weighted imaging (DWI) is routinely incorporated into the standard clinical protocol, it is clinically relevant to determine whether DWI after gadoxetic acid is comparable to pre-contrast DWI, with regard to the detection and characterization of focal liver lesions.
Purpose: To compare DWI before and after administration of gadoxetic acid in the detection and characterization of small (≤2.5 cm) focal hepatic lesions.
Material and methods: One hundred and fifty-eight patients with 237 focal hepatic lesions (≤2.5 cm) (124 HCCs, 50 metastases, 2 cholangiocarcinomas, 43 hemangiomas, and 18 cysts) were included. DWIs were obtained before and after administration of gadoxetic acid. Non-breath-hold DWI was performed with b values of 0, 100, and 800 s/mm(2). Signal-to-noise ratio (SNR), lesion-liver contrast-to-noise ratio (CNR), and apparent diffusion coefficients (ADCs) of the liver and lesion were calculated. Lesion detection with each DWI was evaluated with alternative free-response receiver-operating characteristic analysis by two observers. The sensitivity of the characterization of focal hepatic lesions as solid (malignancy) or non-solid (benignity) with each DWI was calculated using a five-point confidence scale. Inter-observer agreement regarding lesion detection and characterization was evaluated using kappa statistics.
Results: SNRs of the liver on post-contrast DWI were significantly lower than on unenhanced DWI at b = 800 s/mm(2) (P < 0.05). SNRs, CNRs, and ADCs of focal hepatic lesions were not significantly different between two DWIs (P > 0.05). The diagnostic accuracy (Az) for lesion detection and the sensitivity for lesion characterization did not show significant difference between two DWIs (P > 0.05). With regard to the detection and characterization of focal hepatic lesions, the kappa values for two DWIs indicated good and excellent inter-observer agreement, respectively.
Conclusion: Gadoxetic acid-enhanced DWI showed comparable diagnostic capability to unenhanced DWI for the detection and characterization of small focal hepatic lesions.