Detection and characterization of small focal hepatic lesions (≤2.5 cm in diameter): a comparison of diffusion-weighted images before and after administration of gadoxetic acid disodium at 3.0T

Abstract

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/mm2. 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/mm2 ( 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.