Characterization of focal liver masses using acoustic radiation force impulse elastography.
OBJECTIVE
To investigate the diagnostic performance of acoustic radiation force impulse (ARFI) elastography for characterizing focal liver mass by quantifying their stiffness.


METHODS
This prospective study included 62 patients with a focal liver mass that was well visualized on conventional ultrasonography performed in our institution from February 2011 to November 2011. Among them, 12 patients were excluded for ARFI measurement failure due to a lesion that was smaller than the region of the interest and at an inaccessible location (deeper than 8 cm) (n = 7) or poor compliance to hold their breath as required (n = 5). Finally, 50 patients with valid ARFI measurements were enrolled. If a patient had multiple liver masses, only one mass of interest was chosen. The masses were diagnosed by histological examination or clinical diagnostic criteria. During ultrasonographic evaluation, stiffness, expressed as velocity, was checked 10 times per focal liver mass and the surrounding liver parenchyma.


RESULTS
After further excluding three masses that were non-diagnostic on biopsy, a total of 47 focal mass lesions were tested, including 39 (83.0%) malignant masses [24 hepatocellular carcinomas (HCC), seven cholangiocellular carcinomas (CCC), and eight liver metastases] and eight (17.0%) benign masses (five hemangiomas and three focal nodular hyperplasias, FNH). Thirty-seven (74.0%) masses were confirmed by histological examination. The mean velocity was 2.48 m/s in HCCs, 1.65 m/s in CCCs, 2.35 m/s in metastases, 1.83 m/s in hemangiomas, and 0.97 m/s in FNHs. Although considerable overlap was still noted between malignant and benign masses, significant differences in ARFI values were observed between malignant and benign masses (mean 2.31 m/s vs 1.51 m/s, P = 0.047), as well as between HCCs and benign masses (mean 2.48 m/s vs 1.51 m/s, P = 0.006). The areas under the receiver operating characteristics curves (AUROC) for discriminating the malignant masses from benign masses was 0.724 (95%CI, 0.566-0.883, P = 0.048), and the AUROC for discriminating HCCs from benign masses was 0.813 (95%CI, 0.649-0.976, P = 0.008). To maximize the sum of sensitivity and specificity, an ARFI value of 1.82 m/s was selected as the cutoff value to differentiate malignant from benign liver masses. Furthermore, the cutoff value for distinguishing HCCs from benign masses was also determined to be 1.82 m/s. The diagnostic performance of the sum of the ARFI values for focal liver masses and the surrounding liver parenchyma to differentiate liver masses improved (AUROC = 0.853; 95%CI, 0.745-0.960; P = 0.002 in malignant liver masses vs benign ones and AUROC = 0.948; 95%CI, 0.896-0.992, P < 0.001 in HCCs vs benign masses).


CONCLUSIONS
ARFI elastography provides additional information for the differential diagnosis of liver masses. However, our results should be interpreted in clinical context, because considerable overlap in ARFI values existed among liver masses.
Division of Gastroenterology, Department of Internal Medicine, CHA Bundang Medical Center, CHA University, Gyeonggi-do 463-712, South Korea.
Hana
H
Park
Jun Yong
JY
Park
Do Young
DY
Kim
Sang Hoon
SH
Ahn
Chae Yoon
CY
Chon
Kwang-Hyub
KH
Han
Seung Up
SU
Kim
D006528:Carcinoma, Hepatocellular / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D003937:Diagnosis, Differential; D004548:Elasticity / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000503:physiopathology; D008107:Liver Diseases / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography
Acoustic radiation force impulse; Cholangiocellular carcinoma; Focal liver mass; Focal nodular hyperplasia; Hemangioma; Hepatocellular carcinoma; Liver metastasis