As radiologists, our aim is to diagnose the hepatic lesion and differentiate the benign masses from malignant masses using a non-invasive imaging technique with a high accuracy to avoid invasive procedures, such as liver biopsies [10].
Although ultrasound elastography has been used in different studies to assess the degree of hepatic fibrosis, few studies have used ultrasound elastography to differentiate focal hepatic masses according to their stiffness [4].
Different ultrasound elastography techniques are available; however, in the current study, we used a semi-quantitative method using a strain index to express the elasticity of the lesion in relation to the surrounding normal liver parenchyma. This method is consistent with the semi-quantitative method used by Mehmet et al. [5] in 2013. In contrast, Hana et al. [2]. used ARFI to differentiate hepatic masses. Aymeric et al. used shear wave elastography [4].
In our study, the highest strain index was detected in cholangiocarcinoma (mean strain index = 6.25 ± 0.44), followed by hepatoblastoma, HCC and hepatic metastases. Metastatic lesions from colon cancer had a higher strain index than other metastases or cystic metastases due to fibrosis, which increased the stiffness of the lesion. Using semi-quantitative strain ratio or shear wave elastography, Aymeric et al. [4], Mehmet et al. [5] and Ji et al. [6] concluded that cholangiocarcinoma and colon cancer metastases had the highest stiffness.
The strain index of the cholangiocarcinoma lesions in our study was 6.25 ± 0.44, which was the highest value among the studied cases. Consistent with Mehmet et al. [5], we found the highest strain index in malignant lesions, particularly in cases with cholangiocarcinoma.
Aymeric et al. [4], Mehmet et al. [5] and Ji et al. [6] detected a higher degree of stiffness in hepatic metastases from colon cancer than that in metastases from other primary tumours due to the presence of fibrous tissue. In addition, we found a high strain index in hepatic metastases from colon cancer reaching up to 5, and this index was third highest in stiffness following hepatoblastoma and HCC.
We found a high strain index in HCC, which is a malignant lesion that is hard in consistency, reaching a value of 3.85 ± 1.14. Mehmet et al. [5] confirmed the stiffness of HCC with a high strain ratio of 3.24 ± 0.48.
Benign lesions, such as hepatic haemangiomas, adenomas and FNH, had a lesser degree of stiffness with a mean strain index of 0.82 ± 0.20, 1.30 ± 0.14 and 1.54 ± 0.27, respectively. This finding was consistent with reports by Mehmet et al. [5] who concluded that these benign lesions had a low strain index of 0.92 ± 0.14 in haemangioma and 1.75 ± 0.16 in FNH.
Mehmet et al. [5] found that the sensitivity and specificity of conventional ultrasound in differentiating benign and malignant hepatic lesions ranged from 28.1 to 58.8% and 34.6 to 50.7%, respectively. In their study, the authors attained a higher sensitivity and specificity using semi-quantitative strain elastography than those attained using conventional sonography. In addition, we attained a higher sensitivity and specificity reaching 100% and 93%, respectively, in differentiating benign from malignant hepatic lesions using strain elastography.