Liver tumours, 40% of which are benign, account for 1% to 4% of all solid tumours in children. The benign tumours are mainly haemangiomas, liver hamartomas, and liver cell adenomas. The malignant tumours are mainly hepatoblastoma, hepatocellular carcinoma (HCC), malignant liver mesothelioma, and rhabdomyosarcoma. The differential diagnosis of liver masses in children is generally based on the child's age, the clinical evaluation (including alpha-fetoprotein test results), and imaging characteristics. Liver tumours seldom produce clear symptoms and signs in the early stages, and they progress rapidly. As a result, most liver tumours are not diagnosed until the middle or late stages. To improve survival among patients with liver tumours, clinicians must find the liver tumours as early as possible and determine whether the tumours are benign or malignant. Conventional ultrasonography is commonly used for screening, and is preferred as the first-line imaging technique for children. Not only does it have a wide range of applications and a high diagnostic yield, but it is well accepted by patients and their parents. It can be performed in the examination room with the parents present, allowing real-time imaging and direct interaction with patient and parents. CEUS is a non-invasive imaging technology that can continuously and dynamically observe blood perfusion in tumours in real-time through injection of a contrast agent to enhance the blood flow reflux signal in the human body. Consequently, CEUS is useful for visualising capillaries and tissue perfusion in the human body. The purpose of this current study is to evaluate the use of Sonazoid™ perfluorobutane (PFB) microbubbles as a contrast medium for CEUS for evaluation of solitary liver masses in children.