BACKGROUND: Contrast-enhanced ultrasound (CEUS) is a dynamic and continuous modality which offers a real time, direct view of the vascularization patterns and tissue resistance for many organs. Thanks to newer ultrasound (US) contrast agents, CEUS has become a well-established, live-imaging technique in many contexts, but it has never been extensively used for brain imaging. In particular, the use of intraoperative-CEUS (iCEUS) imaging in Neurosurgery is very limited. in this study, we provide the first dynamic and continuous iCEUS evaluation of a variety of brain lesions. METHODS: We evaluated 96 patients undergoing iCEUS imaging in an off-label setting while being operated on for different brain lesions; iCEUS imaging was obtained before resecting each lesion, after intra-venous (IV) injection of ultrasound contrast-agent (UCA). A semi-quantitative, offline postoperative inter-observer analysis was performed, in order to visualize each brain lesion and characterize its perfusion features in correlation with histopathology. RESULTS: In all cases, the brain lesion was visualized intra-operatively with iCEUS; the afferent and the efferent blood vessels were identified, allowing to evaluate the time and the features of the arterial and venous phases and facilitating the surgical strategy. iCEUS also proved to be useful in highlighting the lesion as compared to standard B-mode. Specific perfusion patterns were identified according to histopathology. No adverse effects were observed. CONCLUSIONS: Our study is the first large-scale implementation of iCEUS in Neurosurgery as a dynamic and continuous real time imaging tool for brain surgery, providing a first iCEUS characterization of different brain masses. iCEUS ability to highlight and characterize brain tumor provides the neurosurgeon with important information, anytime during a surgical procedure, in order to refine and optimize the surgical strategy and, possibly, to further understand tumor biology. SECONDARY CATEGORY: Clinical Neuro-Oncology.