**4. Antitumor therapies**

Ultrasound exploration can be an effective procedure for the assessment of liver tumors response to treatment. Over the years, different criteria for assessing the effectiveness of curative or palliative therapies have been considered. Now it has been proved that the degree of tumor necrosis is not correlated with tumor diameter, therefore simple measurement of the tumor diameter (RECIST criteria) is not enough for therapy assessment. Currently, local response to treatment is focused on tumor necrosis diagnosed by contrast dynamic imaging techniques and recognized by the presence of intratumoral non-enhanced areas. Local response to treatment is defined as:

a. complete response, defined as complete disappearance of all known lesions (absence of tumor enhanced areas, reflecting total tumor necrosis) and absence of other new lesions determined by two observations not less than 4 weeks apart;

