Quantification of enhancement in contrast ultrasound: a tool for monitoring of therapies in liver metastases

Ultrasound techniques are presented using the contrast agent SonoVue (Bracco, Italy) for microvascular imaging of liver metastases and for the detection of treatment-related changes in tumour perfusion. Technical requirements and examination protocols for contrast-enhanced ultrasound (CEUS) in the detection of microvascularity are described. Procedures for the quantitative analysis of perfusion in follow-up examinations are explained. Compared to contrast-enhanced computed tomography, low-MI (mechanical index) CEUS with SonoVue better reflected the arterial perfusion of liver metastases. Changes of tumour perfusion after stereotactic radiotherapy or chemotherapy of liver metastases could be sensitively detected using CEUS. In addition, possible changes of the liver perfusion after therapy could be assessed. Replenishment kinetics of the contrast agent allowed for a quantitative analysis of the arterial and portal venous perfusion in the tumour and the liver tissue. CEUS is a promising method to non-invasively monitor systemic or local-ablative therapies of liver metastases by sensitively detecting changes of tumour perfusion.