Concentration Estimation of Ultrasound Targeted Microbubbles for Improving Cancer Detection: a Preliminary in Vivo Study

Ultrasound imaging can be combined with specific targeted contrast agents for noninvasive detection of pathology using disease-associated molecular signatures. The quantification of contrast agents effectively bound to receptors indicative of disease can provide additional information on the presence of pathology. This paper focuses on the opportunity of exploiting the echoes produced by targeted contrast agents to remotely estimate the volumetric concentration in a desired resolution cell. Tumor growth was induced by subcutaneous injection of prostate cancer cells in mice. A contrast-enhanced specific technique was used to image the region of interest subdivided in resolution cells of 1 mm-side. Radio frequency data were acquired for offline processing. A method based on the support vector machine was employed to estimate the contrast agent concentration in each resolution cell. The preliminary in vivo experiments demonstrated a correlation between the extent of the primary tumor and the estimated concentrations. The combination of molecular imaging and contrast agent quantification provides the potential for earlier characterization of pathologies on molecular level.