Combined photoacoustic and magneto-motive ultrasound imaging

Ultrasound imaging can provide excellent resolution at reasonable depths while retaining the advantages of being nonionizing, cost-effective and portable. However, the contrast in ultrasound imaging is limited, and various ultrasoundbased techniques such as photoacoustic (PA) and magneto-motive ultrasound (MMUS) imaging have been developed to augment ultrasound imaging. Photoacoustic imaging enhances imaging contrast by visualizing the optical absorption of either tissue or injected contrast agents (e.g., gold or silver nanoparticles). MMUS imaging enhances the sensitivity and specificity of ultrasound based on the detection of magnetic nanoparticles perturbed by an external magnetic field. This paper presents integrated magneto-photo-acoustic (MPA) imaging - a fusion of complementary ultrasound-based imaging techniques. To demonstrate the feasibility of MPA imaging, porcine ex-vivo tissue experiments were performed using a dual contrast (magnetic/plasmonic) agent. Spatially co-registered and temporally consecutive ultrasound, photoacoustic, and magneto-motive ultrasound images of the same cross-section of tissue were obtained. Our ex-vivo results indicate that magneto-photo-acoustic imaging can be used to detect magnetic/plasmonic nanoparticles with high resolution, sensitivity and contrast. Therefore, our study suggests that magneto-photo-acoustic images can identify the morphological properties, molecular information and complementary functional information of the tissue.