Ferromagnetic ultrasound microbubbles contrast agent

Microbubbles have attracted attention as ultrasonic contrast agents because their ultrasonic scattering property is excellent in comparison with other ultrasonic contrast agents. In the development of ultrasound contrast agent, the main difficulties accounted are the making of small microbubbles less than 10 /spl mu/m and the elongation of the lifetime of microbubbles. A new ultrasonic contrast agent, which is microbubbles typed coating by surfactant, has been developed. The contrast images produced by different-sized microbubbles contrast agents are studied quantitatively. Furthermore, a ferromagnetic ultrasound contrast agent was also studied for its potential as a Drug Delivery System (DDS). In this paper, a new ultrasonic contrast agent for the Drug Delivery System will be discussed. Ferromagnetic materials are placed on the surfaces of the surfactant microbubbles developed in our laboratory for the above purpose. Multivalent ions such as calcium ions are used to put the ferromagnetic materials on the surfaces of the microbubbles. It is confirmed that the developed magnetic microbubbles could be lead by a permanent magnet. The performance of the magnetic microbubbles is evaluated by measuring the time dependence of the attenuation constant as one of their acoustic properties.