Ultrasound contrast agents and ultrasound molecular imaging

Ultrasound imaging in combination with microbubble contrast agents has demonstrated its potential for molecular imaging of vascular targets. In this article, we systematically review the technologies related to ultrasound molecular imaging. First, we introduce the basic principles of ultrasound molecular imaging. Then, we discuss ultrasound microbubble contrast agents. This includes selection requirements for targeted contrast agent ligands and receptors, targeted ultrasound contrast agent preparation, targeted ultrasound contrast agent ligands connection methods, and microbubble ultrasound contrast agent safety issues. The use of ultrasound molecular imaging in diagnosis and treatment, as well as some issues relating to high intensity focused ultrasound and ultrasound molecular imaging applications in disease diagnosis are also discussed. Applications include detection of inflammation, thrombus, tumors, and neovascularization. Consideration is also given to the acoustic characteristics of microbubbles and the acoustic principles underlying microbubble ultrasound imaging. Several microbubble scattering models are highlighted (including the Rayleigh-Plesset model, the Rayleigh-Plesset-Noltingk-Neppiras-Poritsky model, the Herring model, the Marmottant model, and the non-spherical bubble dynamics model). The interaction between two microbubbles and the effect of radiation on the microbubbles is also discussed. Finally, from an engineering perspective, we summarize the techniques used to improve the quality of ultrasound molecular images (harmonic imaging, perfusion imaging, and deconvolution technology). It is inevitable that ultrasound molecular imaging will continue to mature and can be expected to play an increasingly larger role in diagnosis and treatment of human diseases in the near future.