Molecular imaging is to study functional molecular events in living organisms at the cellular and molecular levels through many imaging technologies

and thus to reflect the living condition at the aspect of qualitative and quantitative research. However

traditional imaging diagnostic technologies

such as X-ray radiology

CT scanning

MR imaging

and ultrasonography

etc.

mainly show anatomic structural damages. Ultrasound molecular imaging as an emerging discipline is to rely largely on the ultrasound contrast agent consisting of acoustic materials and substances binding with interesting targets

and to offer the potential and new direction for early diagnosis and targeted treatment of various diseases. Ultrasound molecular imaging has a wide prospect of clinical application due to its high soft tissue resolution

no radiation damage

no invasion

and portable instrument. The purpose of this article is to summarize the development of ultrasound contrast agent

the application in the field of ultrasound targeted diagnosis and targeted treatment

and to illustrate challenges in this field.