中文摘要：

Weissleder于1999年首先阐述了分子影像学的定义,即分子影像学是通过发展新的工具、试剂及方法,应用影像学方法（X线、CT、MR、超声等）来探查疾病过程中细胞和分子水平的变化。它能使疾病在尚无解剖结构改变前被检测出来,从而有利于探索疾病的发生、发展、转归以及药物疗效的评价,

英文摘要：

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.