Contrast-Enhanced Ultrasound Has Come of Age

Microbubble ultrasound contrast agents (USCA) became clinically available in the mid-1990 s. They were originally developed for the enhancement of insufficient Doppler signals. Given the rapid improvement of Doppler techniques with increasing sensitivity, this soon became a relatively small niche indication for USCA. However, soon after their commercial availability, it became obvious that USCA have a much greater clinical potential than simple “Doppler rescue”. USCA can be used for contrast enhancement of normal and abnormal tissues like contrast agents are used in CT and MRI.

Two important innovations made it possible for the potential of USCA to become a clinical reality: the development of contrast-specific imaging techniques and the advent of low solubility gas agents such as SonoVue (Bracco, Milan, Italy) in the early 2000 s. The combination of these two innovations allowed for real time low MI imaging with USCA. With this technique it is possible to assess the wash-in and wash-out of USCA in various organs in real time and this provides crucial diagnostic information on a large number of pathologies.

In the first half of this decade numerous scientific papers investigated the role of contrast-enhanced ultrasound (CEUS). These publications provide a sound body of knowledge and are the basis of the current use of CEUS in clinical practice. The first organ with convincing evidence of the clinical utility of CEUS was the liver. This was reflected by the first edition of EFSUMB guidelines for the use of contrast agents in ultrasound in 2004 [1], which dealt almost exclusively with liver indications. In recent years, CEUS has been shown to be useful in several other organs such as the kidney (especially for the assessment of vesico-ureteric reflux in children), the spleen, the pancreas, the brain using the transcranial approach and in blunt abdominal trauma. All these indications have recently been endorsed by the second edition of the EFSUMB guidelines in 2008 [2].

CEUS has come of age and is now an integral part of routine clinical imaging at many centers worldwide. For some indications such as imaging of focal liver lesions, it is now mandatory to use USCA and conventional unenhanced US is regarded as inadequate in most such cases.

References

• 1 Albrecht T, Blomley M, Bolondi L. et al . Guidelines for the use of contrast agents in ultrasound. January 2004.  Ultraschall in Med. 2004;  25 249-256
• 2 Claudon M, Cosgrove D, Albrecht T. et al . Guidelines and Good Clinical Practice Recommendations for Contrast Enhanced Ultrasound (CEUS) – Update 2008.  Ultraschall in Med. 2008;  29 28-44