Clinical utility of contrast-enhanced ultrasound in neurosonology

Extracranial and transcranial colour-coded duplex sonography (TCCD) are used routinely in clinical practice to assess physiologic and pathologic arterial blood flow to the brain. Such investigations are straightforward, safe, and cost effective, and can be repeated frequently for patient follow-up. In addition, the portability of extracranial colour-coded duplex sonography and TCCD provides the option of bedside investigations, particularly useful for evaluation of the critically ill patient. However, duplex ultrasound can be hampered by insufficient acoustic penetration, an unfavourable insonation angle, or by conditions of low or no flow. Echocontrast agents capable of surviving pulmonary and capillary transit have been developed, and such agents increase the Doppler signal and, therefore, the success rate of neurosonographic investigations. Approximately 20% of TCCD studies involve poor insonation conditions and, therefore, the use of echocontrast agents is of particular interest for this application. Levovist and SonoVue are the two agents currently approved for use in neurosonography. Such agents have a relatively long-lasting effect (up to 7 min), and can be administered as a single injection or, alternatively, a fractionated injection protocol can be used, depending on the quality of the window.