Ultrasound contrast media - Their importance for neurosonological diagnostics

Transcranial colour-coded duplex ultrasound is frequently hampered by an in sufficient temporal or foraminal window (in our experience this makes up fo r approximately 20% of the cerebrovascular patients). Correspondingly. extr acranial colour-coded duplex ultrasound has its limitations by plaque calci fication and shadowing of the ultrasound beam. Weak Doppler signals due to a large insonation angle or low flow volume are another problem for both te chniques. These limitations led to the development of echocontrast agents w hich were able to survive pulmonary and capillary transit and improved the echogenecity of the flowing blood. During Doppler sonography, these echocon trast agents enhance the signal by up to 30 dB. Echocontrast increases the success rate of ultrasound examinations, shortens the time needed for the e xamination, and allows for visualisation of more vessels and longer vessel segments. Still under investigation are brain perfusion mapping, harmonic i maging, a technique based on harmonics, and stimulated emission based on ul trasound scattering by bursting echocontrast microbubbles.