Continuous administration of contrast medium for transcranial colour-coded sonography

Since the introduction of contrast media, transcranial colour-coded sonography (TCCS) has become increasingly important for examination of the intracranial vessels. However, the widely practised bolus injection of these agents leads to initial blooming artefacts and thereafter the level of contrast enhancement decreases rapidly, reducing the effective time of enhancement. It was our aim to investigate the effect of continuous administration of contrast medium at a defined infusion rate. We performed 28 TCCS examinations of the intracranial vessels in 26 patients using a 2.25 MHz phased-array transducer during administration of 4 g Levovist (Schering, Berlin, Germany) 300 mg/ml with a constant infusion rate of 60 ml/h into an antecubital vein. The degree of enhancement was graded over time in a subjective analysis by two independent observers. During continuous administration, a constant level of contrast enhancement was reached after 60.1+/-26.2 s and this lasted 663.4+/-55.8 s as assessed by the first observer (66.6+/-26.2 s and 664.3+/-55.9 s according to the second observer). The limits of inter-observer agreement ranged from -10.1% to 9.9%. No major blooming effect was seen in the initial phase of the examination.