Contrast enhanced pulsed Doppler and colour-coded duplex studies of the cranial vasculature.

INTRODUCTION: The aim of this study was to assess the effect of Albunex, a vascular contrast agent based on albumin-coated air microbubbles, on pulsed Doppler and colour-coded duplex sonography of the cranial vasculature. METHODS: Twenty healthy male volunteers received intravenous injections of contrast in single doses ranging from 0.08 to 0.30 ml/kg. Pulsed wave Doppler sonography examination and colour-coded duplex sonography were carried out in the right internal carotid artery (ICA) and middle cerebral artery (MCA) before and after i.v. contrast. The relative intensity increase of the Doppler signal was measured in decibels. RESULTS: Transpulmonary passage of contrast occurred in sufficient amounts to enhance the intensity of the Doppler signal significantly, but the duration of this effect was short. Contrast enhancement also improved visualization of both the ICA and MCA in all subjects. For the transcranial examinations, this resulted in visualization of a greater length of the middle cerebral arteries and additional vessels in the Circle of Willis. CONCLUSIONS: These results confirm that contrast enhancement can significantly improve the quality of Doppler examination and colour-coded duplex sonography of both the intracranial and extracranial vessels. However, the use of Albunex in neurosonology will be of limited value due to its relatively short duration.

[Cerebral microembolism detected by transcranial Doppler ultrasonography]. / Cerebrale mikroemboli pvist med transkranial ultralyddopplerundersøkelse.

The clinical diagnosis of brain embolism has traditionally been based on evidence suggesting a potential embolic source. However, it is now possible to detect circulating cerebral microemboli by means of transcranial Doppler ultrasound. We explain the theory behind microembolus detection, and discuss initial clinical experience of this method. During invasive cardiovascular investigations and surgery this method can warn the physician that microemboli are entering the cerebral circulation, and preventive measures can be taken. Cerebral microemboli are quite often detected in stroke prone patients, and their presence probably indicates increased risk of stroke. In the acute phase of ischemic stroke, microembolus detection may help to decide the etiology and the source of the emboli. When microemboli are detected in cases of acute embolic stroke, serial detections can be performed which, in future studies, might be of help when evaluating the effect of the treatment.

Air-filled ultrasound contrast agents do not damage the cerebral microvasculature or brain tissue in rats.

RATIONALE AND OBJECTIVES: Air microemboli may damage the cerebral microvasculature. The aim of this study was to evaluate the safety of ultrasound contrast agents composed of air microspheres with regard to cerebral damage when administered into the arterial system (ie, when not filtered by the capillary system of the lungs). METHODS: Three experimental methods were used in 75 rats after injection of either Albunex, Echovist, or Levovist into the left heart ventricle. The alkaline phosphatase (ALP) method to demonstrate small segmental brain capillary and arteriolar dilatations (SCADs), intravenous injections of Evans blue and fluorescence microscopy to detect increased vascular permeability (blood-brain barrier damage), and histologic examination of the brain to detect microinfarction. Intracardiac injections of saline, air, and corn oil were used as controls. RESULTS: Brain microinfarcts and SCADs formation of the brain microvasculature occurred only after control injections with corn oil. None of the brains from animals that received ultrasound contrast agent showed gross discoloration, as an indication of increased vascular permeability, with the Evans blue/fluorescence microscopy method. Definite leakage of Evans blue occurred only after large doses (150 microL) of air. CONCLUSIONS: This study indicates that ultrasound contrast media composed of air microspheres do not cause lesions of the brain microvasculature or parenchyma.