Transcranial Doppler sonography - Stereotactically guided examinations using magnetic resonance angiography

The accurate localization of specific intracranial blood Vessels is a major difficulty with transcranial Doppler sonography (TCD). It was the purpose of this study to develop a system enabling stereotactic navigation during a TCD examination on the basis of high-resolution three-dimensional magnetic resonance angiographic (MRA) data. During TCD, the examiner is provided - on a computer screen - with a projec ted view of the respective intracranial vessel anatomy. With the aid of an optoelectronic localization system, the spatial orientation and localizatio n of the US probe is determined in real time, and correlated with the patie nt's MRA data using a dedicated stereotactic mask. Subsequently, the US bea m and the points of insonation are displayed on the screen overlaid on the vessel anatomy. In this way the examiner gains real time control of the loc alization of the respective intracranial vessel insonated. Points of insona tion can be stored and recalled for follow-up examinations. In addition to the successful verification of the system, it was shown that, in comparison with conventional TCD, stereotactic navigation distinctly improves the rep roducibility of repeat TCD examinations.