Real-time ultrasound imaging of cerebral lesions during "target point" stereotactic procedures through a burr hole. Technical note.

Stereotactic burr-hole procedures like biopsies of brain tumours based on CT scan or MRI and angiographic data have so far usually been carried out without real-time ultrasound image control. Intra-operative real-time ultrasound imaging was carried out during twelve target-point stereotactic procedures via a single standard burr-hole using a new slender ultrasound transducer with a diameter of 8 mm. The technical parameters of the transducer are: frequency range of 5 < - > 3.5 MHZ, phased array sector scan, 90 degree sector. The transducer has a bayonet-like configuration and can be sterilized. Sufficient quality of the images was achieved in these twelve cases with different pathological entities such as malformation cysts (3 cases), gliomas (7 cases), one metastasis and one intracerebellar haemorrhage. Moreover, co-ordinate values may be calculated from the ultrasound images generated peroperatively, allowing the surgeon to choose additional targets. Colour flow mapping provides the visualization of vascular structures. For the beginner stereotaxy may be easier to learn using ultrasound real-time imaging.