gms | German Medical Science

Objective: Today the development of intraoperative 3D ultrasound in neurosurgery offers new horizons in real time image presentation. Previous papers described the advantages in brain shift detection, orientation with different instruments, avoidance of eloquent regions, possibilities of resection control in combination with acceptable costs. But until now the ultrasound datasets based on B-Mode images. Now for first time, we integrated the power duplex sonography as a technique of vascular imaging into our 3D ultrasound dimension.

Methods: A freehand 3D ultrasound navigation system consisting of a standard personal computer containing a video grabber card in combination with an optical tracking system (NDI Polaris) and a high performance ultrasound device (Siemens G60 S) with a 6,0 – 7,5 MHz array probe was used. Volume data was constructed by mapping the video images into the corresponding voxel plane of the volume. 3D-iUS datasets were acquired transdurally (12cm depth, B and Duplex Mode), at different times during the tumor resection and overlayed with preoperative MRI. The extracted slices from the volume data (duplex mode) demonstrated three orthogonal orientations of vascular images relative to the pointer, microscope or ultrasound probe. Vessels could be displayed in different colours superimposed on the brain tissue image (B-Mode, MRI) or for the construction of blood circulation in the brain. Therefore the power, persistence and PRF (pulse repetition frequency) varied depending on the flow rate of the blood vessels.

Results: Currently we analysed more than 10 patients with brain tumors using the new vascular image technique. Visualisation of blood vessels in 3D ultrasound were successful in all cases, but the quality ranged from acceptable to excellent. Reasons for the differences in the results were a learning curve, oedema and surgical approaches. The expenditure of time for one Doppler dataset was at least 7 minutes. The new 3D-technique displayed small tumor vessels with different flow directions during the operative procedure and assisted in the prevention of vessel injury of the blood circulation.

Conclusions: The new display technique of real 3D power Doppler ultrasound is useful for tumor operations as well as for vascular operations by implementing the segmentation technique. 3D Power Doppler offers harmonic signals of different vessels in one colour for re-construction of the blood circulation in real spatial orientation.