Thomas Töppel

The sampling of brain tissue in veterinary medicine usually underlies a freehand performance without exact localization. The aim of the project was the accuracy evaluation of a 3D-printed subject specific system for brain biopsy in dogs. At the beginning of the procedure, three small bone screws were fixed (bilateral and occipital/frontal) to the dog skull. Subsequently, three MR-markers filled with contrast agent were adapted and MRI scans performed (layer-thickness 1.0 mm). Within the MR images the coordinates of the target and entry point are determined by the surgeon. For evaluation an additional pre-CT (layer-thickness 0.7 mm) was realized. After image recording the MR-markers were removed. Due to a self-made algorithm a patient individual template was constructed. The final biopsy device made of ABS M30 was produced by a 3D printer (FDM).To perform the biopsy the device was connected with the already embedded bone screws. Through a guidance track the skull was minimally invasive accessed at the intended location. Controlled by a depth stop the biopsy needle could be exactly moved in a desired direction up to the target point. A further post-CT (thickness 0.7 mm) with inserted needle was performed to determine the final position of the biopsy needle tip. For receiving information about the difference between preoperative planned and achieved tip position the pre-CT was matched with the post-CT. Therefor 10 dog cadavers (n=20 target points) were applied. The results showed an accuracy of 0.58 mm ± 0.34 mm (ranging from 0.09 mm to 1.17 mm) between the preoperative planned and the achieved needle position. A patient specific 3D-printed biopsy system based on MR images was developed which enables a high precise brain biopsy. Moreover, the system matches up to current costly diagnosis techniques of image-guided neurosurgery and robot systems. Prospectively, it shall be transferred to human medicine