Authors:
D. Ruijters1, L. Spelle2, J. Moret2, D. Babic1, R. Homan1, P. Mielekamp1, B. M. ter Haar Romeny3, P. Suetens4; 1Best/NL, 2Paris/FR, 3Eindhoven/NL, 4Leuven/BE
DOI:
10.1594/ecr2008/C-591
Methods and Materials
Before the puncture is performed, the optimal needle paths are planned on the morphological data set. This can be a pre-operative CT dataset, or a rotational soft-tissue reconstruction, acquired with the C-arm system (XperCT dataset).
Within the anatomy of interest a target point is selected (mid point of the lesion location, see figures 1-3). Then a 3D view showing unobstructed access to the target, avoiding the impenetrable bones and major vessels, determines the incision entry point, see figure 4. After the target and the entry point have been established, a straight trajectory to the target is planned.
The resulting puncture path can be inspected with respect to the soft-tissue, bones and vessel anatomy, see figure 5. Multiple paths can be stored in this way.
At the beginning of the intervention an XperCT dataset is acquired, and the pre-operative CT dataset is registered to the peri-operative XperCT, which also registers the CT and C-arm coordinate systems, see figure 6.
The fluoroscopy image is overlaid with the planned needle trajectory and an oblique slice of the soft-tissue data, perpendicular to the viewing incidence and passing through the target point. The overlay image is real-time updated for any change in viewing incidence (L-arm, rotation, angulation), field of view, and source-image distance [Söderman et al., Racadio et al.]. The needle path is compensated for parallax distortion.
The C-arm viewing incidence is steered to be tangent to the planned path: the entry view. Since this view is tangent to the needle trajectory, the path is foreshortened to a single point. When the needle is positioned at the entry position and its orientation is tangent to the fluoroscopy image, it can be inserted.
The C-arm viewing incidence is then steered to be perpendicular to the planned path: the progression view. In this orientation, the needle can be navigated along the planned trajectory.
The entry view and progression view steps are repeated for all planned puncture paths. The views can be selected at table side. Optionally, new paths can be planned during the intervention. After the insertion, a new XperCT can be acquired to verify the needle position with regard to the soft-tissue structures and anatomical landmarks.