Fig. 3.

Deformable registration for K-wire guidance. (a) Experimental setup using a mobile C-arm and spine phantom. (b) Axial views of the pre-op CT showing the registered position of deformed registered components (yellow) in comparison to truth (magenta). (c–d) TRE of the K-wire tip $\left({\text{TRE}}_x,\text{ mm}\right)$ and trajectory $\left({\text{TRE}}_{\varphi },{ }^{°}\right)$ evaluated as a function of B-spline order. The deformable registration is found to be stable over a fairly broad range of spline order $(n=3-7)$ but fails from overfitting for order $\ge 8$.