Algorithm 1: Multimodal CT-EBUS Registration Algorithm.

1.Initialize optimization (7) with captured EBUS frame ${\mathbf{I}}_{\mathrm{US}}$ and VB view ${\mathbf{I}}_{\mathrm{CT}}^{p_i}$ at pose $p_i$. 2.Segment ROI ${\mathbf{R}}_{\mathrm{US}}$ in ${\mathbf{I}}_{\mathrm{US}}$ using the method of Zang et al. [42]. 3.Derive a modified pose $p_i$ and a simplex $N_{p_i}$ that constrains the possible candidate neighboring poses to be situated on the airway wall, as depicted in the chest CT scan. 4.Using cost function $\mathbf{C}(·,·)$ defined by ((2)–(6)) and simplex $N_{p_i}$, run the simplex algorithm on (7) to update pose $p_o$ until it does not change for T iterations. 5.Repeat steps 3–4 using $p_i=p_o$ until $p_o$ no longer changes. 6.Output $p_o$ and virtual EBUS view ${\mathbf{I}}_{\mathrm{CT}}^{p_o}$.