Algorithm 2.

Technician-Free Image-Guided Bronchoscopy Strategy.

1:	Inputs:
	CT-based 3D airway-tree model
	route r = {b1, b2, …}
	navigation plan {Tj, Mj}, j = 1, 2, …, a
	bronchoscope video stream
2:	Present VB View $I_{\text{CT}}^{{\mathrm{\Theta }}_1}$ // Initialization at main carina
3:	Move bronchoscope so $I_{\mathrm{V}}^{{\mathrm{\Theta }}_1^{\prime }}\approx I_{\text{CT}}^{{\mathrm{\Theta }}_1}$
4:	for all bj, j = 1, …, a such that Mj ≠ NULL do
5:	// Perform rotate-flex-advance maneuver set
6:	Invoke “rotate” command
7:	Present VB-rotate-movie $\left(I_{\text{CT}}^{{\mathrm{\Theta }}_j},T_j\right)\to I_{\text{CT}}^{{\mathrm{\Theta }}_j^T}$
8:	Rotate bronchoscope so $I_{\mathrm{V}}^{{({\mathrm{\Theta }}_j^T)}^{\prime }}\approx I_{\text{CT}}^{{\mathrm{\Theta }}_j^T}$
9:	Invoke “advance” command
10:	Save base-camp pair $\left\{I_{\mathrm{V}}^{{({\mathrm{\Theta }}_j^T)}^{\prime }},I_{\text{CT}}^{{\mathrm{\Theta }}_j^T}\right\}$
11:	Present VB-advance-movie $\left(I_{\text{CT}}^{{\mathrm{\Theta }}_j^T},{\mathbf{b}}_{j+1}\right)\to I_{\text{CT}}^{{\mathrm{\Theta }}_{j+1}}$
12:	Flex and advance bronchoscope so $I_{\mathrm{V}}^{{\mathrm{\Theta }}_{j+1}^{\prime }}\approx I_{\text{CT}}^{{\mathrm{\Theta }}_{j+1}}$
13:	// Position-verification mechanism
14:	if “verify” command invoked then
15:	Present targeting circles on video
16:	Move bronchoscope so a bifurcation fits inside circles → IV
17:	Invoke “verify” command
18:	global-register $(I_{\mathrm{V}},{\mathbf{b}}_j)\to I_{\text{CT}}^{\mathrm{\Theta }}$
19:	Present base-camp pair {IV, $I_{\text{CT}}^{\mathrm{\Theta }}$}
20:	if depicted registration deemed correct
	then
21:	if bronchoscope in correct position
	then
22:	continue // Navigation on track
23:	else // bronchoscope deemed to be in incorrect position
24:	Pull back bronchoscope to branch bj
25:	go to 6 // Back up to last correct branch
26:	else // Depicted registration is incorrect
27:	go to 14
28:	else if “back” command invoked then
29:	repeat
30:	j−1 → j
31:	until Mj ≠ NULL // Back up to first proper branch
32:	Present VB View $I_{\text{CT}}^{{\mathrm{\Theta }}_j}$ // Present “Arrive” VB view for previous proper branch
33:	Pull back bronchoscope to indicated branch
34:	go to 6