Fig. 24.5  The main processor of the SuperDimension navigation system

shearing force and collect multiple tissue samples with a single pass. In a recent study, the GenCut TBNA alone had a diagnostic yield of 37.3%, lower than the average of TBBx. However, the GenCut increased the diagnostic yield by 7.4% from 43.2% with TBBx alone to 50.6% when both biopsy tools were used [15].

Procedural Steps

The procedure of EMN is performed in the following steps:

Planning

Planning involves identifying the target, selecting anatomical landmarks, and identifying a virtual approach to the target using digital software provided by the system.

Identifcation of the Target

Target(s) are identi ed by scrolling through the CT cross sections in axial, coronal, and sagittal axes. Once identi ed, the location of the target(s) is marked using a cursor and highlighted. The dimensions of the target are also measured.

Detecting Anatomical Landmarks

A virtual bronchoscopy image extending to the 4th generation of tracheobronchial tree is required to enable automatic superimposition of the CT images on the patient’s body. If a 3D map is not available, anatomical landmarks (primary and secondary carinas) can be identi ed using the CT cross sections. Five or more easily recognizable endobronchial locations (landmarks) are selected for the purpose; more speci cally main carina as well as two points in each lung, one in the upper lobe and one in its middle or lower lobe. These radiographic landmarks are matched with the actual anatomic landmarks of the patient during the bronchoscopic procedure either automatically or manually.

Pathway Planning

If a 3D map is available, one or more automatic pathways to each target can be constructed to assist in navigation. The automatic pathway is constructed using the 3D map as a reference. A review of the automatic pathway should be completed utilizing the CT cross sections and the 3D map. Additionally, a virtual navigation of the pathway can be performed using the pathway preview feature. The suggested pathway can be modi ed, extended with waypoints or it can be accepted for guidance as it is.

Saving the Plan and Exiting

When the procedure plan is complete, it is exported to a CD, a removable disk (USB), or to a network storage location for transfer to the procedure system.

Registration

The information gathered during the planning stage is uploaded into the system’s main computer using the external memory device. The

electromagnetic sensors are placed on the patient’s chest wall to accommodate for respiratory motion, coughing, and nominal patient movements. Flexible bronchoscopy is performed in a usual fashion to clear any excess airway secretions. The Edge catheter is inserted via the working channel of the scope.

During the automatic registration process (Fig. 24.6), the system records the location of the LG while the bronchoscopist performs a bronchoscopic airway examination, creating a virtual cloud of navigation points that approximates the tracheobronchial tree. The system completes the registration process by matching the navigation cloud to the 3D map. The virtual bronchoscopy (VB) will appear during the bronchoscopic survey when the system has collected the minimal amount of data needed to match to the 3D tree. After completing the balanced survey, visual ver- i cation and image rotation the registration is accepted and the navigation phase of the procedure begins.

In a small percentage of procedures, the CT images will not support generation of a 3D tree. In this case, manual registration will be required. The radiological landmarks (registration points) selected on the virtual bronchoscopy images in planning are identi ed in vivo and touched with the tip of the LG to register their location in the

system’s main computer to establish radio- graphic–anatomic alignment. Registration of all the above information into the computer software automatically synthesized a navigation scheme to approach the lesion with precision. Accuracy of the navigation depends upon this Radiographic– Anatomic alignment also referred as “averageducial target registration error” (AFTRE); which de nes registration quality. The AFTRE can be improved or corrected by repositioning the misplaced landmarks or by eliminating that with a greatest deviation. The registration error of 5 mm or less can be considered acceptable [16].

Real-Time Navigation

Following a successful registration, the scope with the LG in place is advanced toward the segmental bronchus of interest. The navigation screen consists of six different viewports. The con guration of viewports is customizable with 11 different viewports available. Each viewport provides information that is meaningful at different points in the navigation procedure. The targets and pathways de ned during planning will be available for selection during Navigation. Once a target and pathway have been selected, the available views are used to guide the LG to the target.

Following are the viewports available to aid navigation (Fig. 24.7):

Fig. 24.7  Target alignment view

•\ Planar CT axial, coronal, and sagittal image (3 views). The views show the selected target and optionally, the selected pathway and waypoints.

•\ Static 3D map. A view of the 3D map showing the selected target, selected pathway, waypoints, and real-time location of the LG tip.

•\ Dynamic 3D map. A view of the 3D map showing the selected target, selected pathway, waypoints, and real-time location of the LG tip. The 3D map is automatically rotated, panned, and zoomed during navigation.

•\ Tip view. A graphical representation of the steering wheel on the LG handle. This view shows the direction to rotate the steering wheel to turn the LG toward the selected navigation object (target, pathway, or waypoint).

•\ 3D CT. A planar projection of the CT volume located directly in front of the LG tip.

•\ Video bronchoscope. Live display of the video input feed, typically used to show the bronchoscope video.

•\ Virtual bronchoscopy. A live display of the virtual bronchoscopy showing the real-time location of the LG tip. The selected pathway, waypoints, and 3D map centerlines can be overlaid on the view.

•\ Local view. A planar CT image located at and aligned with the LG tip. The view shows the selected target, selected pathway, waypoints, and 3D map branches.

•\ Alignment view. A view of target alignment with the LG tip.

•\ MIP (Maximum intensity projection). A pseudo three-dimensional projection of the CT volume below the LG tip. MIP shows high intensity structures, such as blood vessels and lesions.

Navigation guidance to the target is primarily given through the selected Pathway. The pathway is displayed in the 3D map, local view, virtual bronchoscopy, and CT cross sections. The objective during navigation is to steer and advance the LG along the pathway. In addition to pathway guidance, steering directions are provided to speci c navigation objects using the tip view. Navigation objects include targets, the automatic pathway, and waypoints, and are represented by spheres in all views.

The lesion is represented as a green sphere on all of the system viewports. As the LG gets closer to the lesion, the green dot continues to get larger in a relative fashion. The screen also shows the