Introduction
Electromagnetic navigation bronchoscopy (ENB) utilizes an electromagnetic field created around the patient to detect and display spatially tracked devices within the magnetic field superimposed over the three-dimensional (3D) virtual bronchoscopic route, i.e., an integrated electromagnetic tracking system within virtual navigational bronchoscopy. The final product is a dynamic, spatially, and temporally tracked virtual representation of the device within the preplanned, patient-specific anatomic “map.”
In the United States, there are two commercially available ENB systems: SPiN Drive (VSPN, Veran Medical Technologies, St. Louis, MO, USA), and superDimension/ILLUMISITE (iSD, Medtronic, Minneapolis, MN, USA). Both systems require thin-cut computed tomography (CT) imaging with a specific protocol to plan biopsy targets and overlay/match the magnetic field to CT scan anatomy. There are three primary differences between the systems. The first is the VSPN system’s use of inspiratory and expiratory CT images to add respiratory gating versus a static inspiratory breath hold (SD). The second is which devices are tracked during ENB (iSD—locatable guide [LG] via an extended working channel [EWC]; VSPN—tip-tracked biopsy instruments). The SD LG is similar to a tracked probe that passes through the EWC. The EWC is offered with various tip angles (45, 90, and 180 degrees), which allows for steerability during navigation. Once the lesion is reached, the EWC is locked in place and the LG is removed, allowing peripheral biopsy instruments to be used to sample the lesion in question and/or radial probe endobronchial ultrasound (rEBUS) is used for real-time confirmation of the target lesion. Though the VSPN system has recently introduced their own version of an LG/EWC combination, the platform’s performance is predicated on the use of “always-on” tipped track biopsy instruments (forceps, brush, and needle) allowing for continuous direct bronchoscopic navigation of the biopsy instrument. The third difference between the systems is a percutaneous approach option provided by the VSPN not found on the iSD system. The percutaneous modality uses a preplanned chest wall entry point to allow for passage of a tracked needle through the chest wall and into the peripheral lung parenchyma/target lesion. Both platforms use similar planning systems and computer software to generate 4D reconstructions of the patient’s chest CT and allowing for peripheral lesion targeting and pathway building.
Preprocedural Preparation
Guidelines recommend that nonsurgical biopsy be performed in patients who have an indeterminate nodule >8 mm in diameter in the following situations :
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When clinical pretest probability of malignancy and imaging results are discordant.
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When the overall probability of malignancy is low to moderate (~10%–60%).
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Suspicion of a benign diagnosis, in which diagnostic confirmation would affect management decisions.
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In high-malignancy risk-patients who desire biopsy of proof of malignancy prior to undergoing surgery.
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In high-surgical-risk patients, in whom a diagnosis is requested prior to initiation of radiosurgery or other nonsurgical ablative therapies.
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Part-solid nodules >8 mm in diameter, persistent on radiographic follow-up; based on pretest probability, surgical risk factors, and patient preference.
Endoscopic-guided peripheral lung biopsy is generally preferred over transthoracic approaches in low-to-moderate malignancy probability patients with mediastinal or hilar lymphadenopathy measuring ≥1 cm in diameter in the short axis (regardless of fludeoxyglucose [FDG] avidity on positron emission tomography [PET] scan within the lymph nodes) due to the ability to stage the mediastinum with EBUS-guided transbronchial needle aspirations (TBNAs, see Chapter 2 ) within a single procedure and anesthesia session.
Equipment Needed for Electromagnetic Navigation Bronchoscopy
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Veran SPiN Drive
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Veran patient tracking pad (vPad) positioned on the chest ipsilateral to the nodule of interest in a T or L shape ( Fig. 4.1 )
Fig. 4.1
Example of Veran patient tracking pad (vPad) placements and confirmation.
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CT scan requirements
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Inspiratory and expiratory images
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Slice thickness and interval: thickness (0.75 mm), interval (0.5 mm)
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Planning station computer with SPiN Drive Planning software installed and USB drive
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Either connected to intranet for DICOM CT scan upload or with CD-ROM/USB reading capabilities
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USB drive for transitioning the procedure plan to the SPiN Drive electromagnetic navigation (EMN) Platform
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Always-On Tip Tracked instruments ( Fig. 4.2 )
Fig. 4.2
Veran Always-On Tip Tracked tools. (A) Always-On Tip Tracked 21-G ANSO cytology needle. (B) Always-On Tip Tracked 22-G SPiN Flex ANSO nitinol needle. (C) Always-On Tip Tracked forceps. (D) Always-On Tip Tracked brush. (E) Always-On Tip Tracked triple needle brush. (F) SPiN access catheter.
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Bronchoscope with at least a 2-mm working channel
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For SPiN Perc
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SPiN Perc Kit
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Always-On Tip Tracked 19 gauge (G) × 105 mm or 155 mm biopsy needle
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20 G × 15 cm or 20 cm fine-needle aspiration (FNA) needle
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20 G × 15 cm or 20 cm biopsy gun
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superDimension/ILLUMISITE Navigation System
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CT scan requirements
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Full inspiratory images
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Slice thickness and interval: thickness (1.0–1.25 mm), interval (0.8–1.0 mm)
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Planning station computer with iSD Planning software installed and USB drive
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Either connected to intranet for DICOM CT scan upload or with CD-ROM/USB reading capabilities
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USB drive for transitioning the procedure plan to the ILLUMISITE platform
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iSD electromagnetic generator and board
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Bronchoscope with at least a 2.6-mm working channel
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ILLUMISITE extended working channel (IEWC—0-, 45-, 90-, and 180-degree angulation) ( Fig. 4.3 )
Fig. 4.3
superDimension ILLUMISITE locatable extended working channel.
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Biopsy instruments
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For fluoroscopic navigation technology
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Fiducial board
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A qualified C-arm fluoroscope for use with the navigation system (determined by Medtronic technical service representative)
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Creates a fluoroscope configuration file installed on the navigation system that corrects fluoroscopic image distortion, allowing recreation of the 3D volume. Each file is specific to the geometric properties of the individual fluoroscope used.
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ENB-guided fiducial placement
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Fiducial markers (for examples, see Fig. 4.4 )
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SuperLock—0.8 × 3.5 mm gold seed with an attached 4-mm nitinol wire (Medtronic, Dublin, Ireland)
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Visicoil—0.5 × 5-mm linear gold wire (IBA Dosimetry, Bartlett, TN, USA)
Fig. 4.4
Preparation for endobronchial fiducial marker placement. (A) Fiducial marker (double black arrows) loaded into a cytology brush (white arrow) . (B) SuperLock nitinol coil fiducial marker. (C) Visicoil fiducial marker.
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Bone wax or surgical lube
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For iSD:
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iSD Marker Delivery Kit, or
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Cytology brush
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For Veran SPiN:
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Always-On Tip Tracked cytology brush, or
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SPiN EWC/access catheter with Always-On Tip Tracked guidewire
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Staff
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Bronchoscopy technician/nurse for equipment assistance and sample handling
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Anesthesia staff
Procedural Techniques
Veran SPiN System
Planning
With the vPad patient trackers appropriately positioned in a T or L configuration, the patient undergoes a noncontrasted CT scan of the chest during end inspiration and expiration. The patient must remain supine until completion of the scan to decrease registration error. Once uploaded to the planning station, the identification of 6 vPad sensors is confirmed ( Fig. 4.1 ). Then the main and secondary carinas ipsilateral to the lesion of interest are marked virtually by right-clicking on the corresponding carina in the program’s generated airway map. The lesion of interest is then chosen by right-clicking, holding, and dragging across the largest diameter of the lesion and clicking save. The software then segments the target lesion and airways creating a high-definition virtual airway map with a proposed pathway to the lesion. Following this, the user will confirm registration by evaluating the overlay of the planned navigation over the expiratory images. If there is significant divergence between the planned route and expiratory images, this is rectified by selecting the “refine airways” button, aligning the inspiratory and expiratory images side by side, and dropping a point on the main carina on the expiratory images by right-clicking, and then placing a second point on the lesion of interest on expiratory images with a right-click. The software then adjusts the overlay, which the user confirms once appropriate. The next screen is the SPiN Perc planning stage, which can be skipped if desired or the target location is not amenable to percutaneous sampling.
If the nodule is in the peripheral one-third of the lung parenchyma and located in an anterolateral position, then electromagnetic-guided transthoracic needle aspiration/biopsy (EMTTNA) can be considered. When planning for EMTTNA, a needle insertion site is selected by right-clicking at the level of the skin such that a needle entry path is created that is the shortest distance from visceral pleura to target and avoids overlying bony structures, pleural fissures, and is less than 10.5 to 15.5 cm from insertion site to targeted lesion (the working distance of the available SPiN Perc Always-On Tip Tracked TTNA needles). The plan then is uploaded to a USB drive, taken to the SPiN Drive navigation platform and uploaded.
Registration
Once the patient is appropriately sedated and anesthetized, position the magnetic field generator over the vPads such that all six markers are recognized by the system. Using one of the Tip Tracked instruments, place the tip of the instrument on the main carina and confirm by clicking “set main carina.” The registration is confirmed by placing the tip of the instrument on the selected secondary carina and affirming that the system is appropriately sensing its location within the virtual map. If there is significant error in the location of the instrument in relation to the secondary or main carina, a point cloud should be created by clicking “create point cloud” and passing the instrument sequentially throughout the right lung, left lung, and trachea. The system collects points in expiration and overlays them on the virtual map; once a system-determined threshold of accuracy is met, the checkmark turns green. Once all three checkmarks have turned green, click “stop collecting,” accept registration, and then reassess accuracy by placing the tip of the instrument physically on the respective carinas and confirming their location within the virtual image.
Navigation and Biopsy
Once airway registration is confirmed, the navigation phase of the procedure begins ( Fig. 4.5 ). Using a Tip Tracked needle positioned at the end of the bronchoscope working channel, the proceduralist drives the bronchoscope according to the virtual route and proceduralist’s knowledge of the anatomic location of the target lesion. The target will appear purple until the instrument is within 1 cm of the lesion and is aligned such that the lesion is within the throw of the needle, at which point it will turn orange. The lesion will turn green when the tip of the needle is virtually within the target. An assisting physician, technician, or nurse extends the needle during expiration. Once the needle is deployed, suction can be applied as the needle is agitated within the lesion during expiration—“green on green” (when the tip of the tool is virtually within the lesion and the system senses that the respiratory cycle is in expiration). After approximately 10 agitations, remove suction and retract the needle. Remove the instrument from the working channel and process the sample by institutional protocols. When using the Always-On Tip Tracked biopsy forceps, we recommend opening the forceps at the proximal edge of the virtual representation of the lesion (while the lesion appears orange), advancing the open forceps during expiration into the lesion and closing the jaws of the forceps during “green on green.” Transbronchial brushing can be performed in a similar manner.
