Transbronchial biopsy with virtual CT bronchoscopy and nodal highlighting

Optimal route planning for image-guided EBUS bronchoscopy

The staging of the central-chest lymph nodes is a major lung-cancer management procedure. To perform a staging procedure, the physician first uses a patient's 3D X-ray computed-tomography (CT) chest scan to interactively plan airway routes leading to selected target lymph nodes. Next, using an integrated EBUS bronchoscope (EBUS = endobronchial ultrasound), the physician uses videobronchoscopy to navigate through the airways toward a target node's general vicinity and then invokes EBUS to localize the node for biopsy. Unfortunately, during the procedure, the physician has difficulty in translating the preplanned airway routes into safe, effective biopsy sites. We propose an automatic route-planning method for EBUS bronchoscopy that gives optimal localization of safe, effective nodal biopsy sites. To run the method, a 3D chest model is first computed from a patient's chest CT scan. Next, an optimization method derives feasible airway routes that enables maximal tissue sampling of target lymph nodes while safely avoiding major blood vessels. In a lung-cancer patient study entailing 31 nodes (long axis range: [9.0 mm, 44.5 mm]), 25/31 nodes yielded safe airway routes having an optimal tissue sample size = 8.4 mm (range: [1.0 mm, 18.6 mm]) and sample adequacy = 0.42 (range: [0.05, 0.93]). Quantitative results indicate that the method potentially enables successful biopsies in essentially 100% of selected lymph nodes versus the 70-94% success rate of other approaches. The method also potentially facilitates adequate tissue biopsies for nearly 100% of selected nodes, as opposed to the 55-77% tissue adequacy rates of standard methods. The remaining nodes did not yield a safe route within the preset safety-margin constraints, with 3 nodes never yielding a route even under the most lenient safety-margin conditions. Thus, the method not only helps determine effective airway routes and expected sample quality for nodal biopsy, but it also helps point out situations where biopsy may not be advisable. We also demonstrate the methodology in an image-guided EBUS bronchoscopy system, used successfully in live lung-cancer patient studies. During a live procedure, the method provides dynamic real-time sample size visualization in an enhanced virtual bronchoscopy viewer. In this way, the physician vividly sees the most promising biopsy sites along the airway walls as the bronchoscope moves through the airways.

Three-dimensional virtual bronchoscopy using a tablet computer to guide real-time transbronchial needle aspiration

Objectives

We proposed a new virtual bronchoscopy tool to improve the accuracy of traditional transbronchial needle aspiration for mediastinal staging.

Methods

Chest-computed tomographic images (1 mm thickness) were reconstructed with Osirix software to produce a virtual bronchoscopic simulation. The target adenopathy was identified by measuring its distance from the carina on multiplanar reconstruction images. The static images were uploaded in iMovie Software, which produced a virtual bronchoscopic movie from the images; the movie was then transferred to a tablet computer to provide real-time guidance during a biopsy. To test the validity of our tool, we divided all consecutive patients undergoing transbronchial needle aspiration retrospectively in two groups based on whether the biopsy was guided by virtual bronchoscopy (virtual bronchoscopy group) or not (traditional group). The intergroup diagnostic yields were statistically compared.

Results

Our analysis included 53 patients in the traditional and 53 in the virtual bronchoscopy group. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for the traditional group were 66.6%, 100%, 100%, 10.53% and 67.92%, respectively, and for the virtual bronchoscopy group were 84.31%, 100%, 100%, 20% and 84.91%, respectively. The sensitivity ( P  = 0.011) and diagnostic accuracy ( P  = 0.011) of sampling the paratracheal station were better for the virtual bronchoscopy group than for the traditional group; no significant differences were found for the subcarinal lymph node.

Conclusions

Our tool is simple, economic and available in all centres. It guided in real time the needle insertion, thereby improving the accuracy of traditional transbronchial needle aspiration, especially when target lesions are located in a difficult site like the paratracheal station.

Hands-Free System for Bronchoscopy Planning and Guidance

Bronchoscopy is a commonly used minimally invasive procedure for lung-cancer staging. In standard practice, however, physicians differ greatly in their levels of performance. To address this concern, image-guided intervention (IGI) systems have been devised to improve procedure success. Current IGI bronchoscopy systems based on virtual bronchoscopic navigation (VBN), however, require involvement from the attending technician. This lessens physician control and hinders the overall acceptance of such systems. We propose a hands-free VBN system for planning and guiding bronchoscopy. The system introduces two major contributions. First, it incorporates a new procedure-planning method that automatically computes airway navigation plans conforming to the physician's bronchoscopy training and manual dexterity. Second, it incorporates a guidance strategy for bronchoscope navigation that enables user-friendly system control via a foot switch, coupled with a novel position-verification mechanism. Phantom studies verified that the system enables smooth operation under physician control, while also enabling faster navigation than an existing technician-assisted VBN system. In a clinical human study, we noted a 97% bronchoscopy navigation success rate, in line with existing VBN systems, and a mean guidance time per diagnostic site = 52 s. This represents a guidance time often nearly 3 min faster per diagnostic site than guidance times reported for other technician-assisted VBN systems. Finally, an ergonomic study further asserts the system's acceptability to the physician and long-term potential.

Optimal procedure planning and guidance system for peripheral bronchoscopy

With the development of multidetector computed-tomography (MDCT) scanners and ultrathin bronchoscopes, the use of bronchoscopy for diagnosing peripheral lung-cancer nodules is becoming a viable option. The work flow for assessing lung cancer consists of two phases: 1) 3-D MDCT analysis and 2) live bronchoscopy. Unfortunately, the yield rates for peripheral bronchoscopy have been reported to be as low as 14%, and bronchoscopy performance varies considerably between physicians. Recently, proposed image-guided systems have shown promise for assisting with peripheral bronchoscopy. Yet, MDCT-based route planning to target sites has relied on tedious error-prone techniques. In addition, route planning tends not to incorporate known anatomical, device, and procedural constraints that impact a feasible route. Finally, existing systems do not effectively integrate MDCT-derived route information into the live guidance process. We propose a system that incorporates an automatic optimal route-planning method, which integrates known route constraints. Furthermore, our system offers a natural translation of the MDCT-based route plan into the live guidance strategy via MDCT/video data fusion. An image-based study demonstrates the route-planning method's functionality. Next, we present a prospective lung-cancer patient study in which our system achieved a successful navigation rate of 91% to target sites. Furthermore, when compared to a competing commercial system, our system enabled bronchoscopy over two airways deeper into the airway-tree periphery with a sample time that was nearly 2 min shorter on average. Finally, our system's ability to almost perfectly predict the depth of a bronchoscope's navigable route in advance represents a substantial benefit of optimal route planning.

Interactive CT-video registration for the continuous guidance of bronchoscopy

Bronchoscopy is a major step in lung cancer staging. To perform bronchoscopy, the physician uses a procedure plan, derived from a patient's 3D computed-tomography (CT) chest scan, to navigate the bronchoscope through the lung airways. Unfortunately, physicians vary greatly in their ability to perform bronchoscopy. As a result, image-guided bronchoscopy systems, drawing upon the concept of CT-based virtual bronchoscopy (VB), have been proposed. These systems attempt to register the bronchoscope's live position within the chest to a CT-based virtual chest space. Recent methods, which register the bronchoscopic video to CT-based endoluminal airway renderings, show promise but do not enable continuous real-time guidance. We present a CT-video registration method inspired by computer-vision innovations in the fields of image alignment and image-based rendering. In particular, motivated by the Lucas-Kanade algorithm, we propose an inverse-compositional framework built around a gradient-based optimization procedure. We next propose an implementation of the framework suitable for image-guided bronchoscopy. Laboratory tests, involving both single frames and continuous video sequences, demonstrate the robustness and accuracy of the method. Benchmark timing tests indicate that the method can run continuously at 300 frames/s, well beyond the real-time bronchoscopic video rate of 30 frames/s. This compares extremely favorably to the ≥ 1 s/frame speeds of other methods and indicates the method's potential for real-time continuous registration. A human phantom study confirms the method's efficacy for real-time guidance in a controlled setting, and, hence, points the way toward the first interactive CT-video registration approach for image-guided bronchoscopy. Along this line, we demonstrate the method's efficacy in a complete guidance system by presenting a clinical study involving lung cancer patients.

Virtual endobronchial ultrasound for transbronchial needle aspiration

OBJECTIVE

Endobronchial ultrasound-guided transbronchial needle aspiration could be performed better with computer-based preparation.

METHODS

Three-dimensional virtual bronchoscopy was used to develop 2 modes of computer-based "virtual endobronchial ultrasound." "Virtual endobronchial ultrasound standard" used conventional virtual bronchoscopy to determine the spot and angle for transbronchial needle aspiration, which was further evaluated by virtual bronchoscopy. "Virtual endobronchial ultrasound advanced" used multiple layers of 3-dimensional images of the target lesions and associated vascular structures in combination with virtual bronchoscopy. Target lesions and associated vascular structures (eg, pulmonary artery) were visualized through half-transparent bronchial walls.

RESULTS

Both methods required 5 to 15 minutes of preparation per case. Virtual endobronchial ultrasound standard required only basic computer software for virtual bronchoscopy, whereas virtual endobronchial ultrasound advanced required an advanced computer application. Virtual endobronchial ultrasound advanced allowed for a more intuitive recognition of the target. Both methods were useful in evaluating the feasibility of transbronchial needle aspiration, especially when the target was out of regular mediastinal lymph nodes, or in targeting a lesion located at a high upper angle (eg, 4L lymph node). Because the puncture spot was predetermined, bronchoscopists did not have to search for the target using ultrasound at the time of actual endobronchial ultrasound-guided transbronchial needle aspiration; rather, ultrasound was used only for confirmation of the target location and visualization of transbronchial needle aspiration.

CONCLUSIONS

Both computer-based preparation methods of virtual endobronchial ultrasound were useful in predetermining the puncture spot of transbronchial needle aspiration, suggesting their potential complementary role to the conventional technique of endobronchial ultrasound-guided transbronchial needle aspiration.

3D MDCT-based system for planning peripheral bronchoscopic procedures

The diagnosis and staging of lung cancer often begins with the assessment of a suspect peripheral chest site. Such suspicious peripheral sites may be solitary pulmonary nodules or other abnormally appearing regions of interest (ROIs). The state-of-the-art process for assessing such peripheral ROIs involves off-line procedure planning using a three-dimensional (3D) multidetector computed tomography (MDCT) chest scan followed by bronchoscopy with an ultrathin bronchoscope. We present an integrated computer-based system for planning peripheral bronchoscopic procedures. The system takes a 3D MDCT chest image as input and performs nearly all operations automatically. The only interaction required by the physician is the selection of ROI locations. The system is computationally efficient and fits smoothly within the clinical work flow. Integrated into the system and described in detail in the paper is a new surface-definition method, which is vital for effective analysis and planning to peripheral sites. Results demonstrate the efficacy of the system and its usage for the live guidance of ultrathin bronchoscopy to the periphery.

Image-based reporting for bronchoscopy

Bronchoscopy is often performed for staging lung cancer. The recent development of multidetector computed tomography (MDCT) scanners and ultrathin bronchoscopes now enable the bronchoscopic biopsy and treatment of peripheral diagnostic regions of interest (ROIs). Because these ROIs are often located several generations within the airway tree, careful planning and interpretation of the bronchoscopic route is required prior to a procedure. The current practice for planning bronchoscopic procedures, however, is difficult, error prone, and time consuming. To alleviate these issues, we propose a method for producing and previewing reports for bronchoscopic procedures using patient-specific MDCT chest scans. The reports provide quantitative data about the bronchoscopic routes and both static and dynamic previews of the proper airway route. The previews consist of virtual bronchoscopic endoluminal renderings along the route and three-dimensional cues for a final biopsy site. The reports require little storage space and computational resources, enabling physicians to view the reports on a portable tablet PC. To evaluate the efficacy of the reporting system, we have generated reports for 22 patients in a human lung cancer patient pilot study. For 17 of these patients, we used the reports in conjunction with live image-based bronchoscopic guidance to direct physicians to central chest and peripheral ROIs for subsequent diagnostic evaluation. Our experience shows that the tool enabled useful procedure preview and an effective means for planning strategy prior to a live bronchoscopy.

Interbronchoscopist variability in endobronchial path selection: a simulation study

BACKGROUND

Endobronchial path selection is important for the bronchoscopic diagnosis of focal lung lesions. Path selection typically involves mentally reconstructing a three-dimensional path by interpreting a stack of two-dimensional (2D) axial plane CT scan sections. The hypotheses of our study about path selection were as follows: (1) bronchoscopists are inaccurate and overly confident when making endobronchial path selections based on 2D CT scan analysis; and (2) path selection accuracy and confidence improve and become better aligned when bronchoscopists employ path-planning methods based on virtual bronchoscopy (VB).

METHODS

Studies of endobronchial path selection comparing three path-planning methods (ie, the standard 2D CT scan analysis and two new VB-based techniques) were performed. The task was to navigate to discrete lesions located between the third-order and fifth-order bronchi of the right upper and middle lobes. Outcome measures were the cumulative accuracy of making four sequential path selection decisions and self-reported confidence (1, least confident; 5, most confident). Both experienced and inexperienced bronchoscopists participated in the studies.

RESULTS

In the first study involving a static paper-based tool, the mean (+/- SD) cumulative accuracy was 14 +/- 3% using 2D CT scan analysis (confidence, 3.4 +/- 1.3) and 49 +/- 15% using a VB-based technique (confidence, 4.2 +/- 1.1; p = 0.0001 across all comparisons). For a second study using an interactive computer-based tool, the mean accuracy was 40 +/- 28% using 2D CT scan analysis (confidence, 3.0 +/- 0.3) and 96 +/- 3% using a dynamic VB-based technique (confidence, 4.6 +/- 0.2). Regardless of the experience level of the bronchoscopist, use of the standard 2D CT scan analysis resulted in poor path selection accuracy and misaligned confidence. Use of the VB-based techniques resulted in considerably higher accuracy and better aligned decision confidence.

CONCLUSIONS

Endobronchial path selection is a source of error in the bronchoscopy workflow. The use of VB-based path-planning techniques significantly improves path selection accuracy over use of the standard 2D CT scan section analysis in this simulation format.

3D CT-video fusion for image-guided bronchoscopy

Bronchoscopic biopsy of the central-chest lymph nodes is an important step for lung-cancer staging. Before bronchoscopy, the physician first visually assesses a patient's three-dimensional (3D) computed tomography (CT) chest scan to identify suspect lymph-node sites. Next, during bronchoscopy, the physician guides the bronchoscope to each desired lymph-node site. Unfortunately, the physician has no link between the 3D CT image data and the live video stream provided during bronchoscopy. Thus, the physician must essentially perform biopsy blindly, and the skill levels between different physicians differ greatly. We describe an approach that enables synergistic fusion between the 3D CT data and the bronchoscopic video. Both the integrated planning and guidance system and the internal CT-video registration and fusion methods are described. Phantom, animal, and human studies illustrate the efficacy of the methods.

Computer-based System for the Virtual-Endoscopic Guidance of Bronchoscopy

The standard procedure for diagnosing lung cancer involves two stages: three-dimensional (3D) computed-tomography (CT) image assessment, followed by interventional bronchoscopy. In general, the physician has no link between the 3D CT image assessment results and the follow-on bronchoscopy. Thus, the physician essentially performs bronchoscopic biopsy of suspect cancer sites blindly. We have devised a computer-based system that greatly augments the physician's vision during bronchoscopy. The system uses techniques from computer graphics and computer vision to enable detailed 3D CT procedure planning and follow-on image-guided bronchoscopy. The procedure plan is directly linked to the bronchoscope procedure, through a live registration and fusion of the 3D CT data and bronchoscopic video. During a procedure, the system provides many visual tools, fused CT-video data, and quantitative distance measures; this gives the physician considerable visual feedback on how to maneuver the bronchoscope and where to insert the biopsy needle. Central to the system is a CT-video registration technique, based on normalized mutual information. Several sets of results verify the efficacy of the registration technique. In addition, we present a series of test results for the complete system for phantoms, animals, and human lung-cancer patients. The results indicate that not only is the variation in skill level between different physicians greatly reduced by the system over the standard procedure, but that biopsy effectiveness increases.

A virtual bronchoscopic navigation system under X-ray fluoroscopy for transbronchial diagnosis of small peripheral pulmonary lesions

We had reported the utility of virtual bronchoscopic navigation system under CT-guidance for the diagnosis of small peripheral pulmonary lesions (PPLs). This study investigated the efficacy of virtual bronchoscopic navigation system for the diagnosis of small PPLs under X-ray fluoroscopy. We performed bronchoscopy with this system for 94 consecutive patients with 96 PPLs (< or =30mm in longest diameter; mean longest diameter, 16.2mm). A standard bronchoscope was used in 38 cases, and an ultrathin bronchoscope in 58 cases. Virtual bronchoscopic images were reconstructed from helical CT data. All the examinations were performed under X-ray fluoroscopy with virtual bronchoscopic navigation system, we referred both virtual bronchoscopic images and actual bronchoscopic images simultaneously to navigate the bronchoscopic pathway to the PPLs. Specimens for pathological examination were collected by transbronchial biopsy (TBB) and/or brushing. Virtual images accorded well with actual bronchoscopic images. The average total examination time was 24.1+/-7.4min (mean+/-S.D.). The overall diagnostic yields were 62.5% (60 of 96 PPLs), 71.1% (27 of 38 PPLs) with the standard bronchoscope, and 56.9% (33 of 58 PPLs) with the ultrathin bronchoscope. Diagnostic rates were 35%, 61.4% and 94.7% for lesions < or =10, 10-20, and >20mm, respectively. There were eight ground glass opacity (GGO) lesions confirmed only on CT scans; seven cases were pathologically diagnosed. All the examinations were performed safely with no complications. Bronchoscopy with virtual bronchoscopic navigation under X-ray fluoroscopy is useful for the diagnosis of small PPLs.

Virtual bronchoscopic navigation system shortens the examination time—Feasibility study of virtual bronchoscopic navigation system

Computed tomography (CT)-guided transbronchial biopsy (TBB) using an ultrathin bronchoscope with simulation by virtual bronchoscopy (VB) is effective for diagnosing small peripheral pulmonary lesions. However, we occasionally lose the proper bronchi to the lesion when a bronchoscope is inserted into peripheral bronchi with severe rotation. To overcome this problem, the virtual bronchoscopic navigation system that can display real-time VB images during TBB procedures in comparison with actual bronchi has been developed. We evaluated the usefulness of the virtual bronchoscopic navigation system for CT-guided TBB using an ultrathin bronchoscope (navigation method) to diagnose small peripheral pulmonary lesions, and compared the results to those with previous method that uses VB images in a simulation (simulation method). We performed CT-guided TBB using an ultrathin bronchoscope for 69 patients with 71 small peripheral pulmonary lesions (mean diameter, 13.7 mm) between November 2002 and November 2005 with the navigation method. CT-guided TBB with the navigation method was performed safely without any serious complications for all patients. Mean time to the initial scan, time to the first biopsy and total examination time were 5.3, 8.5 and 24.5 min, respectively. Fifty lesions (70%) were diagnosed by this procedure. Compared to simulation method, diagnostic sensitivity was higher in the navigation method, but the difference was not significant. However, the time to the first biopsy and total examination time were significantly shorter in the navigation method than in the simulation method (p<0.05). In summary, the virtual bronchoscopic navigation system was safely used, effective for diagnosing small peripheral pulmonary lesions, and useful for shortening the examination time of CT-guided TBB using an ultrathin bronchoscope.

A virtual bronchoscopic navigation system for pulmonary peripheral lesions

STUDY OBJECTIVES

We performed ultrathin bronchoscopy for pulmonary peripheral lesions using a system that displays virtual bronchoscopy (VB) images to the lesion simultaneously with actual images and navigates the bronchoscope to the target bronchus. We then evaluated the system with regard to its usefulness and problems.

DESIGN

A pilot study.

SETTING

A tertiary teaching hospital.

PATIENTS

The subjects were consecutive patients with small pulmonary peripheral lesions (< or = 30 mm).

INTERVENTIONS

Using this system, the rotation, advancement, and retreat of VB images were possible, and the bronchus into which the bronchoscope was to be advanced was displayed. VB images were displayed along with actual images, and the ultrathin bronchoscope was advanced to the target bronchus under direct vision. Under CT and radiographic fluoroscopy, a pair of forceps was inserted into the lesion via the bronchoscope. Thin-section CT images were obtained; after confirming the advancement of the bronchoscope into the target bronchus and the arrival of the forceps at the lesion, a biopsy was performed.

RESULTS

Study subjects included 37 patients with 38 lesions. VB images to a median of the sixth- (third- to ninth-) order bronchi could be produced. Using this system, the ultrathin bronchoscope could be advanced into the planned route for 36 of the 38 lesions (94.7%). The system was used for a median of 2.6 min, and the median examination time was 24.9 min. The biopsy forceps could be advanced to the lesion in 33 of the 38 lesions (86.8%), and diagnosis was possible for 31 lesions (81.6%).

CONCLUSIONS

This navigation system is useful for ultrathin bronchoscopy for pulmonary peripheral lesions.

Fluoroscopy-assisted thoracoscopic resection of pulmonary nodules after computed tomography--guided bronchoscopic metallic coil marking

OBJECTIVE

To localize small and deeply situated pulmonary nodules during thoracoscopy with roentgenographic fluoroscopy, we developed a marking procedure that uses a metallic coil.

METHODS

Nine patients underwent video-assisted thoracoscopic surgery for the removal of 11 pulmonary lesions. Fluoroscopy-assisted thoracoscopic surgery after computed tomography-guided bronchoscopic metallic coil marking was performed with an ultrathin bronchoscope, with simulation by means of virtual bronchoscopy. During thoracoscopy, a C-arm-shaped roentgenographic fluoroscope was used to detect the radiopaque nodules.

RESULTS

The marking procedure took 15 to 60 minutes from insertion to removal of the bronchoscope. There were no complications from the marking, and all 11 nodules were easily localized by means of thoracoscopy. The metallic coil showed the nodules on the fluoroscopic monitor, which aided in nodule manipulation. Nodules were completely resected under thoracoscopic guidance, except in one case in which a minithoracotomy was performed at an early stage of the trial. The pathologic diagnosis was primary adenocarcinoma in 9 patients, pulmonary metastasis from colon cancer in 1 patient, and pulmonary lymph node in 1 patient. Two cases of bronchioloalveolar adenocarcinoma with an invasive component and a well-differentiated adenocarcinoma were converted to open thoracotomy to perform curative lobectomy.

CONCLUSIONS

In this pilot study computed tomography-guided transbronchial metallic coil marking with an ultrathin bronchoscope with virtual bronchoscopic simulation might be a useful method for the fluoroscopy-assisted thoracoscopic resection of pulmonary nodules.

Transbronchial biopsy using endobronchial ultrasonography with a guide sheath and virtual bronchoscopic navigation

STUDY OBJECTIVES

We evaluated the feasibility, safety, and efficacy of transbronchial biopsy (TBB) using endobronchial ultrasonography with a guide sheath (EBUS-GS) and virtual bronchoscopy (VB) navigation for small peripheral pulmonary lesions < or = 30 mm in diameter.

DESIGN

Pilot study.

SETTING

A national university hospital.

PATIENTS

We performed TBB using EBUS-GS with VB navigation for 29 patients with 30 small peripheral pulmonary lesions (average diameter, 18.6 mm) between January 1, 2004, and August 31, 2004.

INTERVENTIONS

VB images were reconstructed from helical CT data. TBB was then performed using EBUS-GS with VB navigation.

RESULTS

In all patients, TBB was performed safely with no complications. Bronchi seen on VB imaging were highly consistent with the actual structures confirmed using fiberoptic bronchoscopy. Following VB navigation, the endobronchial ultrasonography (EBUS) probe was inserted into third- to sixth-generation bronchi. Twenty-four lesions (80%) were visualized on EBUS images. Average durations of the initial EBUS examination of lesions, first biopsy, and the total procedure were 9.56 min, 11.99 min, and 25.72 min, respectively. Nineteen lesions (63.3%) were diagnosed from histopathologic or cytologic examination. Diagnostic sensitivities were 44.4% (8 of 18) for lesions < 20 mm in mean diameter and 91.7% (11 of 12) for lesions 20 to 30 mm in mean diameter.

CONCLUSIONS

In summary, TBB using EBUS-GS with VB navigation was safely performed and was effective in diagnosing small peripheral pulmonary lesions.

Virtual Bronchoscopy: Accuracy and Usefulness—An Overview

Multidetector CT generated virtual bronchoscopy (VB) represents one of the most recent developments in three-dimensional (3D) visualization techniques which allows a 3D evaluation of the airways down to the sixth- to seventh-generation. In comparison with real bronchoscopy, VB has some advantages: it is a non-invasive procedure that can visualize areas inaccessible to the flexible bronchoscope. Virtual bronchoscopy is able to evaluate bronchial stenosis and obstruction caused by both endoluminal pathology (tumor, mucus, foreign bodies) and external compression (anatomical structures, tumor, lymph nodes), can be helpful in the preoperative planning of stent placement and can be used to evaluate surgical sutures after lung transplantations, lobectomy or pneumectomy. In children, in some indications, VB can replace fiber optical bronchoscopy (FB) when this technique is considered too invasive. Finally, VB can also be used to evaluate anatomical malformations and bronchial variants. Virtual bronchoscopy is accurate but its accuracy is not 100% because false-positives and false-negatives occur. Virtual bronchoscopy contributes to a better understanding of tracheo-bronchial pathology. Fiber optical bronchoscopy will, without doubt, remain the golden standard but it can be expected that in the near future, the technique of VB will find a place in the daily routine.

Is Virtual Bronchoscopy an Efficient Diagnostic Tool for the Thoracic Surgeon?

Virtual bronchoscopy has emerged over the past decade as a potentially complementary investigation to conventional bronchoscopy in the diagnosis, grading, and monitoring of pulmonary disease. A meta-analysis reporting on the use of virtual bronchoscopy has not yet been performed. The primary aim of this study is to evaluate its diagnostic accuracy compared to the gold standard investigation of conventional bronchoscopy (fiberoptic or rigid). Quantitative data synthesis included the calculation of independent sensitivity and specificity, construction of summary receiver operating characteristic curves, pooled analysis, and sensitivity analysis. Seventeen studies were identified comprising 459 patients. The calculated pooled sensitivity was 84% (95% CI, 78% to 89%), specificity 75% (95% CI, 62% to 85%) and area under the curve was 0.92, which shows good diagnostic performance. Meta-analysis confirms virtual bronchoscopy is very discriminating in the evaluation of patients with significant airway stenosis that is due to a wide spectrum of pathologic conditions. It can potentially have a beneficial role in selected thoracic patients (with bronchoesophageal fistulas, postlung transplantation, anastomoses, and suspected foreign body aspiration).

Three-dimensional path planning for virtual bronchoscopy

Multidetector computed-tomography (MDCT) scanners provide large high-resolution three-dimensional (3-D) images of the chest. MDCT scanning, when used in tandem with bronchoscopy, provides a state-of-the-art approach for lung-cancer assessment. We have been building and validating a lung-cancer assessment system, which enables virtual-bronchoscopic 3-D MDCT image analysis and follow-on image-guided bronchoscopy. A suitable path planning method is needed, however, for using this system. We describe a rapid, robust method for computing a set of 3-D airway-tree paths from MDCT images. The method first defines the skeleton of a given segmented 3-D chest image and then performs a multistage refinement of the skeleton to arrive at a final tree structure. The tree consists of a series of paths and branch structural data, suitable for quantitative airway analysis and smooth virtual navigation. A comparison of the method to a previously devised path-planning approach, using a set of human MDCT images, illustrates the efficacy of the method. Results are also presented for human lung-cancer assessment and the guidance of bronchoscopy.

CT-Guided Transbronchial Biopsy Using an Ultrathin Bronchoscope With Virtual Bronchoscopic Navigation

STUDY OBJECTIVES

We evaluated the feasibility, safety, and efficacy of CT-guided transbronchial biopsy (TBB) using an ultrathin bronchoscope with navigation by virtual bronchoscopy (VB) for small peripheral pulmonary lesions of < 20 mm in diameter.

DESIGN

A pilot study.

SETTING

A national university hospital.

PATIENTS

We performed CT-guided TBB after VB navigation for 25 patients with 26 small peripheral pulmonary lesions (average diameter, 13.2 mm) between June 1, 2001, and October 31, 2002. Of the 26 lesions, 10 were in the right upper lobe, 2 were in the right middle lobe, 6 were in the right lower lobe, and 8 were in the left upper lobe. Nineteen lesions were not detected on chest radiographs.

INTERVENTIONS

VB images were reconstructed from helical CT scans. CT-guided TBB was performed using an ultrathin bronchoscope after studying the VB image.

RESULTS

CT-guided TBB was performed safely without any complications for all patients. The bronchi seen under VB imaging were highly consistent with the actual bronchi confirmed using an ultrathin bronchoscope. The ultrathin bronchoscope was inserted between the fifth and eighth generation bronchi. The average durations of the initial scan, the first biopsy, and the total examination were 5.46, 12.96, and 29.27 min, respectively. Seventeen lesions (65.4%) were diagnosed from pathology examinations (primary lung cancers, 13; atypical adenomatous hyperplasia, 1; metastatic cancer, 1; sarcoidosis, 1; and nontuberculous mycobacteriosis, 1). Diagnoses were not obtained for the remaining lesions due to an insufficient number of specimens (six specimens) or to the inability to reach the lesions even using the ultrathin bronchoscope (three specimens).

CONCLUSIONS

In summary, CT-guided TBB using an ultrathin bronchoscope with VB navigation was safely performed and was effective for diagnosing small peripheral pulmonary lesions.

Grading Airway Stenosis Down to the Segmental Level Using Virtual Bronchoscopy

OBJECTIVE

To assess the sensitivity of noninvasive virtual bronchoscopy based on multirow detector CT scanning in detecting and grading central and segmental airway stenosis using flexible bronchoscopic findings as the reference standard.

MATERIALS AND METHODS

In a blinded controlled trial, multirow detector CT virtual bronchoscopy and flexible bronchoscopy were used to search for and grade airway stenosis in 20 patients. CT scan data were obtained with a multirow detector CT scanner using 4 x 1 mm collimation. Flexible bronchoscopy findings were graded by a pulmonologist and served as the reference standard for 176 central airway regions (ie, trachea, main bronchi, and lobar bronchi) and 302 segmental airway regions. The extent of airway narrowing was categorized as grade 0 (no narrowing), grade 1 (< 50%), or grade 2 (> or =50%).

RESULTS

Flexible bronchoscopy revealed 30 stenoses in the central airways and 10 in the segmental airways. Virtual bronchoscopy detected 32 stenoses in the central airways (sensitivity, 90.0%; specificity, 96.6%; accuracy, 95.5%) and 22 in the segmental airways (sensitivity, 90.0%; specificity, 95.6%; accuracy, 95.5%). The number of false-positive findings was higher in the segmental airways (13 false-positive findings) than in the central airways (5 false-positive findings), which caused a lower positive predictive value for the segmental airways (40.9%) than for the central airways (84.4%). Flexible and virtual bronchoscopic gradings correlated better for central airway stenosis (r = 0.87) than for segmental airway stenosis (r = 0.61).

CONCLUSION

Although a high sensitivity was found for the detection of both central and segmental airway stenosis, the number of false-positive findings was higher for segmental airways. However, noninvasive multirow detector CT virtual bronchoscopy enables high-resolution endoluminal imaging of the airways down to the segmental bronchi.