Tomography Bronchoscopy Research Articles

CT-guided transbronchial biopsy using an ultrathin bronchoscope with virtual bronchoscopic navigation

Chest 2004;125:1138–1143. Shinagawa N, Yamazaki K, Onodera Y, et al. Study Summary: In this study, the authors report their experience of performing computed tomography (CT)-guided transbronchial biopsy (TBB) with an ultrathin bronchoscope with navigation by virtual bronchoscopy in 25 patients with 26 small peripheral lung nodules. The average diameter of lung nodules was 13.2 mm. Nineteen lesions were not seen on the chest radiograph. CT examinations were performed using a multidetector CT scanner and virtual bronchoscopy images were reconstructed to fifth-order bronchi. The authors used an ultrathin bronchoscope with an external diameter of 2.8 mm and working channel of 1.2 mm. Information from virtual bronchoscopy was used to guide the ultrathin bronchoscope to the lung nodule. The biopsy forceps was introduced and its position was adjusted under real-time CT scan. Diagnostic tissue was obtained from 17 of 26 lesions (65%). The diagnoses were lung cancer (13 patients), atypical adenomatous hyperplasia (1 patient), and benign diagnosis (2 patients). Of the remaining 9 lesions, the specimen was inadequate in 6 cases and the lesion was inaccessible in 3 cases. Five of the 9 patients with nondiagnostic bronchoscopy had surgical resection. Lung cancer was found in 4 cases, and atypical adenomatous hyperplasia was found in 1 patient. The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of CT-guided TBB were 75%, 100%, 29%, 100%, and 77%, respectively. The average duration of bronchoscopy was approximately 30 minutes. The procedure was safe in all 25 patients. Virtual bronchoscopy guidance was felt to be accurate during actual bronchoscopy. Comments: Physicians and patients face difficult choices when a small lung nodule is detected incidentally or as part of a screening process. Although the majority of lung nodules detected during the screening process are benign, 1.3% to 3.1% of them represent early lung cancer (Radiology 2002;222:773–781, Lancet 1999;354:99–105, Am J Respir Crit Care Med 2002;165:508–513). Studies have shown that 5% to 15% of patients undergoing a screening process are referred for biopsy, and the majority of these patients receive a diagnosis of lung cancer (Ann Intern Med 2004;140:740–753). Although surgical resection is the gold standard for diagnosis, it is invasive and is not suitable for many patients with limited pulmonary reserve. In a recent study, surgery was unnecessary in as many as 20% patients (Am J Respir Crit Care Med 2003;168:1167–1173). A less invasive approach to management of small peripheral lung nodules is, therefore, highly desirable. Traditional bronchoscopy has a low diagnosis yield for solitary lung nodules, ranging from 10% to 33% for lesions smaller than 2 cm in diameter (Cleve Clin J Med 1998;65:315–326). An important reason for low yield of bronchoscopy in this circumstance is inability to visualize some of these lesions on fluoroscopy. Biopsy under CT fluoroscopy is more successful in such cases (Chest 2000;118:1630–1638). Another reason is failure to navigate the bronchoscope and the biopsy forceps to the intended target. A recent study found information from multiplanar CT reconstruction to be useful for more accurate navigation of biopsy instrument to the lesion (Chest 2003;124:1985–1992). Recent data also suggest a potential role of ultrathin bronchoscope in improving diagnostic yield from peripheral lung nodules. For instance, a recent study reported 70% diagnostic yield for lesions <3 cm when an ultrathin bronchoscope was use as an adjunct to standard bronchoscope (Respiration 2002;69:63–68). In the current study, virtual bronchoscopy, ultrathin bronchoscopy, and CT-fluoroscopy were used together, and the authors were able to obtain tissue diagnosis from 65% of lung nodules. This was impressive considering the size of the lesions biopsied. Clearly, this approach is safer than transbronchial needle aspiration or surgical biopsy. Some limitations of this study should be noted. The negative predictive value of bronchoscopy was only 30%. Therefore, negative bronchoscopy results have no clinical value. These patients will either need a more definitive biopsy or a close radiologic follow up. The other major issue is the risk of excessive radiation exposure to both the patient and the operator. Depending on the case volume, there is risk for considerable cumulative exposure, especially if appropriate radiation protection guidelines are not followed (Clin Chest Med 1999;20:33–38). The third major problem is logistic difficulty in scheduling and performing bronchoscopy in the CT suite. Undiagnosed lung nodules cause considerable patient anxiety. A firm diagnosis allows patients to make an informed decision, and it opens options for alternative treatments such as radiation therapy for nonsurgical candidates. In this context, the method used in this study has a better diagnostic yield than conventional bronchoscopy and is less invasive than surgical biopsy.

A barium marking method using an ultrathin bronchoscope with virtual bronchoscopic navigation

CT scanning in a 77-year-old woman showed a ground-glass opacity pattern shadow(9 x 7 mm) in the right lower lobe. To allow identification of the location of the lesion during thoracoscopic surgery, preoperative barium marking was performed using an ultrathin bronchoscope and virtual bronchoscopic navigation. Virtual bronchoscopy was performed based on thin-section CT images, and virtual bronchoscopic images to the target sites were obtained. Subsequently, using virtual bronchoscopic images to right B8aiibetax, B6biibeta for navigation, an ultrathin bronchoscope was advanced to this site under direct observation. A special catheter for ultrathin bronchoscopy was advanced to sites near the lesion, and barium was infused. Barium was clearly observed by radiographic fluoroscopy during thoracoscopic surgery and was useful for determining the area for resection. Pathological examination of the resected specimen revealed atypical adenomatous hyperplasia. There were no complications with this method, and a number of target areas could be readily marked in a short time. This method may be useful before thoracoscopic surgery for small peripheral pulmonary lesions.

Congenital pulmonary venolobar syndrome: spectrum of helical CT findings with emphasis on computerized reformatting.

The term congenital pulmonary venolobar syndrome refers to a wide spectrum of pulmonary developmental anomalies that may appear singly or in combination. The main components of congenital pulmonary venolobar syndrome are hypogenetic lung (including lobar agenesis, aplasia, or hypoplasia), partial anomalous pulmonary venous return, absence of pulmonary artery, pulmonary sequestration, systemic arterialization of lung, absence of inferior vena cava, and accessory diaphragm. The recent introduction of multisection helical computed tomography (CT), combined with use of advanced postprocessing graphic workstations, allows improved noninvasive delineation of complex congenital anomalies. A single fast (5-15-second) CT scan now enables the radiologist to (a) generate angiogram-like images of the anomalous pulmonary arteries and veins; (b) demonstrate tracheobronchial abnormalities by generating simulated bronchographic or bronchoscopic images; and (c) depict associated parenchymal abnormalities on axial, coronal, or sagittal images, which once represented an important advantage of magnetic resonance imaging over CT. Multisection helical CT is a helpful diagnostic tool in the preoperative evaluation of patients with suspected congenital pulmonary venolobar syndrome.

Laser-based endoscopic measurement of airway dimensions

Bronchoscopy is the technique of choice for the evaluation of a stenosis in the large airways. However, no system has been successfully employed for the bronchoscopic measurement of airway stenosis. The purpose of these study was the development and validation of a method for measuring the cross-sectional areas in the large airways. Furthermore, this application should be used for the 3D-reconstruction and visualisation of airway stenosis. A laser probe inserted into the operating channel of the bronchoscope enabled assessment of the distance between the images and the tip of the bronchoscope by means of projecting a ring of light on to the endoluminal wall. Image distortion due to the wide-angle lens was corrected by a computer program developed by us. Plastic tubes with known diameters were used for validation. Additionally, distortion-corrected bronchoscopic images were compared with distortion-free videoscopic image analysis of tracheal slices taken from pigs. When plastic tubes were used, the correlation coefficient (r) was slightly higher (r = 0,99, p < 0,01) than the correlation of cross-sectional areas between bronchoscopic and videoscopic images of tracheal slices (r = 0,88, p < 0,01). Furthermore the system could be used in a few patients for 2D and 3D measurement and visualisation of airway stenosis. Application of the present method offer quantitative assessment of airway stenosis located in the large airways.

P-448 Red/green ratio of full-color fluorescence bronchoscopic images is increased in the cancerous lesions compared with the normal bronchial areas

P-448 Red/green ratio of full-color fluorescence bronchoscopic images is increased in the cancerous lesions compared with the normal bronchial areas

Selective Bronchography

Selective Bronchography

CT virtual bronchoscopy in the evaluation of children with suspected foreign body aspiration

Objective: Computed tomography (CT) virtual bronchoscopy is a noninvasive technique that provides an internal view of trachea and major bronchi by three-dimensional reconstruction. The aim of this study was to investigate the usefulness of virtual bronchoscopy in the evaluation of suspected foreign body aspiration in children. Materials and methods: Twenty-three children (12 girls, 11 boys) with a mean age of 2.4 years (8 months–14 years) who were admitted to emergency room with a suspicion of foreign body aspiration were included in this study. Chest radiograms, spiral computed tomography scans and virtual bronchoscopy images were obtained. Then, rigid bronchoscopy was performed within 24 h. Results: CT virtual bronchoscopy and conventional bronchoscopy revealed the location of the foreign body in seven patients. It was in the right main bronchus in four patients, in the right lower lobe bronchus in one patient, and in the left main bronchus in two patients. There was no discordance between two modalities. CT examination revealed hyperaeration of the ipsilateral lung in four patients, hyperaeration of the ipsilateral lung and mediastinal shift in one patient and bronchiectatic changes in one patient. CT detected no additional finding in one patient with a foreign body in the right main bronchus. In 10 of 16 patients without foreign body, CT examination demonstrated atelectasis, infiltration, peribronchial thickening, and paratracheal lymphadenpoathy. Conclusion: Helical CT scanning with virtual bronchoscopy should be performed in only selected cases with suspected foreign body aspiration. When the chest radiograph is normal and the clinical diagnosis suggests aspirated foreign body, helical CT and virtual bronchoscopy can be considered in order to avoid needless rigid bronchoscopy.

Tracking of a bronchoscope using epipolar geometry analysis and intensity-based image registration of real and virtual endoscopic images

This paper describes a method for tracking the camera motion of a flexible endoscope, in particular a bronchoscope, using epipolar geometry analysis and intensity-based image registration. The method proposed here does not use a positional sensor attached to the endoscope. Instead, it tracks camera motion using real endoscopic (RE) video images obtained at the time of the procedure and X-ray CT images acquired before the endoscopic examination. A virtual endoscope system (VES) is used for generating virtual endoscopic (VE) images. The basic idea of this tracking method is to find the viewpoint and view direction of the VES that maximizes a similarity measure between the VE and RE images. To assist the parameter search process, camera motion is also computed directly from epipolar geometry analysis of the RE video images. The complete method consists of two steps: (a) rough estimation using epipolar geometry analysis and (b) precise estimation using intensity-based image registration. In the rough registration process, the method computes camera motion from optical flow patterns between two consecutive RE video image frames using epipolar geometry analysis. In the image registration stage, we search for the VES viewing parameters that generate the VE image that is most similar to the current RE image. The correlation coefficient and the mean square intensity difference are used for measuring image similarity. The result obtained in the rough estimation process is used for restricting the parameter search area. We applied the method to bronchoscopic video image data from three patients who had chest CT images. The method successfully tracked camera motion for about 600 consecutive frames in the best case. Visual inspection suggests that the tracking is sufficiently accurate for clinical use. Tracking results obtained by performing the method without the epipolar geometry analysis step were substantially worse. Although the method required about 20 s to process one frame, the results demonstrate the potential of image-based tracking for use in an endoscope navigation system.

Bronchomalacia associated with pulmonary atresia, ventricular septal defect and major aortopulmonary collateral arteries, and chromosome 22q11.2 deletion.

Respiratory distress is one of the major complications in young infants with pulmonary atresia, ventricular septal defect and major aortopulmonary collateral arteries (PA-VSD-MAPCA); however, its aetiology remains obscure. We have previously reported an association of bronchomalacia with PA-VSD-MAPCA in patients with a hemizygous deletion of chromosome 22q11.2 (del.22q11). To clarify the clinical relevance of bronchomalacia in patients with PA-VSD-MAPCA and del.22q11, we reviewed the clinical and laboratory records of four patients with PA-VSD-MAPCA who had del.22q11 and bronchomalacia. External bronchial compression by anomalous patterning of the aorta and MAPCA was documented in three of the four patients, using combinatorial examination of angiocardiography, bronchography, fibreoptic bronchoscopy and magnetic resonance imaging. One of the four patients died suddenly of severe respiratory distress at 4 years of age, while the remaining three were inoperable for complete surgical repair. Our study indicates that bronchomalacia as a result of external vascular compression may be an aetiology of early-onset respiratory distress in some patients with PA-VSD-MAPCA and del.22q11, and can significantly affect the clinical outcome.

Low-dose spiral CT: application to surface-rendered three-dimensional imaging of central airways.

The purpose of this work was to assess the utility of low-dose spiral CT for three-dimensional imaging of the central airways. Spiral CT was performed in 15 patients using two tube currents (50 and 240 mA), producing 30 CT data sets. Surface-rendered virtual bronchoscopy (VB) and shaded surface display (SSD) images were assessed by three radiologists for image quality. The radiologists were also asked to compare 15 matched pairs each of 50 and 240 mA VB and SSD images, blindly select the 240 mA image, and record differences in diagnostic quality between the matched images. No significant difference in image quality was noted with 50 or 240 mA. Only 51.1% of 240 mA SSD and 51.1% of 240 mA VB images were correctly identified. Differences in diagnostic quality, noted in 84.4% of SSD and 33% of VB image pairs, were not ascribed to image noise. Image quality of surface-rendered three-dimensional images of the central airways is preserved using a lower tube current.

Transbronchial Diagnosis of A Pulmonary Peripheral Small Lesion Using an Ultrathin Bronchoscope with Virtual Bronchoscopic Navigation

We report a patient with a pulmonary peripheral small lesion that was diagnosed using an ultrathin bronchoscope with virtual bronchoscopic (VB) navigation. In a 83-year-old man with pulmonary emphysema, chest computed tomography (CT) revealed a small lesion (18 × 14 mm) in the periphery of right segment 3. For diagnostic bronchoscopy, the area from the segmental bronchus to the lesion was examined by thin-section CT, and VB images up to the 11th bronchus as the route to the lesion were produced. Using these VB images, an ultrathin bronchoscope (external diameter, 2.8 mm) was inserted into the target bronchus. Because the VB images were in good agreement with the real bronchoscopic images, the ultrathin bronchoscope could be inserted readily at the 10th bronchus under direct vision. In addition, after confirming the positioning of the bioptome at the lesion by thin-section CT, a biopsy was acquired, and a diagnosis of pneumonia was made. This diagnostic method using an ultrathin bronchoscope with VB navigation is more accurate and can be performed in a shorter time than conventional bronchoscopy, and may be useful for evaluating pulmonary peripheral lesions.

A new method to perform quantitative measurement of bronchoscopic images.

Bronchoscopy is a commonly used clinical tool that provides a direct image of the bronchial lumen. However, bronchoscopy has seen little use as a quantitative measurement tool, mainly because of the wide-angle lens which distorts the image. The present authors have tested the ability of numerical algorithms and commercial software to correct for this distortion. Test objects of known size were imaged with four different bronchoscopes. Commercial image analysis software was used to measure the size of features in the images before and after applying distortion correction algorithms. The technique was then applied by measuring airway narrowing in anaesthetized pigs during vagal stimulation. Without correction, object size near the edge of the field of view is underestimated by approximately 40%. The error in measured diameter of concentric circles was dependent on the radius of the circle, increasing to 25% for circles occupying 90% of the field. Third order polynomial functions were required to correct these errors. After correction, errors were independent of object size or location in the image. Correction for lens distortion was independent of the distance between bronchoscope and object. The authors conclude that modern image processing software can correct for the distortion produced by wide-angle bronchoscope lenses.

Interventional Bronchoscopy

Interventional Bronchoscopy Edited by C.T. Bolliger and P.N. Mathur. Switzerland: Karger, 2000, 257 pp., $172.25. The field of interventional bronchoscopy is rapidly progressing. With this new growth, pulmonologists, especially interventional bronchoscopists, must keep abreast of the rapid developments in technology and the various techniques of therapeutic modalities. Because most of the indications, contraindications, and techniques of endobronchoscopic modalities are still evolving, together with a new generation of pulmonologists trying to gain experience in this field, this book by Bolliger and Mathur could not have come at a better time. It is an excellent, concise monograph encompassing the field of interventional bronchoscopy from the days of development of the bronchoscope to its modern use in various endobronchial diseases.emtpy The book is organized into five sections. The first section begins with the general aspects of bronchoscopy starting from its inception, from the days of Killian to the present day of modern bronchoscopy. With the forgotten art of rigid bronchoscopy, Dr. John Beamis has written an outstanding review on the modern use of the rigid bronchoscope. The various techniques of performing rigid bronchoscopy are supplemented with stepwise illustrations of the actual technique. The next chapter deals with the expertise, personnel, and equipment required as well as the maintenance of this equipment, making this chapter a must-read for the technical support staff of a bronchoscopy suite. The last two chapters in this section deal with the functional evaluation of the patient before and after endoscopy. This includes administration of anesthesia and preoperative evaluation for interventional bronchoscopy. How these investigations impact interventional strategies, technical success rates, and outcome is discussed at length.emtpy The second section deals with diagnostic bronchoscopy, including techniques of transbronchial needle aspiration and endobronchial ultrasound. The technique of transbronchial needle aspiration is very well explained by leading authorities in this field. Color figures and line diagrams add a great deal to this chapter. The authors think that the reader would acquire a better understanding, greater confidence, and improved yield with this important diagnostic tool. The evolving role of endobronchial ultrasound in airway and mediastinal diseases is depicted beautifully in the figures, which are very well described in the legends. The description clearly illustrates the addition of a new technique in pulmonologists' armamentarium and its research potential.emtpy The third section consists of thorough discussions of various therapeutic endobronchoscopic techniques, including foreign body removal, laser therapy, electrocautery, argon plasma coagulator, cryotherapy , brachytherapy, photodynamic therapy, and placement of tracheobronchial stents. All these techniques are very well described by well-known authorities on these techniques. The precise description of techniques is complemented with color photographs and references. The concluding chapter, which is certainly a highlight of this section, deals with the multimodality treatment of lung cancer, and it gives a concise and excellent review of managing terminal cancer by combining the traditional methods, like radiotherapy and chemotherapy, with the new endobronchial therapeutic modalities. The chapter adequately illustrates the role of endoscopic procedures in the management of advanced lung cancer. Although the authors briefly describe the role of flexible bronchoscopy in endoscopic procedures, better-detailed descriptions of actual techniques and safeguards would have been more appropriate because most of the centers still lack the expertise of using the rigid bronchoscope.emtpy The fourth section deals with the new techniques coming into the realm of pulmonologists and intensivists. The chapter on percutaneous dilatational tracheostomy and long-term transtracheal oxygen therapy are precise, easy to read, and supported by properly placed figures and tables that are helpful to the beginner. The reader will also be happy to see the chapter on image-guided interventional procedures in the thorax, which also adequately compares the yield of these procedures to those of traditional procedures.emtpy The last section deals with the potential future uses of bronchoscopy and includes autofluorescence bronchoscopy, virtual bronchoscopy, and the use of optical, diagnostic, and therapeutic technologies in pulmonary medicine and gene therapy in lung cancer. The illustration of virtual bronchoscopic images provides the reader with a practical approach, which in the future may take the place of conventional bronchoscopy as the standard of evaluating bronchial lesions.emtpy Apart from the lack of an adequate description of the use of flexible bronchoscopes in endobronchial therapeutic techniques, this book really provides a comprehensive and up-to-date overview of endobronchial therapeutic modalities and is highly recommended for those individuals who are currently performing the interventional procedures or who are planning to learn them in the future. This book is also recommended for pulmonologists who are not in the field of interventional bronchoscopy, but who want to learn about the various ways in which they can help their patients. Sandeep Mehrishi, M.D. Interventional Pulmonary Unit,Nassau University Medical Center,East Meadow, New York, U.S.A. Suhail Raoof, M.D. Pulmonary and Critical Care Medicine,Nassau University Medical Center,East Meadow, New York, U.S.A.

The role of CT virtual endoscopy for evaluation of the airway

Emergency evaluation of airway compromise secondary to head and neck lesions has been routinely performed with a CT scan followed by fiberoptic endoscopy. Fiberoptic endoscopy requires the use of sedation, which in a patient with airway compromise may precipitate further airway obstruction. CT Virtual Endoscopy (CTVE) provides a non-invasive means of evaluating the airway while simultaneously studying the head and neck soft tissues. We performed CTVE on 37 patients with history of airway compromise. Direct axial images as well as coronal and sagittal reconstructions were obtained and evaluated. Virtual bronchoscopic images of the tracheobronchial lumen were generated, employing General Electric Navigator Software and read on a standard workstation. The airway was effectively evaluated in all patients. There were no complications during the CT examinations. The findings delineate lesions requiring immediate open intervention or can direct the safe completion of subsequent FOB. CTVE is a safe, non-invasive and cost effective means of evaluating the airways in selective cases. It offers 24-h availability, no need for sedation, and the ability to evaluate submucosal and lymph node extension of lesions.

Virtual bronchoscopy for directing transbronchial needle aspiration of hilar and mediastinal lymph nodes

OBJECTIVE: We conducted a preliminary investigation of virtual bronchoscopy as a guide for transbronchial needle aspiration of hilar or mediastinal lymph nodes to assess the usefulness of this technique. CONCLUSION: Virtual bronchoscopic images derived from routine helical CT scans were useful for directing transbronchial needle aspiration in a clinical setting. In addition, virtual bronchoscopy may have been responsible for improving the yield of transbronchial needle aspirations done by our bronchoscopists when 22-gauge needles were used.

VIRTUAL BRONCHOSCOPY

Three-dimensional endoluminal tracheobronchial simulations can be derived successfully from thoracic helical CT scans, and can reproduce the appearances of major endobronchial abnormalities confirmed during FB. The prospects of ever-faster CT scanners (capable of submillimeter resolution) merged with greater computer power make it likely that current versions of virtual bronchoscopy images will seem primitive in the future. Initial descriptive reports suggest great potential, but the startling visual appeal of these 3-D portrayals of a patient's airway and mediastinal anatomy and the prospects of exploring this information in real time do not establish its clinical role. Such virtual bronchoscopy findings are generally predictable on the basis of currently available axial CT images alone. The extent to which these 3-D endobronchial renderings improve the already high predictive values of CT requires critical study. In their patients with lung cancer Cicero et al observed that neither the staging nor diagnosis was modified substantially, but virtual bronchoscopy contributed to enhanced understanding of the pathology of the neoplastic process. Whether this added perspective translates to tangible benefits for patients is an intriguing possibility that has yet to be proved. The unique 3-D endobronchial view may offer particular advantages in some individuals and contribute to the patient's noninvasive evaluation. Because of the already high yield of conventional CT, diagnostic yield alone is not likely to be the sole best measure of this evolving technology. Accordingly, future multidisciplinary research investigations will also need to prospectively address nuances of decision-making and measure appropriate patient outcomes. In these efforts the active dialogue between chest clinician and radiologist will remain essential to defining and realizing the true potential of virtual bronchoscopy.

Virtual bronchoscopy for directing transbronchial needle aspiration of hilar and mediastinal lymph nodes: a pilot study.

We conducted a preliminary investigation of virtual bronchoscopy as a guide for transbronchial needle aspiration of hilar or mediastinal lymph nodes to assess the usefulness of this technique. Virtual bronchoscopic images derived from routine helical CT scans were useful for directing transbronchial needle aspiration in a clinical setting. In addition, virtual bronchoscopy may have been responsible for improving the yield of transbronchial needle aspirations done by our bronchoscopists when 22-gauge needles were used.

CT virtual bronchoscopy of simulated endobronchial lesions: effect of scanning, reconstruction, and display settings and potential pitfalls.

V irtual bronchoscopy is a type of three-diniensional reconstruction of the airways in which the obserVatiOt point is placed within the airway lumen to produce an endoscopelike display I 1-31. One potential use of virtual bronchoscopy is detection and size nieasurenient of’ endobronchial masses 31Size measurements are now son etinies difficult to make troti source CT inlages because the axes of the lesion may not niatch those of the imaging plane and during conventional bronchoscopy because of distortions in the bronchoscopic images. For nieasuren ents of lesion size from virtual bronchoscopy to be useful they must be valid. In this study. we assess the capability of a coniiiiercially available virtual endoscopy system in detection and measurement of simulated endobronchial lesions in a phantom niodel and we describe potential pitfalls in measurement due to the perspective rendering effect and poorer hetween-sec-

Registration of real and CT-derived virtual bronchoscopic images to assist transbronchial biopsy.

This paper describes research work motivated by an innovative medical application: computer-assisted transbronchial biopsy. This project involves the registration, with no external localization device, of a preoperative three-dimensional (3-D) computed tomography (CT) scan of the thoracic cavity (showing a tumor that requires a needle biopsy), and an intraoperative endoscopic two-dimensional (2-D) image sequence, in order to provide assistance in transbronchial puncture of the tumor. Because of the specific difficulties resulting from the data being processed, a multilevel strategy was introduced. For each analysis level, the relevant information to process and the corresponding algorithms were defined. This multilevel strategy, thus, provides the best possible accuracy. Original image processing methods were elaborated, dealing with segmentation, registration and 3-D reconstruction of the bronchoscopic images. In particular, these methods involve adapted mathematical morphology tools, a "daemon-based" registration algorithm, and a model-based shape-from-shading algorithm. This pilot study presents the application of these algorithms to recorded bronchoscopic video sequences for five patients. The preliminary results presented here demonstrate that it is possible to precisely localize the endoscopic camera within the CT data coordinate system. The computer can thus synthesize in near real-time the CT-derived virtual view that corresponds to the actual endoscopic view.

Virtual Bronchoscopy with Perflubron Enhancement. † 1814

The advent of helical computerized tomography (CT) has allowed for volumetric data acquisition with markedly improved multiplanar reconstruction as well as three dimensional rendering. Post-processing software has permitted changing the viewer frame of reference thus allowing direct visualization of the inside of large airways or so called virtual bronchoscopy. Air within the lumen supplies contrast; however, in bronchial tree branches, the walls are thin thereby reducing contrast and resolution. We hypothesized that the instillation of a dose of liquid perflubron (LiquiVent®, Alliance Pharm Corp, San Diego, CA) would increase airway contrast and therefore increase airway resolution. To test this hypothesis, we compared helical CT images in an anesthetized, intubated, adolescent New Zealand rabbit model during mechanical gas ventilation at end inspiration and expiration. Imaging was performed without and with 15 ml/kg of perflubron in the lungs. A Picker PQ 5000 helical CT scanner was used and targeted 10 cm FOV, 3mm slice thickness, with a pitch of 1.25, images reconstructed every 3mm with a smooth spatial reconstruction algorithm, and mA/kVp of 200/120. The bronchoscopic CT without perflubron only allowed visualization of the first 2 generations with poor resolution of 3rd order branches and beyond. In contrast, images with perflubron permitted improved resolution of the tracheobronchial tree to the 5th order branches. These preliminary studies demonstrate that perflubron liquid in the lungs can enhance bronchoscopic CT images of the tracheobronchial tree by improving contrast and resolution of more distal generations of airways. This new innovation represents a potentially favorable combination of perfluorochemicals as contrast medium with the emerging technology of virtual bronchoscopy. (Perflubron provided by Alliance Pharm Corp & Hoechst Marion Roussel)