Hybrid 3D visualization of the chest and virtual endoscopy of the tracheobronchial system: possibilities and limitations of clinical application

Update on multidetector computed tomography imaging of the airways

Recent advances in multidetector computed tomography (MDCT) technology have transformed the imaging evaluation of the trachea and bronchi. Multiplanar 2-dimensional and 3-dimensional volume reconstruction techniques, including external rendering and virtual bronchoscopy, can be generated in mere minutes, thereby complementing conventional axial CT imaging in the depiction of various central airway disease processes including airway stenoses, central airway neoplasms, and congenital airway disorders. Paired inspiratory and dynamic expiratory MDCT imaging, along with newer cine CT imaging methods, have enhanced the assessment of tracheobronchomalacia in both adults and the pediatric population. In addition, MDCT imaging plays an essential complementary role to conventional bronchoscopy, facilitating planning and guidance of bronchoscopic interventions, and providing a noninvasive method for postprocedural surveillance.

Multimodal virtual bronchoscopy using PET/CT images

OBJECTIVE

To demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT).

MATERIALS AND METHODS

Eight consecutive patients with non-small cell lung cancer (NSCLC) underwent PET/CT. PET was performed with a glucose analog, 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG), using a state-of-the-art full-ring Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. The tracheobronchial system was segmented using the CT data set with an interactive threshold interval volume-growing segmentation algorithm. The primary tumors and lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual hybrid bronchoscopy using the PET/CT data set. The structures of interest were visualized with a color-coded shaded-surface rendering method.

RESULTS

The use of CT and virtual CT-bronchoscopy primarily facilitates visualization of the anatomical details of the tracheobronchial system and detection of anatomical/morphologic structural changes caused by disease. PET/CT and virtual hybrid bronchoscopy, or virtual PET/CT-bronchoscopy, give superior results to virtual CT-bronchoscopy because the hybrid bronchoscopy uses both the CT information and the molecular/metabolic information about the disease obtained from PET.

CONCLUSIONS

PET/CT imaging has proven to be a highly valuable oncological diagnostic modality. Virtual hybrid bronchoscopy can be performed using a low-dose CT scan or diagnostic CT. However, it is expected to improve diagnostic accuracy in identification and characterization of malignancies, verification of infections, and differentiation of viable tumor tissue from atelectases and scar tissue, as well as assessment of tumor staging and therapeutic response, and detection of early stage recurrences that are not detectable or are liable to be misjudged using virtual CT-bronchoscopy. It could also be useful as a screening examination method for patients with suspected endobronchial malignancy. Virtual hybrid bronchoscopy with a transparent color-coded shaded-surface rendering model offers a useful alternative to fiberoptic bronchoscopy, and is particularly promising for patients for whom fiberoptic bronchoscopy is not feasible, contraindicated or refused.

Tracheobronchial Anomalies and Stenoses: Detection with Low-Dose Multidetector CT with Virtual Tracheobronchoscopy—Comparison with Flexible Tracheobronchoscopy

PURPOSE

To prospectively assess the sensitivity and specificity of low-dose multidetector computed tomography (CT) with virtual tracheobronchoscopy (VT) for evaluation of suspected airway stenoses and/or abnormalities by using flexible tracheobronchoscopy (FT) as the reference standard.

MATERIALS AND METHODS

The study was approved by the local ethics committee; parental consent was obtained. Forty-five patients with clinically and/or radiographically suspected tracheobronchial stenosis and/or anomaly underwent FT and contrast material-enhanced single-phase multidetector CT with VT. CT was performed with an age- and weight-adjusted low-dose protocol: 120 or 80 kV; 120 or 60 mA; collimation, 1.5 or 0.75 mm; gantry rotation, 0.5 second. Mean effective dose was calculated for all examinations. Postprocessing was performed with surface rendering of VT images and multiplanar reformations. CT images were analyzed in consensus by two radiologists who were blinded to FT results. Statistical analysis was performed with 2 x 2 contingency tables; 95% confidence intervals (CIs) were calculated with the Blyth-Still-Casella procedure.

RESULTS

Mean patient age was 4.4 years (range, 2 months to 16 years; 53% male patients). Tracheobronchial narrowing and/or abnormality were depicted at FT in 38 of 45 patients. In 33 of 38 patients, multidetector CT with VT depicted a tracheobronchial narrowing and/or anomaly. In 10 of 38 patients, tracheobronchial stenosis was induced by vascular anomalies. Five patients with normal findings at multidetector CT with VT had tracheobronchomalacia with inspiratory airway stenosis at FT. Sensitivity and specificity of CT with VT were 86.8% (95% CI: 73.3%, 94.7%) and 85.7% (95% CI: 44.6%, 99.3%), respectively. Positive and negative predictive values were 97.1% (95% CI: 84.9%, 99.9%) and 54.5% (95% CI: 25.0%, 80.0%), respectively. Overall accuracy was 86.7% (95% CI: 74.3%, 94.0%). Mean effective dose was 1.1 mSv (range, 0.5-1.8 mSv).

CONCLUSION

Multidetector CT with VT with a low-dose protocol had high sensitivity and specificity for depiction of tracheobronchial narrowings and/or anomalies. However, tracheal narrowing due to tracheobronchomalacia was difficult to diagnose at single-phase multidetector CT with VT.

Virtual positron emission tomography/computed tomography-bronchoscopy: possibilities, advantages and limitations of clinical application

The aim of this study was to demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT). Twelve consecutive patients with lung cancer underwent PET/CT. PET was performed with F-18-labelled 2-[fluorine-18]-fluoro-2-deoxy-D: -glucose ((18)F-FDG). The tracheobronchial system was segmented with a volume-growing algorithm, using the CT data sets, and visualized with a shaded-surface rendering method. The primary tumours and the lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual PET/CT-bronchoscopy using the PET/CT data set. Virtual CT-bronchoscopy using the low-dose or diagnostic CT facilitates the detection of anatomical/morphological structure changes of the tracheobronchial system. Virtual PET/CT-bronchoscopy was superior to virtual CT-bronchoscopy in the detection of lymph node metastases (P=0.001), because it uses the CT information and the molecular/metabolic information from PET. Virtual PET/CT-bronchoscopy with a transparent colour-coded shaded-surface rendering model is expected to improve the diagnostic accuracy of identification and characterization of malignancies, assessment of tumour staging, differentiation of viable tumour tissue from atelectases and scars, verification of infections, evaluation of therapeutic response and detection of an early stage of recurrence that is not detectable or is misjudged in comparison with virtual CT-bronchoscopy.

CT bronchoscopy in the diagnosis of Williams-Campbell syndrome

Williams-Campbell syndrome, a rare disorder, is characterized by a congenital deficiency of cartilage, typically involving the fourth to the sixth order bronchi, and resulting in expiratory airway collapse and bronchiectasis. The authors report a patient with Williams-Campbell syndrome with type II respiratory failure due to extensive cystic bronchiectasis and secondary emphysema. CT of the thorax showed the affected bronchi had characteristic ballooning on inspiration and collapse on expiration. Three-dimensional images of the tracheobronchial tree were constructed from a volume of data acquired by thin-slice CT scanning. Apart from confirming expiratory collapse of the affected bronchi, these images revealed an absence of the cartilage ring impressions in the bronchial wall, extending bilaterally from the mainstem down to subsegmental bronchi, suggesting cartilage deficiency.

Depth-map-based scene analysis for active navigation in virtual angioscopy

This paper presents a new approach dealing with virtual exploratory navigation inside vascular structures. It is based on the notion of active vision in which only visual perception drives the motion of the virtual angioscope. The proposed fly-through approach does not require a premodeling of the volume dataset or an interactive control of the virtual sensor during the fly-through. Active navigation combines the on-line computation of the scene view and its analysis, to automatically define the three-dimensional sensor path. The navigation environment and the camera-like model are first sketched. The basic stages of the active navigation framework are then described: the virtual image computation (based on ray casting), the scene analysis process (using depth map), the navigation strategy, and the virtual path estimation. Experimental results obtained from phantom model and patient computed tomography data are finally reported.

Evaluation of tracheobronchial anomalies in children using low-dose multidetector CT: report of a 13-year-old boy with a tracheal bronchus and recurrent pulmonary infections

Tracheobronchial anomalies in children may be associated with recurrent episodes of pulmonary infections and symptoms of recurrent or persistent airway obstruction. Diagnosis by conventional imaging may be difficult. Multidetector computed tomography (MDCT) offers the possibility to generate a virtual three-dimensional bronchoscopy, thus enabling detailed overview of the tracheobronchial system. We report on a 13-year old boy, admitted to hospital after recurrent episodes of bronchial infections. Functional studies showed airway obstruction with no response to bronchodilators. A chest radiograph was normal. Flexible bronchoscopy revealed tracheobroncho malacia of the distal trachea and the right main bronchus. The ostium of an accessory right-sided tracheal bronchus, which could not be entered by the endoscope, was also detected. MDCT using a low-dose protocol was performed on a four-section scanner (Somatom Volume Zoom, Siemens, Erlangen, Germany). A three-dimensional virtual bronchoscopy based on surface rendering was generated, which confirmed moderate narrowing of the trachea and right main bronchus. Furthermore, an accessory and stenotic tracheal bronchus including poststenotic segments, ventilating parts of the right upper lobe, could be clearly visualized. MDCT can be a valuable instrument in the diagnostic pathway of assessing tracheobronchial anomalies in children, including visualization of poststenotic bronchial structures. The use of low-dose protocols provides adequate image quality to perform virtual bronchoscopy, thus reducing administered radiation to a tolerable amount.

Accuracy of virtual bronchoscopy to detect endobronchial lesions

BACKGROUND

Virtual bronchoscopy (VB) could obviate flexible bronchoscopy (FB) if no endobronchial lesion is detected in patients presenting with a suspicion of malignancy. Our objectives were to evaluate the accuracy (in terms of sensitivity and specificity) of VB in detecting endobronchial lesions, and to determine the anatomical limit of detection of endobronchial lesions by VB.

METHODS

This study involved, in a blind comparison of VB and FB, consecutive patients presenting with symptoms or plain chest radiography abnormalities raising the suspicion of pulmonary neoplasm. After the standard chest computed tomography (CT), additional helical CT data were acquired from the aortic arch to the origin of the segmental bronchi of the inferior lobes in one 20-second breath hold using an helicoidal CT scan (3.0-mm collimation with a pitch of 1.5 and 1.5-mm reconstruction intervals).

RESULTS

One hundred ninety patients were enrolled; 136 patients (including 63 with an endobronchial lesion at FB) contributed to the primary analysis. The sensitivity and specificity of VB to detect endobronchial lesions were 68% (95% confidence interval [CI]: 55% to 79%) and 90% (95% CI: 81% to 96%), respectively. Overall, the agreement between VB and FB regarding the location on endobronchial lesions was substantial (weighted kappa: 0.66). However, VB detected only 26 of the 34 lobar lesions (sensitivity: 76%; CI: 59% to 89%) and 11 of the 23 segmental lesions (sensitivity: 48%; CI: 27% to 69%).

CONCLUSIONS

Beyond the mainstem bronchi, VB is not accurate enough to detect endobronchial lesions and to obviate FB in patients presenting with a suspicion of malignancy.

Computed Tomographic Colonography (CTC): Possibilities and Limitations of Clinical Application in Colorectal Polyps and Cancer

Colorectal cancer is the second leading cause of cancer-related deaths in Europe and the United States. Most colorectal cancers develop from adenomatous polyps over a number of years. Early detection of polyps eliminates the risk of subsequent carcinomas.

Computed tomographic (CT) colonography is a diagnostic technique detecting colorectal neoplasms. With the introduction of multidetector-row computed tomography (MD-CT), CT colonography (CTC) has gained influence as a new diagnostic tool in early detection of colonic pathologies by acquiring volumetric CT data sets of the abdomen. This volumetric data is analyzed using CTC workstations, which provide an interactive display of 2D and 3D images of the colon. In several studies, CTC revealed a high accuracy (sensitivity/patient: 83–100% and specificity/patient: 93–100%) in detecting pathological colonic changes. Furthermore, CTC is an excellent diagnostic technique for the evaluation of patients with incomplete conventional colonoscopy and allows the assessment of extracolonic abdominal and pelvic organs.

In this article, the status of CT colonography as a method of detecting colonic polyps and colorectal carcinomas using single- and multidetector-row CT will be reviewed.

Comparative evaluation of super high-resolution CT scan and virtual bronchoscopy for the detection of tracheobronchial malignancies

OBJECTIVES

Novel imaging modalities are currently available for the noninvasive evaluation of the tracheobronchial tree. This study was undertaken to compare the diagnostic potentials of conventional CT scanning, super high-resolution CT (SHR-CT) scanning, and virtual bronchoscopy (VB) directly with fiberoptic bronchoscopy (FB) for the detection of tracheobronchial neoplasms.

DESIGN

Prospective observer study, in which 44 consecutive patients with thoracic malignancies were evaluated using several diagnostic imaging modalities. Images of the thorax were interpreted by individuals blind to the results of FB for the detection of endoluminal, obstructive, or mucosal lesions.

MEASUREMENTS AND RESULTS

Image acquisition and simulation of the tracheobronchial anatomy were created successfully in all patients. Thirty-two patients who underwent both SHR-CT scanning and VB had correlative FBs within 1 month. In all nine patients who had a normal anatomy, SHR-CT scanning and VB accurately correlated with the FB findings. However, CT scanning demonstrated two false-positive obstructive lesions in one patient. Twenty-three patients had a total of 35 abnormal FB findings. The sensitivities of SHR-CT scanning and VB for the detection of endoluminal, obstructive, and mucosal lesions were 90%, 100%, and 16%, respectively. The overall sensitivities and specificities of SHR-CT scanning and VB were 83% and 100%, respectively. In contrast, CT scanning had sensitivities of 50%, 72%, and 0% for the detection of endoluminal, obstructive, and mucosal lesions with an overall sensitivity and specificity of 59%, and 85%, respectively. There was no case in which conventional CT scanning was better at detecting lesions than either SHR-CT scanning or VB.

CONCLUSIONS

SHR-CT scanning and VB are accurate, noninvasive methods for identifying obstructions and endoluminal lesions within the respiratory tract. Thus, these novel imaging techniques are valuable as complementary modalities to FB, providing information that is useful for the detection and management of airway malignancies.

Virtual bronchoscopy: comparison of different surface rendering models

The aim of this study was to compare different representation models of surface-rendered virtual bronchoscopy. 10 consecutive patients with inoperable primary lung tumors underwent thin-section spiral computed tomography. The structures of interest, the tracheobronchial system and anatomical and pathological thoracic structures were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with the aid of a color-coded surface rendering method. For virtual bronchoscopy, the tracheobronchial system was visualized using a triangle-surface rendering model, a shaded-surface rendering model and a transparent shaded-surface rendering model. The triangle-surface rendering model allowed optimum detailed spatial representation of the dimensions of extraluminal anatomical and pathological mediastinal structures. As the lumen of the tracheobronchial system was less well defined, the rendering model was of limited use for depiction of the airway surface. The shaded-surface rendering model facilitated an optimum assessment of the airway surface, but the mediastinal structures could not be depicted. The transparent shaded-surface rendering model provides simultaneous adequate to optimum visualization and assessment of the intraluminal airway surface and the extraluminal mediastinal structures as well as a quantitative assessment of the spatial relationship between these structures. Fast data acquisition with a multi-slice detector spiral computed tomography scanner and the use of virtual bronchoscopy with the transparent shaded-surface rendering model obviate the need for time consuming detailed analysis and presentation of axial source images by providing improved the diagnostic imaging of endotracheal and endobronchial diseases and offering a useful alternative to fiberoptic bronchoscopy.

Use of three-dimensional computed tomographic angiography of pulmonary vessels for lung resections

BACKGROUND

Identification and appropriate treatment of the pulmonary artery (PA) is a key to successful anatomic resection of the lung. Preoperative identification of branching pattern of the PA seems to make pulmonary resection easier and safer especially when there is severe adhesion or incomplete fissure between the lobes. With the development of the multidetector row spiral computed tomography (MDCT), three-dimensional (3D) CT angiography can be obtained easily and can provide very useful information about various organs. We studied the usefulness of 3D-CT pulmonary angiography (3D-CTPA) in evaluating the PA branching pattern before anatomic pulmonary resection.

METHODS

Fourteen patients with primary lung cancer undergoing anatomic pulmonary resections were the subjects of this study. The 3D-CTPA images were obtained using MDCT. The obtained images of the PA branching pattern were compared with intraoperative findings in each case at the time of thoracotomy.

RESULTS

MDCT scanning required approximately 15 seconds per patient during a single respiratory pause and the 3D images were processed within 10 minutes after scannning. According to intraoperative findings, 98% (84 of 86) of PA branches were revealed to be successfully identified on preoperative 3D-CTPA. Two missed branches on 3D-CTPA were small vessels, which were less than 1.5 mm in actual diameter. Pulmonary vessels were clearly identified even when contrast medium was not administered intravenously.

CONCLUSIONS

Obtaining 3D-CTPA using MDCT is noninvasive yet it provides precise preoperative information regarding pulmonary vessels. This technique is a far less invasive and an easier investigation than conventional pulmonary angiography. The 3D-CTPA navigation may have the potential to increase the safety of surgical procedure and to reduce surgical morbidity in anatomic lung resection.

Innovative molecular and imaging approaches for the detection of lung cancer and its precursor lesions

Current approaches for the therapy of lung cancer, the majority of which being advanced cancers, have failed to impact on long term survival. The key to improvement lies in the combination of early diagnosis and the introduction of novel targeted therapies. In this article we review some of the innovative approaches, both imaging and molecular, that are currently under investigation for early detection. Because lung cancers may arise in the central or peripheral compartments of the lung, newer approaches must target tumours arising in both of these compartments. Specimens available for analysis include sputa and blood. Detection of genetic changes in peripheral blood is a promising avenue being explored by several groups. Molecular techniques discussed include gene mutations, detection of nuclear riboprotein, methylation related silencing of genes and malignancy associated changes. Newer imaging technologies include autofluorescence bronchoscopy, virtual bronchoscopy, optical coherent tomography and confocal microscopy. Although the impact of these new technologies on survival has not been determined, they offer a wide range of exciting new approaches. In time they may completely revamp the present highly conservative and unsuccessful approaches to early diagnosis.