Advances in computer technology have permitted development of virtual bronchoscopy or virtual reality images of the tracheobronchial tree using data sets derived from multidetector computed tomography (CT) of the chest. Its utility in bronchoscopic lung and lymph node biopsy has been previously reported.1
Software such as Bf-NAVI (Olympus, Tokyo, Japan) and LungPoint (Broncus, Mountain View, CA) are available to provide virtual bronchoscopic images.2,3 The process of reconstructing virtual bronchoscopic images from CT data is automated; the process of finding an adequate path to a lesion is partially automated. Although these software programs are very useful, they are not widely used because of their high cost.
OsiriX (OsiriX Foundation, Geneva, Switzerland) is an image-processing software dedicated to DICOM images produced by medical equipment such as CT scanners.4 OsiriX has been specifically designed for navigation and visualization of multimodality and multidimensional images, including virtual endoscopy.5,6 OsiriX is an open source software and only works on Mac OS (Apple, Cupertino, CA). A notable advantage of OsiriX is that the 32-bit version is free; OsiriX MD, the 64-bit version cleared by the Food and Drug Administration for primary diagnosis, costs only 599 US dollars. OsiriX has made virtual bronchoscopic images available at a low cost, which can help virtual bronchoscopy gain popularity.
In this paper, we present the ability of OsiriX to reconstruct virtual bronchoscopic images.
PATIENTS AND METHODS
The institutional review board approved the protocol, and written informed consent was obtained from all patients. We obtained approval from our institution to use patient medical records for our study and patient confidentiality was maintained.
Subjects consisted of 10 patients with lung nodules, evenly split between the right and left lungs. Chest CT without contrast was performed using a 16-row multidetector scanner with 2 mm slices pitch without overlap from one lung.
Reconstruction of Virtual Bronchoscopic Images
OsiriX version 5.5 (32-bit) was installed on a Mac Mini with OS 10.7 Lion. DICOM data from the patients’ chest CT were copied to the computer. The chest CT images were automatically converted to a bronchoscopic view using the “3D endoscope” function in OsiriX (Fig. 1, Video 1, Supplemental Digital Content 1, http://links.lww.com/LBR/A105). This process takes less than 30 seconds.
We can move freely in the 3-dimensional (3D) virtual bronchial tree using the mouse buttons (Video 2, Supplemental Digital Content 2, http://links.lww.com/LBR/A106). The current position and direction of the virtual bronchoscope is indicated on the multiplanar reconstruction CT images.
Visualization of Bronchi
To examine the ability to visualize small bronchi, we attempted to visualize the most distal bronchi possible. We selected B1a and B10c for the right lung and B1+2a and B10c for the left lung. It takes approximately 5 to 10 minutes to reconstruct the path from the trachea to the most distal bronchi (Video 2, Supplemental Digital Content 2, http://links.lww.com/LBR/A106).
Virtual Bronchoscopic Lung Biopsy (VBLB)
Bronchoscopy was not performed in 2 of 10 patients because the lesion was not bronchoscopically accessible. Three patients who underwent bronchoscopy did not undergo surgery because 2 patients were diagnosed with lung infection and the other patient was diagnosed with metastatic lung cancer. In 5 of 10 patients, transbronchial lung biopsy followed by lung resection was performed.
To predict whether the transbronchial lung biopsy resulted in the correct pathologic diagnosis, we reconstructed virtual bronchoscopic images toward the lung nodule. If the virtual bronchoscopic pathway reaches the lung nodule, we expect that transbronchial lung biopsy would result in an accurate diagnosis.
Visualization of Bronchi
Bronchoscopic images were successfully reconstructed for all patients. It takes several seconds to convert CT images into bronchoscopic images.
The third to the seventh bronchi were visualized, except in one patient whose right B10 was occluded by a tumor (Table 1). The smallest bronchial diameter visualized was approximately 1.5 mm.
For all cases, the second-order bronchus, such as B1 and B10, were easily visualized. To visualize the third and higher-order bronchi, it was sometimes necessary to manually adjust the brightness and contrast. The pathway can be recorded and retrieved using the “Fly Through” function.
The virtual bronchoscopy pathway was reconstructed in only 5 to 10 minutes. In all cases, the path reached the lung nodule (Fig. 2, Video 3, Supplemental Digital Content 3, http://links.lww.com/LBR/A107). Therefore, we predict that bronchoscopic biopsy would have been successful in all cases. On the basis of transbronchial biopsy, 4 patients were diagnosed with lung carcinoma and 1 patient was suspected of having adenocarcinoma. In all cases, the lung nodules were successfully diagnosed (Table 2).
In previous reports, the usefulness of virtual bronchoscopic navigation has been described.2,3 It can shorten the duration of bronchoscopic examination and improve the rate of accurate diagnosis.
Software programs such as Bf-NAVI and LungPoint have been developed to easily reconstruct virtual bronchoscopic images; these programs can automatically extract the trachea and bronchi from CT images and reconstruct virtual bronchoscopic images. However, one limitation of the software is the prohibitive cost, which has limited its use. These programs cost at least 30,000 US dollars. In contrast, OsiriX 32-bit is a free software for Mac. Even the 64-bit version cleared by the Food and Drug Administration costs only 599 US dollars. Virtual bronchoscopic images can be reconstructed on a Mac platform at a low cost.
We demonstrated that OsiriX has enough functionality to reconstruct virtual bronchoscopic images. Everhardt et al2 reported that LungPoint detects and visualizes 3 mm or larger airways. As shown in Table 1, we were able to visualize airways smaller than 2 mm. OsiriX has an additional advantage over Bf-NAVI and LungPoint. Sometimes Bf-NAVI and LungPoint fail to detect and extract the trachea and bronchi from the CT data because of anatomic anomalies. As OsiriX does not use an extraction process, virtual bronchoscopic images can be obtained in all cases using OsiriX.
In addition, OsiriX is not only useful for reconstructing virtual bronchoscopic images but it may also be useful for predicting whether transbronchial biopsy can be successful. If the path reaches the lung nodule, there is a high probability that transbronchial biopsy will be successful. We named this prediction process “virtual bronchoscopic lung biopsy.” Using VBLB, we can select patients for whom bronchoscopic biopsy can yield a diagnosis. By identifying patients for whom bronchoscopic biopsy would have a low yield, other appropriate modalities such as CT-guided percutaneous biopsy and thoracoscopic biopsy can be selected.
With OsiriX virtual bronchoscopy, although virtual bronchoscopic image reconstruction is automated, we have to manually reconstruct the VBLB pathway. However, the process is so easy that a VBLB pathway can be reconstructed in only 5 to 10 minutes. Most bronchoscopists can reconstruct virtual bronchoscopic images using OsiriX in a short period of time at a low cost.
Recently, increasing medical costs pose an important problem in many countries. Nevertheless, many new technologies have been developed and applied. Virtual bronchoscopy is a popular example in the field of respiratory medicine. Although virtual bronchoscopy has great potential for meaningful clinical application, it is difficult to implement because of the high price of commercial software. However, OsiriX can efficiently reconstruct virtual bronchoscopic images at a low cost. With OsiriX, virtual bronchoscopy can become popular at a relatively low cost. OsiriX can contribute to the widespread adaptation of virtual bronchoscopy.
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Keywords:© 2014 by Lippincott Williams & Wilkins.
bronchoscopy; cost benefit; imaging-guided biopsy; lung cancer; 3D imaging