Conventional Autofluorescence and Virtual Bronchoscopy

Conventional bronchoscopy is a valuable technique for localizing preinvasive lung cancer within the airways. In general, conventional bronchoscopy can detect nodular or polypoid lesions >2 mm in size and flat or superficially spreading lesions >2 cm in diameter [21,57]. With regard to carcinoma in situ, 75% of lesions are superficial or flat and 25% are nodular or polypoid [21,56].

Table 4 Biomarkers

Biomarker

Analysis

Biological role

Application

HnRNP A2/B1

Protein I in spu

mRNA processing

Early detection/

tum cells

monitoring

K-ras

DNA in sputum

Cell-cycle regu-

Early detection/

homogenates

lation

risk assessment

Genomic instability

DNA in sputum

Chromosomal

Early detection/

homogenates

integrity

risk assessment

Source: Ref 52.

Source: Ref 52.

Autofluorescence bronchoscopy (AF) is a recently developed optical imaging method that is designed to improve the detection of small preinvasive lesions that are not visible by conventional, ''white light'' bronchoscopy [53, 56-60]. AF involves illuminating the bronchial surface with violet or blue light (400 to 440 nm) in order to distinguish normal from abnormal tissues. Upon such illumination, dysplastic lesions and carcinoma in situ will show a diminution in the intensity of autofluorescence.

The light-induced fluorescence endoscopy (LIFE) device, which was designed to capitalize on differences in autofluorescence properties in order to aid in the detection and localization of preinvasive lung cancer, has been approved by the FDA for the detection of early lung cancer [56,57]. Except for differences in the illuminating light and the addition of a special camera, the LIFE device is similar to conventional bronchoscopy [56,57]. In the hands of a bronchoscopist who has received extensive training in using this device, it adds only a few minutes to a conventional bronchoscopic procedure. A recent multicenter trial using LIFE showed that it improved the detection rate of preinvasive lung cancer by severalfold compared to conventional fiberoptic bronchoscopy alone [57].

Because of its invasive nature and high cost, screening with AF should currently be reserved for patients with a very high pretest probability of lung cancer [21]. For widespread screening, AF should ideally be coupled with a noninvasive, first-line study that selects patients with a high pretest probability of harboring early lung cancer [21]. For example, a recent study by Phillips et al. describes the use of a breathalyzer to identify volatile organic compounds that may serve as potential markers for lung cancer [61]. Future studies are needed to determine the precise role of this exciting new technology in the detection of early lung cancer.

Virtual bronchoscopy (VB) is a novel noninvasive method for assessing the airways which combines helical computed tomography data and virtual reality computing in order to create three-dimensional endobronchial simulations (Fig. 5) [62-64]. This technique is described in detail in Chapter 9. A recent preliminary investigation by Summers et al. assessed the computerassisted detection of polypoid airway lesions on virtual bronchoscopy images [63]. This technique was associated with a relatively high sensitivity (90%) for lesions >5 mm in diameter, but was limited by a poor specificity.

Current limitations of VB include its labor-intensive nature, the limited experience of most radiologists with this technique, and its inability to differentiate malignant from benign lesions [21,62-64]. Future technological advances will hopefully overcome many of these obstacles.

Figure 5 Virtual airway imaging. Virtual bronchoscopic image (internal rendering) reconstructed from a helical CT data set (2.5-mm collimation; 1.25-mm reconstruction interval) reveals an endoluminal lesion anteriorly (arrows), which proved to represent a benign polyp. The limited ability of virtual bronchoscopy to distinguish benign from malignant lesions is a current limitation of this technology.

Figure 5 Virtual airway imaging. Virtual bronchoscopic image (internal rendering) reconstructed from a helical CT data set (2.5-mm collimation; 1.25-mm reconstruction interval) reveals an endoluminal lesion anteriorly (arrows), which proved to represent a benign polyp. The limited ability of virtual bronchoscopy to distinguish benign from malignant lesions is a current limitation of this technology.

The Smoker's Sanctuary

The Smoker's Sanctuary

Save Your Lungs And Never Have To Spend A Single Cent Of Ciggies Ever Again. According to a recent report from the U.S. government. Centers for Disease Control and Prevention, more than twenty percent of male and female adults in the U.S. smoke cigarettes, while more than eighty percent of them light up a cigarette daily.

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