Volumetric optical frequency domain imaging of pulmonary pathology with precise correlation to histopathology

Abstract

Background: Lung cancer is the leading cause of cancer-related mortality. Radiology and bronchoscopy techniques do not have the necessary resolution to evaluate lung lesions on the microscopic scale, which is critical for diagnosis. Bronchial biopsy specimens can be limited by sampling error and small size. Optical frequency domain imaging (OFDI) provides volumetric views of tissue microstructure at near-histologic resolution and may be useful for evaluating pulmonary lesions to increase diagnostic accuracy. Bronchoscopic OFDI has been evaluated in vivo, but a lack of correlated histopathology has limited the ability to develop accurate image interpretation criteria.

Methods: We performed OFDI through two approaches (airway-centered and parenchymal imaging) in 22 ex vivo lung specimens, using tissue dye to precisely correlate imaging and histology.

Results: OFDI of normal airway allowed visualization of epithelium, lamina propria, cartilage, and alveolar attachments. Carcinomas exhibited architectural disarray, loss of normal airway and alveolar structure, and rapid light attenuation. Squamous cell carcinomas showed nested architecture. Atypical glandular formation was appreciated in adenocarcinomas, and uniform trabecular gland formation was seen in salivary gland carcinomas. Mucinous adenocarcinomas showed alveolar wall thickening with intraalveolar mucin. Interstitial fibrosis was visualized as signal-dense tissue, with an interstitial distribution in mild interstitial fibrotic disease and a diffuse subpleural pattern with cystic space formation in usual interstitial pneumonitis.

Conclusions: To our knowledge, this study is the first demonstration of volumetric OFDI with precise correlation to histopathology in lung pathology. We anticipate that OFDI may play a role in assessing airway and parenchymal pathology, providing fresh insights into the volumetric features of pulmonary disease.

Figure 1.

In vivo bronchoscopic catheter-based optical frequency domain imaging (OFDI) of a normal airway. A, OFDI cross-section of airway. B, Higher magnification view of airway cross-section visualizing typical layering of airway, including respiratory epithelium (e), transition between epithelium and underlying basement membrane/lamina propria (b), lamina propria (lp), perichondrium (p), and cartilage (c). C, Representative histology from a normal airway demonstrating similar layering to the in vivo OFDI airway image in B (hematoxylin and eosin stain). D, Higher magnification view of airway cross-section with attached alveolar attachments (arrows), with overlying respiratory epithelium (e), transition between epithelium and underlying basement membrane/lamina propria (b), and lamina propria (lp). E, Representative histology from a normal airway demonstrating similar layering and alveolar attachments as seen in the in vivo OFDI airway image in D (hematoxylin and eosin stain). OFDI imaging artifacts are denoted by asterisks. Tick marks in OFDI images are 0.5 mm. Scale bars on histology images are 0.5 mm.

Figure 2.

Parenchymal OFDI of mucinous adenocarcinoma. A, OFDI catheter-based longitudinal section (scale bar = 5.0 mm). B, OFDI catheter-based cross section at site of red line on A (scale bar = 1.0 mm). C and D, OFDI benchtop longitudinal section (C) and corresponding histology (D) (hematoxylin and eosin stain, scale bars = 1.0 mm). E and F, Higher magnification of OFDI benchtop longitudinal section from C and D (E) and corresponding histology at location of box in C and D (hematoxylin and eosin stain, scale bar = 1.0 mm). Narrow arrows indicate thickened, signal-intense alveolar walls, and wide arrows indicate tumor-associated scar. Ink marks are denoted by the asterisks. V denotes blood vessel. See Figure 1 legend for expansion of abbreviation.

Figure 3.

Bronchoscopic catheter-based OFDI of squamous cell carcinoma, basaloid type. A, OFDI longitudinal section. B, Corresponding histology (hematoxylin and eosin stain). C, OFDI cross-section. D and E, Higher magnification OFDI longitudinal section (D) and corresponding histology (E), showing epithelium (e), lamina propria (lp), and cartilage (c) (hematoxylin and eosin stain). Arrows indicate nests of hyperintense squamous cell carcinoma with signal-poor central necrosis. Ink marks are denoted by asterisks. Scale bars = 1.0 mm. See Figure 1 legend for expansion of abbreviation.

Figure 4.

Bronchoscopic catheter-based OFDI of adenoid cystic carcinoma. A, OFDI cross section. B, OFDI cross section with trabecular structures (wide arrows). C and D, OFDI cross section (C) and corresponding histology (D), showing epithelium (e), lamina propria with mild fibrosis (lp), and cartilage (c) (hematoxylin and eosin stain). E, Higher magnification of OFDI cross section. Wide arrows indicate uniform trabecular and glandular structures. Narrow arrows indicate small microcystic spaces filled with mucin. Scale bars = 1.0 mm. See Figure 1 legend for expansion of abbreviation.

Figure 5.

Parenchymal benchtop OFDI of cartilaginous hamartoma. A, OFDI longitudinal section. B, Corresponding histopathology (hematoxylin and eosin stain). OFDI reveals a lobulated mass with well-defined boundaries and evenly dispersed, fine-scale regions of high signal intensity in a background of uniform, moderate signal intensity. Scale bars = 1.0 mm.

Figure 6.

Pleural catheter-based OFDI of usual interstitial pneumonitis showing the pleural surface (P) and subpleural fibrosis (F). A, En face OFDI at location of red side tick marks in B. B and C, OFDI longitudinal section (B) and corresponding histopathology (C) (hematoxylin and eosin stain). D, OFDI cross section. E, Histopathology from the longitudinal section corresponding to subpleural cyst in D (hematoxylin and eosin stain). Boxed regions indicated subpleural cystic spaces, and ink marks are denoted by asterisks. Scale bars = 1.0 mm. See Figure 1 legend for expansion of abbreviation.

Figure 7.

Pleural catheter-based OFDI of mild pleural and subpleural interstitial fibrosis. P indicates pleura, and F indicates focal mild pleural fibrosis. A, En face OFDI at location of red side tick marks in B. B and C, OFDI longitudinal section (B) and corresponding histopathology (C) (hematoxylin and eosin stain). D and E, Higher magnification of OFDI longitudinal section (D) and corresponding histopathology at location of boxed region in B and C (D) (hematoxylin and eosin stain). Arrows indicate alveoli, and ink marks are denoted by asterisks. Scale bars = 1.0 mm. See Figure 1 legend for expansion of abbreviation.