There is significant histopathological and clinical evidence that near-infrared auto-fluorescence (NIRAF) complements optical coherence tomography (OCT) for detecting high-risk coronary plaque. Here, we determined the accuracy of an OCT-NIRAF imaging system and catheter for detecting NIRAF in human coronary lesions. OCT-NIRAF pullback imaging was performed on human cadaver coronary arteries (n=33 from 14 patients) during PBS perfusion via a fully integrated OCT-NIRAF imaging system and catheter (NIRAF ex. 633 nm, 1 mW power; em. 660-740nm). Confocal NIRAF images were acquired from corresponding unstained formalin-fixed paraffin-embedded sections (Olympus FLUOVIEW FV1000; ex. 635 nm; em. 655-755nm). OCT-NIRAF and confocal NIRAF images were registered using known pullback speed, anatomical landmarks, and fiducial features (e.g., calcification), and spatially overlapped by affine transformation of the confocal NIRAF images. Each image was split into 8, 45º-sectors, emanating from the catheter location. Each 45°-sector was determined to be positive if <5% of the intima contained confocal NIRAF, and if <5% of 45°-arc (2.25°) of the catheter-based NIRAF signal was above the system’s detection limit. A total of 1896 45°-sectors from 291 distinct coronary locations were analyzed using confocal NIRAF as the gold standard. Considering superficial confocal NIRAF foci within 0.5 mm from the luminal surface, sensitivity and specificity were 90.0% (95%CI: 69.8- 100.0%) and 90.2% (95%CI: 88.8-91.7%), respectively. Within 0.5 mm to 1.0 mm depth from the luminal surface, the sensitivity was 36.4% (95%CI: 15.0-57.8%) and specificity was 90.1% (95%CI: 88.6-91.5%). These results indicate that the OCT-NIRAF system/catheter’s ability to detect NIRAF is depth dependent and accurate in plaque regions (within 0.5 mm from the luminal surface) that are most responsible for precipitating coronary events.
Background: Common path probes are highly desirable for optical coherence tomography (OCT) as they reduce system complexity and cost. In this work we report an all-fiber common path side viewing monolithic probe for coronary artery imaging.
Methods: Our common path probe was designed for spectrometer based Fourier domain OCT at 1310 nm wavelength. Light from the fiber expands in the coreless fiber region and then focussed by the ball lens. Reflection from ball lens-air interface served as reference signal. The monolithic ball lens probe was assembled within a 560 µmouter diameter drive shaft which was attached to a rotary junction. The drive shaft was placed inside an outer, transparent sheath of 800 µm diameter.
Results: With a source input power of 25 mW, we could achieve sensitivity of 100.5 dB. The axial resolution of the system was found to be 15.6 µm in air and the lateral resolution (full width half maximum) was approximately 49 µm. As proof of principal, images of skin acquired using this probe demonstrated clear visualization of the stratum corneum, epidermis, and papillary dermis, along with sweat ducts.
Conclusion: In this work we have demonstrated a monolithic, ball lens common, path probe for OCT imaging. The designed ball lens probe is easy to fabricate using a laser splicer. Based on the features and capability of common path probes to provide a simpler solution for OCT, we believe that this development will be an important enhancement for certain types of catheters.
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