Improved sensitivity roll-off in dual reference, buffered spectral-domain optical coherence tomography.

SIGNIFICANCE: While spectral-domain optical coherence tomography (SD-OCT) is a preferred form of OCT imaging, sensitivity roll-off limits its applicability for certain biomedical imaging applications. AIM: The aim of this work is to extend the imaging range of conventional SD-OCT systems for imaging large luminal organs such as the gastrointestinal tract. APPROACH: We present an SD-OCT system operating at a center wavelength of 1300 nm that uses two delayed reference arms to reduce sensitivity roll-off and an optical switch and a fiber optic delay line to ensure that the interference spectra are acquired from the same sample time window. RESULT: The proposed system was used to image swine colon ex vivo and duodenum in vivo, demonstrating improved image quality due to a ∼14 dB increase in sensitivity at the edges of the ranging depth. CONCLUSION: The proposed system requires modest hardware implementation and is compatible with catheter-based endoscopic helical scanning with enhanced sensitivity for the samples at a distance of ∼6 mm from the zero delay point.

Plaque burden can be assessed using intravascular optical coherence tomography and a dedicated automated processing algorithm: a comparison study with intravascular ultrasound.

AIMS: Plaque burden (PB) measurement using intravascular optical coherence tomography (IVOCT) is currently thought to be inferior to intravascular ultrasound (IVUS). We developed an automated IVOCT image processing algorithm to enhance the external elastic lamina (EEL) contour. Thus, we investigated the accuracies of standard IVOCT and an IVOCT enhancement algorithm for measuring PB using IVUS as the reference standard. METHODS AND RESULTS: The EEL-enhancement algorithm combined adaptive attenuation compensation, exponentiation, angular registration, and image averaging using three sequential frames. In two different laboratories with intravascular imaging expertise, PB was quantified on 200 randomized, matched IVOCT and IVUS images by four independent observers. Fibroatheroma, fibrocalcific plaque, fibrous plaque, pathological intimal thickening (PIT), and mixed plaque were included in each set. Pearson's correlation coefficients between IVUS and standard IVOCT measurements of PB were 0.61, 0.67, 0.76, 0.78, and 0.87 for fibroatheromas, mixed plaques, fibrocalcific plaques, fibrous plaques, and PIT plaques, respectively. Pearson's correlation coefficients increased to 0.81, 0.83, 0.83, 0.84, and 0.90 when using the EEL-enhanced images (P = 0.003, P = 0.004, P = 0.08, P = 0.12, and P = 0.23, respectively). EEL-enhanced IVOCT analysis was associated with a lower EEL-area measurement absolute error for fibroatheromas, mixed plaques, and all pooled plaques (P = 0.006, P = 0.02, and P < 0.001, respectively). Compared with standard IVOCT, the EEL-enhanced IVOCT images had a higher sensitivity (79% vs. 28%, P < 0.001) and specificity (98% vs. 85%, P = 0.03) for plaques with an IVUS PB ≥70%. CONCLUSION: EEL-enhanced IVOCT can be used to reliably measure PB in all types of coronary atherosclerotic lesions, including fibroatheromas and mixed plaques.