Catheter-based intraluminal optical coherence tomography: comparison with digital light microscopy of ureter wall morphometry in porcine specimens
Objective: Reproducibility and agreement of width estimates for urothelium, lamina propria, and muscle layer of normal porcine ureter wall ex vivo were compared between catheter-mounted, intraluminal cross-sectional optical coherence tomography (OCT), as a new destruction-free optical imaging method that could be applied clinically to examine the upper urinary tract from within if found to reliably delineate its different anatomical layers, and whole-mount low-power digital light microscopy (DLM).
Materials and Methods: Eleven ex-vivo-specimens of porcine ureter were flushed with normal saline solution prior to OCT (catheter diameter, 0.014 inch, wavelength, 1300 ± 20 nm, LightLab Imaging, Inc., Westford, MA, USA) at marked locations. Ring-shaped (3 mm) ureter specimens were fixed in 4%-formalin, cut, whole-mounted, and hematoxilin-eosin-stained. Respective thicknesses of urothelium, lamina propria, and muscle layer of the ureter wall were compared between OCT and matching DLM slides (Axioplan2, Carl-Zeiss-Corporation, Jena, Germany) by two independent observers, applying Bland-Altmann plots and paired-data-Student-T-testing at P < 0.05.
Results: Width estimates were reproducibly higher for urothelium by a factor of about 1.4 at OCT (60 ± 9–96 ± 18 μm) compared to DLM (45 ± 12–68 ± 9 μm, P < 0.01), similar for lamina propria (OCT, 191 ± 21–233 ± 44 μm; DLM, 189 ± 48–326 ± 58 μm), and variable for muscle layer (OCT, 355 ± 109–631 ± 42 μm; DLM, 454 ± 97–527 ± 121 μm).
Conclusions: It appears that OCT reliably delineates ureter wall layers demonstrated by DLM, and that intra-observer reproducibility of the width of urothelium and lamina propria is high for both OCT and DLM, width estimates of lamina propria are reliable at OCT, and width of urothelium is reproducibly overestimated at OCT when compared with DLM.
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