Hypothesis: Otitis media (OM) can be successfully visualized and diagnosed by dynamic microscopic optical coherence tomography (dmOCT). Background: OM is one of the most common infectious diseases and, according to the WHO, one of the leading health problems with high mortality in developing countries. Despite intensive research, the only definitive treatment of therapy-refractory OM for decades has been the surgical removal of inflamed tissue. Thereby, the intra-operative diagnosis is limited to the surgeon’s visual impression. Supportive imaging modalities have been little explored and have not found their way into clinical application. Finding imaging techniques capable of identifying inflamed tissue intraoperatively, therefore, is of significant clinical relevance. Methods: This work investigated a modified version of optical coherence tomography with a microscopic resolution (mOCT) regarding its ability to differentiate between healthy and inflamed tissue. Despite its high resolution, the differentiation of single cells with mOCT is often impossible. A new form of mOCT termed dynamic mOCT (dmOCT) achieves cellular contrast using micro-movements within cells based on their metabolism. It was used in this study to establish correlative measurements with histology. Results: Using dmOCT, images with microscopic resolution were acquired on ex vivo tissue samples of chronic otitis media and cholesteatoma. Imaging with dmOCT allowed the visualization of specific and characteristic cellular and subcellular structures in the cross-sectional images, which can be identified only to a limited extent in native mOCT. Conclusion: We demonstrated for the first time a new marker-free visualization in otitis media based on intracellular motion using dmOCT.

Here we present a forward-looking endoscope for dynamic microscopic OCT reaching a lateral resolution of 1.3 µm and 0.8 mm field of view. Since tissue motion degrades dynamic imaging, tissue was immobilized by suction. The endoscope was placed in a 4 mm stainless-steel sheath, which was connected to a vacuum pump. In mice, the endoscope can access various inner organs using open surgery or laparoscopy. The potential of the dynamic endo-microscopic OCT was demonstrated on relevant murine tissue such as liver, spleen and kidney. Otherwise invisible cellular and subcellular structures were imaged by dynamic mOCT with high contrast.

Imaging airway tissue, optical coherence tomography (OCT) provides cross-sectional images of tissue structures, shows cilia movement and mucus secretion, but does not provide sufficient contrast to differentiate individual cells. By using fast sequences of microscopic resolution OCT (mOCT) images, OCT can picture small signal fluctuations (dynamic) OCT and overcomes the lack in contrast caused by speckle noise. In this way, OCT visualizes airway morphology on a cellular level and allows to track the dynamic behavior of immune cells, as well as mucus transport and secretion. Here, we demonstrate that mOCT, by using temporal tissue fluctuation as contrast (dynamic OCT), provides the possibility to study physiological and pathological tissue processes in vivo.

SignificanceEndoscopic optical coherence tomography (OCT) is a valuable tool for rectal imaging, enabling noninvasive visualization of transmural structures with near-histological resolution, critical for accurate tumor staging and diagnostic/therapeutic monitoring. However, anatomical variability of the rectum and the resulting changes in tissue-to-probe distance challenge optimal circumferential imaging.AimWe aim to develop a dual-mode endoscopic OCT system, enabling real-time switching between high-detail and extended-range imaging for improved assessment of rectal wall morphology under varying anatomical conditions.ApproachA single fiber-optic ferrule containing two fibers with differing mode fields was integrated into a MHz-OCT rectoscope, enabling an extended-range mode for full circumferential imaging and a high-detail mode for close examination of fine structures with seamless live switching mechanism. The system was tested in situ on a postmortem human rectum preserved with ethanol-glycerol-lysoformin fixation.ResultsPostmortem rectum imaging demonstrated the feasibility of real-time switching between the two modes. Extended-range imaging provided full circumferential coverage, whereas high-detail imaging revealed distinct rectal wall layers and fine transmural structures, validated by histological correlation.ConclusionsThe dual-mode MHz-OCT system offers a flexible and practical solution for adaptive rectal imaging, providing high-resolution detail and full circumferential coverage with the potential to enhance diagnostics and treatment monitoring.