Dual-resolution megahertz optical coherence tomography prototype rectoscope for enhanced visualization of colorectal microstructures.

SIGNIFICANCE: Endoscopic 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.

AIM: We 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.

APPROACH: A 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.

RESULTS

Postmortem 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.

CONCLUSIONS

The 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.