The visualization of submucosal blood vessels by color doppler flow imaging using optical coherence tomography: potential use in peptic ulcer hemorrhage

BACKGROUND: The visualization of submucosal blood vessels (SMBV) may allow for better selection and more directed endoscopic therapy in patients presenting with bleeding ulcers. Optical Coherence Tomography (OCT) is a novel imaging modality by which it is possible to accomplish cross-sectional imaging in biological tissues in vivo with resolution greater than 10 times superior to endoscopic ultrasound (< 15 microns in 3-D). Color Doppler OCT (CDOCT) is an innovative extension of OCT technology which allows for blood flow mapping (both velocity & direction) simultaneous with high resolution tissue imaging. AIM: To develop CDOCT as a high resolution in vivo imaging technology for future endoscopic applications. Hopefully, this will lead to more objective parameters for the assessment, prognostication and treatment of peptic ulcer hemorrhage with improved outcomes. METHODS: OCT and CDOCT imaging were performed upon 5 animals (in vivo) in a rat dorsal skin flap model. Surgical skin exposure was performed allowing for visualization of blood vessels embedded in connective tissue. Imaged sections were marked with dye microinjections and histologically processed following animal sacrifice. RESULTS: OCT images of sub-surface tissue cross-sections correlated well with histology including identification of connective tissue, sub-dermal muscle and dermis. These appeared as separate and distinct layers. CDOCT allowed for visualization of blood vessels varying in diameter from < 50 to > 200 microns, at tissue depths ranging from < 50 to ∼ 500 microns. These blood vessels appeared in cross-section as rounded structures with color Doppler signal indicating direction of blood flow. Bi-directional blood flow velocities in these vessels were observed to range from -10 to 10 mm/second, consistent with previous observations of flow velocities in this model. CONCLUSIONS: OCT and CDOCT are novel techniques with strong potential for use in imaging SMBV in gastrointestinal mucosa.