Assessment of chronic radiation proctopathy and radiofrequency ablation treatment follow-up with optical coherence tomography angiography: A pilot study

Figure 1 Depth-resolved en face optical coherence tomography and optical coherence tomography angiography images and cross-sectional optical coherence tomography and optical coherence tomography angiography images of a normal rectum. A: En face optical coherence tomography (OCT) image at 150 μm depth; B: En face OCT at 350 μm depth showing regular circular mucosal patterns characteristics of normal rectum; C: En face OCT angiography (OCTA) image at 150 μm depth showing regular honeycomb-like microvascular pattern of the subsurface capillary network in the mucosal layer; D: En face OCTA image at 350 μm depth showing rectal microvasculature corresponding to arterioles and venules in the submucosal layer, in addition to shadowing from the superficial mucosal microvasculature; E: Cross-sectional OCT image from the solid green lines in A and B, showing regular columnar architecture of normal rectum. The submucosal layer can be identified by the vertical layers traversing across the image (arrows). A dilated mucosal gland can be observed in both en face and cross-sectional image (asterisk); F: Cross-sectional OCTA image from the solid blue lines in C and D. Subsurface capillaries in the mucosal layer can be identified as horizontal structures connecting submucosal layer to the mucosal layer (solid arrows), while the arterioles and venules can be identified as vertical structures in the submucosal layer traversing across the images (dashed arrows). Cross-sectional OCTA image was averaged over a 50 µm projection range in the longitudinal direction to improve contrast and reduce noise. Dashed and solid lines in E and F indicate 150 μm and 350 μm depth levels, respectively. Scale bars are 1 mm in A-D, 500 μm in E and F. OCT: Optical coherence tomography; OCTA: Optical coherence tomography angiography.

Figure 2 Depth-resolved en face optical coherence tomography and optical coherence tomography angiography images, cross-sectional optical coherence tomography and optical coherence tomography angiography images, and corresponding endoscopy image over the dentate line of a radiofrequency ablation-naïve chronic radiation proctopathy patient. A: En face optical coherence tomography (OCT) image at 150 μm depth showing regular circular mucosal patterns on the rectal side and squamous epithelium with a smooth appearance on the anal canal side; B: Shows the corresponding endoscopy image at the dentate line showing ulcerations, and edematous and non-confluent telangiectasias (rectal telangiectasia density = 2). White arrows highlight areas of telangiectasias on the rectal side; C: En face OCT angiography (OCTA) image at 150 μm depth showing distortions to the honeycomb-like microvascular pattern, and ectatic and tortuous rectal microvasculature (red oval) in the mucosal layer; D: En face OCTA image at 350 μm depth showing vessels with heterogonous and unusually large diameters (red oval) suggesting presence of abnormal arterioles and venules in the submucosal layer; E: Cross-sectional OCT image from the solid green line in A showing mucosal and submucosal layers; F: Cross-sectional OCTA image from the solid blue lines in C and D. Cross-sectional OCTA image was averaged over a 50 μm projection range in the longitudinal direction to improve contrast and reduce noise. Dashed and solid lines in E and F indicate 150 μm and 350 μm depth levels, respectively. Scale bars are 1 mm in A-D, 500 μm in E and F. OCT: Optical coherence tomography; OCTA: Optical coherence tomography angiography.

Figure 3 Depth-resolved en face optical coherence tomography and optical coherence tomography angiography images, cross-sectional optical coherence tomography and optical coherence tomography angiography images, and corresponding endoscopy image over the dentate line of a previously-treated chronic radiation proctopathy patient. A: En face optical coherence tomography (OCT) image at 150 μm depth showing regular circular mucosal patterns on the rectal side and squamous epithelium with a smooth appearance on the anal canal side; B: Shows the corresponding endoscopy image at the dentate line showing some residual telangiectatic areas (arrows, rectal telangiectasia density = 1); C: En face OCT angiography (OCTA) image at 150 µm depth showing regular honeycomb-like microvascular pattern in the mucosal layer; D: En face OCTA image at 350 μm depth showing vessels with heterogonous and unusually large diameters (red oval) suggesting presence of abnormal arterioles and venules in the submucosal layer; E: Cross-sectional OCT image from the solid green line in A showing mucosal and submucosal layers; F: Cross-sectional OCTA image from the solid blue lines in C and D. Cross-sectional OCTA image was averaged over a 50 μm projection range in the longitudinal direction to improve contrast and reduce noise. Dashed and solid lines in E and F indicate 150 μm and 350 μm depth levels, respectively. Scale bars are 1 mm in A-D, 500 μm in E and F. OCT: Optical coherence tomography; OCTA: Optical coherence tomography angiography.

Figure 4 Summary of normal and abnormal microvasculature in the mucosal and submucosal layers of the rectum. A: Normal rectal mucosal microvasculature consisted of a honeycomb-like microvascular pattern corresponding to subsurface capillary network; B: Abnormal rectal mucosal microvasculature had distortions to the honeycomb-like microvascular pattern, and had ectatic and tortuous microvasculature; C: Normal rectal submucosal microvasculature consisted of arterioles and venules with homogeneous vessel diameters typically of < 200 μm, in addition to shadowing from the superficial mucosal microvasculature; D: Abnormal rectal submucosal microvasculature had arterioles and venules with heterogonous and unusually high vessel diameters (> 200 μm). Scale bars are 1 mm.