Exploring optical coherence tomography imaging depth to differentiate tissues at surgical margins.

Optical coherence tomography (OCT) is an imaging modality that provides real-time visualization of tissue microstructure. The goals of this study were to assess OCT image tissue depths (TD) with image processing, and other objective characteristics of tissue types at surgical margins in canine soft tissue sarcoma (STS). In this study, a single observer reviewed 248 images of four tissue types (sarcoma, skeletal muscle, adipose and fascia) collected from 24 dogs with STS. The observer evaluated for tissue characteristics and measured TDs utilizing ImageJ software. Images were evaluated in normal, Threshold and Binary conditions. Measurements were repeated 1 week later to evaluate for intra-observer variability. In all three image processing conditions, the order of TD from greatest to least light penetration was adipose, skeletal muscle, fascia and sarcoma tissue. Neovascularization was observed in 53.2% sarcoma, and lines of fascia surrounding muscle bundles was present in 93.5% of skeletal muscle images. These observed differences between tissue types in OCT images can be utilized to improve observer evaluation, aid in development of algorithms, and improve the accuracy of surgical margin assessment.