Polarisation‐Sensitive Optical Coherence Tomography for Surgical Margin Evaluation and Diagnosis of Excised Canine Cutaneous and Subcutaneous Tumours

Intraoperative surgical margin evaluation is not routine in veterinary medicine. Polarisation-sensitive optical coherence tomography (PS-OCT) is a variant of spectral domain optical coherence tomography (SD-OCT) that can provide real-time cross-sectional imaging of surgical margins with additional information about the polarisation of light in tissues. The aims of this study were (1) to compare PS-OCT surgical margin images to histopathology of excised canine skin and subcutaneous tumour specimens, and (2) to determine if the addition of PS-OCT images improved the diagnostic accuracy of surgical margin assessment. The authors hypothesised that PS-OCT image features would resemble histopathologic tissue features and the addition of PS-OCT images would improve the accuracy of margin assessment. Sixty-one dogs with 79 skin and subcutaneous tumours were prospectively enrolled. Tumours were excised, the surgical margins were imaged with OCT and then submitted for histopathology. Six masked readers first received image interpretation training in SD-OCT only, followed by training in combined SD-OCT and PS-OCT 1 week later. The readers interpreted each image or video for the presence of cancer and the results were compared to histopathology. PS-OCT imaging features of surgical margin tissues were consistent with tissue histopathologic features at low power. The overall reader median sensitivity and specificity were 90.9% and 95.6% for SD-OCT only and 90.9% and 91.3% for combined SD-OCT and PS-OCT. The addition of PS-OCT images did not improve the diagnostic accuracy of the surgical margin assessment for skin and subcutaneous tumours but resulted in high accuracy of margin interpretation with readers of varying experience.