Objective assessment of multimodality optical coherence tomography and second-harmonic generation image quality of ex vivo mouse ovaries using human observers

Ovarian cancer is particularly deadly because it is usually diagnosed after it has begun to spread. Transvaginal sonography (TVS) is the most common imaging screening technique. However, routine use of TVS has not reduced ovarian cancer mortality. The superior resolution of optical imaging techniques may make them attractive alternatives to TVS. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and second-harmonic generation (SHG) microscopy (with collagen as the targeted fluorophore). OCT provides a gross anatomical image of the ovary while SHG provides a closer look at a particular region. Knowing these anatomical features, we sought to investigate the diagnostic potential of OCT and SHG. We conducted a fully crossed, multi-reader, multi-case study using seven human observers. Each observer classified 44 ex vivo mouse ovaries as normal or abnormal from OCT, SHG, and simultaneous, co-registered OCT and SHG images and provided a confidence rating on a three-point ordinal scale. We determined the average receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show that OCT has diagnostic potential with an average AUC of 0.91 +/- 0.03. The average AUC for SHG was less promising at 0.71 +/- 0.06. Interestingly, the average AUC for simultaneous, co-registered OCT and SHG was not significantly different from OCT alone. This suggests that collagen may not be a useful fluorophore for ovarian cancer screening. The high performance of OCT warrants further investigation.