Development and application of Optical Coherence Tomography for the assessment of mammalian oocytes and embryos

This thesis explores the application of optical coherence tomography (OCT) to the assessment of mammalian oocytes and early-stage embryos. A high-resolution spectral-domain OCT system was developed, and over 50 oocytes and embryos from several species were imaged. The results support a complementary role of OCT relative to conventional brightfield microscopy: in the observation of a common maturity marker, the oocyte's polar body, in imaging through the oocyte's surrounding cell layers and in assisting cell counting in cleavage embryos.

A fully automated time-lapse swept-source OCT system was designed to monitor the complete early development of mouse embryos in vitro within an incubator. Embryos were imaged for 5 consecutive days from zygote stage to blastocyst stage, and their dynamics were probed with several methods throughout the entire timelapse duration. Dynamic OCT methods proved valuable in detecting the main cellular events, such as mitotic divisions, blastocyst formation and cell death.

Imaging resolution was found to be hindered by speckle noise, and repeated exposure to infrared light during time-lapse imaging was identified as a possible cause of embryonic developmental failure, not only resulting from instantaneous irradiance, but from overall light dose, which was estimated to have exceeded 10 kJ/cm2.

Overall, these findings highlight OCT's potential as a valuable tool in the in vitro fertilisation (IVF) protocol, potentially offering a means to enhance IVF success rates through improved assessment and monitoring of embryo development, while providing a guide for research teams looking to understand the development of reproductive cells with OCT.