Ultrasound-based geometric modeling of the human ovary with applications to cryopreservation

Successful cryopreservation of the whole ovary outside of the body, while a woman undergoes cancer treatments, may help preserving fertility and regaining hormone balance during recovery. One of the key challenges in whole ovary cryopreservation is adequately loading the organ with cryoprotective agents (CPAs). Another notable challenge in developing the application is the lack of geometric data needed for designing matching thermal protocols. The objective of the current study is twofold: (i) to develop an effective geometric reconstruction method for the ovary, based on transvaginal ultrasound (TVUS) data, and (ii) to perform a pilot study on the thermal effects associated with CPA loading with application to vitrification. This study includes screening of 127 TVUS imaging datasets of ovaries from healthy ovulatory participants, reconstruction of 14 geometric models, and thermally analyzing two representative geometric models of low and high mature follicles-to-organ volume ratios. Results of this study demonstrate that the proposed reconstruction method is faster and more accurate than that facilitated by commercially available software (SonoAVC, GE Healthcare). Two extremes were investigated: (1) complete vitrification of the ovary, and (2) crystallization of mature follicles while the remaining ovarian stroma vitrifies. CPA loading into the mature follicles is considered an outstanding cryopreservation challenge, but with very little impact on long-term fertility preservation. Results of this study suggest that ovarian preservation by vitrification is feasible when sufficient CPA loading is achieved, while identifying the most suitable CPA for the task remains a challenge beyond the scope of the current study.