Who invented vaginal brachytherapy?

Vaginal brachytherapy, a form of internal radiation therapy used primarily for gynecological cancers, was developed and refined by several researchers over time. Notably, Dr. J. M. S. "Jim" O'Sullivan is recognized for his contributions to advancing this technique in clinical practice. While it's difficult to attribute the invention to a single individual, advancements in brachytherapy techniques have been a collaborative effort in the medical community.