Safety and efficacy are important endpoints in the treatment of gynecologic, breast and prostate cancers. Brachytherapy is a method of accurately delivery high dose of radiation to a target organ. Brachytherapy can therefore contributes to local control as well as morbidity in the treatment of aforementioned malignancies. Understanding the relationship of the applicators, sources, and resultant dose distributions to the tumor and critical organs, to guide applicator insertion and dose specification, is pivotal in maximizing local control and minimizing complications. This course will give a brief overview of brachytherapy and how it has evolved over the years . It will also provide a detail practical and reliable approach to image guided brachytherapy using CT and MR images before, during and after prostate, breast and gynecologic brachytherapy procedures. The necessary QA and safety practices that accompany image-based brachytherapy will also be discussed. At the conclusion of this activity, the learner will be able to do the following: 1. Explain the fundamentals of brachytherapy and the changing roles in patients care. 2.