Gynecologic interstitial brachytherapy procedure: (a) 3D model showing organs at risk surrounding the clinical target volume (CTV). Catheters are introduced to regions around and within the tumor. The plastic catheters are filled with rigid metallic stylets during insertion, but thereafter filled with radioactive sources, with the dwelling points during radiation delivery shown as red spheres. Care must be taken not to puncture the bowel, rectum or bladder dung catheter insertion. (b) Photograph of typical equipment used in an MRI-guided procedure. A template (purple), which is a plastic plate with numerous holes, is sutured onto the patient’s skin. A plastic central obturator (white) is then inserted into the vagina to anchor the assembly in place. Multiple catheters are then placed through designated holes in the template and driven towards prescribed locations.