Magnetic Resonance-Guided Gynecologic Brachytherapy.

Gynecologic brachytherapy consists of positioning radioactive sources in catheters implanted inside a tumor. MR imaging provides tumor visibility and is ideal for image-guided insertions and treatment planning. It is important at first insertion and during treatment of large residual tumors potentially needing interstitial needles. Clear visibility of the tumor and the catheters is necessary for MR-guided brachytherapy. T2 sequences are ideal for tumor visibility but catheter visualization may be difficult. Active tracking and alternative sequences to improve catheter visibility have been explored. The use of digital applicator models, dummy markers, and CT-MR fusion is reviewed.