Radiotherapy application performed in the operating room during surgery is called intraoperative radiotherapy. This treatment is applied with mobile X-ray generators in a single session. During the application, after the tumor is removed, the special applicator of the device is placed in the tumor area. Following the necessary measurements, high-dose radiation is given only to this area, while intact tissues are completely protected. In short, radiation therapy is also completed in one go during surgery. Intraoperative radiotherapy started to be used routinely for breast cancer in Europe in 1999 for the first time. This treatment method is a treatment method that has been used widely in the world for an average of ten years and has a lot of clinical studies in breast cancer. It has been most commonly used in early stage breast cancer. In patients who have undergone breast conserving surgery, it is very advantageous to perform partial breast irradiation with intraoperative radiotherapy, since most of the recurrences in the breast area in the tumor bed. In these patients, intraoperative radiotherapy has advantages over conventional radiotherapy, especially in terms of time and cosmetics.