Particle knife (also called 125I Seed Implants) is applied to a variety of primary and metastatic tumors nowadays. 125I seeds are some small iodine radioactive particles that can give off short-range γ-ray to kill tumor cells continuously. 125I seed implantation can achieve the same internal radiation effects as surgery does. Hence, it is also called particle knife. These iodine particles are 0.8 mm in thickness, about 0.4 cm in length.