Use Monte Carlo （MC） Methods To Simulate The Dose Of¹²⁵I And¹⁰³Pd Seeds

Cancer is harm to people’s life and health. The rate of death induced by canceris growing every year. Seventy percent of cancer patients need to receiveradiotherapy. Radiotherapy has become the main method in cancer treatment.In many methods of radiotherapy, the brachytherapy has been used in manyhospitals around the world. So it is important to study the dose distribution of lowenergy seeds in the tumor for the reliable treatment. In this paper, the dosedistribution of¹²⁵I and¹⁰³Pd seeds in water is studied by the Monte Carlo method.1. In this article, the dose distribution of a¹²⁵I seed in water is simulated by theMCNP5. The seed is placed in the center of the water sphere model, filled by2*2*2mm3’s cubes. The dose distribution in each cube is recorded. The results ofMCNP5simulation and theoretical calculation in TG-43are equal. So the simulationof dose distribution by the MCNP5is reliable.2. Several seeds are often used to kill malign tumor in clinical treatment, so thecombined distribution of several¹²⁵I seeds is analyzed. For0.8mCi¹²⁵I seeds, everyseed’s center distance should be less than1cm in order to avoid the cold dose spots.3. The dose of a¹⁰³Pd seed in water is simulated. The effective dose region of¹⁰³Pd seed is smaller than that of¹²⁵I seed. In the same radioactivity, the dose of¹²⁵Iand¹⁰³Pd seeds decrease rapidly with time. And the dose of Pd-¹⁰³ decrease morequickly, so it is more suitable for the treatment of low differentiated, rapidproliferated tumor.4. In clinical application, the catheter and stent are often used to assist the treatment. In this article, the dose distribution of¹²⁵I and¹⁰³Pd seeds is simulated incatheter and stent. Either the catheter or the stent decreases the dose of the seeds.