ABSTRACT
OBJECTIVE: To explore the radiation shielding problem of Halcyon linear accelerator room. METHODS: According to the dose estimation method recommended by GBZ/T 201.2—2011 Radiation Shielding Requirements for Radiotherapy room--Part 2: Radiotherapy Room of Electron Linear Accelerators(hereinafter referred to as GBZ/T 201.2—2011) and NCRP report No.151 Structural Shielding Design and Evaluation for Megavoltage X-and Gamma-Ray Radiotherapy Facilities the required shielding thickness of 6.0 MeV Halcyon linear machine room is evaluated and compared with the existing machine room. After the equipment was put into use, we measured and verified the dose equivalent rate around each point. RESULTS: ⅰ) The transmittance of the main beam passing through the self-shielding system was 0.06%. The theoretical shielding thickness of the main beam path sites A, C and L of the accelerator(two main shielding walls and room top sites respectively) was 136.00, 130.00 and 136.00 cm, which was lower than the required shielding thickness of the main shielding area specified in GBZ/T 201.2—2011 for 6.0 MeV accelerator. ⅱ) Compared with the existing equipment rooms in the hospital, except that the thickness of the top secondary shield(80.00 cm) and the thickness of the west section of the outer wall of the labyrinth(100.00 cm) are smaller, the rest meets the shielding requirements. ⅲ) After the transformation of the computer room and the installation of Halcyon linear accelerator, the surrounding dose equivalent rate was lower than the control level required by GBZ/T 201.2—2011. CONCLUSION: The self-shielding design of Halcyon linear accelerator can effectively protect 6.0 MeV rays used for treatment, reduce the shielding thickness required for the main shielding area, reduce the shielding construction cost of the equipment room and increase the usable area of the equipment room.