Abstract: In order to analyze the time required for the decaying of the surface contamination level of the clothing used by the patients who received ¹³¹I treatment to the clearance level, and to write the Python code to discuss the minimum area and optimal layout of the clothing decay room needed in the ¹³¹I treatment site in the department of nuclear medicine at different scales. 50 quilts used by patients with differentiated thyroid cancer treated in the Department of Nuclear Medicine of a Grade 3A Hospital in Taiyuan City, Shanxi Province from August to September 2023 were selected and the surface contamination level of the quilt was measured at the same time period every day. Python code was written to discuss the minimum space area and optimal layout of clothing decay under different parameters. The surface contamination decay constant of clothes used by patients treated with ¹³¹I was 0.097 0±0.242 1. Two hours after discharge, the surface contamination level of the clothing ranges from 0.42 to 8.67 (2.23±1.64) Bq/cm². The time required for the clothing to decay to the clearance level ranges from 0 to 24.57 (8.67±6.35) days. A set of Python code for calculating the minimum area of clothing decay room under different conditions is compiled, and the layout of the clothing decay room is divided into three types according to the number of storage shelves. Taking our institute in Grade 3A Hospital as an example, at least 7.5 m2 clothing decay room is needed. In clinical practice, by running Python code and defining relevant parameters, we can give reference to the area planning of clothing decay room, and provide some reference for the problems such as insufficient decay room and insufficient space in clinical work. The code is also applicable to the area planning and calculation of radioactive waste decay room or storage room.

Key words: nuclear medicine department, clearance, clothing, decay room, iodine-131