Shielding and operational zoning design of a stand-alone I-131 isolation ward in a resource-constrained setting

Purpose: This paper reports preliminary shielding calculation, facility design and dose rate evaluation for a stand-alone 131I isolation facility to be developed for a tertiary government hospital in Davao City, Philippines. In the Philippines, high-dose radioactive iodine therapy isolation is typically conducted within hospital wards, supported by administrative radiation safety measures rather than purpose-built facilities, mainly due to limited yet overflowing demands of private rooms in government hospitals. This work proposes a practical design and shielding calculation within a constrained allocated area. Methods: The facility was designed within a 7.5m x 19.5m building footprint, with an additional 3m restricted perimeter. The design has four isolation rooms with 20 cm concrete walls and 5mm lead-lined doors. The placement of beds, toilets and baths, and door openings were designed to minimize direct bed-to-door line of sight. The only routinely occupied working area is the nurse station and the rest of the rooms are controlled and with very low occupancy. A conservative 200mCi point-source shielding calculation was done for partially and fully occupied facility. Results: For 20 cm thickness of concrete walls with density of 2.35 g/cm3, the primary 364 keV gamma transmission was computed to be below 1%, while 5 mm lead doors reduced transmission to about 24%. The calculated nurse station dose rate is at ~0.05 μSv/h for one occupied room, and ~0.19 μSv/h with all four rooms simultaneously occupied. The external 3m perimeter did not appreciably limit the dose but maintain the facility surroundings to almost zero occupancy. Conclusion: Safety of staff, patients, and public is not compromised even with space constraint using selective shielding, proper operational zoning, and an optimized room layout. This setup will guide hospitals with template and estimation of shielding thickness and dose rate based on area and not purely traditional administrative controls.