A Radiation Levels Measurement at Workplace of Cyclotron-PET/CT Facilities (in Karachi) using TLD Dosimeters

Abstract

Cyclotron is the most widely used proton particle accelerator for production of short lived radionuclides particularly F-18 for diagnostic purpose in oncology imaging. Currently, only Fluorine [F-18] is being produced in Pakistan. F-18 is tagged with glucose analogue and converted into [18F] FDG (Fluorodeoxyglucose) by synthesis process. [18F] FDG emits positron and, via annihilation process, produces two gamma photons of 511keV energy, which is of great concern for occupational safety. Therefore, a study was carried out to assess the dose incurred by radiation workers working in controlled and supervised areas of cyclotron facility. In this study, the ten (10) calibrated Thermoluminescene dosimeters (TLD-100) were annealed and placed in different locations of four Cyclotron-PET/CT facilities for determination of dose in work area. In the selected cyclotron facilities, one out of four was unshielded cyclotron and other three were self-shielded. Ten (10) TLDs were placed in preselected controlled and supervised areas of facilities for the duration of 30 days. After four weeks of exposure, TLDs were removed and assessed on TLD reader for dose evaluation. The evaluated results of radiation levels from TLDs are in good agreement with the criteria for classification of areas as defined in Regulations on Radiation Protection (PAK/904). The measured doses of work area are well below the defined regulatory dose limits for controlled area (>6mSv/yr) as well as supervised area (>1mSv/yr) except in case of unshielded cyclotron vault. It is concluded that the facilities have implemented the requirement 27 of PNRA Regulations on Radiation Protection (PAK/904) and also have established strong radiation safety measures for minimization of occupational exposure.