Abstract
The Cyclotron Center in Shin Kong Wu Ho-Su Memorial Hospital (SK Cyclotron Center) produced the 18F-FDG compound and provided it to the Positron Emission Tomography (PET) center for diagnosis services. In this study, the exposure doses of workers during the procedures of production of 18F, dispensation, and transportation of the compound (18F–FDG) (2-fluoro-2-[18F]-fluoro-D-glucose) are estimated. Besides, this study discussed the variations of neutrons spectra induced from the niobium and silver water targets during the production of fluoride (18F) using the medical cyclotron (GE MINI-trace). Then, To estimate the exposure for the staffs working in the SK Cyclotron Center, the dual-TLD chips (TLD-600/700) method was used to measure the doses contributed from photons and neutrons during the operation of the cyclotron, and the doses contributed from photons during the dispensations and transportations. The neutron activation methods of gold foils with and without 113Cd covered were used to correct the doses and to measure flux of thermal neutrons. Furthermore, the method of 6LiI(Eu) detector with Bonner Sphere Spectrometer (BSS) was used to measure neutron spectra. The variations of neutron spectra as the medical cyclotron was performed in different target systems (Target 1, Target 2 and Target 4) and beam currents are discussed. According to results of this research, for the staffs working in SK Cyclotron Center, Hp(10) of 309.06 and 22.48 μSv y-1 for photons and thermal neutrons due to operating cyclotron, Hp(10) of 5.30 mSv y-1 and Hp(0.07) of the finger of 252.35 mSv y-1 for photons due to dispensation, and Hp(10) of 1.04 mSv y-1 and Hp(0.07) of the finger of 25.56 mSv y-1 for photons due to transportations, respectively. The contributions of thermal neutron dose rate (15.93 nGy min-1) and thermal neutron flux (19.7 n cm-2s-1) for using Target 2 at the outside of self-shielding were 2.5 times as larger as Target 1. The energy fluence rates in Target 2 were 2 times as larger as Target 1. The volumes of targets affected the induced neutron spectra and doses. In addition, the mean saturation yield for using niobium water target (Target 4) (93.3 mCi μA-1) was 10.1 mCi μA-1 higher than Target 1. However, the energy fluence rates in Target 4 were 2.7 times highter than Target 1. Volumes, materials, geometric and components of targets impacted the induced neutron spectra. In conclusions, the mean Hp(10) and Hp(0.07) of the finger for a worker in the SK cyclotron center were 2.18 mSv y-1 and 92.64 mSv y-1, respectively, moreover, the maximum dose contribution appeared in dispensations. Besides, the cyclotron was operated in different targets system and beam currents that induced different saturation yield and neutron spectra. These variations were no ignoring.