Effective dose to staff members in a positron emission tomography/CT facility using zirconium-89

Abstract

Cite this article as: Alzimami KS, Ma AK. Effective dose to staff members in a positron emission tomography/CT facility using zirconium-89. Br J Radiol 2013;86: 20130318. FULL PAPER Effective dose to staff members in a positron emission tomography/CT facility using zirconium-89 1 K S ALZIMAMI, PhD F-FDG to the staff near the patient. This interesting result raises apparently contradictory implications in the radiation protection considerations of a PET/CT facility. Advances in knowledge: To the best of our knowledge, radiation exposure to staff and public in the PET/CT unit using 89 Zr has not been investigated. The ultimate output of this study will lead to the optimal design of the facility for routine use of 89 Zr.Positron emission tomography (PET)/CT scanners have quickly become the preferred technology for PET imaging, as the integration of functional PET images with the anatomical visualisation of CT has allowed more accurate diagnosis [1]. However, the doses delivered to patients and staff owing to the procedure should be considered and should be kept as low as reasonably achievable (ALARA) [2-4], i.e. the dose of a classified staff member should not exceed one-third of the annual dose limit.Radiation exposure of technical staff operating PET units with the use of fluorine-18 fludeoxyglucose ( 18 F-FDG) has been a controversial issue in the use of high-energy photons (511 keV), added to by a sharp increase in the number of scans undertaken using a limited number of PET/CT facilities [5][6][7]. However, the doses received by staff in PET/ CT procedures may vary considerably among facilities depending on the practices, positron emitter used, facility layout, injected activities and patient workload. Lately, several studies [5][6][7] have been carried out to assess and optimise radiation exposure to staff in the PET/CT unit when using 18 F-FDG and these studies were in agreement with a slight variation owing to different facilities and unit design. Alsafi et al [5] showed that an average staff dose per patient is 5.762.7 and 5.061.7 mSv per procedure for mobile and static facilities, respectively, using 18 F-FDG. The study of Al-Haj et al [6] reported that the estimated dose at the waiting area was 0.8 mSv per procedure. Dalianis et al [7] showed that the staff (nurse) dose during injection was in the range of 2.7-4.0 mSv and the dose to the technologist during positioning was in the range of 3.5-5.0 mSv over 10 months. Al-Haj et al [6] revealed that the estimated doses to staff working in PET/CT were within safe limits but would increase with patient workload and stay time. The 21 annual increase in patient workload necessitates that staff dose estimation be done and the protocol be reviewed for possible decrease in the 18 F-FDG activity to be administered. Elschot et al [8] studied the shielding requirement of a PET/CT facility using Monte Carlo methods with the MCNPX code [9] and the Medical Internal Radiation Dose full body phantom [10]. They found that the self-absorption of 18 F-FDG emission by ...

Recent Advances in Zirconium-89 Chelator Development

“…While several isotopes of Zr including 86 Zr ( t 1/2 : 17 h, γ 100%, E γ = 241 keV), 88 Zr ( t 1/2 : 85 d, γ 100%, E γ = 390 keV), and 89 Zr ( t 1/2 : 78.4 h, β + 22.8%, E β + max = 901 keV; 901 keV, EC 77%, E γ = 909 keV) can be produced on a cyclotron [ 66 , 67 ], 89 Zr has received the most attention for radiopharmaceutical development because of its favorable nuclear decay properties that make it useful in the labeling of antibodies for immuno-PET applications ( Figure 1 ) [ 68 , 69 , 70 ]. The availability of carrier-free 89 Zr as either zirconium-89 oxalate ([ 89 Zr]Zr(ox) 2 ) or zirconium-89 chloride ([ 89 Zr]Zr Cl 4 ) is essential to the development of effective immuno-PET agents.…”

Investigation of 18F and 89Zr Isotopes Self-Absorption and Dose Rate Parameters for PET Imaging

“…6 In a Monte Carlo study, for radiation protection purposes, when using 89 Zr in an imaging facility that is optimized for the annihilation photons only, the results showed that the low 89 Zr injected activity (75 MBq) would deliver a lower effective dose near the patient than 18 F (500 MBq) would; however, 89 Zr would give a higher effective dose than the 18 F outside the patient room due to the greater penetration power of the prompt g-ray. 6 In PET procedures utilizing 18 F-FDG, the 511 keV annihilation radiation is the main radiation protection concern, delivering a dose to the staff of 2.7-4.0 mSv during injection and 3.5-5.0 mSv during patient set-up. 7 The dose to the general public in the waiting area is about 0.8 mSv per procedure.…”

“… 5 89 Zr decays to 89 Y through β + emission (22.7%) and electron capture (77.3%) followed by a prompt γ-ray at 909 keV (99.04%). 6 …”

“…In a Monte Carlo study, for radiation protection purposes, when using 89 Zr in an imaging facility that is optimized for the annihilation photons only, the results showed that the low 89 Zr injected activity (75 MBq) would deliver a lower effective dose near the patient than 18 F (500 MBq) would; however, 89 Zr would give a higher effective dose than the 18 F outside the patient room due to the greater penetration power of the prompt γ-ray. 6 …”

“…The SAF is defined as the ratio of the amount of energy absorbed by the patient’s body to the amount of energy emitted by the radionuclide. 6 The American Association of Physicists in Medicine (AAPM) has recommended values of DRC and SAF for some commonly used radionuclides such as 11 C, 18 F, 124 I, for example, DRC = 0.143 μSv·m 2 ·MBq −1 ·hr −1 and SAF = 0.64 for 18 F. 8 The AAPM values for 18 F are further supported by studies in clinical setting 2 , 9 and with Monte Carlo methods 10 at distances beyond 1 m from the patient. However, studies near the patient (less than 1 m) concluded that the DRC provided by AAPM was a conservative value that over-estimated the dose.…”