Radiation dose to technicians per nuclear medicine procedure: comparison between technetium-99m, gallium-67, and iodine-131 radiotracers and fluorine-18 fluorodeoxyglucose |
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Authors: | C Chiesa V De Sanctis F Crippa M Schiavini C E Fraigola A Bogni C Pascali D Decise R Marchesini E Bombardieri |
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Institution: | (1) Unita’ PET, Divisione Medicina Nucleare, Istituto Nazionale Tumori, Milano, Italy, IT;(2) Divisione Fisica Sanitaria, Istituto Nazionale Tumori, Milano, Italy, IT |
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Abstract: | The aim of this study was to determine the non-extremity gamma dose received by a technician while performing an ordinary
nuclear medicine procedure or a static (i.e. without blood sampling) fluorine-18 fluorodeoxyglucose (FDG) positron emission
tomography (PET) study. The dose per patient was measured by means of a commercial electronic pocket Geiger Mueller dosimeter,
worn in the upper left pocket of the overalls. This was previously tested by exposure to known point sources of technetium-99m,
gallium-67, iodine-131 and fluorine-18 in the air. A further test was performed with 99mTc, 131I and 18F sources inserted in a water phantom to simulate the condition of high scattering degradation of the primary radiation due
to the patient’s tissues. Subsequently, the dose was measured by two technicians for a total of 314 clinical cases, covering
the most common nuclear medicine procedures, including 44 static, two-level FDG PET studies with repositioning of the patient
on the couch between the transmission and the emission scan and seven whole-body PET studies. The dose read by the dosimeter
was corrected for environmental background and for detector efficiency measured with sources in the air. For a limited subset
of cases, the time spent close to patients was also measured. Doses were then estimated by a crude non-absorbing point source
approximation and by using experimental dose rates. A comparison between experimental and estimated doses, as well as with
previously published data, completed the work. For most of the conventional procedures, the measured dose per procedure proved
to be within the range 0.2–0.4 μSv, except for equilibrium angiocardioscintigraphy (1.0±0.5 μSv) and 99mTc-sestamibi single-photon emission tomography (1.7±1.0 μSv). Comparison with data published in the last 20 years shows that
our values are generally lower. The current more favourable working conditions are a result of technological improvements
(for instance two-head gamma cameras capable of whole-body studies), and safer shielding and distance from patients. Two-level
PET gave 11.5±4.4 μSv and whole-body PET 5.9±1.2 μSv. In a subset of patients these values could be subdivided into the separate
contributions from each phase of the procedure. They were: 0.11±0.04 μSv for daily quality assurance, 2.9±3.0 μSv for two
transmission scans, 0.3±0.1 μSv for syringe preparation, 2.8±1.8 μSv for injection and escorting the patient to the waiting
room, 1.7±1.5 μSv for a whole-body emission scan, 7.7±5.2 μSv for two emission scans, and 0.8±0.2 μSv for patient departure.
The higher value from PET by comparison with conventional procedures is attributable to the higher specific gamma constant
of 18F, as well as the longer time required for accurate positioning.
Received 11 March and in revised form 5 July 1997 |
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Keywords: | : Technician dose Positron emitters Fluorine-18 fluorodeoxyglucose Positron emission tomography Nuclear medicine procedures |
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