Radiation dose around a PET scanner installation: comparison of Monte Carlo simulations, analytical calculations and experimental results.
OBJECTIVE
Monte Carlo study of radiation transmission around areas surrounding a PET room.


METHODS
An extended population of patients administered with (18)F-FDG for PET-CT investigations was studied, collecting air kerma rate and gamma ray spectra measurements at a reference distance. An MC model of the diagnostic room was developed, including the scanner and walls with variable material and thickness. MC simulations were carried out with the widely used code GEANT4.


RESULTS
The model was validated by comparing simulated radiation dose values and gamma ray spectra produced by a volumetric source with experimental measurements; ambient doses in the surrounding areas were assessed for different combinations of wall materials and shielding and compared with analytical calculations, based on the AAPM Report 108. In the range 1.5-3.0 times of the product between the linear attenuation coefficient and thickness of an absorber (μ x), it was observed that the effectiveness of different combinations of shielding is roughly equivalent. An extensive tabulation of results is given in the text.


CONCLUSIONS
The validation tests performed showed a satisfactory agreement between the simulated and expected results. The simulated dose rates incident on, and transmitted by the walls in our model of PET scanner room, are generally in good agreement with analytical estimates performed using the AAPM Publication No. 108 method. This provides an independent confirmation of AAPM's approach. Even in this specific field of application, GEANT4 proved to be a relevant and accurate tool for dosimetry estimates, shielding evaluation and for general radiation protection use.
ENEA, Via Martiri di Monte Sole 4, I-40129 Bologna, Italy. Electronic address: sergio.lomeo@enea.it.
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Lo Meo
Medical Physics Department, Malpighi - S. Orsola University Hospital, Via Massarenti 9, I-40138 Bologna, Italy.
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Cicoria
Ionizing Radiation Laboratory, National Institution for Insurance against Accidents at Work (INAIL), Via Fontana Candida 1, I-00040 Monte Porzio Catone, Rome, Italy.
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Campanella
Ionizing Radiation Laboratory, National Institution for Insurance against Accidents at Work (INAIL), Via Fontana Candida 1, I-00040 Monte Porzio Catone, Rome, Italy.
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Mattozzi
Ionizing Radiation Laboratory, National Institution for Insurance against Accidents at Work (INAIL), Via Fontana Candida 1, I-00040 Monte Porzio Catone, Rome, Italy.
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Panebianco
Medical Physics Department, Malpighi - S. Orsola University Hospital, Via Massarenti 9, I-40138 Bologna, Italy.
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Marengo
D019788:Fluorodeoxyglucose F18; D005720:Gamma Rays; D006801:Humans; D009010:Monte Carlo Method; D049268:Positron-Emission Tomography / Q000009:adverse effects / Q000295:instrumentation*; D011835:Radiation Protection; D011874:Radiometry; D014057:Tomography, X-Ray Computed / Q000009:adverse effects
D019788:Fluorodeoxyglucose F18
Monte Carlo; PET; Shielding