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

ABSTRACT: OBJECTIVE: Positron emission tomography (PET) using zirconium-89 ((89)Zr) is complicated by its complex decay scheme. In this study, we quantified the effective dose from (89)Zr and compared it with fluorine-18 fludeoxyglucose ((18)F-FDG). METHODS: Effective dose distribution in a PET/CT facility in Riyadh was calculated by Monte Carlo simulations using MCNPX. The positron bremsstrahlung, the annihilation photons, the delayed gammas from (89)Zr and those emissions from (18)F-FDG were modelled in the simulations but low-energy characteristic X-rays were ignored. RESULTS: On the basis of injected activity, the dose from (89)Zr was higher than that of (18)F-FDG. However, the dose per scan from (89)Zr became less than that from (18)F-FDG near the patient, owing to the difference in injected activities. In the corridor and control rooms, the (89)Zr dose was much higher than (18)F-FDG, owing to the difference in attenuation by the shielding materials. CONCLUSION: The presence of the high-energy photons from (89)Zr-labelled immuno-PET radiopharmaceuticals causes a significantly higher effective dose than (18)F-FDG to the staff outside the patient room. Conversely, despite the low administered activity of (89)Zr, it gives rise to a comparable or even lower dose than (18)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.

SUBMITTER: Alzimami KS

PROVIDER: S-EPMC3798335 | biostudies-other | 2013 Oct

REPOSITORIES: biostudies-other

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Project description:Selection of the right drug for the right patient is a promising approach to increase clinical benefit of targeted therapy with monoclonal antibodies (mAbs). Assessment of in vivo biodistribution and tumor targeting of mAbs to predict toxicity and efficacy is expected to guide individualized treatment and drug development. Molecular imaging with positron emission tomography (PET) using zirconium-89 ((89)Zr)-labeled monoclonal antibodies also known as (89)Zr-immuno-PET, visualizes and quantifies uptake of radiolabeled mAbs. This technique provides a potential imaging biomarker to assess target expression, as well as tumor targeting of mAbs. In this review we summarize results from initial clinical trials with (89)Zr-immuno-PET in oncology and discuss technical aspects of trial design. In clinical trials with (89)Zr-immuno-PET two requirements should be met for each (89)Zr-labeled mAb to realize its full potential. One requirement is that the biodistribution of the (89)Zr-labeled mAb (imaging dose) reflects the biodistribution of the drug during treatment (therapeutic dose). Another requirement is that tumor uptake of (89)Zr-mAb on PET is primarily driven by specific, antigen-mediated, tumor targeting. Initial trials have contributed toward the development of (89)Zr-immuno-PET as an imaging biomarker by showing correlation between uptake of (89)Zr-labeled mAbs on PET and target expression levels in biopsies. These results indicate that (89)Zr-immuno-PET reflects specific, antigen-mediated binding. (89)Zr-immuno-PET was shown to predict toxicity of RIT, but thus far results indicating that toxicity of mAbs or mAb-drug conjugate treatment can be predicted are lacking. So far, one study has shown that molecular imaging combined with early response assessment is able to predict response to treatment with the antibody-drug conjugate trastuzumab-emtansine, in patients with human epithelial growth factor-2 (HER2)-positive breast cancer. Future studies would benefit from a standardized criterion to define positive tumor uptake, possibly supported by quantitative analysis, and validated by linking imaging data with corresponding clinical outcome. Taken together, these results encourage further studies to develop (89)Zr-immuno-PET as a predictive imaging biomarker to guide individualized treatment, as well as for potential application in drug development.

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

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